How to build a reliable PCB

[jfitzpat]

Originally Posted by MPaulHolmes

Maybe there should be 2 threads: One for people that solder for a living, and this one, which is basically in the open source dc motor controller forum because it's here to help people reliably solder a single thru-hole control board for this motor controller. I know that "How to build a reliable PCB" sounds pretty broad, but it's intended scope really wasn't meant to be the final say on industry solder policy. There have been a couple problems with solder not sticking on this control board, or use of too much solder, crossing the isolation rings, from people that have never soldered in their life (and many happen to live in one of the 49 states where lead solder is allowed).

If you aren't a proficient at the basic skill, leaded vs. unleaded solder is the least of your worries. Or, put it another way, I've been seeing bad solder joints from DIY's for 30+ years. Look at a trouble shooting guide from a 40 year old "Heath Kit" radio, it will list exactly the same problems you describe, decades before anyone even contemplated lead free solder.

On the other hand, if you become proficient at the basic skill, the transition to lead free is a non issue. That's not just opinion, look at companies that sell DIY kits in CA. Initially, there was annecdotal reports that lead free was creating more problems, but when JPL looked at actual customer support data it became clear that it made no difference in measurable results. That is, the CA DIY crowd made bad solder joints at exactly the same rate as before.

Ignoring all those DIY people out of 40 million folks driving one of the largest economies in the world who made the transition with essentially the same 'chaos' as 'y2k' - it matters to the other 49 because we are a global economy. Manufacturers aren't continuing most leaded parts. Look at Digikey. You go to build your small project, and you wind up with lots of lead free components. Suprise surprise, leaded solder doesn't flow well over the tinning on those leads. The parts are made to be soldered with lead free alloys...

Bottom line, I just don't like disinformation. Blanket statement that lead free = unreliable. Uh, no, that doesn't match actual testing and perhaps more to the point, the mission critical components in a new car are largely lead free now.

Worse (to me) '100 years of no problem use'. Try checking WebMD, or even Wikipedia. Before it was understood it was lead, terrible maladies were named for the *professions* that used leaded paints and solders!

The CDC puts a maximum level on lead, but we have no known safe level. That is, every time we lower the limit, further research shows that it is a seriously dangerous neurotoxin. Also, different people have different reactions, even genetically - see the UC Davis MIND Institute's latest studies.

This whole conversation reminds me of the same complaints and excuses I always hear any time anyone suggests a common sense transition for the sake of the environment. I just didn't expect it on a site dedicated to fuel economy. Sure, one way to get better fuel economy is to say to hell with the air and water. I just didn't get the sense that is the sort of folks generally here.

-jjf

[MPaulHolmes]

Some poor guy who has never soldered in his life, making this control board because he wants to cut his vehicle emissions, uses some solder that he buys from Radio Shack. He wants to know good technique so that the solder sticks well, and so that he doesn't use too much, and so that he doesn't overheat his components, and etc.... He's not saying that he cares nothing for the water and air because of the makeup of the solder that he buys at the store for his little project. I went to Radio Shack yesterday, and they only had 60/40 solder with the lead in it. I'll probably end up ordering it on Ebay.

I also went fishing last week with lead weights. I even lost one of the sinkers! hehe. Heck, I even bit it down on it to close it around the fishing line. That probably wasn't a good idea.

This thread is called "building a reliable PCB". Williamson has been in the industry for a long time, and I am interested in his opinions about technique for building a reliable PCB. I want people to reliably solder my control board. Would it be good if the pcbs that was used in the making of their car contains no lead? sure! And the tires are low rolling resistance? yes! and the new car smell doesn't make them sick? ya! um... their brake pads not use asbestos? definitely! I'm serious abouit that last one. I have an old super beetle, and it had bad brakes, and I wasn't thrilled about messing with the asbestos.

I understand that you don't like misinformation, but I doubt Clyde was lying about his experience. Let's keep our tone a little more civil. "that doesn't sound like an engineer, more like a technician." or whatever. Spicy meatball!

OK, lead free is the way to go! Let's talk about technique for making a reliable pcb. ya!

[Tweety]

It will never, ever be as black & white as you make it out jfitzpat... You are dead wrong on numerous counts... That's a fact... Not open for dicussion... Swallow it and move on...

Yeah, leadfree is the way forward... But nope, it simply not true that it's as easy to solder... It's as easy once you have mastered it... yeah, true... But then again, that applies to just about anything right?!

The simple truth is that lead free solder requires a higher temperature, and physics say if a component can take a fixed amount of heat before breaking, the time you can apply heat is shortened when you increase the temperature...

If you apply a higher temperature to a local spot on a PCB you get higher levels of expansion on the copper layer vs the substrate, making it easier to separate them... Same applies for the legs on a component vs the silicate body...

And no... The manufacturers didn't really change their component in terms of heat tolerances... But they did change their tinning like you said...

You want me to go on?!

Face fact... Life is a gray area... And responding to "disinformation" with more of the same is just as bad...

But I wholeheartedly agree that you should use leadfree solder... Even with it's downsides... Now stop throwing stones in glass houses and carry on...

[jfitzpat]

Originally Posted by Tweety

It will never, ever be as black & white as you make it out jfitzpat... You are dead wrong on numerous counts... That's a fact... Not open for dicussion... Swallow it and move on...

In case you are actually interested in physics, as opposed to simply trying to make an emotional appeal, you need to look at the thermodynamics more closely.

The irons did not really get any hotter, nor did assembly times. What happened was that folks generally use thinner solder and cleaner tips. Component stress is largely dependant on contact time.

If the contact time is unchanged, then there is no significant change in thermal stress to the part proper. Also, the melting point isn't the only property that is different in the alloys. They don't thermally conduct as well. So heat doesn't travel up the pin as well.

We don't have to speculate, we can look at reality. Products built for international sale are already largely lead free. In statistical quality control, we are not seeing upticks in component failure.

As for the "Poor" guy:

The reality is that the 'poor' guy has been buying lead free in CA for years, and we have no evidence that he is less proficient at assembly than any other state's consumers. Further, since CA is a big market, kitting often includes lead free solder in products sold nationally.

Now, we could make the hypothesis that Californians are simply smarter and more deft than the rest the nation, but one look at our state government would pretty much disprove it. And, of course, non CA consumers are using those same little packets of lead free solder.

And, in terms of civility:

Interesting that MY remark seems unsuitable, but the one it is in response to is not. For what it is worth, one modern reality is that realllllly cheap labor is used in electronic assembly. Generally, we are talking children and young women. The two groups most at risk from heavy metal poisoning.

I have had first hand experience with such groups, and seen their blood work and developmental test scores. Anyone who makes light of that form of modern child abuse (and heavy metal poisoning from manufacturing is still rampant in workers in several parts of the world), or who makes light of the horrific suffering that these lead products have put on workers for most of the industrial age, is not going to get my polite response. Once you've watched those children cough and spasm, it's really personal.

Similarly, I will not find the argument 'But I would have to practice for an hour and actually learn how to solder!' very compelling. I recently taught a group of 7th and 8th graders all how to solder for a workshop on, oddly enough, physics (we built a fairly interesting experiment using air cooled yag lasers). We're in CA, and they all mastered it in about an hour. If we'd had leaded solder, the only difference would have been that they would have made their first, bad, solder joints faster.

I'll give you all the last words...

-jjf

[MPaulHolmes]

My last word is that I'm going to try to learn lead free soldering, and I'm sorry for being sort of snotty with my comments.

[MPaulHolmes]

I was just reading an article on Tin Whiskers developing with non-lead solders. The military evidently is concerned about the reliability of non-lead solders:
Lead-free solder: A train wreck in the making - Military & Aerospace Electronics

This was a Military & Aerospace Electronics article from 2005. Have they improved the lead free solders since then? That makes me feel a little concerned. I don't want any tin whiskers developing under a very high power environment.

[Tweety]

Originally Posted by jfitzpat

In case you are actually interested in physics, as opposed to simply trying to make an emotional appeal, you need to look at the thermodynamics more closely.

The irons did not really get any hotter, nor did assembly times. What happened was that folks generally use thinner solder and cleaner tips. Component stress is largely dependant on contact time.

If the contact time is unchanged, then there is no significant change in thermal stress to the part proper. Also, the melting point isn't the only property that is different in the alloys. They don't thermally conduct as well. So heat doesn't travel up the pin as well.

We don't have to speculate, we can look at reality. Products built for international sale are already largely lead free. In statistical quality control, we are not seeing upticks in component failure.

As for the "Poor" guy:

The reality is that the 'poor' guy has been buying lead free in CA for years, and we have no evidence that he is less proficient at assembly than any other state's consumers. Further, since CA is a big market, kitting often includes lead free solder in products sold nationally.

Now, we could make the hypothesis that Californians are simply smarter and more deft than the rest the nation, but one look at our state government would pretty much disprove it. And, of course, non CA consumers are using those same little packets of lead free solder.

And, in terms of civility:

Interesting that MY remark seems unsuitable, but the one it is in response to is not. For what it is worth, one modern reality is that realllllly cheap labor is used in electronic assembly. Generally, we are talking children and young women. The two groups most at risk from heavy metal poisoning.

I have had first hand experience with such groups, and seen their blood work and developmental test scores. Anyone who makes light of that form of modern child abuse (and heavy metal poisoning from manufacturing is still rampant in workers in several parts of the world), or who makes light of the horrific suffering that these lead products have put on workers for most of the industrial age, is not going to get my polite response. Once you've watched those children cough and spasm, it's really personal.

Similarly, I will not find the argument 'But I would have to practice for an hour and actually learn how to solder!' very compelling. I recently taught a group of 7th and 8th graders all how to solder for a workshop on, oddly enough, physics (we built a fairly interesting experiment using air cooled yag lasers). We're in CA, and they all mastered it in about an hour. If we'd had leaded solder, the only difference would have been that they would have made their first, bad, solder joints faster.

I'll give you all the last words...

-jjf

Just FYI... I also work with this... And since I'm in Sweden, we have been using lead free even before Ca... And I know probably as much as you about the physics behind...

And yes, the guys making dodgy solder work was promptly forced to do things the way they where supposed to all along by necessity... Clean the tip, use the appropriorate tip size and shape for what they where soldering, as well as the appropriorate sized solder and fluss (unfortunately the english name escapes me at the moment...)

But yeah, I have looked at the physics behind it... Applies to when soldering correctly before and after, using SMD components in 0603/0402 sizes... (that's 0201 and 01005 for the metric challenged) And yes, I'm talking about hand soldering...

The statements above as for pad lift and heat damaged components is still valid... If you want to confirm or rebuke it, go ahead, present your numbers... I have a few of my own I can dig up...

[williamson]

This site is "How to make a reliable PCB", not how to solder! jfitzpat should open a thread on "How to solder" instead of highjacking this thread. Let him put his skill where his mouth is. He disagrees with any one who doesn't share his sacred cow. What happened to free speech? And, dissemination of knowledge? People can make up their own minds. Jfitzpat, are you making or driving an electric car?? I can send anyone a dvd of my car under construction. How many miles do you drive a year in a gas car? As to the engineer crack, I have an engineering degree from a presigious engineering college (at least for enginnering) (Manhattan College) because it is a BEE degree, not a BSEE. A BEE is more specialized in engineering. I've been soldering for 60 years. I held the level of Director at CBS Laboratories, and Vice-president of engineering at a div. of Hitachi. I started a company with a partner, and we sold it for 24.3 million dollars. THERE IS AN OLD EXPRESSION; 'THOSE THAT CAN, DO, THOSE THAT CAN'T, TEACH, AND THOSE WHO CANT TEACH, TEACH TEACHERS" I think you posted to feed your own ego, for instance, "when I fly my plane"

[Tweety]

Oi... williamson... I said above that this wasn't BLACK OR WHITE... It implies that you are also in the wrong on a few issues...

I agree with jfitzpat that leadfree is the way forward... I agree with you that leadfree introduces complications... And I think both of you are getting of track...

We aren't comparing degrees... (I have some as well...) we are trying to get people to make reliable PCB's... You are both sitting in glass houses and throwing rocks... Put down the rocks and break out your soldering irons...

[williamson]

Tweety: You are right. I posted two replies to jfitzpat's first two posts that agreed with his major points. But his Technician post was too much. Even Paul commented on it. He started offwith the first insult. I made none (insults) until the last. I don't intend to make any future ones. Kindest regards to all.