Soldering Electrical Connections to NASA standard

[Michael GilliganParticipant @michaelgilligan61133]

Posted by David Colwill on 24/04/2021 08:16:23:

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I thought that the latest mars rover was using some off the shelf cameras in it.

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FLIR is quite proud of that : **LINK**

https://www.flir.co.uk/discover/iis/flir-machine-vision-cameras-capture-high-definition-footage-of-nasas-perseverance-rover-landing-on-mars/

MichaelG.

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https://www.flir.co.uk/about/company-history/

Edited By Michael Gilligan on 24/04/2021 08:49:03

[CirclipParticipant @circlip]

"So much doom and gloom is attributed to the use of lead in its various guises and I have yet to see scientific evidence to support these assertions."

It's well known that if you stand in front of a cylindrical dome ended piece of Lead travelling rather quickly the results can be life changing. Do the boxes containing quantities of these carry a health warning???

I wonder how many ton(nne)s of domestic electronic equipment reside in recycling centres due to failed Leadless solder joints?

Was taught many, many, many moons ago how to solder by me dear departed pater whose mantra was "Killed spirits" for tinplate constructions and "Ersin 60/40" for electronic builds.

My three reels of Ersin, when prised from my cold dead hands are willed to my lads.

Regards Ian.

[John Doe 2Participant @johndoe2]

I would imagine the number of people affected by the lead in solder would be a small number, but I wonder if the huge increase in dementia in our populations can be attributed to the lead in paint and petrol as there used to be? And amongst plumbers who of course used to use heated lead to make joints.

[John HaineParticipant @johnhaine32865]

It isn't called "unleaded" petrol for nothing! Petrol used to contain tetraethyl lead as an anti-knock additive, until a huge body of evidence built up on the effect of environmental lead on, IIRC, brain development in children.

[Tony Pratt 1Participant @tonypratt1]

I'm now worried about a piece of lead water pipe in my house, many millions of homeowners will be in the same position.

Tony

[CirclipParticipant @circlip]

"It isn't called "unleaded" petrol for nothing! Petrol used to contain tetraethyl lead as an anti-knock additive, until a huge body of evidence built up on the effect of environmental lead on, IIRC, brain development in children."

Yes, but the Game Boy and Sonic took over.

Regards Ian.

[Martin KyteParticipant @martinkyte99762]

The point about moving to lead free solder for commercial products is not that anyone is at risk whilst handling or using leaded solder but that the amount of electronics goods currently going into landfill poses a significant risk of contaminating ground water. Why we should be junking such a large amount of valuable material is a separate question.

regards Martin

[SillyOldDufferModerator @sillyoldduffer]

Posted by Robert Butler on 23/04/2021 22:25:01:

So much doom and gloom is attributed to the use of lead in its various guises and I have yet to see scientific evidence to support these assertions. How many deaths in wildlife and humans have a direct and proven link to lead ingestion or poisoning.

Robert Butler

I suggest Robert hasn't looked hard enough! Almost any book on Toxicology tells all, if you can find one.

Unfortunately most ordinary libraries don't hold technical material – there's a lot of it, and only specialists read it. The libraries of big Medical Schools and Technical Universities are a better bet, but you have to know what to ask for.

No-one knows how many deaths in wildlife and humans have a direct and proven link to lead ingestion or poisoning. The information is too difficult to gather. However, there are a multitude of smaller incidents and laboratory experiments from which the toxicity of Lead is well understood. We know how many micrograms of ingested Lead it would take to bump off Robert. We know tiny quantities damage the brains of unborn children, and slightly larger quantities effect the brains of adults.

When most paints contained Lead, it was common for children who chewed toys to be hospitalised, and painters were often poisoned – especially when stripping paint with a scraper and blowlamp. Industrial illnesses also common in Roofers, Miners, Plumbers, Glaziers, Agricultural Spraying and even some Anglers. In the ordinary population, much illness has been traced to Lead leaching into water from land-fill or shot from hunting water-fowl. Also from lead piping, in which water has been allowed to stand for a few months, or when the Lead comes into contact with certain otherwise harmless water treatment chemicals.

The Flint Water Crisis is a recent example: apart from the massive clean-up costs, victims are to receive damages set at nearly half a billion pounds. Pollution isn't cheap!

Fortunately, Lead has been steadily phased out in most countries since the 1950s. You have to be over 50 in the UK to have been exposed as a child to Lead in entirely unregulated quantities, and over 90 to have lived in a Lead free for all. This may be why Robert doesn't see a problem: we've benefited from tighter controls applied in the past.

Two main exceptions:

• Lead in petrol. This may be partly responsible for high-levels of dementia, the possibility that people are more stupid than they used to be, and violent crime.
• Lead from discarded electronics is slowly getting into drinking water. Irresponsibly dumping toxic waste of any sort is likely to have consequences, unfortunately years after the polluter escaped punishment by dying of old age.

Dave

Edited By SillyOldDuffer on 31/01/2022 14:51:46

[MikeKParticipant @mikek40713]

Lead doesn't have to directly result in deaths to be a hazard…That's really a ridiculous threshold. Removal of lead in gasoline/petrol correlates with a decline in violent crime. And, no, that doesn't mean it should result in NO violent crime.

[John HaineParticipant @johnhaine32865]

**LINK**

**LINK**

And I recall from history at school that at one point those toffee bonbons coated in powdery sugar were adulterated by adding white lead to the sugar because it was cheaper and tasted sweet. And of course for quite a long time white lead was used in cosmetics.

**LINK**

[Andy AshParticipant @andyash24902]

There is no way this is overkill. The early developers of space flight systems learned the hard way that satellites go into space and disappear. They soon learned that the need for meticulous quality is very high indeed.

The main problem for aircraft electronics is vibration, and the main problem for space flight is thermal vacuum.

Vibration causes work hardening and fatigue. Thermal vacuum causes the growth of tin whiskers and outgassing.

For space, most manufacturers use special PCB substrates that are not based on epoxy resin due to outgassing of volatiles. If they can, they avoid solder altogether in favour of gold plated mechanical connections. Otherwise electronic systems have to go through vacuum bake-out to ensure reliability "on orbit".

If the soldering isn't good enough the system won't pass bake-out, but it might still fail in space even if it passes. There's no mechanic up there to fix anything, and the launch alone will cost millions.

You have to get it right first time.

 

Edited By Andy Ash on 31/01/2022 18:52:53

[Steve GarryParticipant @stevegarry36500]

It was a long time ago now, but when lead free first came into use, I understood one of the main reasons was to protect the workers that were being affected by the fumes coming off flow solder baths or other assembly lines that were used to assemble all the PCB's that were being used in just about everything electronic at that time.

I also am quite willing to admit to still having a significant quantity of leaded solder that I was using for repairs to computer PCB's at that time, then I moved into other areas of computing, and as a result, we moved to Ireland over 30 years ago, so work that one out in terms of the age of those 2 drums of solder. I also have some lead free, but in comparison for some work, it's muck. and I don't get to use it very often for that reason, I need things to work, and stay that way when they are repaired, not fail not long after reassembly.

[Danny M2ZParticipant @dannym2z]

Posted by Paul Lousick on 21/04/2021 23:53:06:

A reference for improving our soldering techniques.

NASA Technical Standard: Soldered Electrical Connections

**LINK**

That document brought back a few memories.

In 1984 myself and another Australian Army member were selected to join six RAAF technicians to undergo training as High Reliability Hand Soldering Instructors (HRHS) Instructors.

This course was of about three weeks duration and our instructor was NASA certified.

The Australian military has a lot of very expensive high-tech equipment and the maintenance and repair techniques are therefore to be undertaken to the highest possible standards.

My area was RADAR/microwave equipment and air defence systems, while many of the RAAF blokes worked with aviation electronics. (No room for errors)

Even the basic preparation of a component required the correct tools and techniques, from lead cleaning and bending tools (of the correct radius) to a small carbide tipped shear tool (never wire cutters – they can send a mechanical shock into delicate components).

Other equipment included a calibrated temperature controlled soldering station, a comprehensive selection of tips, visual inspection equipment, solder pots, liquid resin flux, PWB Printed Wiring Board) holders and many other essential tools.

Even the preparation and handling of solder was carefully controlled. For a start, it comes in many sizes and much of our work involved using reels of 0.020" and 0.050" solder (that incidentally had traceabilty documentation).

After selecting the appropriate grade of solder, the working length was then cleaned with a white cloth dampened with isopropyl alcohol. The amount of black gunk that comes off is amazing. (Try it)

After completing a joint it is then carefully inspected before commencing another joint. The molten end of the solder is snipped-off to expose a fresh resin core before commencing another joint (as the composition of the molten 'blob' is unknown and one requires that the resin flow is immediate.

There is heaps more, anybody interested should study the document that Paul linked to.

At the end of the course we were offered a sample student PWB to assemble or we could submit our own project if of similar difficulty. I chose a 364K memory expansion board with multiple I/O ports for my Z80 computer.

It passed and is still working well 38 years later, no solder joints have failed.

* Danny *

[James Hall 3Participant @jameshall3]

That's a bit of a hoot really when we're talking about an organization that suffered disasters from neglecting to ensure booster o-rings could stand up to low launch pad temperatures and sending off a moon landing mission containing an O2 tank with a history of faults.

"Well, we lost the craft and its crew, but there were no soldering failures".

[SamsarandaParticipant @samsaranda]

My grandson works for a multinational engineering group, he works in the circuit board assembly area and recently showed me a video he took of one of their flow solder baths working, you can see this river of molten solder flowing over a weir at the end of the machine, very very impressive. He assures me that they only use lead free solder, just imagine how much lead fumes that one of these workstations would give off if using leaded solder. Dave W

[HowiParticipant @howi]

Good question about lead poisoning, do you have any of the following symptoms:

• High blood pressure
• Joint and muscle pain
• Difficulties with memory or concentration
• Headache
• Abdominal pain
• Mood disorders
• Reduced sperm count.

Dave

Well, I'll be blowed, I thought it was all down to old age.

[Ady1Participant @ady1]

Getting as much lead and mercury and cadmium out of the general system as is possible was always going to be a good idea, all these heavy metals screw up carbon based life forms

The cost isn't really in dead bodies, it's in the still living with their brains and bodies wrecked who need a lot of resources for dealing with an incurably poisoned system

If humans only lived for 10-20 years max a lot of poisonous stuff wouldn't really be such a big deal

Edited By Ady1 on 01/02/2022 10:03:18

[Clive SteerParticipant @clivesteer55943]

Maybe electronics equipment is becoming too reliable and the tin whiskers helps give them a finite life so you can buy the next model.

Clive S

[SamsarandaParticipant @samsaranda]

I think you’ve cracked it Clive. Dave W

[Martin KyteParticipant @martinkyte99762]

Do the tin whiskers come from the solder or from the tinned tracks? Tin plating on boards being pretty much 100% Tin. I would hazard a guess that NASA gold plate everything destined to fly.

regards Martin

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