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Old 15th December 2012, 08:18 PM   #111
roline is offline roline  United States
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The precurser to SMD PCB's was the ceramic hybrid field that was very strong in the 70's. We would silkscreen .005" traced and spaces with gold ink, mount IC's , transistors as cut from the wafers and wire bond with gold wire. The resistors were thick film Ruthenium oxide laser cut to 1%, ceramic or tantalum capacitors could be soldered/ epoxied to the substrate. The most complex was a 6 metal layer, 19 IC die 256 wire bond hybrid that we did for HP. Approx 1"x3" in size. Raytheon was doing pacemakers with this technology.
The fastest circuit that we did slewed at 6,000V/u second.... We also did RF and IF circuits used in handheld radios, DTMF filters and other custom AF circuits... I did a power op-amp design but power density was a limitation of getting the heat out. I could only get 60watts out of it.
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Old 16th December 2012, 09:54 AM   #112
marce is online now marce  United Kingdom
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They are still being done today, though instead of a ceramic inteposer standard PCB materials are used (though usually a higer Tg grade), BGA's etc.
QPI-21LZ
One example with bottom terminations, others use gold plated semicircle s on the outer edges.
We did a coule of modules back in the days, the biggest problem was the difference in thermal expansion between FR4 and the ceramic, not so bad when they had through hole legs on a 0.1mm pitch, but became problematic as SMD apeared and sizes reduced.
They looked cool though especially if you had them hermeticaly sealed and gold flashed legs...

Just for the record, my favorite amps are my class A EL84 monoblocks in triode mode, so while I do favour PCBs I have a point to point amps, it will be these that one day I shall make machined copper interconnects and put in a clear polycarbonate case...one day.

Last edited by marce; 16th December 2012 at 09:57 AM.
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