Serious Soldering Problem - Photo

Thread Starter

Lumenosity

Joined Mar 1, 2017
461
Hello,
Today I ran into a problem where solder from two adjacent pads on a PCB hve joined and I cannot seem to get the two pads to seperate.
I use copper braid to remove the solder and I removed the IC chip successfully but ran into a horrible problem soldering the new IC chip into place.
I've tried lots of flux, more heat, reflowing the solder and wicking it up again....all to no avail. etc.
No matter what I try, the two pads show refuse to separate. What is the correct wat to fix this problem?
I can't seem to get the solder out from between the two pads to save my life.
NEVER had this kind of problem between two pads before.
Thanks!

SolderPadProblem.jpg
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
461
The chip is a TL494CN

From the datasheet schematic, I don't think they should be connected??
Pins 13,14,15

But you know what? On the PCB, it DOES look like 13,14,15 ARE connected ?

TL494CN.jpg
 

crutschow

Joined Mar 14, 2008
23,334
The joints look bad or like possible cold solder joints.
Use flux and much less solder. All you want is just sufficient solder to connect the pad to the pin.
See picture below.
Your joints should look like the OK ones.

 

ebp

Joined Feb 8, 2018
2,332
It makes reasonable sense to me that they might be connected together. Try shining a bright light on the component side of the board in that area while you're looking at the solder side.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
461
Thanks for the assist guys.

Looking carefully at the PCB, it does appear those three pins are connected. (Thank God)

So I just resoldered them and the circuit now works.

That could be why the solder flowed between those two pads so easily and was so difficult to remove...they're all on the same one large solder mask.

May have had nothing at all to do with my soldering technique. (this time)
 

MisterBill2

Joined Jan 23, 2018
3,869
But Crutschow is right about there being way too much solder. No question there. Also, it looks like the temperature was not quite right. Or else lead free solder was used.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
461
But Crutschow is right about there being way too much solder. No question there. Also, it looks like the temperature was not quite right. Or else lead free solder was used.
"Way too much solder"? No.
Slightly too much solder? Maybe.
I think the photo makes it look that way due to being directly overhead.

Temperature was set according to the solder and for the situation.

Lead free solder was not used.

The issue here (as others correctly pointed out) was that I confused several pads for ONE large solder pad.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
3,869
OK, the angle being what it was, it may just be more than enough instead of "way too much". But towards the end that we don't see it looks like there is more. My comment about lead free solder is because that stuff is just not as good as the "real solder." But that is for a different discussion area.
A small goof in setting on a wave soldering machine can cause a large drop in production yield on boards that have things that close, and some of us are way sensitive about the amount of solder, as a result.
 

ian field

Joined Oct 27, 2012
6,543
I concur. Those three pads are joined, and the solder mask has been abraded.

Don't worry about it. There is no problem here.
My eyesight isn't getting any younger, so I sometimes completely unsolder the suspect pads and scrape off the varnish so I can see easily.
 

crutschow

Joined Mar 14, 2008
23,334
"Way too much solder"? No.
Slightly too much solder? Maybe.
Sorry, but it's too much solder (maybe not "way" but certainly more than "slightly"). :rolleyes:
If you can't see the outline of the pins as shown in the two "OK" joints diagram, it's too much solder and a potential bad joint (or one that can go bad with time).
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
461
OK, the angle being what it was, it may just be more than enough instead of "way too much". But towards the end that we don't see it looks like there is more. My comment about lead free solder is because that stuff is just not as good as the "real solder." But that is for a different discussion area.
A small goof in setting on a wave soldering machine can cause a large drop in production yield on boards that have things that close, and some of us are way sensitive about the amount of solder, as a result.
Sounds good. I don't do a lot of soldering.....just occasionally. I'll see if I can use less solder next time.
It might be I need a better quality solder. I'm using a Chinese 60/40 (MingShida Hardware Co - probably not very good stuff) and this time I used 1.5mm instead of 1mm, mainly because I couldn't locate the 1mm at the time.

But as mentioned.....the circuit is working now so alls well that ends well.

It helped a lot when a few of you guys mentioned that the pad was actually one big pad. I had missed that.
 

MisterBill2

Joined Jan 23, 2018
3,869
Spotting joined pads takes a good magnifier and adequate light, plus knowing what you are looking for. The other way to spot it would have been to remove all of the solder, cleanly and then examine the trace. It is hard to do tat with a device in place. So asking was the way to learn, which is part of why this forum exists.
 

Sensacell

Joined Jun 19, 2012
2,446
Three words:

Flux,
Flux,
Flux,

A bit of flux helps make soldering much less of a mysterious process, the solder then behaves in a friendly and predictable manner.
 

MisterBill2

Joined Jan 23, 2018
3,869
Three words:

Flux,
Flux,
Flux,

A bit of flux helps make soldering much less of a mysterious process, the solder then behaves in a friendly and predictable manner.
Certainly flux is important in soldering to copper. But in soldering to some other materials it is absolutely VITAL!! And there is a big difference among different brands and kinds.
AND, it is very important, for some kinds of fluxes, to clean off every single bit of the flux after the soldering is done, because some fluxes are horribly corrosive. So always read and follow the instructions with the flux.
 

Tonyr1084

Joined Sep 24, 2015
3,578
Just a few more words on solder, and on inspection: First, when you're soldering a pin to a pad that has a small trace to it - you can expect solder to wet and flow much more quickly than when you're soldering to a ground plane (or power plane). The larger the trace going to the pin the longer the solder joint takes to heat up and melt. The wrong flux can evaporate before the critical temperature is reached. You'll need more thermal mass when soldering to larger traces; and in the case of these pins, while not being a ground plane, it's going to take more heat and take longer. If you have an adjustable temperature iron you can turn it up 25˚ (F). Just be sure not to dwell too long on smaller traces.

Now, on inspection: The amount of light on a joint will make a difference in how it looks. Straight down, as in your picture, can be difficult to determine how well the solder flowed and how much solder is present. I must agree with MisterBill2 on this one. I've been inspecting solder just over 30 years, and yes, it looks like there is excessive solder. In the illustration MisterBill2 gave you shows two pins that are classified as "OK". Those two pins ARE "OK". The right pin being the preferred amount, where the left pin is bordering on the excess side. The redeeming factor of that pin is that you can still discern the lead at the top of the joint. It would not be a rejection in any class of electronics assembly (1, 2 or 3), but would be (again) borderline as a process indicator. Both J-STD-001 and IPC-A-610 rev F say the same thing about such solder joints. When you can not discern the lead protrusion in the solder, classes 2 & 3 are rejects.

Lighting and angle of view are important. You really need to be able to tilt and roll the board to get a good idea of how much solder is present. Straight down and ONLY straight down view is difficult. But the angle of light can also make a difference. The two afore mentioned standards also have standards on how much magnification should be used when inspecting solder joints. So looking at the picture you posted, it DOES look like there is excessive solder. Certainly pin 7 would be candidate for rework. But since this is a DIP chip the decision to NOT rework it would be made on the basis that there's a high probability the pin is in the solder, though it can not be discerned. Had that been an axial lead component you'd be reworking it.
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
461
Three words:
Flux,
Flux,
Flux,
A bit of flux helps make soldering much less of a mysterious process, the solder then behaves in a friendly and predictable manner.
I like "No Clean Flux Paste" from MG Chemicals.

HIGHLY rated. I use it like water when soldering :)
 

Thread Starter

Lumenosity

Joined Mar 1, 2017
461
Certainly flux is important in soldering to copper. But in soldering to some other materials it is absolutely VITAL!! And there is a big difference among different brands and kinds.
AND, it is very important, for some kinds of fluxes, to clean off every single bit of the flux after the soldering is done, because some fluxes are horribly corrosive. So always read and follow the instructions with the flux.
My FAVORITE....and what I use all the time....



 
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