The NEW Way to Get the Lead Out

Article as seen in Circuitree Magazine, July 1996, by John S. Eddy, President and Co-founder of Eddy Electronics Mfg. Ltd.

With environmental concerns and increasing regulations on industrial pollution, lead is looming large as a major problem for the PCB and electronics industry.

Environmental problems are compounded by widely differing and uneven environmental regulations and practices across the globe that have led to political and financial obstacles for our industry.

Most PCB manufacturers live with some fear that the consequences of these practices could overtake them suddenly in some change in law or environmental policy.

As a conscientious industry in the developed world, PCB manufacturers are already pursuing ways to reduce lead consumption in our industry and with the threat of unfair offshore competition, it is of even greater concern. If lead in electronic products can be reduced, we can also reduce the threat of lost contracts, jobs, and competitiveness. If lead consumption is to be reduced, PCB manufacturers can benefit the most by leading the way.

There has been much development in lead free solders and interconnects. Conductive ink has been promoted for years but has failed to gain broad acceptance, especially as a replacement for copper traces. Indium solders show great promise but are very costly. Tin-bismuth solders are considered safe but oxidize easily and lack ductility. Even if there is no immediate replacement for tin-lead solder, there is considerable interest in replacing it. Wave solder machines, their fumes and waste materials are considered health and safety hazards.

Perhaps the greater impact on the consumption of lead is not in the soldered connections, but rather in the printed circuit itself. The processes required for putting lead on the printed circuits are inefficient and, in themselves, present occupational hazard and waste treatment problems that are out of all proportion to any value they add.

A promising new development now exists in Canada where Eddy electronics Mfg. Ltd has developed a manufacturing process which is lead-free. Standard and non-value adding process steps have been abandoned and only simpler and cleaner steps are in place.

Manufacturing starts in a very conventional way with the normal drilling and electroless copper. Then, Eddy Electronics panel plates the copper to the specified thickness in a pyrophosphate bath. Pyrophosphate is preferred for its ductility and strength. Lamination and imaging follow to produce a "tent and etch" bare copper printed circuit. The last wet process step is an efficient immersion silver bath which is self regulating and produces a layer 2-4 microns thick. Solder mask and overlay are of course normal, and the silver provides excellent adhesion with a low profile relative to solder plated PCBs.

The cost of waste management is far less in the absence of lead. Hot Air Solder Leveling, once favored for low solder profile and relative cleanliness, has been identified by the October Project consortium as a process to be eliminated.

This process offers other advantages including: Copper bearing waste is free of lead and recycling can proceed on-site at a PCB plant. Phototool film with its silver emulsion can be used as a valuable resource rather than a waste treatment problem.

High quality PCBs are manufactured with this process that are comparable to common SMOBC types with the added benefit of wide design latitude. Very fine features and very large copper areas can be manufactured reliably with no concern for plating densities or warpage. Eddy Electronics has manufactured PCBs with .003 lines and .004 spaces.

As the only solder on the finished product is applied by the assembler, many different combinations of solder or conductive ink may be used. Tin-lead solder may also be used. The low profile nature of the product allows accurate placement of solder pastes for SMD applications.

Eddy Electronics' product is a little different but has been gaining acceptance in local and export markets for more than ten years. Many similar approaches to the same end exist and are under development. Organic coatings, like Entech, and various electroless and immersion coatings have emerged over the past few years. With future environmental sensibilities, acceptance of all of these approaches are likely to grow.

A lead-free printed circuit allows manufacturers to choose solders or bonding systems according to their own criteria and makes a lead free electronic product a viable option. Even if lead free is not the way they choose to go, the benefits ot PCB fabricators can hardly be ignored.