60/40 vs. 63/37 Solder

I'm not an expert on the physics of materials, but this flies in the face of what I think I understand.

How can a eutectic mixture ever be "close to" the liquid stage? To paraphrase Yoda -- "It either is, or is not."

You might not consciously not be telling the truth, but that doesn't mean what you say is correct.

The difference in price is not just "a few dollars extra per ton". A significantly higher price is almost certainly the explanation.

When I was a kid and assembled kits, the instructions always warned that the connection /had/ to be mechanically strong before it was soldered. (I remember the Knight-Kit photographs very well.) This isn't true in practice -- as I commented in a recent posting, J Gordon Holt fought against it -- but it virtually guaranteed that the wires wouldn't move during the soldering process. If the solderer heated the joint sufficiently, a cold joint was essentially impossible, eutectic solder or not.

This didn't keep customers from making bad joints, or altogether missing joints to be soldered. These, I believe, were the principal causes of non-working kits. Eutectic solder would have helped only a little (ie, there's a limit to how much you can prevent human error).

About a year ago I had to replace a high-current driver in an electronic crossover. The device was a five-pin TO-style product. Removing the PC board to unsolder it would have required removing all the input and output jacks. (Yes!) So I had to clip the device's pins near the body, unsolder and pull out the pin stubs, then suck out any remaining solder. I was grateful I had eutectic solder, because it made it easy to re-fill the holes and suck them clean, then solder in the new chip with virtual certainty the connection would be good. (It was.)

Confession time... One basic rule of soldering is "Get the joint hot enough to melt the solder. Do not melt the solder directly with the iron." I've been ignoring that for nearly half a century, and have never had a bad joint.

According to the Kester Website...

"Sn60 has a plastic range and puts down a slightly thicker coating of solder. Sn60 is often preferred for lead tinning and other solder coating applications. Sn63 is eutectic and as such has no plastic range. Generally it flows better than Sn60 and is the preferred alloy for wave soldering and surface mount applications."

This isn't a complete answer -- I assume the cheaper 60/40 makes sense when coating, because no joint is involved. However, "flows better" seems to be a desirable characteristic when soldering joints.

I'm willing to be proved wrong about anything. I'd like to see a document -- preferably from a solder manufacturer -- that explains why 60/40 is less likely to produce a cracked joint than 63/37.

sounds like bullshit, alpha particles aren't energetic enough to get even 1/10 of the way through the encapsulation on a RAM chip.

fraction of the

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Correct. The original writer was probably confused by the fact that the materials ceramic ICs are made of can contain radioactive materials that can cause errors.

Happened in plastic too. Intel once helped the problem along by using Kr instead of Ar, IIRC, in a hermaticity test.

Battleship steel has a lot of uses, too, since it was forged before the first atmospheric tests.

William, Parts Express sells to hobbyists. Their prices are meaningless as a reference. I buy solder, as I have for 25 years, from industrial suppliers. Since you didn't state either the diameter or the core, (and diameter can make a huge difference in price) I looked up your comparison rolls on Parts Express. I see you referred to Kester 44 with a 66 core and at .031 diameter.

To compare apples to apples, I called my supplier yesterday for current pricing: 63/37, $13.80/lb. 60/40, $13.30/lb. I also asked how many people were buying 60/40, and she confirmed that well over 90% of customers use 63/37.

1. You're paying nosebleed prices whichever formula you buy.
2. The cost difference is indeed pennies when purchased from real supply houses
3. Regardless of the cost difference, 63/37 *is* the standard now, as it has been for 20 years.
4. Based on #3 above, your assertion that companies will cut corners anyway they can is false.
5. Therefore, my contention that the widespread switch was made due to improved performance of 63/37 seems to be the only logical conclusion.

Now, you said that 63/37 eutectic nature was known 50 years ago. That may or may not be true, but what is true is that the widespread industrial changeover happened much more recently, about 20 years ago.

Here I'm going to agree with William and others that you're mistaken. Eutectic means that the transition from liquid to solid occurs at the same temperature as the transition from solid to liquid. By definition, the joint *cannot* move with a eutectic mixture, except when the solder is liquid. It's the plastic state of non-eutectic stuff that has the potential to cause problems.

Fascinating. It raises the question of why there is such a huge difference in the pricing of Kester's solders.

Hey, I read it in Popular Electronics in the '60s. It was probably known back in the '30s.

If you're referring to widely different prices from different suppliers, it's the same with any product or service, of course. When the 99% isopropyl topic come up, I plugged it into google's "shopping" tab. Prices ranged from 2.79 to 14.50 for a pint of the stuff.

That isn't what I meant. There's a 20% difference in the price between Kester's 60/40 and 63/37 solders.

Oh, so you didn't read my post after all. To reiterate, 63/37 is 13.80,

60/40 is 13.30. That's uh, let's see, oh yeah, less than 4%.

Yes, I DID read your post, and Yes, I did understand exactly what you said. To wit... that there was almost no difference in the prices of the 60/40 and

63/37 solders from your supplier. That's why I raised the question about why there WAS such a large difference between Kester's solders.

I think it was plain from what I wrote that I was wondering why there was almost no difference in your supplier's prices for solders from (presumably) the same manufacturer, while Kester solders had a 20% difference. (See above.) Must /everything/ be explained in excruciating detail five times over?

This happens over and over and over and over and over and over and over and over, and not just to me. It's because people don't read carefully, then think about what they've read. Believe me, I sometimes am about to respond to a post, then discover I'm mis-understood it.

There were some problems with first-generation DRAM chips back in the late 1970s, which were attributed to alpha-particle upsets due to radio-isotopes in the encapsulating materials.

Cite:

Not having read the article I don't know how close to the silicon it was necessary for the radioisotope in question to be, in order for the resulting alpha particle to disrupt the chip's operation.

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If the flux burns it becomes conductive and WILL mess up CMOS modestly high impedance nodes. That's why i clean it off.

G=B2

I would NEVER add a pound of solder to an existing solder pot at one time. When I bought my 6" diameter solder pot I had enough used solder to more than fill it. It came from the use of a smaller solder pot to salvage ICs from scrap PC boards. Float the board, then tap the corner of the solder pot. A bunch of solder balls hit the aluminum plate the pot was on. I would use a large pair of channel lock pliers to pick up the hot pot to pour out some solder into a small aluminum pan, then dump all the loose solder into the pot.

Solder pots are required to have an exhaust fan, in industrial settings in my area.

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AH-SO! At last we're communicating. Yep, usenet is tough that way sometimes. Here's the missing piece: The solder I buy IS KESTER. The EXACT same stuff that you buy. Only two differences: The disparity in formulations is less, and the price is roughly half.

Fascinating. Perhaps someone, somewhere will have an explanation.

Actually, I bought the solder at least 20 years ago, and I believe it came from an electronics-supply store, not a "hobby supplier". I also paid less than $10.

"William Sommerwerck" wrote in news:i1upmh$14a$ snipped-for-privacy@news.eternal-september.org:

different businesses mark up at different prices. name brands often go at higher rates,and less popular items may get priced lower to move them.

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Jim Yanik
jyanik
at
localnet
dot com

Because 60/40 is just solder, while 63/37 solder is an allowed under special circumstances lead-free replacement and needs certification?

I know it's not lead free, but it's the solder you use when you have to use leaded solder under lead free regulations.

Geoff.

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Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
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