Solid Logic Technology

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Solid Logic Technology cards
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A double-width SLT card. The square metal cans contain the hybrid circuits.
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Three single-width SLT cards
SLT cards in situ
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Many SLT cards plugged into a board
IBM 129 SLT modules.jpg
SLT cards in an IBM 129 keypunch

Solid Logic Technology (SLT) was IBM's method for hybrid packaging of electronic circuitry introduced in 1964 with the IBM System/360 series of computers. It was also used in the 1130, announced in 1965. IBM chose to design custom hybrid circuits using discrete, flip chip-mounted, glass-encapsulated transistors and diodes, with silk-screened resistors on a ceramic substrate, forming an SLT module. The circuits were either encapsulated in plastic or covered with a metal lid. Several of these SLT modules (20 in the image on the right) were then mounted on a small multi-layer printed circuit board to make an SLT card. Each SLT card had a socket on one edge that plugged into pins on the computer's backplane (the exact reverse of how most other companies' modules were mounted).

Contents

IBM considered monolithic integrated circuit technology too immature at the time. [1] SLT was a revolutionary technology for 1964, with much higher circuit densities and improved reliability over earlier packaging techniques such as the Standard Modular System. It helped propel the IBM System/360 mainframe family to overwhelming success during the 1960s. SLT research produced ball chip assembly, wafer bumping, trimmed thick-film resistors, printed discrete functions, chip capacitors and one of the first volume uses of hybrid thick-film technology.

SLT replaced the earlier Standard Modular System, although some later SMS cards held SLT modules. SLT had several updates during its life, the last being the Monolithic System Technology (MST) which replaced the single transistors of SLT with small-scale integrated circuits that held four or five transistors. MST was used in the System/370, which began to replace the System/360 in 1970.

Details

SLT used silicon planar glass-encapsulated transistors and diodes. [2]

SLT uses dual diode chips and individual transistor chips each approximately 0.025 inches (0.64 mm) square. [3] :15 The chips are mounted on a 0.5 inches (13 mm) square substrate with silk-screened resistors and printed connections. The whole is encapsulated to form a 0.5 inches (13 mm) square module. Up to 36 modules are mounted on each card, though a few card types had just discrete components and no modules. Cards plug into boards which are connected to form gates which form frames. [3] :15

SLT voltage levels, logic low to logic high, varied by circuit speed: [3] :16

High speed (5-10 ns) 0.9 to 3.0 V
Medium speed (30 ns) 0.0 to 3.0 V
Low speed (700 ns) 0.0 to 12.0 V
IBM SLT wafers.agr.JPG
Steps in manufacturing Solid Logic Technology hybrid modules. The process starts with a blank ceramic wafer, 12 inch (13 mm) square. Circuits are laid down first, followed by resistive material. Pins are added, the circuits are soldered and the resistors trimmed to the desired value. Then individual transistors and diodes are added and the package is encapsulated.

Later developments

The same basic packaging technology (both device and module) was also used for the devices that replaced SLT as IBM gradually transitioned to the use of monolithic integrated circuits:

See also

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References

  1. Boyer, Chuck (April 2004). "The 360 Revolution" (PDF). IBM. p. 18. Retrieved 27 May 2018.
  2. Davis, E.M.; Harding, W.E.; Schwartz, R.S.; Corning, J.J. (April 1964). "Solid Logic Technology: Versatile, High-Performance Microelectronics". IBM Journal of Research and Development. 8 (2): 102–114. doi:10.1147/rd.82.0102. S2CID   13288023.
  3. 1 2 3 4 5 6 7 Logic Blocks Automated Logic Diagrams SLT, SLD, ASLT, MST (PDF) 86 pages
  4. Ken Shirriff. "A circuit board from the Saturn V rocket, reverse-engineered and explained". 2020.
  5. Dr. Wernher von Braun. "Tiny Computers Steer Mightiest Rockets". Popular Science. Oct 1965. p. 94-95; 206-208.
  6. Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1991). IBM's 360 and Early 370 System. MIT Press. p. 425. ISBN   9780262161237 . Retrieved August 8, 2022.