RCA soldering on a PCB?

[KozmoNaut]

I recommend 63/37 over 60/40, if you can find it. It melts easier and solidifies faster, reducing the risk of bad solder joints.

The reason is that its melting point is a precise temperature, not a range of temperatures, which makes it much more predictable.

 

[boXem]

OK on the not lead-free.

My soldering skills are fine(not SMD). Lots of use over nearly 50 years.

Can you explain the very high melting point of the solder?? That was the problem.

Your soldering skills are certainly better than mine .
On the melting point, I am not a solder expert, and since I do not intend to become one, I didn't do any research. In addition to the oxydation mentioned, I have two hypothesis:
- thermal cycles have an effect on the melting point
- some electrolytics structure act as a radiator, making the melting point of the old solder even more difficult to reach.

 

[Killingbeans]

- some electrolytics structure act as a radiator, making the melting point of the old solder even more difficult to reach.

That's actually a better bet on an explanation than oxydation. Especially if the negative pin was soldered to a large solid ground plane. Most of the PCB + the capacitor would have acted as a cooling profile.

 

[Wombat]

Your soldering skills are certainly better than mine .
On the melting point, I am not a solder expert, and since I do not intend to become one, I didn't do any research. In addition to the oxydation mentioned, I have two hypothesis:
- thermal cycles have an effect on the melting point
- some electrolytics structure act as a radiator, making the melting point of the old solder even more difficult to reach.

Small electrolytics, narrow traces and small pads. Never been a problem before. I think it was the solder.

I have read of multi-pass board soldering where the melting point of first-pass solder is high, then reducing for each subsequent pass. I don't know if this was the case for the board in question.

Note the globular nature of the solder joints on passive components, rather than flowed. Unusual. The board I had was identical.

 

[restorer-john]

Note the globular nature of the solder joints on passive components, rather than flowed. Unusual. The board I had was identical.

The board also appears to have a conformal coating (common in vehicle pcbs).

I would strip that off with acetone around the components you are de-soldering.

 

[Wombat]

The board also appears to have a conformal coating (common in vehicle pcbs).

I would strip that off with acetone around the components you are de-soldering.

I did that. Bloody tough coating it was.

 

[yavormoskov]

Alright folks, it's official. Just ordered Hakko FX888D-29BY/P. I ordered from official Hakko distributor but should have checked Amazon first. Now I have to wait a week. I decided I am not so rich to buy cheap products over and over. I will buy Kester 63/37 solder and will practice a little on junk electronics from Goodwill before opening my amp.

 

[Wombat]

Google 'NASA soldering' for some great references.

 

[captain paranoia]

Can you explain the very high melting point of the solder?? That was the problem

Lead-free solders are a completely different alloy, with a much higher melting point than Pb-Sn.

Bit temperatures of 700F are not uncommon.

For large metal connectors, you need a high power iron and a good contact area, and a well-wetted bit. Adding more solder to the joint, and flux, can increase the ability to transfer heat to the joint.

If there's a ground or power plane that the component is soldered to, it can act as an effective heatsink, making it harder to desolder.

 

[DonH56]

Bunch of online descriptions of lead-free solder. It is, or was at least, also more likely to form stringers causing shorts down the road.

https://www.digikey.com/en/maker/blogs/rohs-vs-non-rohs-soldering
https://en.wikipedia.org/wiki/Solder

 

[Killingbeans]

The risk of tin whiskers developing over time is definitely my main concern when using lead-free solder.

Good quality lead-free solder actually have a melting point that's not unreasonably much higher than the old school stuff, but it comes at the price of using particularly nasty varieties of flux, and proper ventilation/filtering is a must when using it.

 

[JohnYang1997]

High quality lead free solder don't make much difference in "solderability" compared to 63/37. Flux makes all the differences as we all use 300C plus for hand soldering anyway. The major difference is the effect on the tip. You don't have to clean the tip as often when using leaded. For through hole stuff or 0805 even soic there is little difference even when the tip is mildly oxidized. If you are doing fine pitch stuff sop or smaller you basically need to clean your tip after every few runs.