Remove a castellated PCB with Weller WRK SMD reflow set

Jan Cumps — Sat, 18 May 2024 19:35:38 GMT

Removing castellated PCBs, once soldered, can be a tricky task. It's not easy to get the solder on all castellations heated up at the same time.

I had to replace the XIAO RP2400 board on my Pi Pico Eurocard Development Board. Doing this with a high capacity iron, or with hot air isn't easy. By the time you get to pin 14, pin 1 has gone solid again.
You may get away with prying under the board while attacking each castellation, but chances are that you 'll tear off the pads from the motherboard.

One possible solution is to ply a thick copper wire in such a way that it surrounds the PCB and touches all castellations. Then, with a decent iron and a lot of flux, heat up that wire.
I decided to try removing the IC with a Weller WRK SMD reflow kit.

This kit has little ovens that you can put on top of something. And it has a vacuum-actioned suction cup that you can stick on top of the device that needs to be removed.

When you then put a hot air pencil in the little oven's opening, the inside gets hot very fast. No risk of burning the neighbour components. And very efficient heat usage.

When I tried this at 380° C, the castellated board lifted off in 20-30 seconds. Without any damage.

This is the motherboard after the action:

And the castellated board survived too:

There is a little alchemy and experience involved. In my case, the XIAO used lead-free solder, and the castellated board was placed with leaded.
That meant that the castellations melted faster than the components on the XIAO. And when the lift-off happened, the whole board came off.
It's not that easy in every case.

But you can prepare for this. In case the castellated board is placed with lead-free, You can first wick off most of that, and replace it with leaded solder (or even lower melting point specialised products). Then use the oven to remove everything.

Anyways, after this exercise, I cleaned up the motherboard and put on a new XIAO RP2040.

Thanks for reading.

I purchased a Weller reflow set

Jan Cumps — Sat, 08 Oct 2022 21:17:58 GMT

The title says it all. I have a Weller solder station. They have IC reflow gizmos that work together with its hot air gun.

image source: sinuss.nl, the element14 retailer in Belgium and the Netherlands

These are little ovens, that you put on top of the IC you want to rework. Then you put the hot air pencil inside, to flow the solder.
There's a chip lifter (think: coal mine headframe) that can then lift the IC.
It can also be used to place ICs. Should help me with BGA designs.

It may be over-fancy. Paul Daniels and Louis Rossmann do all of this with just a heat gun. But I'm not that skilled - don't do it enough to be repeatedly successful.
My kit is also expensive. The one I bought, with support for 10x10 mm to 33x33 mm (with 6 steps in between), costs 500 €. An amount that I do not easily give away for tools.

Here's a video from Weller:

https://youtu.be/-7GZz-C5peI

I have now burned my budget for the next two years (three years actually, but last year I didn't buy anything). It 'd better work as promised.
Send me your old PCBs, so that I can practice.

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Remove a castellated PCB with Weller WRK SMD reflow set

I purchased a Weller reflow set