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28 PCB007 MAGAZINE I JUNE 2023 In my very first column, "Etch Uniformity and e Puddle Problem," I wrote about a phe- nomenon in the PCB etching process called the "puddle effect," which causes large PCB panels to have varying etch quality across the board, typically on the top side. is variation exists because as you are spraying etchant onto the top of a panel, you begin to accumulate spent etchant. It creates a layer that inhibits the fresh etchant from reaching the board's copper sur- face that needs to be etched. With this problem, oen the edges of pan- els will have the fastest etching while the mid- dle has the slowest. is is because the flow of etchant as it accumulates onto the top of Solutions for Better Etch Uniformity the panel will to run out to the sides and fall through. Hypothetically, if someone were try- ing to etch large PCBs or a sheet of multiple PCBs on a single stock panel, they could place through-holes around the panel. If holes could be created through the middle parts of the panel, to provide another area for the etchant to escape, then the puddle effect would be signifi- cantly reduced. Of course, in most cases, this is not realistic for PCB manufacturers. Since the solution is not so straightforward, manufactur- ers oen must depend on wet processing tech- nology that focuses on obtaining better etch uniformity. Here are some of today's technolo- gies to approach the puddle effect. The Chemical Connection Feature Column by Christopher Bonsell, CHEMCUT