Identifying Soldering Faults

[Richie_asg1]

Just thought this is worth a look for examples of good practice -

http://workmanship.nasa.gov/lib/insp...uirements.html

As a newbie to most of this. This kind of information is needed so we can spot a good one from a bad one.

Please post other example pictures in this thread as you see fit.

Other pictures from the net - copyright of their original owners.

(All of the above are actually bad)

[MegaOne302]

Re: Identifying Soldering Faults

Check this site out; they have mostly every type of PCB defect possible.

PCB Troubleshooter

[Wizard]

Re: Identifying Soldering Faults

Here's extremes.

Was in 2002:
You have a circuit board that passes all visual tests till a experienced tech showed me and I was shocked. Through hole capacitor lead is not bonded to the solder even you had all good signs of solder! It was easy test, Wiggle the component back and forth, it will break the weak bond.

Hot glue on the component will and does wick down into the through hole and destroy the solder bond by thermal cycling due to thermal expansion cycles in 1 to 2 years and low-level ultrasonic vibration (unavoidable with switching regulators, *any* transformers in 20-100KHz range. That was original manufacture. So I do no longer use hot glue. I use RTV to secure components where necessary.

Now exact device that DID not get the hot glue on same component, said failure did not happen.

This also depend on OEM design to keep resistors and component within thermal envulope when item is operating. Exceed that and you will have cracked solder.

Cheers, Wizard

[krazykev64]

Re: Identifying Soldering Faults

just to inform forum members that it is not just computers and other similar items that have bad solder joints. i have a friend who owns a business specialising in Nissan cars. there are various models of nissan that are prone to faulty air flow meters. this is the part on the inlet manifold that looks like a carb. if it is the type with an alloy plate around 2 by 2.5'' then i will let you into a little secret. first of all you need to remove the unit which is easy. make sure you disconnect the battery first. if you remove the little plate by cutting the black sealant and then prising it off with a small screwdriver you will see a 2 small circuit boards. the problem is the solder joints as they are prone to breaking down causing the car to run rough. 99 times out of a 100 there is no faulty part. you just desolder then resolder the joints on the top board and fix the plate using silicone sealant and the job is done. i have been repairing these units for my friend for around 4 years and virtually every one has worked ok. i have even included a picture of the board with the alloy plate removed. before you remove the throttle position sensor make sure you mark it first so it goes back the same way. a full guide can be downloaded from
https://cdn.badcaps-static.com/pdfs/...50931bd89c.pdf

[japlytic]

Re: Identifying Soldering Faults

In 1975 (the same year colour TV started broadcasting in Australia), my parents bought a Rank Arena C1851 (if the model is correct, because they said that the size matches the description). This was a rebadge of an NEC set.
I was told that it had a number of bad solder joints and apparently worked when warm. It was even put on top of the barbecue and worked then, then it finally stopped working completely in 1983 (if that is correct), when they bought a more reliable Thorn (Mitsubishi rebadge) set (still working today, never required repair since day one!)

In a valve (or tube) radio which I use every day, it developed an intermittent problem, which was caused by a bad solder joint when replacing the paper capacitors.

A heat gun can help identify areas with bad solder joints.

[Player2]

Re: Identifying Soldering Faults

Here's extremes.

Was in 2002:
You have a circuit board that passes all visual tests till a experienced tech showed me and I was shocked. Through hole capacitor lead is not bonded to the solder even you had all good signs of solder! It was easy test, Wiggle the component back and forth, it will break the weak bond.

Hot glue on the component will and does wick down into the through hole and destroy the solder bond by thermal cycling due to thermal expansion cycles in 1 to 2 years and low-level ultrasonic vibration (unavoidable with switching regulators, *any* transformers in 20-100KHz range. That was original manufacture. So I do no longer use hot glue. I use RTV to secure components where necessary.

Now exact device that DID not get the hot glue on same component, said failure did not happen.

This also depend on OEM design to keep resistors and component within thermal envulope when item is operating. Exceed that and you will have cracked solder.

Cheers, Wizard

Wow! That's good to know. I've used hot glue a couple times, even Googled it and couldn't find anyone saying it was a bad idea. Will definitely use the RTV silicone from now on.