Assembly of Large PWBs in a RoHS Environment
As early as 2001,leading cellular phone manufacturers had established stable assembly processes that were RoHS compliant for their cellular phone products. Since this time,the products manufactured on these lines have demonstrated equal or better
quality and reliability as compared to cellular phones assembled with tin-lead solder and non-RoHS compliant components. This success may have created the belief that there are few issues remaining in RoHS compliant assembly. This belief is far from the truth. Organizations that need to assemble a wide range of large,thick printed wiring boards (PWBs) continue to have considerable process challenges. These difficulties – combined with the need to assemble RoHS 5 (tin-lead solder paste and components with tin-lead finished leads,the remaining hardware being RoHS compliant),RoHS 5.5 (RoHS 5 with BGAs that have SAC or SACX solder balls) and RoHS 6 (fully compliant RoHS assembly) in one facility – create not only assembly technical challenges,but considerable material handling and logistics issues.
This paper is a review of the work done at Jabil in Billerica,Mass.,to address these challenges. An overview of the process development work in stencil printing,component placement and reflow soldering that was required to develop optimized assembly processes for PWBs with dimensions exceeding 56 cm and thicknesses approaching 0.3 cm will be discussed. The methods developed to handle the logistics issues of having RoHS 5,RoHS 5.5 and RoHS 6 assembly in one facility will also be presented.
The paper will conclude with a review of several of the products currently being assembled with these processes and logistics.