Heat Resistance Research Of High Density Interconnection (HDI) PCB

With the continuous progress of the lead-free requirement, PCB (PrintCircuit Board) soldering of the world has come into the times of lead free.Higher soldering temperature in lead free soldering process broughtunprecedented challenges to the heat resistance of the PCB. However,most base material manufacture factories, PCB manufacturers andSMT(Surface Mounted Technology) plants have not completely readywhen a large number of HDI (High Density Interconnection) ordersquickly rushed into the Chinese market, then, Delamination of HDI boardcame out and became a critical problem for all factories.The paper systematically studied delamination problem caused byhigher soldering temperature of lead-free process based on the actualsituation of our company. Through the failure mode analysis ondelamination of HDI board and studies of raw materials, design,manufacturing and packaging, we fully understood the impact factors toheat resistance of HDI board, and based on the results of the study, weproposed some improvement programs and ideas. The main contentsinclude the following items:1. According to the analysis of actual problems we encountered, wesummaried four kinds of HDI delamination failure mode and madedetail analysis one by one.2. Based on the failure mode analysis, we learned the main factors inthe base material influenced HDI board heat resistance are resinand glass-fiber cloth, so, we brought forward some requirements tothe base material used in HDI board. Meanwhile, we selected thematerials suitable to our company’s HDI board by relevant experiments according to these requirements, It will be a guidelinefor HDI material selection in future.3. Via the analysis to HDI board manufacturing process,we identifiedan important influence on the heat resistance of the HDI boardprocesses are black/brown oxide, lamination and resin plugginghole, and then analyzed the process one by one and found the keyfactores affecting the heat resistance of the HDI board. Such as, therelation between black or brown oxide and lamination times,lamination parameters, board baking before and after lamination,prepreg dehumidifying, the bubbles in the resin of plugging hole,solvent and water vapor in the plugging resin, CTE of pluggingresin, and so on. Improvement actions were raised for each factor.4. By the analysis of HDI board design, summarized the designfactors to HDI board heat resistance, they are the density of buriedhole in inner layer, big copper in outer layer and the design ofdielectric layer thickness. Address these design issues, we putforward suggestions for improvement.5. Through water absorption analysis of base material and PCB,summaried the main factors affect its water absoption. As waterabsoption of base material and PCB is inescapable, we broughtforward the requirement improving HDI packaging method, andgot good packaging method suitable for our HDI boards based onexperiment results.6. To ensure long-term stability on the heat resistance of HDI board,we highlighted the daily monitoring methods and means for HDIboard and base material.Overall, the paper provided improvement actions and orientation forHDI heat resistance in future through the study on HDI delamination.