Tony

You don't say what type of screen is being used. If it's a
nylon/polyester one, then I'd say you're in deep trouble. If it's a
stainless steel one, it can still stretch as the squeegee distorts it.
You really should use a stencil.

Brian

> tony steinke wrote:
>
> Ladies and Gentlemen,
>
> We are having a major problem with an assembly house with registering
> the solder paste to surface mount features prior to pick and place.
> They
> are claiming that the boards are growing/shrinking some 15-20 mils.
> We have done extensive measuring on unpopulated boards in-house
> and cannot see more than 3-5 mils misregistration. The panel size
> is approximately 14.00 x 16.00 inches, 20-24 mil pitch, and 15 BGA's
> throughout the panel. Overall thickness .080. Is it possible that the
> mesh
> screen that they are using can expand/contract over time? has anyone
> heard of this experienced this situation before. Any information would
> be
> greatly appreciated.
>
> Thanks
> Tony Steinke
> AIT-Atlanta

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