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Developments in Wet Processing: Beyond Spraying and Dipping

Spraying and dipping! Wet processing is based on two simple principles: Spray the work piece or immerse it in a bath. Most of the things you do in a complex machine you could also do with a series of buckets, but the results are likely to be much less reliable or efficient.

My work in the printed circuit industry has involved roles in many factories and using a wide variety of equipment, both new and old. At times, the major battle was just to keep the conveyors turning for another day. Enhancing the process effect was often a matter of slowing down the process to give a little more time for things to happen. Right now, I am involved with the supply of a variety of equipment, some of which I would regard as pretty standard and others that involve new ideas that have the potential to solve particular problems.

The target for equipment sellers is to be able to offer a machine that has advantages over the competition. This drives development, but it is still sometimes difficult to let the end users know what is new on the market. Some of the following examples may be reasonably well known and understood but they show how the equipment can be tailored towards a purpose even though the working basis of the machine is standard.

Earlier this year I was involved in installing an immersion tin line for a customer. The process and the chemistry are not new or special in any way. However, the machine was built to overcome a problem with the immersion tin chemistry, which makes the process more labour intensive to maintain. Immersion tin chemistry does not like to be agitated very much. Bubbles in the solution cause solids to form, which degrades the solution and causes problems with the hardware. The solids settle to the bottom and can damage pumps and heaters, or at the very least make them less effective. The machine I was working on was a horizontal process, which means the immersion tin chemistry is applied in a flood rinse. This effectively means that the conveyor is flooded with chemistry, so the panel is in a complete bath while it is passing through that section of the line.

To read the full version of this article which originally appeared in the June 2018 issue of PCB007 Magazine, click here.