Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Is there a safe way to fix this scratch on the hot side of PSU?

Status
Not open for further replies.

eagle1109

Full Member level 4
Joined
Nov 20, 2014
Messages
226
Helped
2
Reputation
4
Reaction score
2
Trophy points
18
Location
Saudi Arabia
Activity points
2,785
Hello,

This is not new problem to me, I encounter power lines come off when desoldering something from the PSU.

Maybe I put the soldering iron a several times on the pin to melt the soldering wire. But that shouldn't happen on commercial grade Dell PSUs! I mean the PCB should handle the temperature of the soldering iron.

20190116_135028.jpg

What should I do? Should I just connect this part by putting some soldering wire? I think that would solve the problem, but I'm afraid of the SMD resistor part, I don't know if I could connect its part to the soldering process, but I guess its end would get connected with the soldering wire I put in that area.

- - - Updated - - -

Also, is this a burnt on this small HFT?

20190116_140750.jpg

20190116_140801.jpg
 

betwixt

Super Moderator
Staff member
Joined
Jul 4, 2009
Messages
14,128
Helped
4,676
Reputation
9,367
Reaction score
4,415
Trophy points
1,393
Location
Aberdyfi, West Wales, UK
Activity points
120,719
Dell PSUs are no better or worse than every other make.

Top picture: not much you can do to restore the original copper, I think I would run a wire link between adjacent solder pads along the track and angle it to touch the SMD resistor. You can get PCB repair kits and glue new copper down but it's a lot of effort just to make it cosmetically better.

Lower pictures: the solder between the third and fourth pins from the top looks pitted as though it has arced at some time. The board seems to have some residue on it which may have become conductive at some time and bridged the pins. All you can do is clean it thoroughly and resolder the joints to make sure no 'spikes' are left that might narrow the gap.

If the board is used in damp conditions, after repair, spray it with HPC or some similar conformal coating to keep moisture out.

Brian.
 

c_mitra

Advanced Member level 5
Joined
Nov 13, 2012
Messages
3,367
Helped
846
Reputation
1,692
Reaction score
797
Trophy points
1,393
Activity points
25,730
The copper film is stuck to the base plastic with glue; this appears to be fiber-glass bonded with epoxy. The copper foil is stuck with epoxy glue. This is a thermoset polymer and bonds well with metal.

However, no bond can stand excessive heat. But you can fix it with a drop of epoxy glue; there are some that set fast. It may not look as new but it may work as well.

About the second (and third pic): YES. you need to remove and clean and check and resolder. A post mortem will be in order.
 

BradtheRad

Super Moderator
Staff member
Joined
Apr 1, 2011
Messages
13,440
Helped
2,656
Reputation
5,306
Reaction score
2,561
Trophy points
1,393
Location
Minneapolis, Minnesota, USA
Activity points
100,500
I used the CircuitWorks silvery conductive pen and silver epoxy. They stuck to PV cells when I needed to attach wires but I vaporized the solderable traces with excess heat.

An auto parts store may have a repair kit for defogger grids. Copper particles suspended in solvent. Examine the packages carefully because I found some had dried out in the tiny bottle.
 

pjmelect

Advanced Member level 2
Joined
May 13, 2012
Messages
519
Helped
120
Reputation
240
Reaction score
119
Trophy points
1,323
Activity points
4,226
The first picture the track has lifted, I would solder a piece of wire in its place, the third picture the solder joints have burnt due to very high peak currents and the second from the bottom joint looks open circuit, I would remove the component connected to these pins, check and clean or replace and refit.
 

eagle1109

Full Member level 4
Joined
Nov 20, 2014
Messages
226
Helped
2
Reputation
4
Reaction score
2
Trophy points
18
Location
Saudi Arabia
Activity points
2,785
The copper film is stuck to the base plastic with glue; this appears to be fiber-glass bonded with epoxy. The copper foil is stuck with epoxy glue. This is a thermoset polymer and bonds well with metal.

However, no bond can stand excessive heat. But you can fix it with a drop of epoxy glue; there are some that set fast. It may not look as new but it may work as well.

About the second (and third pic): YES. you need to remove and clean and check and resolder. A post mortem will be in order.
Could you send me a link in aliexpress for this kit?

I used the CircuitWorks silvery conductive pen and silver epoxy. They stuck to PV cells when I needed to attach wires but I vaporized the solderable traces with excess heat.

An auto parts store may have a repair kit for defogger grids. Copper particles suspended in solvent. Examine the packages carefully because I found some had dried out in the tiny bottle.
Well, in my country and specifically in the city I'm in, I don't think there are repair shops that could have professional repair tools. I always buy anything from Aliexpress. So I would appreciate it if you send me links for the stuff you told me about.

The first picture the track has lifted, I would solder a piece of wire in its place, the third picture the solder joints have burnt due to very high peak currents and the second from the bottom joint looks open circuit, I would remove the component connected to these pins, check and clean or replace and refit.
The 2nd and 3rd pictures are for the same spot, I just took a picture from very close and little far for more observation to the area because that is a high frequency transformer located along the other high frequency transformers between the high / low voltage sides of the PSU.


=====================================================================================================

I have another question:
I want to buy thermal pads for the power mosfets, which one should I get? I found a conductive one on aliexpress:
https://www.aliexpress.com/item/100...lgo_pvid=c58bb9b1-a9d5-4efd-b90b-a04d5d085c8c

Would this one work?
 

BradtheRad

Super Moderator
Staff member
Joined
Apr 1, 2011
Messages
13,440
Helped
2,656
Reputation
5,306
Reaction score
2,561
Trophy points
1,393
Location
Minneapolis, Minnesota, USA
Activity points
100,500
I always buy anything from Aliexpress. So I would appreciate it if you send me links for the stuff you told me about.
Aliexpress lists it but 'no longer available'. (US $44.80) It isn't flux and it isn't thermally conductive paste. Its formulation must be a trade secret because it worked like magic so I could attach wires to solar cells, headphone transducers, and inside a Honeywell calculator. (I only paid $12 for the pen. I'm not sure I'd pay $44.80.)

https://www.aliexpress.com/item/Cir...lver-Conductive-Pen-Dispenser/1874633569.html

Aliexpress lists defogger grid repair kits. Varying prices. Here is one for US $7.49:

https://www.aliexpress.com/item/Loc...nes-Make-Permanent-Invisible/32864938550.html

My bottle had liquid containing copper particles similar in size to fine sand. There's a question how suitable it is for miniaturized electronics.

Because I found a few dried out glue bottles in the auto store, it might pay you to ask them to examine the kit they send you, to make sure the glue is good.
 

c_mitra

Advanced Member level 5
Joined
Nov 13, 2012
Messages
3,367
Helped
846
Reputation
1,692
Reaction score
797
Trophy points
1,393
Activity points
25,730
Could you send me a link in aliexpress for this kit?
There are several - this one is one example: high viscous 5 seconds quick to dry metal machine glass fiber ceramic hard plastic epoxy resin adhesive super AB glue

I want to buy thermal pads for the power mosfets, which one should I get? I found a conductive one on aliexpress:
Silicones are plastics (polymers) and they are good conductors of heat (compared to other plastics and do not compare them with metals). Use the thinnest one that will meet your requirements.
 

i200yrs

Advanced Member level 4
Joined
Aug 23, 2016
Messages
117
Helped
1
Reputation
2
Reaction score
1
Trophy points
18
Activity points
874
1st pic: If you want faster repair, just add jumper wire replace the broken line, it should be fine. Using repair kits need some skills.
2nd pic: It's true heat marks, possible got bad solder already. Suggest to solder touch-up that pins.

Some repaire tips https://elex518.blogspot.com/
 

eagle1109

Full Member level 4
Joined
Nov 20, 2014
Messages
226
Helped
2
Reputation
4
Reaction score
2
Trophy points
18
Location
Saudi Arabia
Activity points
2,785
Aliexpress lists it but 'no longer available'. (US $44.80) It isn't flux and it isn't thermally conductive paste. Its formulation must be a trade secret because it worked like magic so I could attach wires to solar cells, headphone transducers, and inside a Honeywell calculator.

Because I found a few dried out glue bottles in the auto store, it might pay you to ask them to examine the kit they send you, to make sure the glue is good.


There are several - this one is one example: high viscous 5 seconds quick to dry metal machine glass fiber ceramic hard plastic epoxy resin adhesive super AB glue

Silicones are plastics (polymers) and they are good conductors of heat (compared to other plastics and do not compare them with metals). Use the thinnest one that will meet your requirements.
Yep the name is long, I think it's some sort of special glue for PCB repairs, am I right? Is it similar to; like, super glue, or it may contain conductive stuff for the conductivity of the copper path of the PCB?

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

In regard to the thermal pads, yes I think anyone would work as it should be a silicon. Yes thank you for the tip.

1st pic: If you want faster repair, just add jumper wire replace the broken line, it should be fine. Using repair kits need some skills.
2nd pic: It's true heat marks, possible got bad solder already. Suggest to solder touch-up that pins.

Some repaire tips https://elex518.blogspot.com/
1. You're right I better repair it with a wire or some solder wire and that's it.

2. That black color is what I think is a spark! It could be the cause of failure of that PSU.
 

eagle1109

Full Member level 4
Joined
Nov 20, 2014
Messages
226
Helped
2
Reputation
4
Reaction score
2
Trophy points
18
Location
Saudi Arabia
Activity points
2,785
Got this thermal pad recently

20190304_145104.jpg

I think it's a bit thick, but anyway, is it suitable for PSU power mosfets?
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search


Welcome to EDABoard.com

Sponsor

Sponsor

Design Fast


×
Top