Well, as you know nothing will fail without mechanical load being applied. If nothing is going to change in the particular situation you describe, then it may be OK, BUT following similar logic you could also "leave" with BP joints. Would you? :-)
Regards,
Vladimir
------Original Message------
From: Inge
To: [log in to unmask]
To: TechNet E-Mail Forum
Sent: Apr 14, 2009 17:15
Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
You mean that such a bond degrades even if just being in constant room
temperature and no power switching?
Inge
----- Original Message -----
From: <[log in to unmask]>
To: "TechNet E-Mail Forum" <[log in to unmask]>; "Inge"
<[log in to unmask]>
Sent: Tuesday, April 14, 2009 11:07 PM
Subject: Re: [TN] Gold/Tin Intermetallics, why are we afraid?
> Hi Inge,
>
> Yes, the intermetallics itself is strong, BUT it doesn't count, as all
> failures I've seen goes at the tin/intermetallics interface. The larger
> were the platelets, the worse it looked.
>
> Regards,
>
> Vladimir
> ------Original Message------
> From: Inge
> Sender: TechNet
> To: [log in to unmask]
> ReplyTo: TechNet E-Mail Forum
> ReplyTo: Inge
> Sent: Apr 14, 2009 16:55
> Subject: [TN] Gold/Tin Intermetallics, why are we afraid?
>
> These infamous IMCs are like parias or ghosts in most people's mind in our
> business. I shocked our production guys recently by giving the advice to
> let
> the boards go on. Large crystals and bad looking. But I always try to
> avoid
> exaggerations. If no serious temp changes are predicted, nor any severe
> power switching, why rework and risk introducing failures? The actual
> components were very hard to rework, the cost had been unacceptable. I can
> see many of you get the coffee wrong. I don't mean to spread quality
> distractions, I talk about very few boards and a unique situation. My
> statement was based on the fact that a gold tin intermetallic bond is
> extremly strong and can last long, if not exposed to what I pointed at
> earlier. I expect to be hammered down in the shop floor until only the
> nose
> is visible....
>
> Inge
>
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