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Old 14th September 2013, 02:15 PM   #1
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Default Solder issues

A friend was trying to solder on a new capacitor on a car amp. The solder he is using will not melt or stick to the solder on the board. He has scraped the surface of the solder on the board. I'm assuming the solder on the board has a higher melting point. He is using the usual Lead based solder.
Are all RoHS compatible solder harder to melt ? Would anyone be using solder with silver content on consumer products ?

Any solution to this ?
Thanks.
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Last edited by ashok; 14th September 2013 at 02:22 PM.
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Old 14th September 2013, 03:00 PM   #2
Einric is offline Einric  United States
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RoHS compliant solder is Silver bearing and it does melt at a higher point.
Some of the silver bearing solders need over 700deg. to melt properly.
A good quality 63/37 eutectic solder will melt much lower but you won't hurt it by overheating, just keep steady while it cools and you will be fine.
You will probably need to use some acetone (nail polish remover) to clean the area really good and then use de-soldering braid to remove the bulk of the old stuff.
I do this all the time at work and it shouldn't fight you at all.
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Old 14th September 2013, 04:55 PM   #3
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Try using flux!
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Old 16th September 2013, 07:04 AM   #4
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It was impossible for me to solder on a VFD board since it had thick copper and plated throughs.

Gajanan Phadte
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Old 21st September 2013, 03:21 PM   #5
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I was my understanding that at typical tip temps (based on PACE PCB repair station training) that after 3 seconds of melt time the Tin & Lead in the alloy can seperate, leaving an overheated joint that is unacceptable, hard as nails, and generally a mess. I've not heard of any solder alloys that are not overheatable.

A lot of soldering problems stem from the use of too-small elements/tips that cannot give quick enough heat capacity and transfer. PACE recommends the larger sizes, and 3 sec. max heat application once the melt occurs. I use 50W minimum element with 3/16" chisel tips. They are 1950's - 1960's NOS Western Electric tips that fit in a cheap (~$18) Weller Iron. The tip I am currently using has been in service for about 4 years and remains perfect. The Weller tips go out in about 6 Mo. and cost more than the iron kit itself!

I was very fortunate to have received the PACE training in the U.S. Navy, and following those methods actually makes soldering pretty easy.

I also lucked out and found some expired shelf-life Kester liquid flux that is the cat's pajamas. Diluted slightly with 99% Isopropyl alcohol, it's as good as it gets (used to get?). It's probably considered super deadly these days.

How many tree huggers do you know of who solder, anyway?

($.02 worth) of MHO
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Old 21st September 2013, 03:32 PM   #6
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If you use solder with 1%copper, that extends the life of the Weller tips.
I use a Metcal Solder Station. 120Watts of heat and a 3/16 bit. Temperature controlled. It will re-solder car battery terminals and 200pin SMD's!
The secret is flux combined with heat.
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Old 21st September 2013, 03:46 PM   #7
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Also the greatest thing I've seen lately are the little foam-core sanding blocks (~3" x 4" x 1") in various grits; nothing cleans a component lead like these darlings.

I can usually find 3M pads at a 99 cent store locally. They are around $5 - $6 at Home Depot.

3M 2-5/8 in. x 3-3/4 in. Medium Sanding Sponges (6-Pack)-CP002-6P-CC at The Home Depot

You can cut them into small pieces and hold one with a hemostat to get into tight places.

I would highly recommend trying these out, you'll be amazed.

Heck, they even work great for the sanding tasks they're intended for!
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Old 21st September 2013, 10:59 PM   #8
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Red face RE: Mixing silver and tin-lead solders

When it was the norm to have almost all joints in a Tektronix scope silver- bearing soldered, unknowing repairers would use standard SnPb solder instead.

the result was a nearly 100% probability of connection failure short-term. Then often the situation would see a "snowball effect" and everything went from bad to much worse.

Admitedly I <once> made the mistake, turning a $50 work surplus Tek 530 into a $195 repair (including a few tubes) and and yet another unscheduled project.

Another lesson learned the hard & $$ way.

I still have a handful of the ceramic, silver bearing solder
terminal strips from NOS Tek repair kits. But THEY can be a handful to solder. Very pretty to look at, though.
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Old 21st September 2013, 11:19 PM   #9
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There are many, many posts about soldering in the endless thread.

http://www.diyaudio.com/forums/analo...t-ii-2163.html
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Old 21st September 2013, 11:23 PM   #10
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Quote: "If you use solder with 1% copper, that extends the life of the Weller tips."

Thanks for the tip tip.

Who is a reasonable priced vendor for the 1% Cu solder? (USA)

I've also had to do repairs on the Weller's (oops, this one's a 40W! Model SP40L) power cord several times, but since ditching their tips it' been a real trooper. One nice feature is a neon lamp inside to indicate power-on.

Ha ha, it's marked "Use Weller replacement tips only".

Forgot to mention also, I use a 100W "Variac" with it to reduce temp. to where the tip does not discolor when tinned (overheated solder). I can "floor" it when needed for heavy joints.

A mechanical "twist timer" AC switch is a good feature for homebrew solder stations. I've ruined and shortened the life span on too many irons to trust such things to real-time cognizance.
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