Materials Testing of PWB Substrates to Determine Survivability Through Lead Free Assembly
Authors: Bill Birch and Jason Furlong Company: PWB Interconnect Solutions Inc. Date Published: 10/13/2013
Abstract: As part of High Density Packaging Users Group (HDPUG) Pb-Free Board Materials Reliability Project 3, material testing was performed on both IST test coupons and WIC- 20 test coupons to determine their survivability through Pbfree reflow. The two techniques use similar principles of measuring capacitance change to determine levels of degradation within the B and C stage dielectric materials. The study compared 24 different Pb-free printed wiring board materials in 20 layer constructions, built in a single printed wiring board (PWB) manufacturing facility. Twelve materials are investigated with 2 different glass styles and resin contents, for a total of 24 different builds. The materials in the test included high Tg, filled FR4 materials, high Tg halogen free FR4 materials, and high speed materials. Data is presented showing the impact of each assembly SMT reflow cycle, relative to the location and magnitude of material degradation (delamination). An important aspect of this study compared the performance differences for a via to via spacing of 1mm/0.040" and 0.8mm/0.032". The results confirmed a major influence from what is considered a relative small design change. The electrical results were compared to traditional microsection analysis to demonstrate the levels of correlation achieved.
IST, WIC- 20, test coupons, reflow, pwb, pcb, materials