Bga Lead-free Ball Placement Process

The global environment protection is one of the most important challenges we face in the 21st century.The semiconductor industry also tries to create Pb-free,or so called "Green" electronic products.In 1990's the US government had boosted the green package standard and even proposed related legislation for its spread.From then on,the "Green" electronics movement is a worldwide phenomenon.Many companies have been active in making contributions under its environmental vision philosophy.Per customer's requirement,the company need to build up the Pb-free packaging capability for the BGA product.In our company BGA product is the biggest business share.So it's a big challenge for R&DNormally,Sn/Pb solder ball's components are Pb 63/Sn 37.Pb-free solder ball's components are Sn95.5Ag4.0Cu0.5/Sn96.2Ag2.5Cu0.8Sb0.5.Base on their characterizations,they have different melting point.Pb-free solder's ball melting point(217℃～218℃) is higher than that of Sn/Pb solder's ball(183℃).Solder ball is the major connector between IC Device and PCB.The ball array must have a very good alignment with the golden pad on the PCB,including the ball size,ball interval and ball integrity,etc.At the early period of the BGA Pb-free prototype production,we designed the packaging process flow,process parameters and the bill of materials.But the yield is less than 80%.After inspection,the major issue is the ball pitch exceeding the spec during ball attach.After investigation and experiments,we found the solder ball type, ball attach process parameters and raw materials were the main factors to affect the Pb-free product quality.In this thesis we got the best process combination to greatly improve the product quality.Product yield increases from 80%to 99.7%.And finally we build up the capability for Pb-free product.