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Author Topic: Slobber: is 63/37 really any better than 60/40?  (Read 3041 times)

Hayden J. Nebus

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Slobber: is 63/37 really any better than 60/40?
« on: June 14, 2018, 10:03:47 PM »

What is the smoke:ass ratio of eutectic solder? All ass, or smoke up the ass?

One of my religious beliefs is that the toxic stuff usually works better. BUT I've been using SAC alloy solder wire seemingly forever, since ROHS was new, for fear of making solder joint gremlins by mixing chemistries in rework. I've largely settled on SAC305 but it's a PITA to work with, i.e. iron temperature is necessarily a bit high for my taste, little traces will lift if not quick and careful, and to boot even the good working joints look ugly and cold when done.

 Recently I've had some after hours fun working on some older HiFi gear, and I almost forgot how nice soldering is with 60/40! Night and day!

I fell down an internet rabbit hole extolling the virtues of eutectic solder, which for SnPb is 63/37. Best I can tell the sales pitch revolves around the phase change, where a eutectic ratio has one unified melting/freezing temperature, whereas a normal ratio has a delta between the phase change of the tin and the lead.

I can see where a singular freeze point might make for a mechanically superior joint with eutectic solder, e.g. one of the documented issues with reworking Pb-free with 60/40 or vice versa is layering and micro-cracking due to a large delta in the set temperatures. But is the difference to 60/40 negligible?

Beating everyone to the punchline, I can only assume it's 3% better. 😁



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John Roberts {JR}

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #1 on: June 15, 2018, 08:51:22 AM »

I never noticed a sound difference between them.

JR
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Frank Koenig

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #2 on: June 15, 2018, 09:36:07 AM »

I never noticed a sound difference between them.

JR

I think 63/37 has a more tinny sound  :o
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Scott Helmke

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #3 on: June 15, 2018, 12:37:42 PM »

These days I mostly use no-lead solder, and I've gotten used to working with it. So yeah, it's kind of fun to work with the old stuff and not need to work as quickly.  Really though the biggest thing I've done over the past few years is reduced the *amount* of solder I use, from the usual old-school big blob to "just enough and you can see where the wire ends".  With that change the phase change difference doesn't really matter.
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Bob Leonard

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #4 on: June 15, 2018, 02:09:32 PM »

I wouldn't lose any sleep over this regardless of type, however, I will only use Kester 60/40 old school solder. I really haven't seen a large number of problems caused by the solder used on the 50-60 year old amplifiers I rebuild. I love the smell of flux in the morning.
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Henry Cohen

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #5 on: June 15, 2018, 02:53:19 PM »

I love the smell of flux in the morning.

I can only presume this is Bob's morning coffee of choice.
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Dave Garoutte

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #6 on: June 15, 2018, 03:19:26 PM »

I wouldn't lose any sleep over this regardless of type, however, I will only use Kester 60/40 old school solder. I really haven't seen a large number of problems caused by the solder used on the 50-60 year old amplifiers I rebuild. I love the smell of flux in the morning.

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Nikhil Mulay

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #7 on: June 15, 2018, 10:48:17 PM »

Always use 60/40. Here in India it hasn't been outlawed yet! @Bob.. The smell! Nostalgic.
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Stephen Kirby

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #8 on: June 15, 2018, 11:20:19 PM »

Solder joint reliability withstanding strain or vibration is all about grain size.  Eutectic solder gives a smaller and more uniform grain during solidification.  There are always other things in the solder, even when not deliberately adding silver.  So the intermediate plastic phase allows for grains of other alloys to grow.  Where with eutectic they tend to be frozen in place.

Lead free doesn't really have any true eutectic alloys so it's always a compromise.

The fatigue failure is a bit different between leaded and lead free solder.  Lead based solder creeps.  Grains enlarge, micro fractures develop at the boundaries and get larger as the grain size grows.  Eventually a fracture will propagate across the micro fractures and you have a failure.  Lead free solder is stronger initially and doesn't creep.  Which means that grain growth comes from stress and fractures develop more quickly when they happen.  You can look at a leaded joint and see a rough almost blistered appearance.  It's starting to develop fractures and will go soon.  With lead free it's hard to tell from the outside until a fracture appears, in which case it's often too late.

Disclaimer, back in the '80s I did a bunch of reliability testing on the then new SMT technology at a defense contractor I worked for.  I was part of writing the book on how to make this work.  I was the first to present to the DoD a successful run of 1000 cycles of thermal cycling from -54 to 125C on an LCC44, which was kind of a benchmark at the time.  The pictures of LCC joints in Mil-Std-2000 and the copies in the current commercial industry standard IPC610 came from me and that research.
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Nathan Riddle

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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #9 on: June 15, 2018, 11:31:22 PM »

My preferred solder is silver solder.

The mechanical connection carries the current (solder is a poor conductor), the solder just makes it permanent.

http://a.co/iAuWiSd
99% Tin, 0.7% Silver, 0.3% Copper * 2.2% Flux * 1.0 mm Diameter * Weight: 1/2 lb (8 oz)

Or 4%
https://www.parts-express.com/4-silver-solder-10mm-(004)-1-2-lb-spool--370-038?utm_source=google&utm_medium=cpc&utm_campaign=pla
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Re: Slobber: is 63/37 really any better than 60/40?
« Reply #9 on: June 15, 2018, 11:31:22 PM »


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