Bill,

My experience with the type ovens you describe have shown them to do an
excellent job of exhausting outgassed material and precluding redeposit on a
board or substrate surface. If it is outgassing, I would tend to believe
that you would see a difference in wire bond pull strengths as well.
Especially when comparing before/after accelerated bakes. Is this the case?
Please forgive me, but are you absolutely sure the same lot and even same
syringe/application of epoxy was used on both board types?

Bruce Misner

> ----------
> From:         Bill Christoffel[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.
> Sent:         Thursday, September 06, 2001 9:03 AM
> To:   [log in to unmask]
> Subject:      [TN] Outgassing of LPI's and Legend Inks
>
> Technetters,
>
> We are experiencing what appears to be the result of some type of
> outgassing of white legend ink.
> Details: Board design uses a white legend ink as an overcoat.
> Subsequent processing includes die attach (COB) using electrically
> conductive epoxy.  Testing shows that the die attach epoxy strength (die
> shear) is greatly reduced on boards that use the white legend ink. I do
> not believe this to be a surface contaminant issue since the epoxy
> failure mode is cohesive.  Epoxy cure temperature is 150C in a air
> circulating oven with a high exhaust rate.   Questions - Is outgassing
> of legend inks and LPI's a probable cause?   Is any information
> available regarding this ?
>
> Bill C.
>
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