Monolithic System Technology

Solid Logic Technology (SLT) was IBM's method for packaging electronic circuitry introduced in 1964 with the IBM System/360 series and related machines. 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).

SLT was a revolutionary technology for 1964 with the reliability improvements over other assembly techniques such as the Standard Modular System, helping propel the IBM/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 SMS cards held SLT modules.

SLT used silicon planar glass-encapsulated transistors and diodes.

SLT uses dual diode chips and individual transistor chips each approx 0.025 inch square. The chips are mounted on a 0.5 inch square substrate with screen resistors and printed connections. The whole is encapsulated to form a 0.5 inch square module. 6 to 36 modules are mounted on each card. Cards plug into boards which are connected to form gates which form frames.

SLT voltages : > +2.08V is up, < 0.90 V is down.

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

...
Wikipedia