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Author Topic: Computer mobo - what kind of high temp solder is this?  (Read 4210 times)
KF6IIU
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« on: November 11, 2012, 04:31:39 PM »

Not really ham related, but work was throwing out a Canon scanner because they lost the wall wart (!) and I got to take it home. The power connector is some kind of odd proprietary format and I'm trying to unsolder it and replace it with a standard coax power socket I happen to have with the same pinouts.

I managed to remove most of the old connector, down to just the pins, to reduce the heat sinking effect. But I can't get the rest of the pins out. The solder on the board won't liquefy, even with several minutes application of my 140 W Weller, which can usually annihilate anything. It doesn't seem to be a multilayer board.

I guess there is such a thing as high melting point solder - anybody dealt with desoldering this stuff in homebrew? I guess I just need a higher temperature .... is an inexpensive butane gun going to be able to hit 300C or so? Otherwise there are really big 200/300W Weller guns, not much use for regular electronics work.

Thanks,
-Wiley KF6IIU
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KF6IIU
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« Reply #1 on: November 11, 2012, 04:42:10 PM »

Fixed - turns out this was a matter of the Weller gun tip not being seated properly. Tightening the nuts holding the tip in place fixed this.

Just as I suspected, a 140W Weller can melt anything......

-Wiley KF6IIU
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W9GB
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« Reply #2 on: November 11, 2012, 08:50:17 PM »

Liquid Flux for DRY solder joints or poor quality Eastern Asia solder removal.
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W5FYI
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« Reply #3 on: November 12, 2012, 12:15:40 AM »

Glad you fixed the Weller. I bought a Weller gun, case, and several tips at a garage sale because "it wasn't working right." Removing all the built-up flux around the contacts, and the oxide from the tips, put it right again--not so bad for a $1 gamble.

For really tough solder, try adding the usual 60/40 mix to the joint. It will likely alloy with the original solder and reduce the melting temperature to something somewhat manageable.
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KE3WD
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« Reply #4 on: November 12, 2012, 09:20:46 AM »



For really tough solder, try adding the usual 60/40 mix to the joint. It will likely alloy with the original solder and reduce the melting temperature to something somewhat manageable.


FYI took the words right outta my big mouth. 

Adding some fresh solder not only lowers the melting point, it adds a bit of flux to the joint.  Boards are washed of flux during the assembly process...

Computer mobos are also multilayer, often there is a Groundplane layer and also the various Vcc layers hidden inside, acting like heatsink.  Adding solder first also helps with this problem, helping to localize heat at the joint. 


73
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K8AXW
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« Reply #5 on: November 14, 2012, 08:57:05 AM »

I think "adding fresh solder to a joint" is actually establishing better heat transfer between the tip of the iron and the old solder.  Instead of the heat being transferred to the old solder at a very small area, the fresh melted solder spreads the available heat to a larger area.
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W0FM
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« Reply #6 on: November 14, 2012, 02:43:48 PM »

"Computer mobo"?  I thought at first that this was a typo.  After reading further and seeing that no one had flamed the OP for the typo I started thinking hard about it.  Took a minute but then I realized "mobo" was probably Hip Hop Jive-five Rap talk for "motherboard".  Wow.  Old dawg learns something new every day.

Glad I solved it or I would have never slept tonight (and possibly even missed Lawrence Welk).   Grin

73, Terry WØFM
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K8AXW
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« Reply #7 on: November 14, 2012, 09:23:41 PM »

Terry:  Mobo has been in use for so long that it's pretty much accepted as a word.

Welcome to the planet Earth.  We have no leader.   Grin
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KE3WD
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« Reply #8 on: November 15, 2012, 12:25:20 AM »

"Computer mobo"?  I thought at first that this was a typo.  After reading further and seeing that no one had flamed the OP for the typo I started thinking hard about it.  Took a minute but then I realized "mobo" was probably Hip Hop Jive-five Rap talk for "motherboard".  Wow.  Old dawg learns something new every day.

Glad I solved it or I would have never slept tonight (and possibly even missed Lawrence Welk).   Grin

73, Terry WØFM

Hey Terry,

For what its worth, the 'mobo' term came from caucasion silicon valley types around two decades ago. 

I'm thinking about what kind of spirit automatically goes for derision, even race baiting when discovering a terminology that they are simply ignorant about. 

obligatory smiley here -  Cheesy 


73
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W0FM
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« Reply #9 on: November 15, 2012, 06:09:40 AM »

KE3WD: 

Wow.  I'm sorry that you read something in my post that wasn't there.  There was no "derision" or "race baiting".  I am a professional musician.  I have good riends who are Hip Hop and Rap artists.  They happen to be black.  I also have white friends who have performed in Lawrence Welk's Orchestra (Google Kenny Trimble, Trombone).  BOTH RAP and WELK were referenced in my post about an electronic term that I was unfamiliar with.

Am I guilty of being a 65 year old from the Midwest who was "ignorant" of a Silicon Valley term?  Yes.  But it's dangerous to make assumptions, so holster your flame thrower.

WØFM
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KE3WD
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« Reply #10 on: November 15, 2012, 07:04:23 AM »

W0FM, no harm no foul.

Thank you very much for your kind response. 

It truly is appreciated here.


73 es GB
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WB6DGN
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Posts: 617




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« Reply #11 on: November 15, 2012, 11:41:59 PM »

Quote
Terry:  Mobo has been in use for so long that it's pretty much accepted as a word.

I've been involved in electronics for nearly 60yrs. and computers for about 30yrs; 40yrs. of which WAS just north of "Silicon Valley" (San Mateo).  My cousin is an engineer in the Valley who tried to push computers at me very early on.  Today is the first time I've EVER heard that expression(?).  Guess I've lead a very sheltered life.  And, like Terry, the same thoughts crossed my mind as well.
Tom
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KH2BR
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« Reply #12 on: November 16, 2012, 07:48:53 AM »

Why waste time with a soldering gun and desoldering wick. I had a old pc board and wanted to remove a 32 pin connector. Spent a hour and it still did not come out, so I took it to the kitchen stove, Flame on, connector came out kind a fast with some other parts as well.
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N8CMQ
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Posts: 355




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« Reply #13 on: November 24, 2012, 06:59:16 PM »

I have used the mobo term because I was repairing
the old arcade video games in the past. Most of the
work was on the mother board.
 
 For removing components from PC boards for recycling,
I have used a propane torch. Heat a section, solder side
up, tap it and most of the components fall out.
 If the components have the leads bent over after
insertion, the technique will not work...
 
 I reuse solderwic spools to hold different sizes of solder.
Sometimes I will pick up a spool with bus wire and
try to solder with it, that is some hi temp solder!
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WB6DGN
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Posts: 617




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« Reply #14 on: December 08, 2012, 11:18:33 PM »

Quote
Sometimes I will pick up a spool with bus wire and try to solder with it, that is some hi temp solder!

I've used the Weller temperature controlled stations for more years than I care to remember.  My "newest" one is a model WTCPT station that I got around the mid 1980s and it was used then.

A few weeks ago I was working on a power supply control board and went to solder a component.  Psssst!  The trace instantly disappeared.  I found out (the hard way) that the thermostat element in the handpiece had stuck closed and I have no idea how hot it was but the bottom 1/4 inch was glowing orange.  And, wouldn't you know, it finally loosened from the barrel of the handpiece and buried itself in the living room carpet where my bench WAS temporarily located pending some repair work in my shop area.  Well, that replacement board was a whole lot cheaper than the other repairs resulting from that fiasco.

The point of all this?  I'll bet that tip was hot enough to melt that bus wire or darn close to it.
Tom
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