Issue link: https://iconnect007.uberflip.com/i/550232
August 2015 • SMT Magazine 59 Outgassing from via-in-Pad Blind via holes can outgas just like plat- ed through-holes. It's not always the paste volatile or air trapped in the via by the paste printing action. Testing vias prior to micro- sectioning allows you to assess the degree of outgassing and the copper plating thickness. The sample on the left has oil in the hole and the sample on the right is shown after testing prior to cleaning. A video of outgassing tests and methods of testing is available on the IPC video channel. Chip Resistor Failure Sulphur Chip resistors were failing in products in ser- vice. The silver layer between the resistive ele- ment and the termination was being corroded in automotive and medical applications. This type of defect has been investigated on a number of occasions and due to sulphur present in the envi- ronment where the products were in operation. The same deposits can be seen on chip ca- pacitors where the silver is exposed but due to the constructions will not lead to open circuit connections. figure 4: example of delamination on the surface of a board (left), and one after cutting the surface of the laminate to show the copper inner layer and epoxy and glass bundles (right). figure 5: The sample on the left has oil in the hole, and the sample on the right is shown after testing prior to cleaning. FeAture CASE STuDY: DETECTING PROCESS DEFECTS continues