Via filling methods are: * Tenting * Plugging * Capping * Flooding
Tented Via. A via covered with dry film soldermask; the via is not filled. When tenting from both sides there may be issues with trapped air that expands during mass soldering.
Plugged Via. An additional operation which is done independent of soldermask application. The via is filled with a non-conductive material.
Capped Via. An additional operation which is done independent of soldermask application on one or both sides of the via. The via is partially filled. When capping from both sides there may be issues with trapped air that expands during mass soldering.
Flooded Via. During soldermask application the via is flooded with soldermask. The via is partially filled. Chemical entrapment is a major concern.
Via Filling Recommendations Surface Finish||Tenting||Plugging||Capping||Flooding HASL||Okay||Okay||Okay||Okay OSP||Okay||Okay||Okay||Not recommended ENIG||Okay||Okay||Okay||Okay ImAg||Okay||Okay||Okay||Not recommended ImSn||Okay||Okay||Okay||Not recommended
["Substrate Topics", Rob Rowland, Process Engineering Manager, RadiSys Corporation, SMTA International, September 2003]
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