APEX 2011 Reliability Testing of PWB Plated Through Holes in Air-to-Air Thermal Cycling

The High Density Packaging Users Group Consortium investigated plated through hole reliability of printed wiring board test vehicles constructed with 20 different Pb-free capable printed wiring board materials. The study contained a total of 27 different constructions built by three high-end Asia based PWB manufacturers. The materials were tested using both air-toair thermal cycling and Interconnect Stress Testing (IST) methodologies. The test vehicles combined both via reliability and materials analysis testing capabilities, using two specially designed IST coupons with via to via spacing of both 0.040" (1mm) and 0.032" (0.8mm), All products were constructed with 20 layers, laminated to an average thickness of 0.115" (2.92mm), and drilled with 0.010" (0.254mm) vias, producing an aspect ratio of 11.5 to 1. Seven of the 20 materials were investigated with two different glass styles and resin contents. The materials were IST tested on the two coupons types, both as built and after 6X Pb-free (260°C) reflow. The air-to-air thermal cycling tested a single configuration after 6X Pb-free reflow only. Materials in the test included eight high Tg, filled FR4 materials, six high Tg halogen-free FR4 materials, and six high speed materials. Correlations between the air-to-air thermal cycling results and IST results are detailed, as are the correlations of these results to independently measured and supplier listed material properties. Introduction A previous HDPUG consortium study identified significant challenges in complex multilayer applications with printed wiring board materials ability to survive multiple exposures through Pb-free assembly reflow [1-3].