Surface-mount technology

Last updated
Surface-mount components on a USB flash drive's circuit board. The small rectangular chips with numbers are resistors, while the unmarked small rectangular chips are capacitors. The capacitors and resistors pictured are 0603 (1608 metric) package sizes, along with a very slightly larger 0805 (2012 metric) ferrite bead. Smt closeup.jpg
Surface-mount components on a USB flash drive's circuit board. The small rectangular chips with numbers are resistors, while the unmarked small rectangular chips are capacitors. The capacitors and resistors pictured are 0603 (1608 metric) package sizes, along with a very slightly larger 0805 (2012 metric) ferrite bead.
Surface-mount capacitor SMD capacitor.jpg
Surface-mount capacitor
A MOSFET transistor, placed upon a British postage stamp for size comparison SMDcompared.jpeg
A MOSFET transistor, placed upon a British postage stamp for size comparison

Surface-mount technology (SMT) is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs). An electronic device so made is called a surface-mount device (SMD). In industry, it has largely replaced the through-hole technology construction method of fitting components with wire leads into holes in the circuit board. Both technologies can be used on the same board, with the through-hole technology used for components not suitable for surface mounting such as large transformers and heat-sinked power semiconductors.

Electronics physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter

Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. The identification of the electron in 1897, along with the invention of the vacuum tube, which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age.

Printed circuit board board to support and connect electronic components

A printed circuit board (PCB) mechanically supports and electrically connects electronic components or electrical components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it.

Through-hole technology mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in printed circuit boards and soldered to pads on the opposite side manually or by automated insertion mount machines

Through-hole technology, refers to the mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in printed circuit boards (PCB) and soldered to pads on the opposite side either by manual assembly or by the use of automated insertion mount machines.

Contents

By employing SMT, the production process speeds up, but the risk of defects also increases due to component miniaturization and to the denser packing of boards. In those conditions, detection of failures has become critical for any SMT manufacturing process.

An SMT component is usually smaller than its through-hole counterpart because it has either smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a matrix of solder balls (BGAs), or terminations on the body of the component.

Lead (electronics) connecting wire or pad within an electronic device; electrical connection consisting of a length of wire or metal pad (SMD) that comes from a device

In electronics, a lead is an electrical connection consisting of a length of wire or a metal pad (SMD) that is designed to connect two locations electrically. Leads are used for many purposes, including: transfer of power; testing of an electrical circuit to see if it is working, using a test light or a multimeter; transmiting information, as when the leads from an electrocardiograph, or ECG are attached to a person's body to transmit information about their heart rhythm; and sometimes to act as a heatsink. The tiny leads coming off through-hole components are also often called pins.

Solder ball

In integrated circuit packaging, a solder ball, also a solder bump is a ball of solder that provides the contact between the chip package and the printed circuit board, as well as between stacked packages in multichip modules. The solder balls can be placed manually or by automated equipment, and are held in place with a tacky flux.

Ball grid array

A ball grid array (BGA) is a type of surface-mount packaging used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors. A BGA can provide more interconnection pins than can be put on a dual in-line or flat package. The whole bottom surface of the device can be used, instead of just the perimeter. The traces connecting the package's leads to the wires or balls which connect the die to package are also on average shorter than with a perimeter-only type, leading to better performance at high speeds.

History

Surface mounting was originally called "planar mounting". [1]

Surface-mount technology was developed in the 1960s and became widely used in the mid 1980s. By the late 1990s, the great majority of high-tech electronic printed circuit assemblies were dominated by surface mount devices. Much of the pioneering work in this technology was done by IBM. The design approach first demonstrated by IBM in 1960 in a small-scale computer was later applied in the Launch Vehicle Digital Computer used in the Instrument Unit that guided all Saturn IB and Saturn V vehicles. [2] Components were mechanically redesigned to have small metal tabs or end caps that could be directly soldered to the surface of the PCB. Components became much smaller and component placement on both sides of a board became far more common with surface mounting than through-hole mounting, allowing much higher circuit densities and smaller circuit boards and, in turn, machines or subassemblies containing the boards.

IBM American multinational technology and consulting corporation

International Business Machines Corporation (IBM) is an American multinational information technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the Computing-Tabulating-Recording Company (CTR) and was renamed "International Business Machines" in 1924.

Saturn Launch Vehicle Digital Computer computer of the Saturn V rocket

The Saturn Launch Vehicle Digital Computer (LVDC) was a computer that provided the autopilot for the Saturn V rocket from launch to Earth orbit insertion. Designed and manufactured by IBM's Electronics Systems Center in Owego, N.Y., it was one of the major components of the Instrument Unit, fitted to the S-IVB stage of the Saturn V and Saturn IB rockets. The LVDC also supported pre- and post-launch checkout of the Saturn hardware. It was used in conjunction with the Launch Vehicle Data Adaptor (LVDA) which performed signal conditioning to the sensor inputs to the computer from the launch vehicle.

Saturn IB

The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It replaced the S-IV second stage of the Saturn I with the much more powerful S-IVB, able to launch a partially fueled Apollo command and service module (CSM) or a fully fueled lunar module (LM) into low Earth orbit for early flight tests before the larger Saturn V needed for lunar flight was ready.

Often only the solder joints hold the parts to the board; in rare cases parts on the bottom or "second" side of the board may be secured with a dot of adhesive to keep components from dropping off inside reflow ovens if the part has a large size or weight.[ citation needed ] Adhesive is sometimes used to hold SMT components on the bottom side of a board if a wave soldering process is used to solder both SMT and through-hole components simultaneously. Alternatively, SMT and through-hole components can be soldered on the same side of a board without adhesive if the SMT parts are first reflow-soldered, then a selective solder mask is used to prevent the solder holding those parts in place from reflowing and the parts floating away during wave soldering. Surface mounting lends itself well to a high degree of automation, reducing labor cost and greatly increasing production rates.

A reflow oven is a machine used primarily for reflow soldering of surface mount electronic components to printed circuit boards (PCB).

Wave soldering

Wave soldering is a bulk soldering process used in the manufacture of printed circuit boards. The circuit board is passed over a pan of molten solder in which a pump produces an upwelling of solder that looks like a standing wave. As the circuit board makes contact with this wave, the components become soldered to the board. Wave soldering is used for both through-hole printed circuit assemblies, and surface mount. In the latter case, the components are glued onto the surface of a printed circuit board (PCB) by placement equipment, before being run through the molten solder wave. Wave soldering is mainly used in soldering of through hole components.

Conversely, SMT does not lend itself well to manual or low-automation fabrication, which is more economical and faster for one-off prototyping and small-scale production, and this is one reason why many through-hole components are still manufactured. Some SMDs can be soldered with a temperature-controlled manual soldering iron, but unfortunately, those that are very small or have too fine a lead pitch are impossible to manually solder without expensive hot-air solder reflow equipment[ dubious ]. SMDs can be one-quarter to one-tenth the size and weight, and one-half to one-quarter the cost of equivalent through-hole parts, but on the other hand, the costs of a certain SMT part and of an equivalent through-hole part may be quite similar, though rarely is the SMT part more expensive.

Common abbreviations

Different terms describe the components, technique, and machines used in manufacturing. These terms are listed in the following table:

SMp termExpanded form
SMDSurface-mount devices (active, passive and electromechanical components)
SMTSurface-mount technology (assembling and mounting technology)
SMASurface-mount assembly (module assembled with SMT)
SMCSurface-mount components (components for SMT)
SMPSurface-mount packages (SMD case forms)
SMESurface-mount equipment (SMT assembling machines)

Assembly techniques

Assembly line with SMT placement equipment Juki KE-2080L by Megger.jpg
Assembly line with SMT placement equipment

Where components are to be placed, the printed circuit board normally has flat, usually tin-lead, silver, or gold plated copper pads without holes, called solder pads. Solder paste, a sticky mixture of flux and tiny solder particles, is first applied to all the solder pads with a stainless steel or nickel stencil using a screen printing process. It can also be applied by a jet-printing mechanism, similar to an inkjet printer. After pasting, the boards then proceed to the pick-and-place machines, where they are placed on a conveyor belt. The components to be placed on the boards are usually delivered to the production line in either paper/plastic tapes wound on reels or plastic tubes. Some large integrated circuits are delivered in static-free trays. Numerical control pick-and-place machines remove the parts from the tapes, tubes or trays and place them on the PCB. [3]

The boards are then conveyed into the reflow soldering oven. They first enter a pre-heat zone, where the temperature of the board and all the components is gradually, uniformly raised. The boards then enter a zone where the temperature is high enough to melt the solder particles in the solder paste, bonding the component leads to the pads on the circuit board. The surface tension of the molten solder helps keep the components in place, and if the solder pad geometries are correctly designed, surface tension automatically aligns the components on their pads.

There are a number of techniques for reflowing solder. One is to use infrared lamps; this is called infrared reflow. Another is to use a hot gas convection. Another technology which is becoming popular again is special fluorocarbon liquids with high boiling points which use a method called vapor phase reflow. Due to environmental concerns, this method was falling out of favor until lead-free legislation was introduced which requires tighter controls on soldering. At the end of 2008, convection soldering was the most popular reflow technology using either standard air or nitrogen gas. Each method has its advantages and disadvantages. With infrared reflow, the board designer must lay the board out so that short components don't fall into the shadows of tall components. Component location is less restricted if the designer knows that vapor phase reflow or convection soldering will be used in production. Following reflow soldering, certain irregular or heat-sensitive components may be installed and soldered by hand, or in large-scale automation, by focused infrared beam (FIB) or localized convection equipment.

If the circuit board is double-sided then this printing, placement, reflow process may be repeated using either solder paste or glue to hold the components in place. If a wave soldering process is used, then the parts must be glued to the board prior to processing to prevent them from floating off when the solder paste holding them in place is melted.

After soldering, the boards may be washed to remove flux residues and any stray solder balls that could short out closely spaced component leads. Rosin flux is removed with fluorocarbon solvents, high flash point hydrocarbon solvents, or low flash solvents e.g. limonene (derived from orange peels) which require extra rinsing or drying cycles. Water-soluble fluxes are removed with deionized water and detergent, followed by an air blast to quickly remove residual water. However, most electronic assemblies are made using a "No-Clean" process where the flux residues are designed to be left on the circuit board, since they are considered harmless. This saves the cost of cleaning, speeds up the manufacturing process, and reduces waste. However, it is generally suggested to wash the assembly, even when a "No-Clean" process is used, when the application uses very high frequency clock signals (in excess of 1 GHz). Another reason to remove no-clean residues is to improve adhesion of conformal coatings and underfill materials. [4] Regardless of cleaning or not those PCBs, current industry trend suggests to carefully review a PCB assembly process where "No-Clean" is applied, since flux residues trapped under components and RF shields may affect surface insulation resistance (SIR), especially on high component density boards. [5]

Certain manufacturing standards, such as those written by the IPC - Association Connecting Electronics Industries require cleaning regardless of the solder flux type used to ensure a thoroughly clean board. Proper cleaning removes all traces of solder flux, as well as dirt and other contaminants that may be invisible to the naked eye. No-Clean or other soldering processes may leave "white residues" that, according to IPC, are acceptable "provided that these residues have been qualified and documented as benign". [6] However, while shops conforming to IPC standard are expected to adhere to the Association's rules on board condition, not all manufacturing facilities apply IPC standard, nor are they required to do so. Additionally, in some applications, such as low-end electronics, such stringent manufacturing methods are excessive both in expense and time required.

Finally, the boards are visually inspected for missing or misaligned components and solder bridging. If needed, they are sent to a rework station where a human operator repairs any errors. They are then usually sent to the testing stations (in-circuit testing and/or functional testing) to verify that they operate correctly. Automated Optical Inspection (AOI) systems are commonly used in PCB manufacturing. This technology has proven highly efficient for process improvements and quality achievements. [7]

Advantages

The main advantages of SMT over the older through-hole technique are:

Disadvantages

Rework

Removal of surface-mount device using soldering tweezers Soldering a 0805.jpg
Removal of surface-mount device using soldering tweezers

Defective surface-mount components can be repaired by using soldering irons (for some connections), or using a non-contact rework system. In most cases a rework system is the better choice because SMD work with a soldering iron requires considerable skill and is not always feasible.

Reworking usually corrects some type of error, either human- or machine-generated, and includes the following steps:

Sometimes hundreds or thousands of the same part need to be repaired. Such errors, if due to assembly, are often caught during the process. However, a whole new level of rework arises when component failure is discovered too late, and perhaps unnoticed until the end user of the device being manufactured experiences it. Rework can also be used if products of sufficient value to justify it require revision or re-engineering, perhaps to change a single firmware-based component. Reworking in large volume requires an operation designed for that purpose.

There are essentially two non-contact soldering/desoldering methods: infrared soldering and soldering with hot gas [14] .

Infrared

With infrared soldering, the energy for heating up the solder joint is transmitted by long- or short-wave infrared electromagnetic radiation.

Advantages:

Disadvantages:

Hot gas

During hot gas soldering, the energy for heating up the solder joint is transmitted by a hot gas. This can be air or inert gas (nitrogen).

Advantages:

Disadvantages:

Packages

Surface-mount components are usually smaller than their counterparts with leads, and are designed to be handled by machines rather than by humans. The electronics industry has standardized package shapes and sizes (the leading standardisation body is JEDEC). These include:

The codes given in the chart below usually tell the length and width of the components in tenths of millimeters or hundredths of inches. For example, a metric 2520 component is 2.5 mm by 2.0 mm which corresponds roughly to 0.10 inches by 0.08 inches (hence, imperial size is 1008). Exceptions occur for imperial in the two smallest rectangular passive sizes. The metric codes still represent the dimensions in mm, even though the imperial size codes are no longer aligned. Problematically, some manufacturers are developing metric 0201 components with dimensions of 0.25 mm × 0.125 mm (0.0098 in × 0.0049 in), [15] but the imperial 01005 name is already being used for the 0.4 mm × 0.2 mm (0.0157 in × 0.0079 in) package. These increasingly small sizes, especially 0201 and 01005, can sometimes be a challenge from a manufacturability or reliability perspective. [16]

Example of component sizes, metric and imperial codes and comparison included SMT sizes, based on original by Zureks.svg
Example of component sizes, metric and imperial codes and comparison included
Composite image of a 11x44 LED matrix lapel name tag display using 1608/0603-type SMD LEDs. Top: A little over half of the 21x86 mm display. Center: Close-up of LEDs in ambient light. Bottom: LEDs in their own red light. Macro photo of LED matrix.jpg
Composite image of a 11x44 LED matrix lapel name tag display using 1608/0603-type SMD LEDs. Top: A little over half of the 21x86 mm display. Center: Close-up of LEDs in ambient light. Bottom: LEDs in their own red light.
SMD capacitors (on the left) with two through-hole capacitors (on the right) Photo-SMDcapacitors.jpg
SMD capacitors (on the left) with two through-hole capacitors (on the right)

Two-terminal packages

Rectangular passive components

Mostly resistors and capacitors.

PackageApproximate dimensions, length × widthTypical resistor
power rating (W)
MetricImperial
02010080040.25 mm × 0.125 mm0.010 in × 0.005 in
030150090050.3 mm × 0.15 mm0.012 in × 0.006 in0.02 [17]
0402010050.4 mm × 0.2 mm0.016 in × 0.008 in0.031 [18]
060302010.6 mm × 0.3 mm0.02 in × 0.01 in0.05 [18]
100504021.0 mm × 0.5 mm0.04 in × 0.02 in0.062 [19] –0.1 [18]
160806031.6 mm × 0.8 mm0.06 in × 0.03 in0.1 [18]
201208052.0 mm × 1.25 mm0.08 in × 0.05 in0.125 [18]
252010082.5 mm × 2.0 mm0.10 in × 0.08 in
321612063.2 mm × 1.6 mm0.125 in × 0.06 in0.25 [18]
322512103.2 mm × 2.5 mm0.125 in × 0.10 in0.5 [18]
451618064.5 mm × 1.6 mm0.18 in × 0.06 in [20]
453218124.5 mm × 3.2 mm0.18 in × 0.125 in0.75 [18]
456418254.5 mm × 6.4 mm0.18 in × 0.25 in0.75 [18]
502520105.0 mm × 2.5 mm0.20 in × 0.10 in0.75 [18]
633225126.3 mm × 3.2 mm0.25 in × 0.125 in1 [18]
745129207.4 mm × 5.1 mm0.29 in × 0.20 in [21]

Tantalum capacitors [22] [23]

PackageLength, typ. × width, typ. × height, max.
EIA 2012-12 (KEMET R, AVX R)2.0 mm × 1.3 mm × 1.2 mm
EIA 3216-10 (KEMET I, AVX K)3.2 mm × 1.6 mm × 1.0 mm
EIA 3216-12 (KEMET S, AVX S)3.2 mm × 1.6 mm × 1.2 mm
EIA 3216-18 (KEMET A, AVX A)3.2 mm × 1.6 mm × 1.8 mm
EIA 3528-12 (KEMET T, AVX T)3.5 mm × 2.8 mm × 1.2 mm
EIA 3528-21 (KEMET B, AVX B)3.5 mm × 2.8 mm × 2.1 mm
EIA 6032-15 (KEMET U, AVX W)6.0 mm × 3.2 mm × 1.5 mm
EIA 6032-28 (KEMET C, AVX C)6.0 mm × 3.2 mm × 2.8 mm
EIA 7260-38 (KEMET E, AVX V)7.2 mm × 6.0 mm × 3.8 mm
EIA 7343-20 (KEMET V, AVX Y)7.3 mm × 4.3 mm × 2.0 mm
EIA 7343-31 (KEMET D, AVX D)7.3 mm × 4.3 mm × 3.1 mm
EIA 7343-43 (KEMET X, AVX E)7.3 mm × 4.3 mm × 4.3 mm

Aluminum capacitors [24] [25] [26]

PackageDimensions
Panasonic / CDE A, Chemi-Con B3.3 mm × 3.3 mm
Panasonic B, Chemi-Con D4.3 mm × 4.3 mm
Panasonic C, Chemi-Con E5.3 mm × 5.3 mm
Panasonic D, Chemi-Con F6.6 mm × 6.6 mm
Panasonic E/F, Chemi-Con H8.3 mm × 8.3 mm
Panasonic G, Chemi-Con J10.3 mm × 10.3 mm
Chemi-Con K13.0 mm × 13.0 mm
Panasonic H13.5 mm × 13.5 mm
Panasonic J, Chemi-Con L17.0 mm × 17.0 mm
Panasonic K, Chemi-Con M19.0 mm × 19.0 mm

Small outline diode (SOD)

PackageDimensions
SOD-9230.8 × 0.6 × 0.4 mm [27] [28] [29]
SOD-7231.4 × 0.6 × 0.59 mm [30]
SOD-523 (SC-79)1.25 × 0.85 × 0.65 mm [31]
SOD-323 (SC-90)1.7 × 1.25 × 0.95 mm [32]
SOD-1285 × 2.7 × 1.1 mm [33]
SOD-1233.68 × 1.17 × 1.60 mm [34]
SOD-80C3.50 × ⌀ 1.50 mm [35]

Metal electrode leadless face [36] (MELF)

Mostly resistors and diodes; barrel shaped components, dimensions do not match those of rectangular references for identical codes.

PackageDimensions, length × diameterTypical resistor rating
Power (W)Voltage (V)
MicroMelf (MMU), 01022.2 mm × 1.1 mm0.2–0.3150
MiniMelf (MMA), 02043.6 mm × 1.4 mm0.25–0.4200
Melf (MMB), 02075.8 mm × 2.2 mm0.4–1.0300

DO-214

Commonly used for rectifier, Schottky, and other diodes

PackageDimensions (incl. leads)
DO-214AA (SMB)5.30 × 3.60 × 2.25 mm [37]
DO-214AB (SMC)7.95 × 5.90 × 2.25 mm [37]
DO-214AC (SMA)5.20 × 2.60 × 2.15 mm [37]

Three- and four-terminal packages

Small-outline transistor (SOT)

  • SOT-23 (TO-236-3) (SC-59): 2.9 mm × 1.3/1.75 mm × 1.3 mm body: three terminals for a transistor [38]
  • SOT-89 (TO-243) [39] (SC-62): [40] 4.5 mm × 2.5 mm × 1.5 mm body: four terminals, center pin is connected to a large heat-transfer pad [41]
  • SOT-143: 3mm x 1.4mm x 1.1mm tapered body: four terminals: one larger pad denotes terminal 1. [42]
  • SOT-223: 6.7 mm × 3.7 mm × 1.8 mm body: four terminals, one of which is a large heat-transfer pad [43]
  • SOT-323 (SC-70): 2 mm × 1.25 mm × 0.95 mm body: three terminals [44]
  • SOT-416 (SC-75): 1.6 mm × 0.8 mm × 0.8 mm body: three terminals [45]
  • SOT-663: 1.6 mm × 1.6 mm × 0.55 mm body: three terminals [46]
  • SOT-723: 1.2 mm × 0.8 mm × 0.5 mm body: three terminals: flat lead [47]
  • SOT-883 (SC-101): 1 mm × 0.6 mm × 0.5 mm body: three terminals: leadless [48]

Other

  • DPAK (TO-252, SOT-428): Discrete Packaging. Developed by Motorola to house higher powered devices. Comes in three- [49] or five-terminal [50] versions
  • D2PAK (TO-263, SOT-404): bigger than the DPAK; basically a surface mount equivalent of the TO220 through-hole package. Comes in 3, 5, 6, 7, 8 or 9-terminal versions [51]
  • D3PAK (TO-268): even larger than D2PAK [52]

Five- and six-terminal packages

Small-outline transistor (SOT)

  • SOT-23-5 (SOT-25, SC-74A): 2.9 mm × 1.3/1.75 mm × 1.3 mm body: five terminals [53]
  • SOT-23-6 (SOT-26, SC-74): 2.9 mm × 1.3/1.75 mm × 1.3 mm body: six terminals [54]
  • SOT-23-8 (SOT-28): 2.9 mm × 1.3/1.75 mm × 1.3 mm body: eight terminals [55]
  • SOT-353 (SC-88A): 2 mm × 1.25 mm × 0.95 mm body: five terminals [56]
  • SOT-363 (SC-88, SC-70-6): 2 mm × 1.25 mm × 0.95 mm body: six terminals [57]
  • SOT-563: 1.6 mm × 1.2 mm × 0.6 mm body: six terminals [58]
  • SOT-665: 1.6 mm × 1.6 mm × 0.55 mm body: five terminals [59]
  • SOT-666: 1.6 mm × 1.6 mm × 0.55 mm body: six terminals [60]
  • SOT-886: 1.5 mm × 1.05 mm × 0.5 mm body: six terminals: leadless
  • SOT-886: 1 mm × 1.45 mm × 0.5 mm body: six terminals: leadless [61]
  • SOT-891: 1.05 mm × 1.05 mm × 0.5 mm body: five terminals: leadless
  • SOT-953: 1 mm × 1 mm × 0.5 mm body: five terminals
  • SOT-963: 1 mm × 1 mm × 0.5 mm body: six terminals
  • SOT-1115: 0.9 mm × 1 mm × 0.35 mm body: six terminals: leadless [62]
  • SOT-1202: 1 mm × 1 mm × 0.35 mm body: six terminals: leadless [63]
Various SMD chips, desoldered Photo-SMDchips.jpg
Various SMD chips, desoldered
MLP package 28-pin chip, upside down to show contacts 28 pin MLP integrated circuit.jpg
MLP package 28-pin chip, upside down to show contacts

Packages with more than six terminals

Dual-in-line

Quad-in-line

  • Plastic leaded chip carrier (PLCC): square, J-lead, pin spacing 1.27 mm
  • Quad flat package (QFP): various sizes, with pins on all four sides
  • Low-profile quad flat-package (LQFP): 1.4 mm high, varying sized and pins on all four sides
  • Plastic quad flat-pack (PQFP), a square with pins on all four sides, 44 or more pins
  • Ceramic quad flat-pack (CQFP): similar to PQFP
  • Metric quad flat-pack (MQFP): a QFP package with metric pin distribution
  • Thin quad flat-pack (TQFP), a thinner version of PQFP
  • Quad flat no-lead (QFN): smaller footprint than leaded equivalent
  • Leadless chip carrier (LCC): contacts are recessed vertically to "wick-in" solder. Common in aviation electronics because of robustness to mechanical vibration.
  • Micro leadframe package (MLP, MLF): with a 0.5 mm contact pitch, no leads (same as QFN)
  • Power quad flat no-lead (PQFN): with exposed die-pads for heatsinking

Grid arrays

  • Ball grid array (BGA): A square or rectangular array of solder balls on one surface, ball spacing typically 1.27 mm (0.050 in)
  • Land grid array (LGA): An array of bare lands only. Similar to in appearance to QFN, but mating is by spring pins within a socket rather than solder.
  • Fine-pitch ball grid array (FBGA)]: A square or rectangular array of solder balls on one surface
  • Low-profile fine-pitch ball grid array (LFBGA): A square or rectangular array of solder balls on one surface, ball spacing typically 0.8 mm
  • Thin fine-pitch ball grid array (TFBGA): A square or rectangular array of solder balls on one surface, ball spacing typically 0.5 mm
  • Column grid array (CGA): A circuit package in which the input and output points are high-temperature solder cylinders or columns arranged in a grid pattern.
  • Ceramic column grid array (CCGA): A circuit package in which the input and output points are high-temperature solder cylinders or columns arranged in a grid pattern. The body of the component is ceramic.
  • Micro ball grid array (μBGA): Ball spacing less than 1 mm
  • Lead less package (LLP): A package with metric pin distribution (0.5 mm pitch).

Non-packaged devices

Although surface-mount, these devices require specific process for assembly.

  • Chip-on-board (COB), a bare silicon chip, that is usually an integrated circuit, is supplied without a package (usually a lead frame overmolded with epoxy) and is attached, often with epoxy, directly to a circuit board. The chip is then wire bonded and protected from mechanical damage and contamination by an epoxy "glob-top".
  • Chip-on-flex (COF), a variation of COB, where a chip is mounted directly to a flex circuit.
  • Chip-on-glass (COG); a variation of COB, where a chip, typically a liquid crystal display (LCD) controller, is mounted directly on glass:.

There are often subtle variations in package details from manufacturer to manufacturer, and even though standard designations are used, designers need to confirm dimensions when laying out printed circuit boards.

Identification

Resistors

For 5% precision SMD resistors usually are marked with their resistance values using three digits: two significant digits and a multiplier digit. These are quite often white lettering on a black background, but other colored backgrounds and lettering can be used.

The black or colored coating is usually only on one face of the device, the sides and other face simply being the uncoated, usually white ceramic substrate. The coated surface, with the resistive element beneath is normally positioned face up when the device is soldered to the board, although they can be seen in rare cases mounted with the uncoated underside face up, whereby the resistance value code is not visible.

For 1% precision SMD resistors, the code is used, as three digits would otherwise not convey enough information. This code consists of two digits and a letter: the digits denote the value's position in the E96 sequence, while the letter indicates the multiplier. [65]

Typical examples of resistance codes

There is an online tool to translate codes to resistance values. Resistors are made in several types; a common types uses a ceramic substrate. Resistance values are available in several tolerances defined in EIA Decade Values Table :

Capacitors

Non-electrolytic capacitors are usually unmarked and the only reliable method of determining their value is removal from the circuit and subsequent measurement with a capacitance meter or impedance bridge. The materials used to fabricate the capacitors, such as nickel tantalate, possess different colours and these can give an approximate idea of the capacitance of the component. [ citation needed ]

Generally physical size is proportional to capacitance and (squared) voltage for the same dielectric. For example, a 100 nF 50 V capacitor may come in the same package as a 10 nF 150 V device.

SMD (non-electrolytic) capacitors, which are usually monolithic ceramic capacitors, exhibit the same body color on all four faces not covered by the end caps.

SMD electrolytic capacitors, usually tantalum capacitors, and film capacitors are marked like resistors, with two significant figures and a multiplier in units of picofarads or pF, (10−12 farad.)

Examples

The electrolytic capacitors are usually encapsulated in black or beige epoxy resin with flat metal connecting strips bent underneath. Some film or tantalum electrolytic types are unmarked and possess red, orange or blue body colors with complete end caps, not metal strips.

Inductors

Smaller inductance with moderately high current ratings are usually of the ferrite bead type. They are simply a metal conductor looped through a ferrite bead and almost the same as their through-hole versions but possess SMD end caps rather than leads. They appear dark grey and are magnetic, unlike capacitors with a similar dark grey appearance. These ferrite bead type are limited to small values in the nH (nano Henry) range and are often used as power supply rail decouplers or in high frequency parts of a circuit. Larger inductors and transformers may of course be through-hole mounted on the same board.

SMT inductors with larger inductance values often have turns of wire or flat strap around the body or embedded in clear epoxy, allowing the wire or strap to be seen. Sometimes a ferrite core is present also. These higher inductance types are often limited to small current ratings, although some of the flat strap types can handle a few amps.

As with capacitors, component values and identifiers for smaller inductors are not usually marked on the component itself; if not documented or printed on the PCB, measurement, usually removed from the circuit, is the only way of determining them. Larger inductors, especially wire-wound types in larger footprints, usually have the value printed on the top. For example, "330", which equates to a value of 33uH (micro Henry).

Discrete semiconductors

Discrete semiconductors, such as diodes and transistors are often marked with a two- or three-symbol code. The same code marked on different packages or on devices from different manufacturers can translate to different devices.

Many of these codes, used because the devices are too small to be marked with more traditional numbers used on larger packages, correlate to more familiar traditional part numbers when a correlation list is consulted.

GM4PMK in the United Kingdom has prepared a correlation list, and a similar .pdf list is also available, although these lists are not complete.

Integrated circuits

Generally, integrated circuit packages are large enough to be imprinted with the complete part number which includes the manufacturer's specific prefix, or a significant segment of the part number and the manufacturer's name or logo.

Examples of manufacturers' specific prefixes:

See also

Related Research Articles

Dual in-line package

In microelectronics, a dual in-line package, or dual in-line pin package (DIPP) is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board (PCB) or inserted in a socket. The dual-inline format was invented by Don Forbes, Rex Rice and Bryant Rogers at Fairchild R&D in 1964, when the restricted number of leads available on circular transistor-style packages became a limitation in the use of integrated circuits. Increasingly complex circuits required more signal and power supply leads ; eventually microprocessors and similar complex devices required more leads than could be put on a DIP package, leading to development of higher-density packages. Furthermore, square and rectangular packages made it easier to route printed-circuit traces beneath the packages.

555 timer IC

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide two (556) or four (558) timing circuits in one package.

Quad Flat Package surface mount integrated circuit package

A QFP or Quad Flat Package is a surface-mounted integrated circuit package with "gull wing" leads extending from each of the four sides. Socketing such packages is rare and through-hole mounting is not possible. Versions ranging from 32 to 304 pins with a pitch ranging from 0.4 to 1.0 mm are common. Other special variants include low-profile QFP (LQFP) and thin QFP (TQFP).

Reflow soldering

Reflow soldering is a process in which a solder paste is used to temporarily attach one or thousands of tiny electrical components to their contact pads, after which the entire assembly is subjected to controlled heat. The solder paste reflows in a molten state, creating permanent solder joints. Heating may be accomplished by passing the assembly through a reflow oven or under an infrared lamp or by soldering individual joints [unconventionally] with a desoldering hot air pencil.

Moisture sensitivity level relates to the packaging and handling precautions for some semiconductors. The MSL is an electronic standard for the time period in which a moisture sensitive device can be exposed to ambient room conditions.

Laser trimming

Laser trimming is the manufacturing process of using a laser to adjust the operating parameters of an electronic circuit.

TO-220

The TO-220 is a style of electronic package used for high-powered, through-hole components. The "TO" designation stands for "transistor outline". TO-220 packages have three leads. Similar packages with two, four, five or seven leads are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink, allowing the component to dissipate more heat than one constructed in a TO-92 case. Common TO-220-packaged components include discrete semiconductors such as transistors and silicon-controlled rectifiers, as well as integrated circuits.

Selective soldering

Selective soldering is the process of selectively soldering components to printed circuit boards and molded modules that could be damaged by the heat of a reflow oven or wave soldering in a traditional surface-mount technology (SMT) or Through-hole technology assembly processes.This usually follows an SMT oven reflow process; parts to be selectively soldered are usually surrounded by parts that have been previously soldered in a surface-mount reflow process, and the selective-solder process must be sufficiently precise to avoid damaging them.

Quad Flat No-leads package

Flat no-leads packages such as quad-flat no-leads (QFN) and dual-flat no-leads (DFN) physically and electrically connect integrated circuits to printed circuit boards. Flat no-leads, also known as micro leadframe (MLF) and SON, is a surface-mount technology, one of several package technologies that connect ICs to the surfaces of PCBs without through-holes. Flat no-lead is a near chip scale plastic encapsulated package made with a planar copper lead frame substrate. Perimeter lands on the package bottom provide electrical connections to the PCB. Flat no-lead packages include an exposed thermal pad to improve heat transfer out of the IC. Heat transfer can be further facilitated by metal vias in the thermal pad. The QFN package is similar to the quad-flat package (QFP), and a ball grid array (BGA).

Automated optical inspection (AOI) is an automated visual inspection of printed circuit board (PCB) manufacture where a camera autonomously scans the device under test for both catastrophic failure and quality defects. It is commonly used in the manufacturing process because it is a non-contact test method. It is implemented at many stages through the manufacturing process including bare board inspection, solder paste inspection (SPI), pre-reflow and post-reflow as well as other stages.

2N7000

The 2N7000 and BS170 are two different N-channel, enhancement-mode MOSFETs used for low-power switching applications, with different lead arrangements and current ratings. They are sometimes listed together on the same datasheet with other variants 2N7002, VQ1000J, and VQ1000P.

Metal electrode leadless face

Metal electrode leadless face (MELF) is a type of leadless cylindrical electronic surface mount device that is metallized at its ends. MELF devices are usually diodes and resistors.

A semiconductor package is a metal, plastic, glass, or ceramic casing containing one or more discrete semiconductor devices or integrated circuits. Individual components are fabricated on semiconductor wafers before being diced into die, tested, and packaged. The package provides a means for connecting the package to the external environment, such as printed circuit board, via leads such as lands, balls, or pins; and protection against threats such as mechanical impact, chemical contamination, and light exposure. Additionally, it helps dissipate heat produced by the device, with or without the aid of a heat spreader. There are thousands of package types in use. Some are defined by international, national, or industry standards, while others are particular to an individual manufacturer.

Chip carrier one of several kinds of surface mount technology packages for integrated circuits

In electronics, a chip carrier is one of several kinds of surface-mount technology packages for integrated circuits. Connections are made on all four edges of a square package; Compared to the internal cavity for mounting the integrated circuit, the package overall size is large.

Small-outline transistor

A small outline transistor (SOT) is a family of small footprint, discrete surface mount transistor commonly used in consumer electronics. The most common SOT are SOT23 variations, also manufacturers offer the nearly identical thin small outline transistor (TSOT) package, where lower height is important.

Film capacitor

Film capacitors, plastic film capacitors, film dielectric capacitors, or polymer film capacitors, generically called “film caps” as well as power film capacitors, are electrical capacitors with an insulating plastic film as the dielectric, sometimes combined with paper as carrier of the electrodes.

References

  1. Williams, Paul, ed. (1999). Status of the Technology Industry Activities and Action Plan (PDF). Surface Mount Technology. Surface Mount Council. Archived (PDF) from the original on 2015-12-28.
  2. Schneeweis, Scott. "Artifact: Digital Computer Memory and Circuit Boards, LVDC, Saturn IB/V Guidance, Navigation and Control". Artifacts. Spaceaholic. Archived from the original on 2015-12-28. Retrieved 2015-12-28.
  3. Jena, Hanings (4 January 2016). "PCB Assembly - Description". www.ourpcb.com. Retrieved 7 February 2018.
  4. "Why Clean No-Clean?". Assembly Magazine. Retrieved 2017-10-03.
  5. "No-clean is a process, not a product". www.ipc.org. Retrieved 2017-10-03.
  6. IPC-A-610E, paragraph 10.6.3.
  7. Vitoriano, Pedro. "3D Solder Joint Reconstruction on SMD based on 2D Images".
  8. Montrose, Mark I. (1999). "Components and EMC". EMC and the Printed Circuit Board: Design, Theory, and Layout Made Simple. Wiley-Interscience. p. 64. ISBN   978-0780347038.
  9. "Power Surface Mounts are small, hermetic, surface mountable packages". www.ametek-ecp.com. Retrieved 2017-01-05.
  10. Judd, Mike; Brindley, Keith (1999). "CS soldering processes". Soldering in Electronics Assembly (2 ed.). Newnes. p. 128. ISBN   978-0750635455.
  11. Williams, Jim (1991). High Speed Amplifier Techniques - A Designer’s Companion for Wideband Circuitry (PDF). Application Notes. Linear Technology. pp. 26–29, 98–121. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  12. Dr. Lee, Ning-Cheng; Hance, Wanda B. (1993). "Voiding Mechanisms in SMT". Indium Corporation Tech Paper. Retrieved 2015-12-28.
  13. DerMarderosian, Aaron; Gionet, Vincent (1983). "The Effects of Entrapped Bubbles in Solder Used for the Attachment of Leadless Ceramic Chip Carriers". Reliability Physics Symposium: 235–241. ISSN   0735-0791.
  14. "Two Prevalent Rework Heating Methods--Which One is Best?". smt.iconnect007.com. Retrieved 2018-07-27.
  15. Murata, Tsuneo (2012-09-05). "Murata's world's Smallest Monolithic Ceramic Capacitor - 0201 <millimeter size> size (0.25 mm x 0.125 mm)" (Press release). Kyoto, Japan: Murata Manufacturing Co., Ltd. Archived from the original on 2015-12-28. Retrieved 2015-12-28.
  16. "White Paper 0201 and 01005 Adoption in Industry" (PDF). Retrieved 7 February 2018.
  17. "SMR Series Ultra-Compact Chip Resistors" (PDF). Datasheet. Rohm Semiconductor.
  18. 1 2 3 4 5 6 7 8 9 10 11 "Thick Film Chip Resistors" (PDF). Datasheet. Panasonic. Archived from the original (PDF) on 2014-02-09.
  19. "Thick Film Chip Resistor - SMDC Series" (PDF). Datasheet. electronic sensor + resistor GmbH. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  20. "SMD/BLOCK Type EMI Suppression Filters EMIFIL" (PDF). Catalog. Murata Manufacturing Co., Ltd. Archived from the original on 2015-12-28. Retrieved 2015-12-28.
  21. "POLYFUSE® Resettable Fuses SMD2920" (PDF). Datasheet. Littelfuse . Retrieved 2015-12-28.
  22. "TLJ Series - Tantalum Solid Electrolytic Chip Capacitors High CV Consumer Series" (PDF). Datasheet. AVX Corporation. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  23. "Tantalum Surface Mount Capacitors - Standard Tantalum" (PDF). Catalog. KEMET Electronics Corporation. 2011-09-06. Archived from the original (PDF) on 2011-12-26. Retrieved 2015-12-28.
  24. "SMT Aluminum Electrolytic Capacitors" (PDF). Datasheet. Panasonic. Archived from the original (PDF) on 2012-03-01. Retrieved 2015-12-28.
  25. "Application Guide - Aluminum SMT Capacitors" (PDF). Resources. Cornell Dubilier. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  26. "Surface Mount Aluminum Electrolytic Capacitors - Alchip-MVA Series" (PDF). Nippon Chemi-Con . Retrieved 2015-12-28.
  27. "NXP SOD923" (PDF). Datasheet. NXP Semiconductors.
  28. "Central SOD923" (PDF). Datasheet. Central Semiconductor.
  29. "Toshiba SOD923". Package Information. Toshiba Corporation.
  30. "Comchip CDSP400-G" (PDF). Datasheet. Comchip Technology Corporation. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  31. "SOD523 Package outline" (PDF). NXP Semiconductors. 2008. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  32. "Package information - SOD323" (PDF). Zetex Semiconductors. 2008. Archived from the original (PDF) on 2012-11-19. Retrieved 2015-12-28.
  33. "SOD128 Package outline" (PDF). NXP Semiconductors. 2008. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  34. "Designer's™ Data Sheet - Surface Mount Silicon Zener Diodes - Plastic SOD-123 Package" (PDF). Motorola . Retrieved 2015-12-28.
  35. "SOD 80C (LL-34) Mini MELF Hermetically Sealed Glass Package" (PDF). Continental Device India Limited. Archived from the original (PDF) on 2012-04-23. Retrieved 2015-12-28.
  36. "Professional Thin Film MELF Resistors" (PDF). Vishay Intertechnology. 2014-04-22. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  37. 1 2 3 "Package Outline Dimensions - U-DFN1616-6 (Type F)" (PDF). Diodes Incorporated. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  38. "Package Outline Drawing - P3.064" (PDF). Intersil. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  39. "3-Lead Small Outline Transistor Package [SOT-89] (RK-3)" (PDF). Analog Devices. 2013-09-12. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  40. "Standards for the Dimensions of Semiconductor Devices" (PDF). Electronic Industries Association of Japan. 1996-04-15. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  41. "Package Information - SOT-89" (PDF). RICOH. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  42. https://www.centralsemi.com/PDFs/case/SOT-143PD.PDF
  43. "SOT-233 Molded Package" (PDF). Fairchild Semiconductor. 2008-02-26. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  44. "SOT323 Package outline" (PDF). NXP Semiconductors. 2008. Archived from the original (PDF) on 2015-12-28. Retrieved 2015-12-28.
  45. "SOT416 Package outline" (PDF). NXP Semiconductors. 2010. Archived from the original (PDF) on 2015-12-28. Retrieved 2015-12-28.
  46. "SOT663 Package outline" (PDF). NXP Semiconductors. 2008. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  47. "Mechanical Case Outline SOT-723" (PDF). ON Semiconductor. 2009-08-10. Retrieved 2015-12-28.
  48. "SOT883 Package outline" (PDF). NXP Semiconductors. 2008. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  49. "D-PAK (TO-252AA) Outline Dimensions" (PDF). Vishay Intertechnology. 2012-12-05. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  50. "Mechanical Case Outline - DPAK-5" (PDF). ON Semiconductor. 2014-05-15. Retrieved 2015-12-28.
  51. "D2PAK Outline Dimensions" (PDF). Vishay Intertechnology. 2015-07-08. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  52. "Phase-leg Rectifier Diode" (PDF). IXYS Corporation. 2002. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  53. "P5.064 Package Outline Drawing" (PDF). Intersil. 2011. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  54. "P6.064 Package Outline Drawing" (PDF). Intersil. 2010. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  55. "Small Outline Transistor Plastic Packages (SOT23-8)" (PDF). Intersil. 2003. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  56. "SOT353 Package outline" (PDF). NXP Semiconductors. 2008. Archived from the original (PDF) on 2015-12-28. Retrieved 2015-12-28.
  57. "SOT363 Package outline" (PDF). NXP Semiconductors. 2008. Archived from the original (PDF) on 2015-12-28. Retrieved 2015-12-28.
  58. "SOT563 Package Details" (PDF). Central Semiconductor. 2015-05-22. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  59. "SOT665 Package outline" (PDF). NXP Semiconductors. 2008. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  60. "SOT666 Package outline" (PDF). NXP Semiconductors. 2008. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  61. "SOT886 Package outline" (PDF). NXP Semiconductors. 2008. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  62. "SOT1115 Package outline" (PDF). NXP Semiconductors. 2010. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  63. "SOT1202 Package outline" (PDF). NXP Semiconductors. 2010. Archived (PDF) from the original on 2015-12-28. Retrieved 2015-12-28.
  64. "IC Package Types". www.SiliconFarEast.com. Archived from the original on 2013-07-26. Retrieved 2015-12-28.
  65. "Resistor SMD code". Resistor Guide. Archived from the original on 2015-12-28. Retrieved 2015-12-28.