Hi Zhang Zhenfeng,
   The best solution is to engineer the device so that your bond pads are
not over the BCB.  There is poor ultrasonic energy transfer to such a soft
material.  We ran into a similar problem with 3um thick layers of polyimide
and solved it by opening windows through the polymer to the oxidized wafer
below in the region of the bond pads only.  Otherwise we used silver epoxy
for our electrical connections.

Good luck!


On Fri, Jul 12, 2013 at 9:32 PM, Zhang Zhenfeng  wrote:

> We have a problem about gold wire Ball bonding process of BCB-Sio2-Gold
> pad :
>   (Bonding machine:Gold Wire Automatic ball bonding 130KHz;Wire diameter
> 0.7mil
>    Pad size 60um )
>
> We use BCB layer for our device to lower the capcitator.
> The structure of layer is BCB 2um--SiO2 0.5um---Ti/Pt/Au 0.7um.
>
> But the SiO2 layer is always peeled off from BCB layer when gold wire
>  bonding even we adjust many parameter.The SiO2 layer is broken at
> the gold bump edge when we do pulling test or bonding process.
> There are always some bad part even we use the best one set parameter.
> And the parameters isn't stable for diffrent wafer.
>
> Do you have any advise? Thanks.
>
> Zhang Zhenfeng
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