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Subject:	Re: Solder Attachment [Au plating in...]
From:	[log in to unmask]
Reply To:	TechNet E-Mail Forum.
Date:	Tue, 9 Mar 1999 16:04:19 EST
Content-Type:	text/plain
Parts/Attachments:	text/plain (45 lines)

In a message dated 05/03/99  05:49:27PM, you write:

> Date:    Thu, 4 Mar 1999 14:23:20 -0500
>  From:    Malewicz Wesley <[log in to unmask]>
>  Subject: Solder Attachment
>
>          I have a part that is made out of .005 thick Beryllium Copper with
a
>  finish per MIL-G-45204 Type 1 with 5 micro-inches Hard Gold.  This part is
a
>  surface mount part and attached to the PCB via solder paste then re-flowed.
>  My question is, should I experience any long term reliability or soldering
>  problems with the attachment of this part?
>
>  Thanking you in advance for your comments.
>
Two issues spring to mind: dewetting and Au embrittlement.
On reflow the Au plate will dissolve into the solder leaving you trying to
make a join to the BeCu. A possible - if not probable - scenario is that as
BeCu is hard to solder (platability is not solderability) the result will be
no- or de- wetting. If your paste is a low res no clean then the probability
is higher than if you are using the higher solids resin type materials which
hang in longer during the dissolving/reflow cycle.
Now that the solder is loaded with Au you need to address this issue as
described in another posting.
If you can get the parts Ni plated before Au plating that might be better. I
know Ni  is also hard to solder but the manufacturing timescales are with you
this way. [ie  strip is made and aged in stock somewhere, then plated. If Ni
and Au plated this will be done sequentially with little delay.]

BoL
Mike Fenner

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