Kulickke and Soffa inc, USA ;Alphasem ,ESEC(SWITZERLAND) -do sell processes 
and equipments for COB.
ashok dhawan
 ----------
From: Lang, Michael
To: [log in to unmask]
Subject: Chip On Board Survey...
Date: Tuesday, April 29, 1997 1:56PM


Micheal, I'm not able to answer all these questions but I can suggest you
the following:

You might look towards High Frequency Ultrasonic Gold Ball Bonding. It will
allow you to do wirebonding to a PCB at very low temperature. FR-4 material
may be used in that type of packaging.

Regards.



I am looking for information regarding Chip On Board (COB) and other
packaging schemes which rely on wirebonding to a PCB.  If you can, please
answer the following:

1) Do you currently use COB or other packaging schemes which rely on
wirebonding directly to a PCB?  If not, is it because of previous bad
experience or other problems?



2) What temperature is wirebonding to PCB's performed at?



3) How it the heat applied (heated stage of wirebonder, heated N2 blowing on
site, etc).  If a heated stage, is the PCB placed directly on the stage?



4) What PCB materials can be used for this type of packaging (polyimide,
Kevlar, FR-4)?  What are the driving characteristics (Coefficient of Thermal
Expansion in the Z direction leading to barrel cracking, glass transition
temperature, etc)



5) Can wirebonds survive outside of a hermetic environment (assuming they
are protected from physical damage)?  Will they survive salt fog, etc.?
 This question assumes the wirebond is NOT used for connection to a chip,
but instead to another PCB, I/O pin, etc.





Thanks,


Michael Lang
[log in to unmask]

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