Hi Barb -

Why would you want them?  LPI solder mask dams between pads in the .025"
pitch and finer end up with a finished thickness less than the external foil
on the board, so they accomplish nothing in the prevention of solder
bridging.  Dry film dams in these same pitch ranges are so fragile that they
often result in a string of rejections during the assemblly process.

My recommendation: no solder mask dams - they're a waste of time.  The
emphasis needs to be on getting the solder paste stencil and process
correct.

Regards - Kelly
-----Original Message-----
From: Barbara Burcham <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, February 08, 2000 9:08 AM
Subject: [TN] Solder mask dams between fine pitch parts


>What is the assembly industry take on the advisability of solder mask dams
>between the pads on fine pitch parts - 25 mil?
>To have or not to have?
>What is the fabrication industry take on the maunfacturability of solder
>mask dams between the pads on fine pitch parts - 25 mil?
>To fab or not to fab?
>
>Barbara J. Burcham, CID
>PCB Designer
>Fairfield Industries
>Sugar Land, TX 77478
>281-275-7687 Work
>281-275-7550 Fax
>[log in to unmask]
>
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