There should be a solder mask dam between the SMT device and its via. We place the dam .005" away from the devices pad and .005" away from the via pad for LPISM. We use .007" min. dam width. If the dam is not present you will draw solder away from the device when you reflow the board causing less than desirable solder joint. ______________________________ Reply Separator _________________________________ Subject: ASM Surface mount w/out soldermask Author: [log in to unmask] at SMTPpost Date: 3/15/96 6:52 AM Please help me resolve a design issue. The board will be assemblied using solderpaste, pick and place, surface mount assembly (both sides). The design has .0135" vias hole centers less than .030" from surface mount pads. The via and pad is connected with a short .008" wide trace. There is no soldermask dam between the surface mount pad and the via hole. Board is a 4 layer .062, which has soldermask already on the board. Any assembly concerns? Should there be a soldermask dam between the land and via? What guidelines do you use/like ? Thanks for your input ==================================================================== George Franck PWB Product Assurance Phone (703) 560-5000 x2648 E-Systems M/S N408 Fax (703) 280-4613 7700 Arlington Blvd E-Mail: [log in to unmask] Falls Church Va 22046 E-Mail: [log in to unmask] ====================================================================