Mixed assembly on PCB of wide variety components (MCM-D, SMDs, bare dies) using wire bonding and SMT

The article describes the process flow of mixed/hybrid assembly module of a MCM-D PLL circuit that exhibiting good electrical performance. The module is a typical example of mixed/hybrid assembly consisting from wire bonding (2 levels of interconnection), mounting of bare dies, SMT on PCB. The main challenge of such type of assemblies is compatibility wire bonding and SMT. Another challenge is 2 levels of wire bonding interconnection. It was done using two type of bonding wires characterizing of different temper. Classical SMT solder reflow process was replaced by more environmentally friendly conductive adhesive glue process. It also helps to decrease thermal exposure down to 150 °C. Temperature of 150 °C was the highest temperature of thermal treatment this assembly. Relatively light thermal treatment eliminates warping of PCB FR4.