Greg,
     Non electrically conductive die attach materials exist. Do you require
an electrical die back side connection? If not then one of these materials
may help. These have ceramic, or even diamond fillers in, though the
diamond ones are expensive, but have the best heat conductivity. They are
available in paste form and can be processed in the same way as the silver
filled adhesives. The silver filled paste manufacturer probably has an
electrically insulating version. I'm afraid that manufacturings worry is
real. The solder mask can have pin holes. Conductive silver epoxies can
short to tracks through them.

regards,  J Drake




Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to Greg Bodi <[log in to unmask]>

To:   [log in to unmask]
cc:    (bcc: Jeremy J Drake/HQ/CUK/Celestica)

Subject:  [TN] Help!! Big problem (solder resist vs die attach)




Hi Designers,

        I'm in need of help!  I have completed a design with some L157 IC's
on the Board. And Manufacturing came back to me after I finished the design
and was about to ship it and said that they use a conductive epoxy to
adhere the die to the Board and they're worried that if the Solder Resist
has pin holes in it that it could leak a signal into the runners below
those Die.  They said they could use Pre-Forms but that would kill their
yeild so they want me to reroute the traces below those die. Unfortuatley
that would be a nightmare and add at least a week to my time.  So can
anyone tell me where I can get info to help prove that this won't be a
problem or are they right and there's a good possiblitiy that this could
happen.

Thank you,

Greg Bodi

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