A reflow profile is proposed which is engineered to optimize soldering perf
ormance based on defect mechanism analysis. In general, a slow ramp-up rate
is desired in order to minimize hot slump, bridging, tombstoning, skewing,
wicking, opens, solder beading, solder balling, and components cracking. A
minimized soaking zone reduces voiding, poor wetting, solder balling, and
opens. Use of a low peak temperature lessens charring, delamination, interm
etallics, leaching, dewetting, and voiding. A rapid cooling rate helps to r
educe grain size as well as intermetallic growth, charring. leaching and de
wetting. However, a slow cooling rate reduces solder or pad detachment. The
optimized profile favors that the temperature ramps up slowly until reachi
ng about 180 degrees C, implementation of the optimized profile requires th
e support of a heating-efficient reflow technology with a controllable heat
ing rate. Emergence of the forced air convection reflow provides a controll
able heating rate. in addition, it is not sensitive to variation in parts'
features, thus allows the realization of the optimized profile.