Circuits Assembly Online Magazine - Whither Due Diligence?

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The EC commits to an RoHS Directive review by 2008. This time, will they review the evidence?

Estimates vary, but the lowest cost to industry for Pb-free implementation I have seen is $8 billion. That’s a sobering number. Are we getting our money’s worth? For that (under)estimated $8 billion, literally the only positive comment on Pb-free soldering I have come across (ignoring the trumpet sounds of those with commercial interests) was from Dr. Ron Lasky: “Pb-free assembly enables closer pad spacing because it does not wet as well as SnPb solder. Because of this benefit, many Pb-free products could not be manufactured with leaded solder.”

Amazing how things change. For years, wetting has been the indicator of solder joint quality and a fair harbinger of said joint’s reliability. With Pb-free solder, we are pushed so hard to find any benefit whatsoever compared to SnPb that we are reduced to touting something that until a year ago would have been reason not to use the technology.

Most experts are out in full force against Pb-free. In reply to comments about Pb-free issues, noted reliability guru Werner Engelmaier says he has witnessed “an increase in wetting problems, delamination, reduced component reliability, open vias and copper pads dissolving during soldering and rework, great increases in tombstoning and spattering.” Then regardless of any perceived “benefits,” plenty of negatives appear to outweigh them.

Indeed, the email channels are alive with issues ranging from cracked joints, through-hole soldering issues, board delamination, lack of wetting and a plethora of other soldering evils. Here’s a typical note: “I have a question on PCBs built to withstand LF processing temperatures. Is anyone experiencing problems with hole wall quality issues or excessive blowhole issues? To what extent? Pervasive? Isolated?”

If this came from a single end-user who may not understand profiling, it could be discounted as an isolated case. This particular query, however, was sent to the IPC’s TechNet forum from IPC vice president of technical programs David Bergman. Should we be concerned?

And the response to this somewhat-late-in-the-game question is even more disconcerting. A PCB fabricator who has conducted ample Pb-free research and cross-sectioning details how the phenomenon cannot be found with traditional right angle to the panel sectioning, but rather by sectioning at 45° to the bare laminate warp/weft. “Most fabricators would not believe they could produce hole walls that look so bad. It appears that when the glass is not aligned with the drill, it gouges and pulls out in chunks. This is especially so with regard to the 170° Tg, high-temp phenolic resin material now being specified by so many OEMs. All laminates gouge this way, but the gouging appears to be deeper and more severe with 170° Tg laminates … I believe this is an industry-wide issue, as I have cross-sectioned numerous boards from a number of other manufacturers. All have exhibited some level of this phenomenon.”

Worst is the November announcement by the UK National Physical Laboratory of a new industry collaborative to address issues stemming from copper pad dissolution into SAC 30x wave solder systems. As it turns out, during extended immersion in the wave, most of the copper on the component pads dissolves – yes, dissolves – into the bath. The project scope is threefold:

1. Develop a monitoring technique to quantify the rate of copper loss due to immersion in a molten metal under static and dynamic conditions.

2. Investigate copper dissolution with a range of solder alloys and PCB styles and temperatures.

3. Produce a best practices guide (including a test method) for minimizing PCB copper dissolution.

I would never diminish the activities of those in the research or analytical field, let alone the NPL. But knowing all this reinforces my opinion that electronics reliability during the next few years will be a rocky road. That the extent and scale of these issues were unknown before the RoHS Directive kicked in is almost unfathomable. Instead, the EU sailed blithely on, assured that replacements for leaded solder and its associated infrastructure were both viable and in place.

Writing on the subject of reliability, Boeing’s Tom Woodrow said, “I was involved with the JCAA/JG-PP Lead-Free Solder Project and would highlight one item not discussed in the Executive Summary. Analysis of the JG-PP vibration data tells me that SnPb BGAs will survive 10 to 30 times longer than SAC BGAs in the same vibration environment. This could be a real problem for some high reliability applications.”

In reply, General Dynamics’ Richard Stadem wrote: “That is exactly what I have seen during shock/vibration testing when qualifying Pb-free solder pastes. Having established an extensive personal database with previous 63/37 solder paste qualifications, I have a benchmark for data comparison. I noticed things like peel strength reduction, slightly shorter thermal cycles to failure, and the time to failure during vibration for Pb-free is 15 to 30% less than 63/37, depending on brand.”

A bigger burden. Ah, but it is all for the protection of the environment, right? Actually, a now widely circulated report, written under an EPA grant, states that the environmental impact of the replacements for leaded solder have about six times the environmental burden of the materials they replace1. Which begs the question, why would the EU persist, given that prior to the RoHS Directive, none of its members had ever banned lead in solders without first performing due diligence?

Only now has the rationale for the ban been stated. Take a look at a letter sent to me by Klauss Koegler, acting head of unit at the EU RoHS office: “I reply on behalf of Vice-President Margot Wallstrom and Commissioner Stavros Dimas. I recall that the aim of the RoHS Directive is the substitution of lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE) in electrical and electronic equipment, where alternatives are available, in order to facilitate sound recovery and prevent problems during the waste management phase.” In fact, the RoHS Directive was adopted in conjunction with Directive 2002/96/EC on waste electrical and electronic equipment (WEEE) relating to waste management.

The communication continues: “The risk to human health and the environment caused by the use of the hazardous substances mentioned above is documented in several studies referred to in the explanatory memorandum that accompanied the proposal for the RoHS Directive back in 1997.” This latter point is interesting, as in the 50-plus years of using lead in electronics solders there is not a shred of evidence of hazards to human health or the environment.

Koegler ends: “It should also be noted that the Commission has committed itself to review the RoHS Directive by 2008 at the latest in order to simplify and clarify its provisions, insofar this would be appropriate. In order to prepare for this review, the Commission will take into account all relevant information coming from studies and ongoing research in the field and prepare an impact assessment.” On this I’ll give the Commission the last word and truly hope they perform due diligence in “amending” the legislation.

As an industry that should be committed to the environment, and that has been derailed into actually causing it more damage because of lack of research by the lawmakers at the EU, we should, in the words of The Who, make sure “we don’t get fooled again.”

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