Avionics and lead free solder

[kiwibrit]

Three years ago the rules on the use of lead free solder came into force. Severe repercussions were forecast (http://mae.pennnet.com/Articles/Article_Display.cfm?Section=ARTCL&ARTICLE_ID=238657&VERSION_NUM=2&p=32). And an allusion to the possible problem (http://www.pprune.org/military-aircrew/380050-dear-taxpayer.html) has been made in the Military Aircrew section of this forum. Now in my day, some environmental concerns did arise - for example, banning cadmium-plated earthing studs. But the lead-free thing did seem to have possible reliability and even flight safety issues. Have these become apparent - or in practice has good quality control been enough to ensure good performance?

[kgoodall]

Thats a really good point - I'm not involved in the aviation industry (just an interested party) but the company I work for has had to make adjustments. I think the most public example so far has been Microsoft with the XBOX 360 games console. There have been a lot of issues with the riser solder points on the main board and has had a serious financial impact of them.

[vapilot2004]

Lead-free electronics are more prone to failure than the decades-old proven methods of construction.

Lead-free construction fails in comparison to traditional electronics manufacture in three key areas: vibrational durability, extreme temperature, and heat/cool cycle performances. Just say no to RoHS on aircraft.

[bnt]

Another potential concern is the growth of Tin Whiskers - more on that here (http://www.empf.org/empfasis/2009/Apr09/tin.html), with pictures. :ooh:

[Dan Winterland]

My son's laptop LAN socket stopped working and then dropped out of the computer. It turns out lead free solder is more brittle and couldn't stand the stresses from the LAN cable.

[Deaf]

It turns out the lead free solder melted with the heat from the processor!

Most of the concoctions (alloy implies a degree of suitability often lacking with these) have a higher melting point than lead/tin. It is difficult to see how this could occur given the processor would "melt" first.

Possibilities are:

1- The RJ45 socket was under stress ie the hole in the case in the wrong place/socket in wrong place and forced matching. What appeared to be melting was in fact fracture which RHOS is good at.

2- Board assembly is often a two stage process with most components automatically loaded and oven (reflow) soldered. Some big components (eg sockets) are through hole, separately loaded and wave/hand soldered. Possibly some production genius got ahead of the curve and used woods metal or conductive glue?

Combination of 1 and 2

Difficult to understand how any of this could happen as there are only about half a dozen laptop manufacturers in the world (think Quanta is the biggest) and they are not given to sloppy manufacture, waaay ahead of avionics people.

[bjornhall]

Lead free soldering was a problem, while people learned how to use it. For those who have now had years to learn how to design and manufacture with it, it is no longer problematic at all. Where I'm currently working everything we do is RoHS compliant and we have no issues with that.

For those who are still learning, with proper quality control it should only be a yield problem, not a reliability problem.

I would not be the least bit worried about RoHS in avionics!

[kiwibrit]

bjornhall, interesting reply. Can we take it you are a manufacturer who has managed to achieve a lead-free soldered joint reliability matching that which you achieved with leaded solder?

[bjornhall]

The short version: If handled correctly, this is a problem for the avionics suppliers, not for the avionics customers.

"I'm a manufacturer" might be a stretch... Sounds as if I'm sitting at my kitchen table with a soldering iron... :E

But, yes, my current client is using lead free solder throughout their product line and has done so for a few years now, and there are no problems I'm aware of because of that. Those are not aviation, life support critical or milspec products, but not short lived consumer products either. Reliability and quality requirements are strict.

However, a lot of effort is required to learn how to do it and make it work. If an existing product has to be upgraded to RoHS compliance it requires a major redesign, including replacing components that will not survive the higher soldering temperatures and altering the board layout. Newly designed products are RoHS compliant from the start. There are major issues with lead free soldering, but those issues can be overcome.

While the company in question learns how to do that, they will probably have problems. If their quality control is good enough it will mostly be yield problems, but if the quality control is lacking substandard products could make it to the customers. The latter is of course the case even if lead free soldering is not used...

However, my point is that it is possible to make products that are just as reliable with lead free solder as with leaded solder. If the supplier knows their stuff, the customer will not even notice the trouble the supplier has to go through to make their products RoHS compliant. Except possibly by a slightly higher price; the supplier needs to recover the significant costs of the upgrade.

Lead free solder is not new anymore; those suppliers who are bound by the RoHS directive have learned how to do it, and that knowledge is available from various sources. Combined with the already strict quality control measures for aviation and military products, I am confident it is possible to deliver lead free soldered avionics products with sufficient quality and reliability. However, it will take a lot of effort from the suppliers.

[BigFootDriver]

There are ROHS execptions for many types of avionics due to reliability.

[IO540]

I have an electronics design and manufacturing business and have been doing this since 1978.

Lead-free soldering works OK for the normal sort of large-ish components used in most industrial products, although for fine pitch devices it remains unproven in the long term, and some firms using very small parts (Swatch was a high profile example) have found reliability poor.

The main reliability issue which remains is the higher soldering temperatures with lead-free solders. These push some items like surface mount electrolytics close to their absolute maximum temperatures and just a few degrees more will damage the parts, but not in a manner which is obvious...

The whole ROHS initiative has caused huge problems for manufacturers because many old and proven components (older embedded processors in particular) never became available in lead-free versions, and consequently many products had to be scrapped. Estimates of how many products were scrapped due to this are obviously hard to find but some suggest it is around 50%. I think that is about right, and results in a massive wastage of design resources (products having to be redesigned), electronics hardware ending up in the landfill, and non-ROHS component stocks ending up in the landfill too.

ROHS is misguided since the vast majority of lead entering the environment is from discarded car batteries and these cannot be banned, and also because the concept of lead escaping from a modern dry landfill has not been established. So this is a hugely expensive precautionary measure.

There are fortunately exemptions to ROHS. The military, internet switching equipment (evidently Cisco had a very good lobbyist in Brussels ;) ), medical, and "control and monitoring" products (the exemption many European companies including mine are making heavy use of). I don't know, without looking it up, whether avionics is exempt but it probably is - most of the designs on the market are 10+ years old.

Distributors of electronic components love ROHS because it forced a huge increase in demand for new components, which command higher prices compared with old ones, and because companies had to scrap a lot of inventory. The distribution industry is constantly lobbying the EU to terminate the existing exemptions, unsuprisingly. Of course, if you have a job as an "ROHS compliance officer" in some company then you will also have a predictable view :) The electronics industry publications are funded mostly by advertising from electronic component manufacturers so they also favour forced obsolescence.

The next gravy train is REACH....

[Phalconphixer]

I retired as an Avionics Engineer in 2005 after 35 years in the business both at the pointy end and in the servicing bay. I have to admit that I knew nothing about this legislation until I saw this thread, but my initial reaction is one of horror.

All of those in this business know the old adage; If it ain't broke don't fix it...

So how long can the interfering bean counters in Brussels continue to screw things up.

Here's a question for you, tongue in cheek but with a degree of seriousness...is there an example of Lead Free Solder technology failure now lying beneath the Atlantic off the coast of Brazil?
From earlier comments in this thread the technology is not as resilient as conventional solder; unfortunately we may never know...

[hawfaheed]

Aircraft are exempt from RoHS. Ships, trains, medical equipment, basically anything that if "unexpected early failure could cause injury, loss of life or harm to the environment" is exempt. Even ground equipment used to calibrate aircraft instruments is exempt. Some heavy reading for you here:- http://ec.europa.eu/environment/waste/pdf/era_study_final_report.pdf

[mitcherator]

Yes you are correct in saying that Aerospace & Military are Exempt from RoHS law....BUT...

1. Electronic Suppliers and Manufacturers are global - Europe & China Market.

2. The Military and Aerospace are about 1% of the World Consumer Market

Most of Aerospace and Military procure electronics and surplus parts through electronic suppliers and manufacturer's globablly, which then affect COTS (commercial-off-the-shelf) parts.

To Maintain Interest in Europe the electronics industry is starting to move over to non-lead solders.

There has been many case studies has been done on this issue and tests that can be done to determin and mitagate the effects of tin-plate whiskering, but currently there is no technique that guarantees the DoD requires for high-reliability systems "except the addition of 3% or more lead to tin.

There is no direct replacement or substitution that "gets the lead out," Lead-Free electronic components are simply unavoidable.

See Lead-free solder: A train wreck in the making - Military & Aerospace Electronics (http://www.militaryaerospace.com/index/display/article-display/238657/articles/military-aerospace-electronics/volume-16/issue-10/news/trends/lead-free-solder-a-train-wreck-in-the-making.html)

And Tin-whisker failure problem from lead-free solder in military electronics is target of Air Force research job - Military & Aerospace Electronics (http://www.militaryaerospace.com/index/display/mae-defense-executive-article-display/1032102426/articles/military-aerospace-electronics/executive-watch-2/2011/3/tin-whisker-failure.html)


For more info.

[Agaricus bisporus]

Lead free solder!

WHY????