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NASA's Through-Hole Workmanship Req (2002)

workmanship.nasa.gov

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Re: NASA's Through-Hole Workmanship Req (2002)

#51

Post by mauvehaus »

jcims wrote: post #41
mauvehaus wrote: post #37

Earlier quoted context omitted.

On several levels. Avgas is still leaded.

Whoa, that's crazy. It's going to take 50+ years to get the current engines out of operation. I wonder if new engines are able to run without.

Not a pilot or aircraft owner, but my understanding is that part of the problem is because certifying a new aero engine is insanely onerous (as is certifying anything that goes on an airplane), a lot of basically obsolete designs requiring leaded fuel were produced long after auto engines switched to not requiring leaded gas.

Why would an engine require leaded gas, you ask? Because it helps keep the valve seats from degrading. We have other anti-knock additives, but nobody has figured out a replacement for the other properties that lead has.

And since aircraft are usually extremely long-lived, we'll be stuck with this problem until a substitute is found. Merely certifying new engines that don't require lead won't solve the problem because of the remainder of the fleet that does require leaded gas.

Re: NASA's Through-Hole Workmanship Req (2002)

#52

Post by _carbyau_ »

konschubert wrote: post #5

I knew I was bad at soldering, I didn't know I was THAT bad. I need to take a course.

You are not alone. I have a cheapo soldering iron with a roll of ... metal melty wire in a plastic bag that I pull out and struggle for 30mins to make a basic connection almost certainly the wrong way.

But I flick the little switch and the little fan comes on and I am happy.

But I should do a course. Or at least google some more. I don't even know many of the terms people are using here...

Re: NASA's Through-Hole Workmanship Req (2002)

#53

Post by lmilcin »

buescher wrote: post #22

The NASA handbooks are good. I like the one for rework that shows neatly staked wires. There are a couple of subtleties you could miss on this one though: 1) On page three, that exposed end of the lead is a defect if you're NOT going to conformally coat the board. If you don't know what a conformal coating is, it's a defect. 2) On page eleven, flux residue. Sure, for NASA's applications. For most commercial applicati…

I dislike no-clean. I like my boards pristine with nice, shining leaded solder and no residues.

Re: NASA's Through-Hole Workmanship Req (2002)

#54

Post by lmilcin »

jcims wrote: post #8

Was curious what their treatment was going to be regarding tin whiskers. Not much there (of course this is point in time inspection so it kind of makes sense), but a quick google revealed quite a bit of study: https://nepp.nasa.gov/whisker/ I thought they were just one of those low probability items until a Sunday morning when I was running live audio for a church service. Singer was mid verse and BOOOOM! Huge boomin…

I believe urethane conformal coating helps control whiskers problem.

Re: NASA's Through-Hole Workmanship Req (2002)

#55

Post by xxs »

gte525u wrote: post #20
jcims wrote: post #8

Was curious what their treatment was going to be regarding tin whiskers. Not much there (of course this is point in time inspection so it kind of makes sense), but a quick google revealed quite a bit of study: https://nepp.nasa.gov/whisker/ I thought they were just one of those low probability items until a Sunday morning when I was running live audio for a church service. Singer was mid verse and BOOOOM! Huge boomin…

NASA and aviation in general are later adopters of lead-free. It definitely wouldn't have been reflected in older standards.

leaded solder is still allowed in the EU for medical equipment for instance.

Re: NASA's Through-Hole Workmanship Req (2002)

#56

Post by xxs »

1996 wrote: post #36
mvgoogler wrote: post #35

Earlier quoted context omitted.

From the HN guidelines: 'Please don't comment on whether someone read an article. "Did you even read the article? It mentions that" can be shortened to "The article mentions that."' It doesn't add anything to the discussion. And in this case it was very clear that the OP read the article and just missed that part. Your comment would have been just as informative and less snarky if it was simply: There's a small part…

> > Did you read the specs? > 'Please don't comment on whether someone read an article. "Did you even read the article? It mentions that" can be shortened to "The article mentions that."' Not an article, but specs. You read specs carefully, you don't skim, especially to write long paragraphs about your personal experience > And in this case it was very clear that the OP read the article I disagree. Not read, skimmed…

"Whiskers" actually 'grow', they are not part of the soldering process[0]. Lead free solder is very susceptible to the phenomenon.

[0] https://en.wikipedia.org/wiki/Whisker_(metallurgy)

Re: NASA's Through-Hole Workmanship Req (2002)

#57

Post by buescher »

lmilcin wrote: post #53
buescher wrote: post #22

The NASA handbooks are good. I like the one for rework that shows neatly staked wires. There are a couple of subtleties you could miss on this one though: 1) On page three, that exposed end of the lead is a defect if you're NOT going to conformally coat the board. If you don't know what a conformal coating is, it's a defect. 2) On page eleven, flux residue. Sure, for NASA's applications. For most commercial applicati…

I dislike no-clean. I like my boards pristine with nice, shining leaded solder and no residues.

That's fine, I like them that way too! But as a hobbyist, you risk leaving corrosive salts on the board or worse, sloshing them into electromechanical parts like switches, pots, unsealed relays, sounders, etc. Getting to "pristine" is harder than a lot of people think. There's a vicious cycle in production where assemblers will use too much flux, get flagged in an IPC-610 evaluation, try to clean the boards, and then get flagged for high ionic contamination in the next evaluation. You can't see the salts you leave behind from incomplete cleaning.

Beginners should not ever clean flux. Most hobbyists should never need to clean flux. Professionals should have data driving any decision to clean flux.

Re: NASA's Through-Hole Workmanship Req (2002)

#58

Post by lmilcin »

buescher wrote: post #57
lmilcin wrote: post #53

Earlier quoted context omitted.

I dislike no-clean. I like my boards pristine with nice, shining leaded solder and no residues.

That's fine, I like them that way too! But as a hobbyist, you risk leaving corrosive salts on the board or worse, sloshing them into electromechanical parts like switches, pots, unsealed relays, sounders, etc. Getting to "pristine" is harder than a lot of people think. There's a vicious cycle in production where assemblers will use too much flux, get flagged in an IPC-610 evaluation, try to clean the boards, and then…

Fortunately, I rarely risk anything if the board fails. And if it does I always try to understand what caused the failure.

I never considered flux compatibility between my solder rosin core and the flux paste and never considered measuring salt residues on the board.

I almost exclusively use the same Kester sn64pb37 rosin core solder and MG Chemicals #8342 RA rosin flux paste. Both must be cleaned promptly. Now, I don't bother cleaning if I don't intend to use the board after I test it (like when I do prototyping) but anything else gets a thorough wash. I use various PCB cleaners, typically ethanol (not IPA!) based and then rinse boards in electronic water. I never saw any oxidation on any of the traces unless there was some external contamination.

Re: NASA's Through-Hole Workmanship Req (2002)

#59

Post by inamberclad »

buescher wrote: post #23
inamberclad wrote: post #16

Earlier quoted context omitted.

Heat control. Cleanliness. High quality tools and solder.

Temperature control is so inexpensive these days you should not bother with heat control. Unless by heat control you mean the right size tip for the job, in which case we agree.

I meant in a more general sense, both temperature and heat flux.

Re: NASA's Through-Hole Workmanship Req (2002)

#60

Post by buescher »

inamberclad wrote: post #59
buescher wrote: post #23

Earlier quoted context omitted.

Temperature control is so inexpensive these days you should not bother with heat control. Unless by heat control you mean the right size tip for the job, in which case we agree.

I meant in a more general sense, both temperature and heat flux.

Not for you, but for those that might not get the point: the world of electronics assembly is really strange - it's like the whole past is present with us. It's 2021 and you can still buy a Weller soldering station with a knob for open-loop power (= heat) control for more than you'll pay for a cheapish station with closed-loop temperature control from any number of Chinese brands. (google "Hakko 936 clone"), Closed-loop temperature control is much superior to open-loop power control.
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