Soldering Tips (pardon the pun)

[drspiff]

This is intended as a brief overview of the fine art of soldering along with somethings to watch out for. If you have never soldered before, then learning on your own can be very daunting. It seems that no matter what you do, the solder does not stick, or the joint looks like it is growing moss, or 'fill in your own horror story'. But it does not have to be this way. You can, with a little practice, solder just like the pros. Let's talk about the tools and materials involved.

Soldering Iron -- not a gun, use an iron. You have much better heat control with an iron. Size range 25 to 45 watts. With increased skills, you can compensate for an iron which is too large or too small, but do not start out that way. Do you need one orf those fancy heat-controlled LED soldering stations? It depends on how much of this you want to do. For most of us hackers, a simple 30 watt iron is adequate. (As a side note, all the electronics in all the Apollo flights was assembled with a hand-soldered with a 30 to 35 watt iron.)

Solder Iron Tip -- get plated tips in an appropriate size. For vintage equipment, a chisel tip, 1/8" to 1/4" wide is ideal.

Solder -- The composition of solder determines its melting temperature and general characteristics. The size of the solder should be matched to the joints you want to make. Typically use solder that is about the same diameter of the wire involed in the joint. A reasonable size is .032". This is small enough not to swamp the joint and large enough for reasonable consumption. Use a eutectic solder with a 63/37 tin/lead mix. If you can't find any, use 60/40. What about lead-free solder? I've never used it and don't intend to start now, so it is YOYO*.

DO NOT, (repeat) DO NOT use acid core or acid activated or acid anything solder. Yes, it will work, but any flux left behind WILL eat your joint. Use only rosin-core solder. And remember that solder does have a shelf-life. If you have a roll that has been sitting around 'forever', be a big spender and buy a new roll of solder. The rosin flux in the core will be fresh and make soldering easier.

Orange Sticks -- or popsicle sticks. You will need one or two to push wires around and to hold a setup 'just so'. They will char but I have never had one catch fire. If you find yourself carving them into intricate shapes, get up and take a walk outside.

Soldering itself is simple. You are going to get something hot enough so that a normally solid metal will melt and stick to whatever is hot. The difficulty is in the details. Let's talk about the process itself. Your iron is the heat source, the termial strip and wire is the thing that is going to get hot and the solder is going to flow and make the electrical connection. There are three rules in soldering to make a good joint, Cleanliness, Heat Control, and Cleanliness. If you have oxidation or debris, you will either be unable to solder or get a joint which is sub-optimal. The purpose of the flux core in the solder is to get underneath the surface oxidation. But this flux is heat activated and oxidation will prevent a good heat flow from the iron to the joint. So the joint and its component parts must be clean to get a good connection. You can use either steel wool or an ink eraser to good effect to remove oxidation.

The "art" in the process is getting the heat from the iron to the joint or Heat Control. When you touch a "dry" iron to the joint, the contact area is microscopic. A small contact patch means low heat flow which leads to clod joints. The fix for this is to use a "wet" iron. Pick up the iron and wipe the tip on a damp sponge. The tip is now "shocked" and bright. Put a touch of solder on the tip. You now have a wet iron. When you apply the wet tip to the joint your contact patch, or solder bridge, is many times larger than with a dry iron. Thus you get heat flowing across the solder bridge and into the joint. The second part of Heat Control is that solder will flow towards the heat. When soldering a large joint, you may have to move the iron tip around to the "cold" side to get adequate heat.

With the iron still in contact with the joint, touch the wire solder on or close to the solder bridge. The solder will flow, increasing the size of the solder bridge and making the electrical connection you want. Only put on enough solder to cover and follow the contours of the joint. A blob takes more heat, might disguise a bad connection, and generally looks like hell. When you have enough solder, pull back on the solder wire and leave the iron tip in contact for a few more seconds. Everything should flow smoothly and be bright and shiny.

For Cleanliness, Part Deux, take some cotton swabs and acohol and clean the joint of any residual flux. This will keep your joints looking good for years to come.

Things to Do
------------
1. Use fresh 63/37 or 60/40 rosin core solder
2. Use a 25 to 40 watt soldering iron
3. Clean the joint components before soldering
4. Unplug the unit you are working on.
5. Remove any oxidation with steel wool or an ink eraser before soldering
6. Use a wet iron and establish a solder bridge to the joint
7. Leave the iron on the joint for a second or two after applying the solder
8. Clean up the joint with alcohol and cotton swabs after soldering

Things Not to Do
----------------
1. Use acid core solder
2. Use a soldering gun
3. Use a dry iron
4. Solder a joint in a "live" unit.

--------------------------------------------------------------------------


<Still looking for a headshell for my Thorens TD160>

 

[MeAN]

Hello!
Really a great and useful post.
If I can, I'd say that I would rate using an even smaller solder (in terms of wattage).
I'd say that 16W (even if not too easy to find) would be a better choice, especially for a beginner.
If you don't have to place large amounts of tin, it would be enought.
I'd prefer such a small iron because usually beginners are prone to stay on the PCB with their iron more then needed. A 30W iron could easily lift the circuit from its board if it's kept too long in place.

Just my two cents.
Respect,
Carlo

 

[Super866]

Thanks for the post. I think wattage is somewhat of a personal preference, and skill. I perfer a hotter iron so i can just hit the joint and be done with it, but like its been said, some people might start warming things up a bit too much.

And sometimes you really need one of those 140 watt soldering guns. Some jobs are just too much for even a 40 watt iron. Desoldering twist lock caps from the chassis of equipment is one of the jobs that comes to mind.

 

[rulerboyz]

Here's a few other topics that would be nice to see covered:

What's your routine when you put on a brand new solder tip?

Adjusting your solder technique based on the part being soldered/desoldered as well as the type of PCB.

How to avoid lifting traces, and what to do if you do?

When do you know it's time for a new solder tip?

 

[Yamaha B-2]

Here's a great soldering iron that won't set you back too much. And, you can dial up the wattage you want. For the average hobbiest, this is an excellent iron. For the pro, you can move up the food-chain and get a higher-end model for something over twice the price.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=372-120

 

[drspiff]

What's your routine when you put on a brand new solder tip?

I admit to burning through a lot of solder. And one of the ways I do that is by keeping the tip "tinned". When I put a new tip on the iron, I let it get hot and slather it up with solder. When I shut down for the night, I put another glob of solder on the tip. This tends to keep the plating from being oxidized. All of this assumes a plated tip. If you have a bare copper tip, then you should tin a new tip, but keep it dry except when actually soldering.

Adjusting your solder technique based on the part being soldered/desoldered as well as the type of PCB.

Good point! What you are attacking will determine the approach to use. If I'm removing something, I first try to unbend or straighten out any mechanical constraints. I'm always amazed how easily I can peel a wire away from a solder lug. When removing a component from a board, I do the same thing. I take a small slot screwdriver which is sharpened, slide it under the bent lead and straighten it out. This makes the desolder much easier.

By doing the mechanical "demolition" before trying to get the lead unsoldered from the pad/trace, I reduce the time actually spent in contact with the trace.

How to avoid lifting traces, and what to do if you do?

The only way I know to eliminate lifted traces is by limiting the time in contact with the trace. For those of you who have not lifted a trace yet, you will. What to do about it? Remember, the trace is nothing more than a flat copper wire glued to the board. If you lift the trace, finish your soldering, grad an orange stick and superglue. Then glue the SOB back in place. It won't pass NASA specs, but you are not launching your board to the moon either.

BTW, some boards, from some manufacturers, are much more sensitive to heat. Sad to say, that like many things, the newer boards are far better than older boards. And it is likely that most of your soldering will be on old boards...

When do you know it's time for a new solder tip?

If it is a plated tip, I will replace when I see pits in the plating. This means that the combination of heta and flux have finally eaten through to the core of the tip. At this point, you will see spots on the tip that will not take any solder. And most tips are only a couple of dollars, so keeping using a tip which is past its prime is false economy. But I never throw out my old tips. There have been times when the replacement was in the mail, and when I ground down an old tip to get to a particular connection.

Since we are sharing URLs, here is the iron I use:

http://www.mpja.com/productview.asp?product=15845+TL.

Mind you that this replaces an American Beauty that I had for 30 years.

 

[glen65]

Things to Do
------------
1. Use fresh 63/37 or 60/40 rosin core solder
2. Use a 25 to 40 watt soldering iron
3. Clean the joint components before soldering
4. Unplug the unit you are working on.
5. Remove any oxidation with steel wool or an ink eraser before soldering
6. Use a wet iron and establish a solder bridge to the joint
7. Leave the iron on the joint for a second or two after applying the solder
8. Clean up the joint with alcohol and cotton swabs after soldering

Things Not to Do
----------------
1. Use acid core solder
2. Use a soldering gun
3. Use a dry iron
4. Solder a joint in a "live" unit.

Good post,
I would just like to add to it.

Don’t skimp when buying solder. The stuff is not all that expensive anyway. I stick to Kester
or Multicore brand. Don’t use solder that’s too
large in diameter. I don’t like to use anything larger than .031 in diameter. And make sure you
heat the connection not the solder itself. If your
working with Mosfets or other static sensitive items make sure you wear a static strap.


Later

 

[gfinlayson]

Standard Lead/Tin solder is becoming hard to find over here in the UK because of the new RoHS legislation. I've switched to using a lead-free 95.5% Sn/4% Ag/0.5% Cu solder. It needs a slightly higher tip temperature than regular 60/40 solder, but works very well and only cost £7.99 (US$14) for 250 g (1/2 lb).

 

[dr*audio]

This is the iron I use.
http://www.newark.com/product-details/image/mcm/image/21-7940.jpg
You can get a very thin tip for it for SMT work, or larger tips for through-hole parts like on most consumer electronics. Not bad for $59.00.
I would like to add, when I tin a new tip, I start applying solder as it heats up, so that as soon as it gets hot enough to melt the solder, it gets coated. This prevents oxidation from building up before you can tin the tip.

 

[john_w]

GREAT thread! Thanks for posting this.

It's been a while, but in the past I've always used standard Rat Shack brand rosin core, circuit board solder. Does that meet the specs quoted above? (I don't recall what kind of options they have - maybe just different diameters?) Do you consider their quality to be decent, or would I be better off switching to a different product?

Also, for thermostat controlled irons, what heat setting do you recommend?

Thanks again!
jw

 

[Fast_Eddie]

This is a great thread. I've about worked up the nerve to try recapping a whole amp board (not the whole receiver yet) and I'll spend some quality time looking this whole thing over.

Anyone want to do a step by step recapping thread?

Take care,

Ed

 

[Yamaha B-2]

The solder that I find works very well is the Welbourne Labs 62/36/2% silver. Flows very well so easy to wet the working parts. As I the TA wiring on my TAs, find it easy to work with for very small wires.

 

[dr*audio]

480 degrees F works well for almost anything. On a large lug, or chassis or ground pad, I crank it up to 570 degrees F.

 

[john_w]

Thanks guys!

So when is somebody gonna turn this into a "sticky" thread?

 

[Yamaha B-2]

Good idea. This should definitely be a sticky.

As is about soldering, I'll ask about solder-suckers. I have a cheapo one just like is listed on all the various e-businesses where we got our soldering irons. I find that the only way this thing will work well enough if if I give it an 'assist' with the regular soldering iron. That is. I place the sucker tip on what I want to suck and then hit it with the regular soldering iron to actually melt the solder, and then release the bulb. PITA, but works. Problem is working on the back of a PCB. Have to put way too much heat into it and can't really get in there with my soldering iron tip was the sucker tip fits over the component lead. Any suggestions?

 

[drspiff]

I find that the only way this thing will work well enough if if I give it an 'assist' with the regular soldering iron. That is. I place the sucker tip on what I want to suck and then hit it with the regular soldering iron to actually melt the solder, and then release the bulb... Any suggestions?

Well, no... this is the only way I know that a solder sucker works. If you are stout of heart and have led a blameless life, you can get the joint hot and blow the solder off. But unless you can pull the sword out of the stone, I wouldn't recommend it. (Sorry, I was listening to Camelot turned up loud.)

 

[dr*audio]

Solder wick is the safest (for the traces on the board) and most complete means of desoldering a joint. Solder wick (or desoldering braid) is a copper braid impregnated with flux, to draw the solder. You hold the braid to the joint and place the tip of the iron on top of the braid, and, presto, it wicks up the solder, even out of a plated through hole. When I have a big glob of solder to remove, or many joints to desolder, I use a solder sucker, but not the one with the bulb. Those are pretty useless. Radio Shack used to sell a very nice compact solder sucker, which is what I use. Oh, look, they still sell it!
http://www.radioshack.com/product/i...4/&fbc=1&kw=soldering+tools&parentPage=search
This little thing is dirt cheap and works great. It provides plenty of suction to gobble up the solder without tearing up the board like the big Soldapullt does. I also have a Soldapullt, which I use only on tube stuff. Anyway, what you do is you push the plunger down, heat the joint and when the solder melts, place the tip on the joint and push the release button. It sucks up the solder. You may still have to finish up with solder wick, but this way you use less solder wick; it's expensive.

 

[outlawmws]

Another tip is when soldering a small wire/lead to a heavier one, keep the heat on the bigger one. The small wire will usually flow solder as soon as the larger one is ready as there is less mass to heat up.

One place where I do use a solder gun is chassis soldering, (Or de-soldering) as irons suitable for leads, wires, and traces are completly inadiquate for the mass involved when working on a chassis joint.

Also applies to heavy gauge wire like 12-14 ga and up. Not likely to surface on audio much but I do much more than electronics. (Learned to solder building slot cars)

 

[Yamaha B-2]

drspiff - there have been a number of threads on Thorens recently on the TT forum. Several website links posted and may have your headshell there.

 

[dr*audio]

For the Thorens part, perhaps this will help
http://www.theanalogdept.com/thorens_part_nums.htm