Editing Solid Logic Technology (section)

{{Short description|IBM hybrid circuit technology introduced in 1964}}
{{multiple image|total_width=330px|header=Solid Logic Technology cards
|image1=Slt1.jpg|caption1=A double-width SLT card. The square metal cans contain the hybrid circuits.
|image2=IBM SLT cards, three.agr.jpg|caption2=Three single-width SLT cards
}}
{{multiple image|total_width=330px|header=SLT cards ''in situ''
|image1=SLT Card Frame.corestore.jpg|caption1=Many SLT cards plugged into a board
|image2=IBM 129 SLT modules.jpg|caption2=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 [[IBM 1130|1130]], announced in 1965. IBM chose to design custom [[hybrid circuit]]s using discrete, [[flip chip]]-mounted, [[glass]]-encapsulated [[transistor]]s and [[diode]]s, with [[screen-printing|silk-screened]] [[resistor]]s 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).

IBM considered [[monolithic integrated circuit]] technology too immature at the time.<ref name=boyer>{{cite web|url=http://www.computer-museum.ru/books/archiv/ibm36040.pdf |title=The 360 Revolution |last=Boyer |first=Chuck |date=April 2004 |publisher=IBM |page=18 |accessdate=27 May 2018}}</ref> SLT was a revolutionary technology for 1964, with much higher circuit densities and improved reliability over earlier packaging techniques such as the [[IBM Standard Modular System|Standard Modular System]]. It helped propel the IBM System/360 mainframe family to overwhelming success during the 1960s. SLT research produced ball chip assembly, [[flip chip|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 circuit]]s that held four or five transistors. MST was used in the [[System/370]], which began to replace the System/360 in 1970.