79
(a) Gold wires connecting SLM to PCB
ιιiιιιι
Γ ITTTlnr
J Я « » » S »
(b) Wire encapsulation
Figure B.11 : Microscope images of the wire-bonded SLM chip from VLSIP Technolo-
gies, Inc., showing the 1-mil gold wires between the die pads and the gold bond fingers
on the SLM board before and after encapsulating the wires with Hysol® FP4450.
100 mils. Cracks later observed on the attached SLM chips after wire-bonding bring
attention to the need for better chip protection (see Section 5.6).
B.6 Auxiliary components
The SLM control system uses a Mastech HY3005D-3 power supply to provide a 5V
input to the FPGA circuit and a 16V input to the line driver circuit. The maximum
current drawn from the 16V power supply is around 0.5A when all SLM pixels are
biased. The FPGA circuit receives a clock input from a Simpson 420 function gen-
erator. Monitored on a Tektronix TDS3054 digital oscilloscope, the system always
ensure synchronization between the pixel switching signals and the output trigger
signal to the Т-ray system. Always remember to set the oscilloscope as DC-coupled,
instead of AC-coupled, for proper operation.
Cables and connectors are purchased from Samtec, Inc. The control system the