A high specification thick film circuit before and after encapsulation
Top: Inside the trimming machine where screen printed resistors are precision trimmed to the required value and tolerance by computer controlled laser beam
Centre Left: Screen printing of conductor and resistor inks is carried out on automatic machines
Centre Right: Reflow soldering furnace
Bottom Left: Projection welding of metal cans is carried out inside a dry nitrogen atmosphere of better than 10ppm
Bottom Right: Typical examples of the range of packaging styles available
Products donated by David Hetherington
Top: Germanium TO3 package 10A power transistor, produced until 1978
Left: Early audio (radio) Germanium transistor
Centre: Audio TO3 package audio Germanium transistor, produced until 1978
NKT 502 25 Amp Power Transistor with box and envelope containing mounting parts, in production 1960 to 1964
Two small signal silicon transistors
Thick film hybrid circuits produced from 1969. The blue epoxy on the left circuit covers silicon transistors. Circuits such as these would be conformally epoxy coated using a powder bath.
Gold and palladium silver printed substrates. The black areas are resistors whose range could be 10's of ohms to several megohms. The top right circuit has resistors which have been air abraded for adjustment - preceded CO2 laser trimming. The lower right circuit has a SAW device wire bonded for connection - probably a TV application.
Lower left, shows a conformally coated circuit and the other three are hermetic packages used in Telecoms, avionics and military applications.
Dual in line hermetic package.
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