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Old 03-25-2002, 08:06 PM   #1
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Hi,

I got a question for you all. When I try to solder some batteries, I saw that my solder was melting but at same time, some yellowish (translucent) liquid is also there when the solder melts. Is this normal? It's not acid cord. But what's that yellowish liquid??

the yellowish liquid harden as it cools down. Anyone have any idea if this is normal??
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Old 03-25-2002, 08:21 PM   #2
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That liquid is rosin flux, it helps the solder to flow over the joint easier. You can remove excess flux with solvents like denatured alcohol.

Here are a couple of good links on soldering...

http://www.epemag.wimborne.co.uk/solderpix.htm
http://www.epemag.wimborne.co.uk/desolderpix.htm
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Old 03-25-2002, 08:35 PM   #3
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LOL, nice name and avatar MUSHU

Yep, that is perfectly normal.
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Old 03-25-2002, 09:21 PM   #4
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Thanks for the reply.

By the way, I found that my solder stickes to the soldering pen more then where it suppose to go on, is there a way to fix this? Lowering the temp? Higer temp?

Thanks
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Old 03-26-2002, 09:35 AM   #5
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Clean your battery and bars with an ink erasor and then alcohol. that will help the solder flow better. Also I would suggest a large chisel tip iron and no less than 750 deg as to speed up the solder melt. the longer on the cell the more heat build up in the batt.

BTW Iam a NASA level qualified soldering tyechnician and hope fully will try to get an article for Trips to post up here.
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Old 03-26-2002, 11:32 AM   #6
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Also make sure to rough up the cells where you are going to solder the bar, with a little sanpaper or a file. It will help the solder stick to the cell better.
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Old 03-26-2002, 12:18 PM   #7
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roughing up the cells with sand paper or a file isnt a good idea. This leaves exposed base metal that will be open to corosion, and then added resistance and less amperage which = less power. all that is needed is a good cleaning with an ink erasor (the pink ones have an oil in them so they will keep solder from flowing properly) or something similar but nothing that will scratch the cells if you had to as a last resort would be VERY fine steel wool but an errasor is the best to use, what this does is remove any surface oxidation letting the solder wet better, which in turn also lessens the time spent soldering those $$$ NMh cells to the soldering heat and risking damage.
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Old 03-26-2002, 02:39 PM   #8
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Sanding the cells only masks a poor solder job.

The solder sticks to the iron better than the cell because the iron is hotter. Having solder on the tip when you solder will transfer heat more effectively because liquid metal is one of the best heat transfer mediums there is.

I would expect an ink eraser to leave a little residue also, I just use some alcohol on a soft cotton rag.

Liquid flux is our friend, even though the solder has has a flux core. It is the key to a beautiful low resistance joint.
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Old 03-27-2002, 07:53 AM   #9
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I was under the impression that using flux on electrical solder connections was a bad idea? I was told it creates a higher resistance joint than one soldered without flux? Anyone know for sure, or maybe it depends on the type of flux...
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Old 03-27-2002, 09:42 AM   #10
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You most definately need flux (besides the solder core) but it has to be rosin core DO NOT USE ACID it will eat away at your electronics. I prefer liquid flux. What this does is as it heats up it turns corosive (only at solder melt temps) this removes any oils and oxides that still may be on you wire etc. letting the solder wet the joint properly and will do it much more quickly which keeps you from over heating your work which is the biggest destroyer of electronics assemblies. This would include damage to the printed wiring board and excess wicking of the wires (we use very flexible wire for a reason why let it turn into a solid core wire?) also excess heat can destroy your expensive cells.
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Old 03-27-2002, 02:27 PM   #11
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You do want to remove the baked on dry flux after your solder joint dries. You can do this with isopropal alcohol and a stiff nylon bristle brush.
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Old 03-27-2002, 02:40 PM   #12
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Right on Pat, the brush I found to be the best is actuallly hog hair. It is very stiff and with a metal handle it is ESD resistant (Electrostaic Discharge) As far as the erasor yes it leaves a residue of rubber but I always clean with isopropal before I solder especially if I handled the work allot as the oils and salts from your hand will cause dewetting of the joint. You should see the solder quite a bit of it is done under a stereo microscope. The work we do can include flexible print repair (mylar ribbon cable) and multi layer PCB board repair going through the layers to repair the circuit runs inside the PCB great fun
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Old 03-27-2002, 06:31 PM   #13
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Sanding the cells does not increase resistance as long as you tin the cells afterwards. Sanding removes oxidation and contaminants which can cause bad solder joints. I see you are most likely in the electronics industry. I also work for a electronics company, small world.
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Old 03-28-2002, 09:33 AM   #14
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the sanding initself does not increase the resistance but the possibility of corosion according to NASA/ISO 9000 specs this reduces the cross-sectional area of the conductor to unaccetable limits as it would actually be gouges. isopropal is the best to use and if there seems still to be oxidation (ie a cell siting in storage /shipment exposed to the elements like moist air) then just an ink erasor should be used. Definately nothing too abrasive. as far as I know the metal in the cells seems to be aluminium which oxidizes quite easily and is already not the best conductor there is.
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Old 03-28-2002, 09:40 AM   #15
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What type of background do you have in electronics? You seem to know quite a bit about the ISO standards. Mine is Manufacturing Engineer/SMT Engineer. Nice to talk to someone who knows their stuff this well.

By the way Buda what type of solder do you use? I use Kester no-clean. Smells terrible but works well.

Last edited by CRASH; 03-28-2002 at 09:43 AM.
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