I am assuming that you actually profiled the board and know that the
temperature profile conforms to the recomendations of the paste
manufacturer.

You need to determine if the board or components are at fault. J-STD-002 and
J-STD-003 provide test methods for the components and the board,
respectively. Did the paste wet to the board and leave the component
non-wetted? I would check the parts.

> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of John Brown
> Sent: Wednesday, November 21, 2001 3:55 AM
> To: [log in to unmask]
> Subject: [TN] Non-wetting
>
>
> Good Morning, this is my first posting to this forum I hope to get some
> help. We are building a small PWB with 4 per panel. The problems we are
> encountering are on 0603 resistors & capacitors and SOIC (8pin) etc. These
> are all located near to or the center of the PWB. There is paste
> on the pad
> and the component placed properly but the paste will not wet onto
> the leads
> or terminations.
> What have we done?
> 1. Run the PWB at various profiles even the highest. Still have problem.
> 2. Changed from no clean to aqueous with an agressive flux. Still have
> problem.
> 3. Changed screen apertures. Still have problem.
> This PWB is multi layer and heavily populated.
> Are there any hints as to what we do next?
>
> _________________________________________________________________
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