Lead free solder

[Andrew C]

I understand from contacts in the Aero industry that BAE tried lead free , and basically said "Stuff that. We know that traditional solder works, we CAN'T trust the lead-free."

[gyro_gearloose]

Full lead is available supposedly for repair and re-work on pre RoHS stuff

 

Unless you are repairing a stained glass window, you shouldn't be using full-lead solder :D 60/40 refers to the percentage of tin and lead in solder, so 60/40 solder is 60 percent Tin and 40 percent Lead and is the stuff you should be using to repair pre-RoHS electronic circuits.

[cedd]

I understand from contacts in the Aero industry that BAE tried lead free , and basically said "Stuff that. We know that traditional solder works, we CAN'T trust the lead-free."

Yep, you won't find any lead-free solder on my repair bench. We've bought quite a lot of leaded stuff just in case.

All I'll say is that the decission is likely to be based on approval rather than directly on performance. The aviation bodies, particularly the CAA, are extremely pessimistic and don't like anything new, hence why most of my safety-critical computer systems are still running on windows 2000 or dos.

Lead free solder is new, largely untested by time and hence not going to be used. The radar at my work is 20+ years old, it still works. If we find out in 8 years time that lead free does something daft with age, imagine the cost involved, both monetary and in terms of safety.

 

Personally, I'm using both depending on which reel at home I reach for first! No real preference although the lead free stuff does seem to look more "cloudy" and less bright when you've made a joint.

[Cougar]

I understand from contacts in the Aero industry that BAE tried lead free , and basically said "Stuff that. We know that traditional solder works, we CAN'T trust the lead-free."

 

Yep, you won't find any lead-free solder on my repair bench. We've bought quite a lot of leaded stuff just in case.

All I'll say is that the decission is likely to be based on approval rather than directly on performance. The aviation bodies, particularly the CAA, are extremely pessimistic and don't like anything new, hence why most of my safety-critical computer systems are still running on windows 2000 or dos.

Lead free solder is new, largely untested by time and hence not going to be used. The radar at my work is 20+ years old, it still works. If we find out in 8 years time that lead free does something daft with age, imagine the cost involved, both monetary and in terms of safety.

 

Personally, I'm using both depending on which reel at home I reach for first! No real preference although the lead free stuff does seem to look more "cloudy" and less bright when you've made a joint.

 

As I understand it BAE and similar companies are allowed to use lead solder for prototypes but must use lead free for commercial products.

[Simon Lewis]

Aside from rosin fumes there is a real risk of lead poisoning. Lead is a poison that slowly builds-up in your body and can have a bad affect on your health because your body can't break it down or get rid of it.

 

I agree that lead is a cumulative poison, and that personal hygiene is good, but the risk arises primarily from inhalation or ingestion. Solid lead is considered to present a relatively low risk. Organolead compounds (such as the tetraetyl lead used in leaded petrol) is a high risk chemical because it can be easily ingested, and even after burning a finely divided airbourne particulate residue is left.

[daifuse]

Some years back, I carried out a small project with a portable pump drawing air samples through a particulate filter which I then analysed using ICP-OES and ICP-MS. The fumes produced during soldering have very little if any lead in them.

The hazard from lead solder arises when the circuit board is scrapped and thrown into landfill. Here, acid leachate may dissolve the lead, and leaks in the landfill liner (presuming it has one!) means that potentially, heavy metal rich leachate liquors can make their way into watercourses.

 

The risk to health during soldering is from the rosin fumes. These are particularly unpleasant and are considered to be the prime cause of occupational asthma. The solid and fume can also cause dermatitis. Therefore it is good practice to use some form of fume extraction. This leaflet explains more.

 

I understand that lead based solder is allowed for repair and maintenance of equipment that already has lead based solder. For this purpose, I bought a few rolls to allow this activity to be carried out ;-)

 

Simon

 

 

During my time in the Navy when repairing PC boards we were informed that the greatest hazard was fumes from PTFE insulation when soldering the inter-connect wiring. No other hazard from other fumes was mentioned and no extraction facilities were provided.

Does anyone have any info on this?

[Simon Lewis]

During my time in the Navy when repairing PC boards we were informed that the greatest hazard was fumes from PTFE insulation when soldering the inter-connect wiring. No other hazard from other fumes was mentioned and no extraction facilities were provided.

Does anyone have any info on this?

 

Not knowing what solder you were using, I can't comment specifically, but the use of rosin based solder does carry the risks mentioned in the HSE's leaflet. Of course, thousands have soldered wires for decades without apparent effects - although as an asthmatic I have found soldering to be a problem at times.

 

With regards to PTFE, the melting point is ~327C but its properties begin to degrade at about 260C. Upon pyrolysis PTFE could produce hydrofluoric acid, carbonyl fluoride and a series of organofluoro compounds, some of which are more toxic than phosgene.

 

In sufficient quantities, inhalation of PTFE decomposition products could lead to Polymer Fume Fever, or even death. However, one would need to balance this against the (hopefully) relatively small amounts of fume produced during soldering of PTFE insulated wire.

 

If in doubt, use a suitable extract system and consider monitoring urinary fluorine content!

 

Simon

(I am no longer a practicing analytical chemist, the information above is for information only etc., etc.!)

[Bobbsy]

I've heard a number of times that the restrictions on lead-based solder have little or nothing to do with hazards to people using it; rather, the concerns were much more to do with the disposal of electronic gear containing heavy metals (including lead) when the items are discarded.

 

I wouldn't want to suck on a piece of 60/40 solder but neither am I over-concerned with the risks of using it.

 

Bob

[Starstruck]

You are correct the banning of 60/40 solder is due to the problems caused when they are disposed of.

 

BAE are one of a few companies that can legally still use 60/40 solder but only for its military and aviation products. Handling 60/40 solder is not considered hazardous but the fumes from the flux is considered dangerous and you should use extraction ! Especially if you are using lead free solder as some of the new fluxes are pretty nasty.

 

There is good reason why BAE do not use lead free solder, lead free solder suffers from a problem called tin whiskers. This is where wiskers grow from the solder joints and can eventually cause a short circuit with adjecent joints. The lead in the mix prevents the whiskers growing. BAE and other companies have exemption from ROHS for certain products (after all you wouldn't want a plane falling out of the sky due to tin whiskers !).

 

Commercial electronics HAVE to use lead free solder and will suffer from tin whiskers but they don't grow over night, most commercial electronics companies only give a years warrenty and tin whiskers normally take more than a year to grow (normally!). Good for them but bad for us.

 

No one has been able to solve this problem yet (including NASA - check there web site for examples) . Many companies have been working on new solder chemistries but they all have other side effects .

 

Starstruck

[karl]

Whilst lead is toxic I can't help but think the threat is being over blown. My grandparents lived most of their lives in houses with lead plumbing and showed no ill affects. I have lived in a house for twenty years with lead supply pipes and I'm still alive.

[Simon Lewis]

Whilst lead is toxic I can't help but think the threat is being over blown. My grandparents lived most of their lives in houses with lead plumbing and showed no ill affects. I have lived in a house for twenty years with lead supply pipes and I'm still alive.

 

There's the problem... Just because you drink from a tap supplied by lead pipes doesn't mean you drop dead immediately. The effects are cumulative and might not necessarily kill but may cause reduced quality of life.

 

Factors which increase lead concentration in drinking water include low Ca+ / Mg+ content (i.e. soft water) and high water temperature. Young people are more susceptible to lead poisoning, affecting their mental and physical development, but it will cause ill health in older people too.

 

Inhaled and ingested lead does have a deleterious effect, and there are a wealth of studies to support this. These were instrumental in the phasing out of leaded petrol.

 

If you live in a hard water area, and you do not use hot water to cook with or fill your kettle, the amount of dissolved lead may be small, with a low residual risk. The present UK water quality regs stipulate a 25 microgram per litre limit, but this will apparently be lowered to 10 microgram per litre in the next few years.

 

As someone who spent many years testing for heavy metals at the sub parts per million range, I can assure you that the level of lead in drinking water is taken quite seriously, and although no one wants to be alarmist, neither do they want high levels introduced into water supplies or the atmosphere.

 

As a last indicator of the problem, lead is one of the few chemicals that has specific legislation covering its use in a work situation.

 

 

Simon

[Jivemaster]

The major production issue with lead free solder is that tinned leads will gain a surface film which some fluxes may not shift in normal soldering (hand or machine) This lead to a possibility of cheap passives (like Rs and Cs) being given a shelf life measured in months!!! After that they may become unsolderable.

[karl]

There's the problem... Just because you drink from a tap supplied by lead pipes doesn't mean you drop dead immediately. The effects are cumulative and might not necessarily kill but may cause reduced quality of life.

 

Yes, I didn't dispute that lead MAY be harmful.

 

As someone who spent many years testing for heavy metals at the sub parts per million range, I can assure you that the level of lead in drinking water is taken quite seriously, and although no one wants to be alarmist, neither do they want high levels introduced into water supplies or the atmosphere.

 

You obviously have far more knowledge on the subject than I do and understand the risks. The problem is that a lot of people don't understand risks and the factors affecting them. Also, some people do want to be alarmist, in fact some people seem to enjoy nothing more than stirring up panic (certain newspapers are a prime examples).

 

I'm not about to suggest we should all go back to using lead plumbing or sprinkle the stuff on our sandwiches. But is there research that shows how much of a hazard lead based solder poses?

[Simon Lewis]

I'm not about to suggest we should all go back to using lead plumbing or sprinkle the stuff on our sandwiches. But is there research that shows how much of a hazard lead based solder poses?

 

Yes - the risk from handling solid lead is very low. There is very little lead released through soldering at normal temperatures. You would have to be heating it excessively (e.g. smelting) to get lead fume. The main risk (apart from such items as PVC or PTFE being heated too much) is the rosin that's used as a flux - which is quite a different effect from lead inhalation. Fume extraction is still recommended for rosin though.

 

The reason for RoHS (the legislation that led to the restriction of lead in electronic and electrical products) is primarily an environmental one, and it was introduced in conjunction with the WEEE regs. The basic premise is that we throw away more and more electrical / electronic equipment. This either gets incinerated or put in landfill. Either way, it is possible that lead from circuit boards may find its way into the atmosphere or the water table, and from there be inhaled or ingested directly or become part of the food chain.

 

Restricting the amount of certain chemicals going into electrical equipment (namely lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether flame retardants) and encouraging the effective reuse and recycling of waste electrical and electronic equipment should lower of bioavailability of such chemicals.

 

Hope this helps,

 

Simon

[Stuart91]

Back when the RoHS legislation was coming into force, I remember reading an argument put forward by a spokesperson for a manufacturer. The theory behind the RoHS restrictions appears to be that electronics end up in landfills, and the lead contained in the solder could eventually find its way into the water supply. On the other hand, we still have lead flashing on roofs, which are getting regularly pelted with increasingly acidic rainfall, and washing straight into the sewage system. Surely that's a bigger, and more urgent health risk?

 

 

(I'm just repeating the argument as I remember it - I don't actually have the knowledge to confirm or back it up!)