Hi John,
        Since I didn't see a response, I thought I'd take a stab at your
questions.  I'm not as familiar as others which is why I waited to respond.
It's hard to be specific as so much falls into the category of "it depends."
Don't you just hate that, but here goes.

A)  What sort of yields can be expected from COB technology?
        In general, I think we plan for 95 to 99 % due to process only with
most around 98, but I'm just guessing here.  Wire bonding only has a very high
final yield rate simply because it can inspected and reworked fairly easily.

B)  How long would an 80 wire bond COB take to complete (on average)?
        Time for wire bonding only would be from 1 1/2 to 4 minutes.  Factors
affecting this would be complexity of design, number of reference points,
setup time, and of course wire bonding equipment.  The whole assembly can take
anywhere from four to 15 days, depending on number of steps.  Limiting factors
I've seen are epoxy cure steps, device screening (burn-in, electrical test),
and capacity issues.

C)  What are the process steps for COB?
        Let's see if I can get this right.  Take for example a complex board
with SMT, Die, heatsink, and interconnect.
1)  SMT
2)  DI wash
3)  Plasma Clean
4)  Die Mount
5)  Wire Bond
6)  Encapsulate or Lid attach
7)  Mark
8)  Heatsink Attach
9)  Pin Attach
10)  Final test

        Now, some of these steps may be interchanged.  For example, if it was
chip on heatsink, you would have to perform heatsink attach prior to die
attach.  Don't forget to add any inline electrical and visual inspection
steps.

D)  What encapsulation material is used?
        Usually an epoxy formulation, but I have seen some silicones.
Sometimes, there is both silicone and epoxy used to provide for greater
environmental and mechanical protection.

Hope this helps,

Glenn
http://www.maxtek.com

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