Bob Conn provides engineering design and
consulting services in the field of high technology:
Silicon Circuit Boards
High performance computing
Prototype design and debug
About Silicon Circuit Boards
I have many things to say about silicon circuit boards, and, to put things in context, a little history.
A silicon circuit board is an interconnect board similar to an FR-4 PCB (Printed Circuit Board) but made from a silicon wafer using traditional IC fabrication equipment. It is a large area, 3-6 metal layer, integrated circuit, without the transistors. Attached to it are the usual sorts of things attached to PCBs but without the packages – just the silicon, the bare die.
Some 10 years ago I started down a path of building silicon circuit boards. I had some high performance computing algorithms I was interested in. Two friends and I thought it would be easy. At the time, I wanted these boards because they would allow me to assembly 4 FPGAs and a lot of memory in an area about 8cm x 6cm. I could stack these up and have 32 maximum performance FPGAs in a 4″ x 4″ stack. Liquid cooling issues hadn’t yet occurred to me. Sitting on my desk this little stack, whose equivalent performance was about 150 to 200 CPUs, could do some heavy duty numerical integration – faster SPICE being my driving motivation.
I figured SiCBs would be easy. I was working at Xilinx at the time and had done some of the original 3D stacking work in early 2000-2002. Ziptronix had just come into existence providing fusion bonding of wafers and silicon die.
Today, October 2012, no one is building a silicon circuit board – an SiCB. Many folks are building interposers. Many folks are doing 3D stacking. Xilinx is shipping the closest to a silicon circuit board that I am aware of. It’s 31mm x 31mm with 4 FPGA die attached.