Solid Logic Technology

Solid Logic Technology (SLT) was IBMs method for packaging electronic circuitry introduced in 1964 with the IBM System/360 series and related machines. Because monolithic integrated circuits were not mature enough at the time. 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, then either encapsulated in plastic or covered with a metal lid. Several of these were then mounted on a small multi-layer printed circuit board to make an SLT module. Each SLT module had a socket on one edge that plugged into pins on the computer's backplane (the exact reverse of how most other company's modules were mounted).