Brazing is a metal-joining process in which two or more metal items are joined by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal.
A gasket is a mechanical seal which fills the space between two or more mating surfaces, generally to prevent leakage from or into the joined objects while under compression. It is a deformable material that is used to create a static seal and maintain that seal under various operating conditions in a mechanical assembly.
In metallurgy, a flux is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining.
Ultrasonic welding is an industrial process whereby high-frequency ultrasonic acoustic vibrations are locally applied to work pieces being held together under pressure to create a solid-state weld. It is commonly used for plastics and metals, and especially for joining dissimilar materials. In ultrasonic welding, there are no connective bolts, nails, soldering materials, or adhesives necessary to bind the materials together. When used to join metals, the temperature stays well below the melting point of the involved materials, preventing any unwanted properties which may arise from high temperature exposure of the metal.
An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, forming a seal at the interface.
Ultra-high vacuum is the vacuum regime characterised by pressures lower than about 1×10−6 pascals. UHV conditions are created by pumping the gas out of a UHV chamber. At these low pressures the mean free path of a gas molecule is greater than approximately 40 km, so the gas is in free molecular flow, and gas molecules will collide with the chamber walls many times before colliding with each other. Almost all molecular interactions therefore take place on various surfaces in the chamber.
A hermetic seal is any type of sealing that makes a given object airtight. The term originally applied to airtight glass containers, but as technology advanced it applied to a larger category of materials, including rubber and plastics. Hermetic seals are essential to the correct and safe functionality of many electronic and healthcare products. Used technically, it is stated in conjunction with a specific test method and conditions of use. Colloquially, the exact requirements of such a seal varies with the application.
A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys.
A heat sealer is a machine used to seal products, packaging, and other thermoplastic materials using heat. This can be with uniform thermoplastic monolayers or with materials having several layers, at least one being thermoplastic. Heat sealing can join two similar materials together or can join dissimilar materials, one of which has a thermoplastic layer.
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.
A glass-ceramic-to-metal seal is a type of mechanical seal which binds glass-ceramic and metal surfaces. They are related to glass-to-metal seals, and like them are hermetic (airtight).
Electronic packaging is the design and production of enclosures for electronic devices ranging from individual semiconductor devices up to complete systems such as a mainframe computer. Packaging of an electronic system must consider protection from mechanical damage, cooling, radio frequency noise emission and electrostatic discharge. Product safety standards may dictate particular features of a consumer product, for example, external case temperature or grounding of exposed metal parts. Prototypes and industrial equipment made in small quantities may use standardized commercially available enclosures such as card cages or prefabricated boxes. Mass-market consumer devices may have highly specialized packaging to increase consumer appeal. Electronic packaging is a major discipline within the field of mechanical engineering.
A fitting or adapter is used in pipe systems to connect sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of fluids such as water for potatory, irrigational, sanitary, and refrigerative purposes, gas, petroleum, liquid waste, or any other liquid or gaseous substances required in domestic or commercial environments, within a system of pipes or tubes, connected by various methods, as dictated by the material of which these are made, the material being conveyed, and the particular environmental context in which they will be used, such as soldering, mortaring, caulking, Plastic welding, welding, friction fittings, threaded fittings, and compression fittings.
Metal bellows are elastic vessels that can be compressed when pressure is applied to the outside of the vessel, or extended under vacuum. When the pressure or vacuum is released, the bellows will return to its original shape, provided the material has not been stressed past its yield strength. They are used both for their ability to deform under pressure and to provide a hermetic seal that allows movement.
Porosity sealing is done through the process of vacuum impregnation. Vacuum impregnation is a preferred OEM process that seals porosity and leak paths in metal castings, sintered metal parts and electrical castings that form during the casting or molding process. Vacuum impregnation stops casting porosity
Glass-to-metal seals are a type of mechanical seal which joins glass and metal surfaces. They are very important elements in the construction of vacuum tubes, electric discharge tubes, incandescent light bulbs, glass-encapsulated semiconductor diodes, reed switches, glass windows in metal cases, and metal or ceramic packages of electronic components.
Soldering is a process of joining two metal surfaces together using a filler metal called solder. The soldering process involves heating the surfaces to be joined and melting the solder, which is then allowed to cool and solidify, creating a strong and durable joint.
Glass frit bonding, also referred to as glass soldering or seal glass bonding, describes a wafer bonding technique with an intermediate glass layer. It is a widely used encapsulation technology for surface micro-machined structures, e.g., accelerometers or gyroscopes. This technique utilizes low melting-point glass and therefore provides various advantages including that viscosity of glass decreases with an increase of temperature. The viscous flow of glass has effects to compensate and planarize surface irregularities, convenient for bonding wafers with a high roughness due to plasma etching or deposition. A low viscosity promotes hermetically sealed encapsulation of structures based on a better adaption of the structured shapes. Further, the coefficient of thermal expansion (CTE) of the glass material is adapted to silicon. This results in low stress in the bonded wafer pair. The glass has to flow and wet the soldered surfaces well below the temperature where deformation or degradation of either of the joined materials or nearby structures occurs. The usual temperature of achieving flowing and wetting is between 450 and 550 °C.
Materials for use in vacuum are materials that show very low rates of outgassing in vacuum and, where applicable, are tolerant to bake-out temperatures. The requirements grow increasingly stringent with the desired degree of vacuum to be achieved in the vacuum chamber. The materials can produce gas by several mechanisms. Molecules of gases and water can be adsorbed on the material surface. Materials may sublimate in vacuum. Or the gases can be released from porous materials or from cracks and crevices. Traces of lubricants, residues from machining, can be present on the surfaces. A specific risk is outgassing of solvents absorbed in plastics after cleaning.
The elements bismuth and indium have relatively low melting points when compared to other metals, and their alloy bismuth–indium (Bi–In) is classified as a fusible alloy. It has a melting point lower than the eutectic point of the tin–lead alloy. The most common application of the Bi-In alloy is as a low temperature solder, which can also contain, besides bismuth and indium, lead, cadmium, and tin.
