Through hole soldering question

Sometimes more solder flow through the hole to the other side than I would like when soldering through hole components. Is it bad practice to hold the board upright while reheating the joint from the bottom? I find if I put a good bit of solder on the iron tip and hit each joint for about 3 seconds from the bottom, it flow out nice on the pad, on topside of the board.

No, I wouldn't say that's bad practice but you should be careful about overheating the board or leaving the heat on for too long. (3 seconds is OK.)

If there is too much solder it's more common to use [u]solder wick[/u] or a [u]solder sucker[/u].

I have both, but I was trying to get it to flow out better on the topside rather than remove it all.

Use less solder when soldering.

It's best to use small diameter solder on PCBs.


Apply a small amount of liquid flux to your solder wick prior to heating.

Limit the downward force from the iron on the wick.


Avoid solder suckers as circuit trace damage can occur.


Clean the PCB with IPA, sparingly wipe your PCB pads with liquid flux before soldering components.

Im using Kester 0.031 leaded solder. If I use less solder it ends up being flat on the backside rather than pyramided at all. Maybe I am trying to hard for aesthetics.

tsperry88:
Sometimes more solder flow through the hole to the other side than I would like when soldering through hole components. Is it bad practice to hold the board upright while reheating the joint from the bottom? I find if I put a good bit of solder on the iron tip and hit each joint for about 3 seconds from the bottom, it flow out nice on the pad, on topside of the board.

The molten solder should flow to the opposite side of the hole and make a nice fillet, just as it should on the top side. Too much solder through the hole tells me the hole does not match the size of the wire lead you have going through the hole.

Paul

I was soldering resistors with just over 0.5mm leads in holes that were 0.7mm. They seemed to fit about right. Maybe slightly too lose. It flow into a fillet, just a taller fillet than I like, as it flows up the lead.

tsperry88:
Im using Kester 0.031 leaded solder. If I use less solder it ends up being flat on the backside rather than pyramided at all. Maybe I am trying to hard for aesthetics.

Flat is normal.

tsperry88:
I find if I put a good bit of solder on the iron tip...

Yep, most beginners do that, and that's the main reason things won't work.

Putting solder on the tip burns off the flux that's inside the resin-core solder (the smoke),
and you can't solder without that.

Look at picture#1 of larryd. Clean tip that heats up both wire and pad.
Then the solder goes to the pad/wire, NOT the tip, to keep that flux from burning off.
If you do it right, then you don't need that (messy) extra gel/flux.
Leo..

Which side of the board are you soldering, component side or bottom?

I only tin the tip when I solder the componants. I meant a good bit of solder when I am reheating from the bottom. Before I do that I hit all the componants lead with a flux pen. The glob of solder on the tip just seems to pull off any extra via gravity. The below photo is the best I can show of what I mean by to much. It looks globby to me.

I solder from the bottom so I don't have a flux mess on the top to clean.

Here is after I let the solder flow back through via gravity while heating from the bottom. When I really magnify the topside, it does leave a matt looking joint. Which means more flux and more cleaning on the top. Does my first picture look well done before reheating?

tsperry88:
I only tin the tip when I solder the componants. I meant a good bit of solder when I am reheating from the bottom. Before I do that I hit all the componants lead with a flux pen. The glob of solder on the tip just seems to pull off any extra via gravity. The below photo is the best I can show of what I mean by to much. It looks globby to me.

I solder from the bottom so I don't have a flux mess on the top to clean.

It doesn't look that bad to be honest. Might use a little bit less solder, but it doesn't look bad.

In my opinion its harder to put solder onto the iron and then glob it onto it. I think its more precise when you stick the iron next to where you want to solder and feed the solder into it. It makes a nice small clump like what LarryD showed in his picture above.

Believe me, I have seen a lot worse. I would recommend using a little less solder. One add to the Adafruit diagram LarryD posted, I initially try to rapidly heat both the lead and the pad. This by wedging the iron carefully between the two. It's shown in step 2, but you can do this better or worse. I apply a little solder directly to that join, now a small solder bridge connects the 3, the iron, the part, and the pad. When I see that dab of solder melt, I go in with the rest of the solder. At that point everything is already up to temperature, so that only takes a short time. It sounds more complicated than it is, once you get in the habit it improves most joins.

I suspect from some of your comments that you are heating for too long. You can easily damage pads or components doing that.

I place the iron tip on the pad and against the lead. I then touch a dab of solder directly on the iron to start it flowing. Once it begins to flow I feed it into the pad oposite the lead from the iron. I pull the solder wait a couple seconds and remove the iron. Is this similar to the procedure you described?

I believe i have my iron set to 350c, I don't feel like going to check right now:) If I don't touch a dab of solder to the iron tip to start the flow, it seems like it takes forever to get the pad hot enough to melt the solder and I'm worried about overheating something.

tsperry88:
I place the iron tip on the pad and against the lead. I then touch a dab of solder directly on the iron to start it flowing. Once it begins to flow I feed it into the pad oposite the lead from the iron. I pull the solder wait a couple seconds and remove the iron. Is this similar to the procedure you described?

I believe i have my iron set to 350c, I don’t feel like going to check right now:) If I don’t touch a dab of solder to the iron tip to start the flow, it seems like it takes forever to get the pad hot enough to melt the solder and I’m worried about overheating something.

Clean your iron on a wet sponge or cotton cloth just before your apply the iron to the pad/lead. Stop as soon as your solder begins to flow around the lead. Your description of your procedure indicates there is a lack of flux, so it is likely burning off. What flux are you using, what solder alloy?

By the way, all components manufactured in the last 15 years have tin coated leads, not solder coated, as they used to be and that makes flux imperative. Your boards may or may not have solder coating on the traces.

Paul

Paul

tsperry88:
I then touch a dab of solder directly on the iron to start it flowing.

Try to put the solder on the wire/via, not on the tip of the iron.
The tip is hotter than the wire, so the flux will burn off faster, which you should try to avoid.
Leo..

tsperry88:
I place the iron tip on the pad and against the lead. I then touch a dab of solder directly on the iron to start it flowing. Once it begins to flow I feed it into the pad opposite the lead from the iron. I pull the solder wait a couple seconds and remove the iron. Is this similar to the procedure you described?

I believe i have my iron set to 350c, I don't feel like going to check right now:) If I don't touch a dab of solder to the iron tip to start the flow, it seems like it takes forever to get the pad hot enough to melt the solder and I'm worried about overheating something.

Tsperry88,
Firstly, I applaud your desire to get a nice conical fillet on both sides of your PCB.

That is the target for a good PTH soldered joint, but it is not essential to achieve that every time.

Have a look at this IPC-A_610 document. It will show you what is considered acceptable and what is a defect.
(Unfortunately I couldn't find a free copy without that annoying watermark.)

Your technique seems to be quite good.

You need to feed in the correct amount of solder, and then remove the soldering tip and the solder at the same time. Don't hold the iron in place after you stop feeding the solder on to the joint or you risk getting a spike as you remove the iron.

You will only get to get to know what the 'correct amount' of solder is by experience. (and the correct amount will change for different PCBs and components).

You could try reducing your tip temperature down to 300°C, so that the solder flows more slowly to enable you to judge the correct amount more easily.

John Hales CIS (Certified IPC Specialist)

Most of the guides miss the no.1 trick, which is to press the solder against the joint with the
tip of the iron. When the rosin core melts it helps to transfer heat to the parts, and protect against
oxygen, then the solder melts and it wets both iron and joint simultaneously.

Pressing an iron against parts without flux present causes premature oxidation, making it harder
to make a joint.

So either pre-coat with rosin gel or paste, or apply solder and iron together to the joint.

Once the solder melts it takes a couple of seconds for the heat to spread and wick more solder into
the joint nicely - this is when you feed the solder in a bit.