Solder Gap

[davidvincent]

Hi this might sound stupid in the link below is a jpeg of a power suppy that I am installing new electrolytic caps my question is if you look at the main tracks there is a very small gap between the wide tracks and the solder joints while desoldering the gap has closed on two of them and even with solder wick I cant get the gap back do the joints connect to the main tracks as I don't see why they are so close

thanks D V


https://www.badcaps.net/forum/attach...4&d=1385209875

[budm]

Re: Solder Gap

Can you point that out in the picture (in the link you posted)? There are many wide tracks on the board.

[davidvincent]

Re: Solder Gap

Hi I have tried to upload a picture with a circle on but it wont upload

if you look at the board in the middle there is a big wide track that looks like a big number 7 at the top of the seven along its top there are two solder joints with a very fine divider between joint and track the joint solder has run into the wide track I have solder wicked it but there now seems to be no small green divider

I will try again to upload a picture

bingo pic was too big

DV

[davidvincent]

Re: Solder Gap

Another pic

[davidvincent]

Re: Solder Gap

I have just ran a pin across the surface and the green stuff is on top of the metal so could it be that it is green paint around the solder joint and it came off during de soldering and the solder joint is part of the big track, seems a bloody stupid way to make a board, I have put my meter over on the primary side it has the same set up were the big tracks don't seem to connect to anything and I get continuity between every solder joint that's right next to it and the wide track, god I wish I cold find a circuit diagram for this board

DV

[davidvincent]

Re: Solder Gap

its looking like its just green paint that came off due to heat desoldering and the solder joint is part of the big rail, if so what a stupid way to lay out a circuit board a mate is calling to give me his opinion as the last thing I want is the board going BOOM

dv

[mariushm]

Re: Solder Gap

You have a large (wide) copper trace there, which would normally be covered all the way with that green paint (which insulates the copper and prevents it from oxidizing, and also prevents shorts).

However, when there's a lot of electricity going through such a copper trace (which is not thick, it's only about 0.16-0.35mm thick), it can heat up and can get damaged. To improve the copper trace's ability to carry current without overheating, it's a common practice to remove a part of that green insulating layer and apply solder over the raw copper and this way, that copper trace becomes thicker and capable of carrying more current and will heat less.

The extra solder acts more or less like a heatsink, and makes the whole "wire" on the pcb bigger and stronger.

Now, since the solder is applied through wave soldering (board moves through a machine and there's a wave of solder from below touching all the exposed copper), they have to leave a tiny bit of insulation between the lead of the part (and the hole in pcb) and the rest of the surface they want to add solder to.

Without a small separation, the solder around the hole and lead could be pulled away by the solder that covers all that large area, because that large surface with solder cools (solidifies) slower than small solder joints.

Basically, it makes for better soldering, less soldering failures.

[davidvincent]

Re: Solder Gap

mariushm
Thank you so much for this info so now I know that the joint is part of the copper trace with solder on, I have done a few lcd power supplies (replace electrolytic caps) but never come across this sort of thing before, my knowledge is much greater thanks to you

regards

DV

[budm]

Re: Solder Gap

The green coating is called Solder Mask. They are applied to section of copper that the board designer do not want it to be cover with solder.

[davidvincent]

Re: Solder Gap

Thanks Budum
always great info on here

DV