EcoModder.com

EcoModder.com (https://ecomodder.com/forum/)
-   Open ReVolt: open source DC motor controller (https://ecomodder.com/forum/open-revolt-open-source-dc-motor-controller.html)
-   -   How to build a reliable PCB (https://ecomodder.com/forum/showthread.php/how-build-reliable-pcb-12131.html)

MPaulHolmes 02-02-2010 01:47 PM

How to build a reliable PCB
 
This is going to be where Clyde, an industry expert, with many years of experience, is going to put his helpful suggestions on soldering, and general assembly of reliable pcbs. It's an important topic that is often ignored.

williamson 02-03-2010 11:44 AM

Topic: Solder: The US Military does not allow lead-free. The only reason we have lead-free is that old electronics fill the land-fill. Lead-free does not solder as well as lead. A special solder is used. If you are hand-soldering, try to not buy lead-free parts.

Topic: Solder iron: PCB's are made by gluing a sheet of 1 to 4 oz. copper sheet to an epoxy sheet. So your copper runs on your delivered PCB are glued on. Therfor you should use an iron temperature controlled at 700 deg. Don't hold the iron on the joint longer than needed, and don't PUSH sideways on the joint. Weller irons on ebay are the best, but for some reason they demand almost a "NEW" price! You can buy a "scope cheaper!

williamson 02-04-2010 11:35 AM

Topic: Soldering; The industry standard iron is Weller WTCPT.
Topic: Solder removal: There are two ways: 1. solder wick: this is a roll of small copper braid. This braid is laid down on the joint and the tip is applied on top. The heated bare copper melts the solder, and it wicks up the braid. After use, the coated braid is cut off and discarded. All military repair work demands this method. It is a huge pain in the butt. Frankly, I only use the second method.
2. A "Solderpullt". This is the industry stand brand. The problem with this tool is that when it triggers on the hot clad run, it can tear or dislodge the run. So I would call this the BAD-BOY approach. The only help I can offer is to not press the tip hard into the joint.

RobertSmalls 02-04-2010 06:12 PM

There's no arguing that lead-tin solder outperforms tin-antimony and other lead-free solders. But I use the lead free stuff despite the 20C higher melting point. Firstly, because it's readily avaiable. Secondly, because lead is harmful to humans and I don't want to be exposed to it while working on a circuit board. Thirdly, if you use lead, your project is destined to become hazardous waste, which is difficult to dispose of.

Leaded solders are illegal in the more civilized jurisdictions, including California and the EU.

Soldering is coming to be an important skill for all EcoModders, EV operators and otherwise. I'll be learning a bit more by trial and error, and hopefully from the tips here, as I'm assembling a PCB for my Honda.

williamson 02-05-2010 03:36 PM

Mr. Smalls is absolutely right. We have 100 years of technicians soldering, and I've never heard of one getting lead poisoning. One should wash your hands after handling lead solder. Each person viewing this site will have to decide his own priorities, when it comes to lead-free. Lead-free is the future. First, we only make one PCB. Any production of more than a few boards should be lead-free. This site is called "a reliable". As stated earlier, the military doesn't allow it because of "wetting". So if you are inexperienced in soldering, you should take into account that lead-free may not "wet" as well. To put this topic to bed, you've heard both sides, and I say, try to do lead-free, if you can.
Topic: "Wetting": In production, parts are sealed in air-tight bags, with a production date sealed in the bag, so it can't be changed. Product is opened and soldered the same day, because old parts develope an oxide coating, that impairs Wetting. We buy left-over parts, that could have spent years on the shelf. So if the component leads look dull, you could clean them just before soldering.

williamson 02-06-2010 03:31 PM

Topic: Electrolytic caps: Never buy 'lytics from a manufacturer whose name starts with an "X". Almost all Chinese company names start with "X". The parts are cheaper. Buy only Japanese, such as Nichicon, or Panasonic. Or any Japanese co. Try to buy 105 degree parts. 'lytics fail by drying out. Therefor higher temp parts last longer, and quality sealed parts, ditto. Ten or twenty years ago, people were cleaning PCB's with fluerines. They leaked past the wire leeds on "lytics and quickly destroyed the cap. So epoxy end seals were invented. They work, but usually cost a penny more. If you look under your caps and you see black epoxy, instead of rubber, you know why. Chinese resistors start with "X" but they are fine, and now may be your only source!

williamson 02-06-2010 03:38 PM

Topic: board cleaning: When I worked in electronics, I asked an engineer at Kester Solder about board cleaning. He said there was no reason to clean a board of ordinary flux, except for good looks. He said Heathkit and Knight kits were around for years with no cleaning. There have been "No clean" fluxes. They stay on the board and "work" because they are meant to be transparent. Unless you overheat them with an iron. THEN they turn black and very hard to remove. If you choose to go the better route of "lead-free", ask the solder manufacturer if the board must be cleaned.

williamson 02-07-2010 05:22 PM

Topic: resistor reliability: small, leaded resistors are a ceramic tube with crimped-on end caps. The carbon coating is then applied. The only failure mode for this construction (the only choice) is to apply a bending force to the end caps. You can buy a bending tool. This tool is a tapered plastic strip, about 5 inches long, with descending widths, to put your part on, and then bend the leads down. If you bend too close to the body, you will loosen the end caps. If your PCB is laid out with minimum leed spacing, you can get into trouble. I don't think anyone can bend a leed with this tool and not tug on the end caps. The SAFEST method is to specify the leed spacing which allows you to use a pair of small needle nose pliers, to hold the leed close the the body, and bend the FREE end.

williamson 02-08-2010 12:43 PM

Topic:Parts sources; Mouser seems the best first try. Lower prices than "D". also, odd stuff from "All Electronics", Jameco", and "Futurlec". On that last one, make sure you go to the USA one. My son has a chemical engineering degree from Johns-Hopkins, and he is the VP- Sales for a PCB company. He said that hand-soldering lead-free is 100 times harder than lead-tin. One problem is that if you buy a lead-free PCB that has all the surface-mount parts already mounted, and the PCB is lead-free, then you have to add the remaining thru-hole parts by hand. Then you have to pay attention to "Wetting". Forwarned is forarmed!

williamson 02-09-2010 02:43 PM

Topic: heat-shrink tubing: If you strip the insulation from a wire, and then solder the end, and the wire can move, such as being within a car, the wire will only move at its weakest point. This is the tiny section of wire which has been striped of insulation. Therefor, when soldering a wire, slip a short piece (read one-half inch) of heat-shink tubing over the wire and down over the terminal. You can shrink the tubing with your iron. In industry, the tubing is shrunk by a heat gun (read:blow-dryer). The tubing is sold by as supplied inside diameter. It comes in many chemistries. For our work, the cheapest chemistry is best. That's usually Polyolifin.The most typical diameter is 1/8 inch. You can solder two wires together "in mid air" by sleeving the joint.

williamson 02-09-2010 03:02 PM

Since I cannot recommend lead-free soldering for hand-soldering, I wanted to post that I support "green". I put less than 2000 miles a year on my ICE car, and I am building an electric car.

williamson 02-12-2010 11:18 AM

Topic: Lead free soldering iron:The new Weller model WESD51 is rated for esd protection. Lead-free requires that the soldering iron be adjusted for 20 deg. C hotter than for lead. This requires an iron with a potentiometer and a digital readout. The most popular of these irons were the EC2001M and 2002.
Topic: heat damage: It is possible to damage an led by lingering with the iron, while soldering very close to the body. The safe way is to hold a pair of needle-nose on the leads, up against the body. This requires a helper, unless you have 3 hands.

williamson 02-16-2010 04:35 PM

Topic: learn to solder: Electronic Kits offers a kit called "learn to solder" kit # AK-100, $19.95. soldering will be discussed here, but it is only one part of the required knowledge you want.
Topic: Static electricity: Integrated circuits (dead bugs) especially CMOS IC's, are susceptable to static elecricity. This may not come as news to you. CMOS IC's are identified by part #'s starting with "MC14xxxB" or "CD4xxxB", or similar. But there is a safer path: parts suppliers ship their parts in static-safe bags. Therefor, keep all parts in the bag they come in. DON'T open the bags. Only open the bag the minute before you will install that part. The second reason is that moisture in the air, or oxygen, cause a very slow corrosion of part leads. Therefor keep the bags sealed as shipped. When you remove partial contents, reseal the bag--as best as is easy. Static-free bags are identified by the slight tint or color-any color. Keep some of these bags. You will want to place any PCB with ANY parts on it, into one of these bags, between work sessions, or when the board is built-that is, up to the minute the board is installed!

jfitzpat 02-16-2010 07:20 PM

Quote:

Originally Posted by williamson (Post 159312)
Mr. Smalls is absolutely right. We have 100 years of technicians soldering, and I've never heard of one getting lead poisoning.

I'm sorry, but that doesn't sound like the sort of argument an engineer makes. Perhaps you are speaking from the point of view of a manufacturing technician?

The primary problem with leaded solders is measurable, direct risk to workers in manufacturing, not secondary risk from waste. That latter exists, but exists with many, many compounds, which is why waste management engineering has to take other steps to prevent exposure and contamination of groundwater, etc.

The danger to workers is measurable, and still of concern in exempted areas of aerospace and the military (ex. see the recent UC Davis study and the work of the JG-PP (see below)). That is, folks working with leaded solder are at statistically higher risks for lead related health problems.

In design engineering, we look at larger statistical samples. That is, making one run on the bench is not the same thing as predicting reliability of 1,000,000 in the field. Also, you are required to account for spectral factors. Severe heavy metal poisoning results in some very obvious symptoms, incoherence, impaired memory, neuromuscular problems, etc. But smaller doses often result in statistical correlation to more subtle problems, or serious problems over a much longer period of time.

This form of statistical-universe-of-one-as-'obvious' argument is a very human reaction. I'm tempted to go over a photo someone sent me recently of a book in a snowdrift, but that is too politically charged, so let's take alum. Aluminum salts are the most common metallic element on earth - the third most common element in the earth's crust overall, so there is no particular reason to suppose that we are not exceedingly well adjusted to it. But alum toxicity, as well as causal relationships to serious long term ailments like alzheimer's disease are quite real. In fact, we add small amounts of alum to some vaccines to trigger a severe immune system response in the human body.

But how should we react to this knowledge? Humans are, instinctively, highly reactionary and subjective creatures. So, the most two common reactions are: 1) panic and be terrified of alum. cookware and products like deodorants (both of which the FDA has deemed to generally safe) or 2) interpret the singular absence of immediate and obvious harm as a definitive proof of 'safe' (ex. "Well I eat Jiffy Pop and I don't become incontinent and yell at clouds, so it must be a load of hooey...") Either way, the instinctive, or emotional reaction has no logical relationship to objective risk assessment and management.

Quote:

Originally Posted by williamson (Post 159312)
Each person viewing this site will have to decide his own priorities, when it comes to lead-free.

If they live here in CA with me, I sincerely hope not. I don't get to pour mercury or MTBE down my ground drain and I don't have to look much beyond the crowd at the airport or current primetime TV to make the case that vast numbers of my fellow citizens are not properly equipped to make intelligent decisions about public heath and environmental toxicology on an individual basis.

Quote:

Originally Posted by williamson (Post 159312)
This site is called "a reliable". As stated earlier, the military doesn't allow it because of "wetting". So if you are inexperienced in soldering, you should take into account that lead-free may not "wet" as well.

The DoD and NASA both participate in something called JG-PP, the Joint Group from Pollution Prevention. JG-PP and JPL both have done studies on the implications of lead free versus leaded solder. There is also a report from the JC-AA (Joint Council on Aging Aircraft), but that is really just a summary of the JG-PP '06 and '07 study reports.

The super short summary is that solder joint reliability turns out to be a lot more complicated than leaded vs. unleaded solder. Lead free compounds appear to be just as reliable in many applications. In those that the joints fail, it isn't generally a deficiency in the solder compound so much as a systemic (design or total material) or a manufacturing problem (remember, it is generally unleaded solder being directly substituted into existing designs and manufacturing processes).

The JPL study is interesting in that it didn't just look at subsystem reliability, but failure based on application technology. Hand soldering had the smallest discernible difference in reliability (essentially zero in industrial temperature range applications). On the flip side, hand soldering represents the highest exposure and statistical risk to the workers.

So, with no disrespect to your personal experience, I can't find any evidence from the military and aerospace studies to support the idea that hand soldered lead free boards are not reliable in consumer automotive applications.

Remember, the military definition of 'reliable' and the common understanding are two different things. A brand new commercial airliner is not reliable enough for military applications, even though it uses lighter and stronger alloys than a mil spec aircraft. The modern nav system in the plane I most often fly is lead free, as are the ECUs and brake module in my daughter's car, and I'll never lose a moments sleep about either.

Consumer electronics are highly sensitive to changes in reliability. Because of the margins, a warrantee repair is catastrophic to the bottom line. Following the work and articles on statistical quality control, consumer manufacturers have, by and large, found the move to lead free fairly smooth.

Automotive applications have some other challenges, but I'd readily bet good money that, say, Toyota's current woes have everything to do with designs and firmware, and nothing to do with the type of solder.

-jjf

MPaulHolmes 02-16-2010 09:10 PM

I tried lead free solder once, and I thought it was a little harder. I knew almost nothing about soldering at the time, though. I think williamson is just saying that if someone is going to make a little control board for this motor controller (one time solder thing), it might be a little easier to use lead solder instead of lead free, and the one time use of lead solder will almost certainly not have any negative health consequences. At least that's how I'm thinking about it.

Lots of people that have ordered the control board from me have had no soldering experience whatsoever, and have no interest in continuing to solder after the controller is done. They just want to get their car on the road without paying $2000 for a freeway capable controller.

However, I'm going to go out and get some lead free solder and give it another try. I don't want to do any behavior that causes a statistical increase in health problems over the long term.

williamson 02-17-2010 03:35 PM

jfitzpat raises important points that we should address. People should get some leadfree solder, and try it for themselves. Maybe someone with lead-free solder, (that they no longer need) could drop about 12 inches in an envelope to any one requesting some. A roll is about $30.00 Secondly, as I think I mentioned, we should never discard a lead-soldered PCB- or any electronics, in any way except approved re-cycling for lead-soldered products. So, if you decide on lead solder, you commit to responsible re-cycling.

jfitzpat 02-17-2010 05:30 PM

Quote:

Originally Posted by williamson (Post 161538)
jfitzpat raises important points that we should address. People should get some leadfree solder, and try it for themselves. Maybe someone with lead-free solder, (that they no longer need) could drop about 12 inches in an envelope to any one requesting some. A roll is about $30.00 Secondly, as I think I mentioned, we should never discard a lead-soldered PCB- or any electronics, in any way except approved re-cycling for lead-soldered products. So, if you decide on lead solder, you commit to responsible re-cycling.

When lead poisoning used to be called "plumber's cough" and "plumbism", your 100 years of leaded solder quip seemed clueless. But this new tact is just silly.

1.2 oz of .032" diameter SAC305 solder (with a 'no clean' flux core) is about $4.50 at Radio Shack. Probably less from Digikey. If the handy little plastic dispenser isn't enough, a .25 lb. roll is $12-$14.

Compliance in CA has been since '07, so most of us engineering types here have been using lead free to hand solder surface mount parts for 3.5-4 years. The bottom line? It is all about a more heat and getting used to it. SAC305 (which I'd recommend for the casual electrical connections) melts at ~217C. SN100 (which you'll see in some manufacturing) melts at ~228C. A 63/37 tin/lead alloy melts at ~183C.

As a practical matter it means that you need to a) be more careful about picking solder diameter b) you need to be more careful about keeping your tip clean and properly 'tinned' and c) you want to be careful about mixing and matching.

That is, 'this tub of flux I've always used' may not be high temp and may turn black at the higher temps involved. Also, the alloys don't flow well on each other. That part is of note because lead free parts, which are becoming the norm, are harder to solder reliably with leaded solder than with the lead free alloys they are designed for.

We could pretend that we are planning an arctic expedition by dogsled, or face the reality that one of the largest densities of electrical hand solders in the country went through this, largely without pain, years ago. Clean and re-tin your tip (or, if you are lazy, buy a new tip), practice a few joints, and get on with your life.

-jjf

williamson 02-17-2010 05:41 PM

jfitzpat is right: there are smaller quantities of solder available, and I should have mentioned them. Because of the higher temperature he points out, you can see that you really need the temperature controlled iron I recommended for lead-free work.

jfitzpat 02-17-2010 06:06 PM

Quote:

Originally Posted by williamson (Post 161553)
jBecause of the higher temperature he points out, you can see that you really need the temperature controlled iron I recommended for lead-free work.

I have the same Weller WP25 in my field kit that has been bouncing in there for years. The tip is 750 degF, which comes out to about 400 degC. Again, it is about being a bit more clean and precise and smart about heat management.

If this one takes a walk and I run out again (which is how this one got in my kit), I'd probably pick up the WP35, which is 100 degF (about 50 degC) hotter. Not so much because of lead free, but because I inevitably end up soldering heavier wires together, not just board work, and the WP25 is underpowered for doing that quickly regardless of the solder.

For bench board work, you want an adjustable iron regardless, really two - for even basic repairs. It's now a surface mount world.

-jjf

MPaulHolmes 02-17-2010 07:16 PM

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).

jfitzpat 02-17-2010 07:55 PM

Quote:

Originally Posted by MPaulHolmes (Post 161565)
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 02-17-2010 08:51 PM

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 02-17-2010 09:34 PM

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 02-17-2010 11:12 PM

Quote:

Originally Posted by Tweety (Post 161612)
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 02-17-2010 11:48 PM

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 02-18-2010 04:02 AM

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 02-18-2010 02:58 PM

Quote:

Originally Posted by jfitzpat (Post 161641)
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 02-18-2010 04:22 PM

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 02-18-2010 05:21 PM

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 02-19-2010 10:42 AM

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.

williamson 02-19-2010 10:57 AM

Topic: component spec's: This is a touchy area. If you buy a kit, the components are included. No problem. If you buy a PCB and a parts list, the exact part #'s should be purchased. Substitutions should not be made, except with the approval of the designer. After all, this site is "reliable". Resistors have a spec of "cl-cl"(clean lead to clean lead). They are conformal coated. The coating goes down the leads. This spec guarantees that you can solder this close to the body. The same is true of dipped film capacitors. BTW, dipped capacitors are the best buy for reliability vs. price. But they are not capable of high currents, as in a controller or P. supply ( in a high current location). There, Polypropylene caps are specified. This is true of electrolytics, also. Only some are rated for high ripple current. Potentiometers deserve special mention. Some are specified as being "sealed." But the fine print takes away what the header gives. They are sealed only for certain solvents, and for certain immersion times. Sealed pots usually cost more.

williamson 02-20-2010 02:00 PM

Tweety posted that I am wrong on a few issues. I can't see how we can let my posting be in error and not correct it because this site is supposed to teach. Facts are facts. They are right or wrong. Opinions are shades of gray. To those, we are all entitled. Can tweety please post any facts where I am wrong, so I can correct my error? I found an inconsequential error: I wrote :Florene". This is a gas. I meant Floride, as in Carbon-tetra-floride, a solvent. Tweety: thanks for your help. Kindest regards to all.

williamson 02-20-2010 02:14 PM

Topic: Newbie solderers vs skilled. Newbie solderers (NBS) don't know what wetting is, or, they cannot identify it as quickly as a highly experienced solderer (ES). A decision to remove the heat is made in an instant. One not sure keeps the heat on, to be sure. Poor wetting causes a weak joint that may crack under stress. Even NBS can guess at that. Well, if the PCB sits in a stereo cabinet, all well and good. Let him solder unreliably. The car doesn't crash. But if the PCB receives constant jarring, as being in a very light-weight electric car, a crack is more likely, and could result in who-knows-what output from the controller. (I'm selling fear)! So a skilled solderer can start using lead-free without any problems, or fear. To him I say: Absolutely go lead-free, since you know what your doing (looking for wetting)!

williamson 02-20-2010 02:29 PM

Topic: Wetting:I assume my audience is building a controller. I just ordered a controller kit from Paul. 'Nuff said. I also assume that you have no or little experience in soldering, or, you don't want a BIG head-ache! There are other problems in soldering, but I don't want to scare you. A common problem is solder bridges, where you use too much solder because you really need more flux to be sure of wetting. This problem is greatly diminished by using a solder masked PCB, which are almost universal today. So it is likely you have automechanic experience, and that's why you're building an electric car. If you have welding experience, then you'll be happy to learn you already know Wetting! The puddle must melt into both surfaces to bond with them. Jfitzpat has accurately described how the iron is put on the joint, heated and then the solder flows in. You have to have the heat flow to both sides of the joint to cause LIQUID SOLDER to be in contact with all surfaces. These surfaces, that is, the PCB and the component lead have a coating that melts. This is those parts doing their job. Now you just add melted solder to fill in the gaps. BUT not stick up. It's a fillet weld! I think someone should be able to get useless PCB's to practice on. Maybe Paul, on request can ship NG PCB's. If I'm not speaking out of turn. The postage is a fair price.

williamson 02-21-2010 04:40 PM

"Watch out for that open manhole cover!" "I didn't see that, thanks". This topic is how to reliably solder with lead-free solder. Don't take it as negative, if I point out the pitfalls. What can I do to make a reliable PCB? Well, the only positive step, is to learn to solder. Can you learn that here by reading? If you stick-weld, you know reading doesn't make you a welder. It's an art. A skill. You have to learn a skill. If I told you how to solder, and you thought you were a skilled solderer, I would be doing you harm. you"re free to buy the kit a posted. I don't know the first thing about the kit, but I have faith. You can get scap PCB's and practice, and if you want, you can mail me your efforts and I will call you back with any comments. It's safer to take the long route, than jump right in and solder Pauls kit. This isn't negative about being a first-time solderer. I recommend you learn, and then jump in with confidence! Now, the pitfalls to watch out for in lead-free soldering: When you are a Newbie, you might keep the iron on the joint longer than an old-timer, looking for wetting. Learn wetting on a junk PCB. Semiconductors don't like a lot of heat. The diode MBR60l45CTG, which is typical, says "lead temperature for soldering purposes: 260 C for 10 seconds. The typical iron temp. for lead solder is 700 F. The typical temp. for lead-free is 750 F. which is 400 C. Jfitzpat mentioned that the Radio Shack lead-free solder has no-clean flux. This flux is a slight compromise on performance, at the expense of being "invisible" Actually, it is only transparent! BUT, my experience has been that if you heat it too much (and SUPPOSED to know what I'M doing!) it turns very dark brown, and nearly insoluble in anything short of AQUA REGIA! (just kidding) I recommend rosin flux, and don't clean.

williamson 02-21-2010 05:25 PM

I find a typo in the above post; You're free to buy the kit (how to solder) that I posted earlier.

williamson 02-22-2010 04:17 PM

Topic: Lead-free works! In industry, there are very tightly controlled proceedures to be followed, such as the applicable section of ISO-9000 #1 Volume production on a surface mount production line using specifically designed equipment #2 The process is monitored by Production Engineers. #3 New parts are used with no oxidation of the solder surfaces. #4 The Quality Control Dept. checks the PCB's The result is that all the electronics in the world are made with lead-free solder-except our military. But, I wouldn't be surprised that when the risks are reduced to lead solder levels, that will change! Hopefully soon.

williamson 02-24-2010 11:42 AM

The post by Paul on 2-18 about the military experience with lead-free, should be read by all. But the post aludes to an excellent compromise FOR US! the author said that adding 3% lead made good soldering. A second thing that might make inhibit the tin wiskers might be comformal coating.

Topic: conformal coating. This is a spray-on from an aerosol can (freon-free). All you do is bake the finished pcb board at about 180 degrees for 24 hours, to drive out the moisture-and any volatile compounds. There is (I was reliably told) moisture within the PCB that takes a while to leave. I'll check this out. Military electronics are coated. Commercial electronics must be coated when they are used near a body of salt-water. Only the thinnest coating you can spray on, is sufficient. In a car, you have dirty air and road salt. I would call it an absolute necessity to coat all pcb's in an electric car!!

dcb 02-24-2010 01:36 PM

re: leadfree, the biggest hurdle for the hobbyist in my opinion is just getting it in hobby sized quantities. The minimum order is like $40.

I did get my hands on a small sample of glowcore after numerous emails to the manufacturer, and it seemed to work ok w just a regular iron, but it definitely takes some getting used to.

williamson 02-25-2010 11:24 AM

There is an excellent site that teaches: electronicprojectdesign. The topics are, among many,:"Soldering tips","soldering techniques", "conformal coating" They mention curing time, but we would read the can. Some coatings cure at room temp. They also say to bake hotter and shorter, but WE are in no hurry.


All times are GMT -4. The time now is 08:23 PM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com