Letter to the Editor: An Expert Weighs in on Dross

Estimated reading time: 1 minute

Ray Chartrand, consultant to the electronics manufacturing industry and "self-appointed Electrovert historian," sent us this reply to editor-in-chief Gail Flower's "Dross: Waste, Revenue Source, or Just Another Process to Optimize?."

There is basically nothing new under the midnight sun when it comes to dross control or reduction. Early machines had static baths of molten solder with a skimmer on the front of the pallet to clear the way for a PCB to be exposed to fresh solder. With the advent of pumped waves, oil similar to the PK Metal concoction have been around since the 1970s. Hollis used to float a blanket of peanut oil on the surface of the solder and then further refined the process by injecting oil into the pump impeller.

Electrovert built all kinds of dross gates to minimize dross production by reducing the vertical fall of the solder. Most of these devices were promptly removed by maintenance personnel when they didn't understand their function.

Inerting the wave actually dates back to 1968 where a joint patent was issued between Union Carbide (Linde) and Electrovert. The gas of choice back then was argon as any inert gas serves the same purpose to displace oxygen and reduce oxidation of the solder. The dross-reclaiming machines all work on the same principle, i.e. they heat the dross and squeeze it to separate the oxidized metal from the molten solder.

Ray Chartrand, CharTrain Consulting, may be reached at www.chartrain.com.

If you'd like to contact the editors, send an e-mail to Gail Flower, editor-in-chief, at gailf@pennwell.com and Meredith Courtemanche, managing editor, at mcourtemanche@pennwell.com.