Stephen,

Have you attached thermocouples around the QFP to verify that the QFP is:
A) Reaching Liquidous?
B) Is at Liquidous for a long enough period of time?

I have had grainy solder joints and found that I was not at liquidous for a
long enough period of time for complete reflow of all of the solder joints.
It was on a very dense assembly and the problem was more in the center of
the assembly.

Just curious.

I have used aluminum fixtures for assembly processes and have never had an
issue with contamination.

Good Luck,

Kathy Palumbo



> -----Original Message-----
> From: Stephen Bonaccorsi [SMTP:[log in to unmask]]
> Sent: Thursday, April 01, 1999 3:34 AM
> To:   [log in to unmask]
> Subject:      [TN] GRAINY JOINTS
>
> Hello  Everybody
>
> I am currently reflowing with a convection oven (No Nitrogen). A board
> that has perfect solder joints apart from grainy solder joints on one
> particular component (QFP). Other components on the board resistors/caps
> and components of similar size are fine.
> Therefore I don't think there is a problem with the oven profile.
>
> This component does go through an extra process before hand.
>  Initially the component is supplied with no pins (Very long story,
> don't ask!)
> These are attached to the body of the component using an aluminum
> jig/fixture to hold them in place. The legs are supplied
> pre-soldered.
>  RMA flux is then applied (liberally) to the area to be soldered.
> The jigs with the components are then placed through a vapour phase oven
> for soldering .
>
> Is it possible that the legs are being contaminated by Aluminum or its
> oxide from the jig/fixture, if the flux is reacting the Aluminum.
>
> Would aluminum contamination give grainy joints?
> What else can cause grainy joints?
>
> Thanks for any help
>
> Stephen Bonaccorsi
>
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