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SMT electronics assembly manufacturing forum.

Solder mask and fine pitch devices

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Solder mask and fine pitch devices | 8 January, 2013

This is a question regarding soldermask between pins of fine pitch devices.

The majority of our production designs end up with at least 2-3 mils of copper thickness on the external layers due to blind vias, wrap plating requirements, etc. Our current design practice has been to add soldermask between pins unless the webbing is less than 4 mil.

One of our PWB/CCA experts says we should gang the fine pitch devices because the webbing is more of a liability than an asset. He suggests that since the soldermask is less than a mil thick it would not act as a dam to prevent solder bridging between pins (2-3 mil copper) and has the potential to flake off.

We are having more issues with cleanliness than shorts. He wants to gang the soldermask apertures and extend them beyond the component body to allow better flow for the cleaning solutions.


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Solder mask and fine pitch devices | 15 January, 2013

We wouldn't advocate extending the soldermask beyond the component body but yes to ganging for fine pitch. To ensure we don't run into issues with flaking our preference is not to add solder mask when the space between pins is less than 6 mil.

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