60/40 vs. 63/37 Solder

Dunno, but... If you do detail work, try water-soluble flux solder. You just wipe off the residue for a sparkling clean circuit.

Good luck and have fun.

60/40 was the standard for many years, until it was learned that 63/37 was more accurately eutectic. 60/40 was kept around as a legacy product since millions of customers worldwide had written the spec into their procedural documentation. But distributors (in my part of the world anyway) stopped stocking much of a 60/40 selection about 20 years ago.

As for water soluble flux, it has at least one significant drawback; it is corrosive at room temperature (unlike RMA for example which is only "active" when heated.) Therefore, any flux residue left on the board (or whatever you're soldering) will lead to corrosion. Without full immersion in a sonic tank, it can be difficult or impossible to wash it all away.

The advantage is when you need a lower melting temperature. However, the difference is slight. 63/37 also does not have as much of a plastic state when melting.

As far as I know, no.

63/37 has been "known" to be eutectic for at least 50 years. (I read about it in "Popular Electronics" as a wee babe.)

The only reason 60/40 was ever manufactured in the first place is that tin is more expensive than lead, so 63/37 solder costs more. Unless you're Really Cheap, 63/37 is always preferable. It has slightly greater mechanical strength, too, though this is rarely a consideration.

J Gordon Holt, who founded "The Stereophile", had his own theories about soldering. Back in the days when people assembled vacuum-tube equipment from kits, he recommended simply poking component leads through the lugs, and soldering them without crimping them. His reasoning was that, if the component ever needed replacement, you wouldn't have to fiddle with uncrimping it. (If you've ever unsoldered old equipment, you know what a tsuris this can be.) The "catch", of course, is that both the lug and the lead have to be very clean, and you're more likely to get a cold or incomplete connection. This is a situation where you would /definitely/ want to use 63/37.

While I'm on the subject... I once asked the late Bob Tucker, * who wrote the user manuals for Dynaco, why the soldering instructions were, at one point, obviously in the "wrong" sequence. He explained that Dynaco's "policy" was that, once a lug had three wires in it, it was to be soldered. There was otherwise too-great a chance of it being overlooked and remaining unsoldered, only to cause problems down the line.

• Bob, who passed on in the late '80s, was one of the nicest, most-gracious people you could ever hope to meet. He was, perhaps surprisingly, also one of the handsomest men I've ever seen -- by comparison, most actors and fashion models are plain -- but he didn't seem aware of it.

Water soluble flux is conductive. You should wash it off not just wipe it.

-- Boris

And one that makes a great humidity sensor.

John

Cite, please? (and I don't mean a link to commodity prices)

No.

For hand soldering, I recommend Sn63Pb37 wire solder with an activated rosin flux core. Use thin solder, about 23AWG; it melts the faster, for less chance of cold joints. For surface mount, use even thinner, about 28AWG.

Avoid organic or water-soluable flux unless you're going to wash the board thoroughly after soldering.

Rosin flux can be removed with 99pct isopropyl alcohol ($1 a bottle at your corner drug store). But frankly, I recommend NOT removing the rosin flux scum. Leave it on; it's inert, airproof, waterproof, sweatproof, so it protects the joint.

--
Been soldering stuff since 1973,
Robbie Hatley
lonewolf [[at]] well [[dot]] com

I can only cite "common sense". 63/37 has always been more-expensive than

60/40.

Yeah, My prototype of a board with several high meg resistors (up to 1 gig.) was put together by myself with old Kester "44" (rosin flux.) Worked great. Production did a few with their favorite water based flux... No good! Now I have to convince them to go back to the old standard. The new ROHS fluxes seem to be even worse. I measured a few meg ohms between pads that had been 'cleaned'.... NOT.

George H.

I had a lot of problems with high Z circuitry. Got under the pads. Some boards I had to clean/dry 10 times. In the interim, some of the cleaner I used got into some caps and started their own circuit mess.

greg

PeterD mentioned the significant parameter in his post. because it is a eutectic mixture 63/37 does not have "much of a plastic state" this means it is more sensitive to movement in the joint while the solder is cooling - if the connections are unstable it forms more dry joints. This was important with point to point wiring but is now less important with PCBs.

You can normally use either solder for any job but the "old timers" experience would suggest 60/40 is the better choice for wiring front panels, flying leads and the like and 63/37 would be better for heat sensitive components.

(for the obnoxious who will claim there is no difference - please note that those doing the jobs *did* find a difference and thought it significant enough to bother about)

My understanding is that 60/40 has somewhat better wetting properties than 63/37, at least with some contact materials. Some people prefer it for that reason.

63/37 makes a sharp transition between liquid state and solid state at a single, well-defined temperature. 60/40 goes through a transition between these two states over a significant range of temperature - in between the fully-solid and fully-liquid states it can have a somewhat mushy texture. Some people feel that 60/40 brings with it a somewhat higher risk of creating a "cold" solder joint (inadequate fusion with the contact surfaces) if the joint is moved or stress while the solder is dropping through its mushy-state temperature region.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

I don't what you meant to say, but what you did say is backwards. Eutectic solder is less likely to produce a dry or crystallized joint.

"William Sommerwerck" wrote in news:i1nqh7$7qt$ snipped-for-privacy@news.eternal-september.org:

I agree; the eutectic joint solidifies faster and thus less likely to move while the solder is still "plastic".

--
Jim Yanik
jyanik
at
localnet
dot com

Then you can't substantiate your contention that 60/40 was THE worldwide standard for tens of years just because it was a few pennies cheaper per pound? That is the statement of yours with which I take issue.

I have no objection to your objection.

However, 60/40 was never, ever, "a few pennies per pound" cheaper than

63/37. For the last 30 years, the price of eutectic solder has been sufficiently higher to make one think twice before buying it. The last time I purchased solder, I decided that a one-pound roll of Kester 44 would last the rest of my life, and I splurged. (At this point in my life, my prediction is coming true. I rarely solder any more. If I drop dead, someone digging through the junk will find a pleasant surprise. Assuming they know what 63/37 is.)

I just checked Parts Express, and a 1# roll of Kester 44 60/40 is $22.23.

63/37 is $26.85. That's a $4.62 difference, almost 21% more -- hardly "pennies per pound". When I bought the same product some years back, my memory is that the price was around $7.50 for the 60/40, $9 for the 63/37. Even that wasn't "pennies per pound".

I looked at the MCM site for Ersin products. Get this... MCM describes its house brand of 60/40 solder as "provid[ing] the lowest possible melting point".

Businesses almost always try to cut every corner they can. If you think your solderers -- or soldering machines -- are doing a good job, you might prefer to buy the less-expensive 60/40.

When I worked at Bendix Field Engineering, I often walked through the section where a bunch of women (never men) soldered assemblies, following NASA standards. I never thought to ask whether they used 60/40 or 63/37.

Strange to see this in print, as everyone seems to spend ages removing flux. I don't and have never had a problem.

--
*The only difference between a rut and a grave is the depth.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

You won't find 99% for $1. (91%, maybe.)