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Question on soldering

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LAN_403

rp181

Fri Dec 12 2008, 01:14AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

I can solder perfectly fine on PCB's, but i can never seem to solder 2 component leads (in this case, 2 942C capacitors) together. The solder always falls off, or doesn't stick. Also, the capacitor never gets up to tempeture, so i just put solder on the tip and brush it =/

How do you do this?

Electroholic

Fri Dec 12 2008, 01:26AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

you need some flux on the lead, light sand will help if the leads are badly oxidized. and make sure you dn't move it until the joint has cooled.

Firnagzen

Fri Dec 12 2008, 05:35AM

Registered Member #567 Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147

You also need a higher wattage iron if you can't heat up the leads. Solder tends to go where the heat is.

coillah

Fri Dec 12 2008, 05:56AM

Registered Member #1517 Joined: Wed Jun 04 2008, 06:55AM
Location: Chico CA
Posts: 304

get a good clip holder for the job. makes life waaay easier

LithiumLord

Fri Dec 12 2008, 06:14AM

Registered Member #1739 Joined: Fri Oct 03 2008, 10:05AM
Location: Moscow, Russia
Posts: 261

By the way I tried out the Keller TT flux, which is really good for any kind of work. As for caps, also make sure you have the proper soldering temperature set in case of using a station (like 300-350 should be fine for heavy rails), if you are using an iron the optimal power feels like 40w to me (well, at least it's optimal for me - actually it's much of personal preference).

Myke

Fri Dec 12 2008, 07:09AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

Are you talking about point to point soldering? What I use is some soldering hands (two movable alligator clips on a stand thing) and hold the leads close together. This prevents movement while the joint is cooling.

Extra flux makes everything flow on and around the lead so nicely. It gets nasty otherwise.
Also I don't recommend that you put solder on the iron first because the flux burns up. The way I do point to point soldering is put a tiny bit of solder on the iron while the iron is on the lead to be soldered to get a better thermal contact. Then I just apply more solder while still holding the iron onto the lead. If the solder won't stick to the other lead then do the same for the one that won't stick. Once the molten solder touches the other solder, the blobs will pull together because of surface tension.

EDIT: Ah, yeah. They were called helping hands. Got the name wrong...

Arcstarter

Fri Dec 12 2008, 07:18AM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

What I use is some soldering hands

Yea, I have recently been using mine, and they are such a helpful little tool! You can get them from Harbor Freight, they are called helping hands there.

LithiumLord

Fri Dec 12 2008, 07:22AM

Registered Member #1739 Joined: Fri Oct 03 2008, 10:05AM
Location: Moscow, Russia
Posts: 261

Myke wrote ...
Also I don't recommend that you put solder on the iron first because the flux burns up.

Actually I see no point at even touching the flux with your iron (a little bit at least - but not always). There are a lot of good grease fluxes (like the mentioned vaseline-based TT one) so just put some on the rails you are soldering, then put some solder on them, then - some more flux and solder them together. For hard flux - just hold a chunk below your rails in progress.

Myke

Fri Dec 12 2008, 07:26AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

LithiumLord wrote ...

Myke wrote ...
Also I don't recommend that you put solder on the iron first because the flux burns up.

Yeah. The flux in the solder burns up if you put the solder on the iron then wait a bit before putting the solder to the lead.

Mattski

Sat Dec 13 2008, 01:14AM

Registered Member #1792 Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527

Another useful tip is to make a good mechanical connection before you solder. This ensures that it is stable while soldering, there's lots of surface area for solder to adhere to, and it will end up being a stronger joint. A simple way is to bend the lead of each part back into a "V" shape, interlock the two V's, then twist the ends around so that can't slip apart (if that makes sense). Of course, the better that you do this the harder desoldering will be without resorting to the wire cutters.

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