It appears from the disassembled 35S photos That HP is using chip face down assembly. When I look at the circuit traces I see some dissapear without a plated thruogh hole. Can someone enlighten me as to there chip assembly method. Ultrasonic? Are there also bond wires? It seems to have too many PC leads to connect them all in one bonding. What happens when the traces seem to disappear?
Thanks, Sam Levy


There is nothing unusual at all here. The chip is most likely mounted using COB (Chip On Board) bonding technology covered with the black potting compound, a very common technique to lower cost in higher volume products.

The "vanishing" tracks are just an illusion caused by light reflection off the gloss black solder mask.

Interesting that they have chosen to use a hand soldered watch crystal rather than a machine assembled surface mount package, they probably saved a cent or two here, but it requires two extra human operations (solder+red blob)


Possibly Related Threads...
Thread Author Replies Views Last Post
  HP35s Program Four Slings Lift Calculation Jean-Marc Biram (Australia) 2 1,273 12-16-2013, 07:21 PM
Last Post: Jean-Marc Biram (Australia)
  HP35s Calculator Max Rope Tension Program Jean-Marc Biram (Australia) 10 2,591 12-12-2013, 12:03 AM
Last Post: Jean-Marc Biram (Australia)
  HP Prime - Reset methods bluesun08 3 1,073 11-21-2013, 09:49 AM
Last Post: Joe Horn
  Trouble entering a HP35s program line Arno 2 899 04-05-2013, 06:28 PM
Last Post: Arno
  HP35s scientific calculator GREG W THOMAS 4 1,162 03-22-2013, 06:49 AM
Last Post: Thomas Radtke
  HP 75 Assembly Language Michael Fehlhammer 7 1,515 10-01-2012, 08:32 AM
Last Post: Michael Fehlhammer
  HP35s "MEMORY CLEAR" flashes Mark Paris 1 774 08-31-2012, 07:35 PM
Last Post: Bart (UK)
  HP35S keyboard Nick R 8 1,692 08-01-2012, 01:27 PM
Last Post: Dave Shaffer (Arizona)
  Entry Methods dbatiz 44 6,806 03-30-2012, 05:13 PM
Last Post: David Hayden
  HP entry methods--please enlighten me Matt Agajanian 7 1,425 03-26-2012, 01:41 AM
Last Post: db (martinez, ca.)

Forum Jump: