Development and implementation of a hybrid process for two-sided surface mount assembly

A hybrid process for assembling a mixture of surface-mount and through-hole components on two sides of a 12 in.*18 in. subpanel has recently been developed and successfully implemented at Hewlett Packard computer manufacturing. The larger surface mount components are assembled on the front side of the board with the HP standard surface-mount process. Then the board is flipped back side up and a nonconductive adhesive is deposited, followed by placement of the smaller passive components on top of the tacky adhesive. The assembly subsequently goes through an IR oven to cure the adhesive. The through-hole parts are then inserted and all the backside and through-hole joints are wave soldered. After about six months of development and pilot testing, this process has successfully been implemented at the production line. With the preliminary defect data available, defect levels have been recorded at <100 p.p.m. for the adhesive process and <200 p.p.m. for the wave-soldering process.<>