Issue link: https://iconnect007.uberflip.com/i/1511625
16 PCB007 MAGAZINE I NOVEMBER 2023 Hack: Use of chemical planarization to eliminate the need for mechanical scrubbing of epoxy via fill Mechanical scrubbing is the archenemy of dimensional stability and the problem wors- ens as the panel thickness decreases. One new development has been the use of epoxy paint strippers from the general metal finish- ing industry to remove the epoxy from the sur- face, while not affecting the epoxy in the holes. is has proven to be a revolutionary solution for thin products with epoxy via-fill require- ments. Hack: Elimination of buttons (use of panel plate + Cu thinning) Button plate surface planarization is another mechanical scrubbing application, particu- larly popular in North America, to compen- sate for low capability of legacy plating equip- ment. Alternative methods today take advan- tage of the latest panel plating cell designs cou- pled with Cu thinning by chemical etch-down. cle report process to determine whether it's necessary to employ. Aside from these qual- ity control checks, I find that the most valu- able use of a non-linear analysis is to optimize press cycles. When we measure eight-point systems before and aer multilayer lamina- tion, I find that about 20% of the non-linear error is already present in the core from post- etch movement, and an average of 80% orig- inates in the press. Since press cycle optimi- zation historically does not involve feedback from non-linear errors, it is oen quite easy to tweak the cycle a little bit and reduce the non- linear error by 50% or more. e key variables to achieve this are lowering melt viscosity, extending gel time, and lowering pressure. Optimizing in this way also reduces Z-axis distortion, which improves back-drill capa- bility and signal integrity as well. Non-linear analysis may even drive the user to select dif- ferent materials with more reasonable press cycles.