Kerry,

Please elaborate on your recommendation, Do not use HASL finish.

What specific problems occur with 0402s on HASL finished PCBs and what
aspect of the HASL finish causes them? Typically HASL is avoided for
things like BGAs fine pitch large pin count packages because of the
relatively poor uniformity compared to other finishes, but I would not
think that this is a concern for a two pin device.  

Jim Verrette
Electrical Engineer
 

------------------------------

Date: Wed, 10 May 2006 09:11:26 -0400

From: Kerry McMullen <[log in to unmask]>

Subject: Re: 0402 Experience and Pitfalls

Hi Ryan,

Approach them the way you would a 0603 DOE. The biggest thing I saw that

keeps tombstoning to a minimum is to keep a large area gap between the

pads, and also try to balance the trace widths that come into the pads.

I use a .006 thk stencil with rectangular pads and 1:1 aperature
openings.

Also, do not use HASL finish.

I stay away from glue.

I could go on, but lets see what everyone else says.

Kerry McMullen

Principal New Product Mfg. Engineer

LTX Corporation

50 Rosemont Road

Westwood, MA 02090-2306

(T) 781-467-5468

 

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