Linksys EA8300 serial connection: soldering pins?

Hello guys,

I've been looking for a way to have a serial connection for my Linksys EA8300 routers, as I am planning to build custom firmwares for it (as for my Linksys WRT3200ACM, which luckily has pins for a serial connection already exposed), so in case things go south, I'd like to have a fallback/troubleshoot plan.
Opening up the EA8300 was easy enough, however there seems to be some "material" in the pin holes, which prevents me from sticking pins through them and soldering them from the back.
Please see the following image (taken from https://openwrt.ifw.cn/_detail/media/linksys/ea8300_pcb_top.jpg?id=toh%3Alinksys%3Alinksys_ea8300 and zoomed in)

I don't think it's soldering tin, as I have been unable to desolder/free up the pin holes, but I might be wrong, as I am not an expert in soldering.

Finally, to my question:
How have you guys realized serial connections to the EA8300? Have you just soldered some wires onto the pin holes or did you drill through the holes and afterwards soldered some pins on it - or maybe just soldered the pins onto the holes?

.. or am I just too stupid to remove the soldering tin from the holes?

Every help is highly appreciated - thanks a lot beforehand!

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It looks like unleaded wave solder bubbles in that picture. The outer 2 pads look rather dark; oxidized or conformal coating?
I use leaded solder and reheat the 3 joints (not 3.3V pad) and insert berg pins there (red rectangle above) to get a serial connection.

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it may be soldering tin, but silver solder, which is higher temperature than leaded solder.

the DIR-882/878/2640/2660/1760/1960 come with that nightmare stuff in the holes, and yes removing it has been a chore.

if it is that stuff, then you will need to increase the heat on the iron to remove it.

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Well, I tried with the max my iron can offer (450 degrees, ERA i-CON nano), although I only tried it for a couple of seconds, as I was afraid, I would damage the board.
Can anybody with a EA8300 and working serial connection maybe share his/her experience on how to solder the pins?

@jeff If I recall correctly, you introduced the support for EA8300 back then, so I would assume you have/had a serial connection.
If so: Could you please share your experience? Thanks a lot!

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if you're afraid, don't do it. but silicon is quite resilient.

what i will say is that removing that stuff was among the more difficult tasks and you would need to hold it there for a few seconds before it would melt.

it was stubborn. but again don't do anything you're not comfortable with and i encourage you to solicit input of others, as you are doing now.

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@broly <--This guy solders.

This would be much more difficult - but there are alternatives.

Based on the picture provided it looks like the holes are only half full (half empty)?

This means you could probably just jam header pins straight in (halfway) and then hot glue it in place temporarily for "test purposes". That would be safer and easier than most commonly available clip on test leads and reversible.

Search:

20pcs 1x40 Row 2.54 Breakable 40 Pins Connector Strip Board Module Electronic Part Elektronik Single Male Pin Header For Arduino

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thanks for the compliment.

never thought of using hot glue to test the signal on those annoying-ass things. that's a good idea.

whatever, i only learned how to solder because of how incredibly difficult they were to deal with.

and imagine using silver solder as your first solder, in addition to having to remove it.

story of my life dawg

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Tip: Use a bunch of fresh solder to help flux and melt old solder.

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Wow. I also really struggled to get the solder bubbles out of the holes. I have so far not succeeded.
Silver Solder has a melting point at 1377F or 743C. Not sure my iron goes that high, but I'm checking.
It would be nice to know what temperature others had to use to deal.

It is only regular solder. The problem is that the ground hole is linked to an internal copper plane in the board which will dissipate heat rapidly from your soldering iron. I use a heat gun to preheat the whole area of the board. You can also use a small drill bit to mechanically remove the solder, but it will still take lots of heat to fully melt the new solder and properly install the pin. Which leads to another workaround of not soldering the pins at all, but just putting them through clear holes (drilled out if necessary) then tilting the pin assembly to the side so they make contact for the one time you need serial.

Most of the time I've been lucky where I have just pushed it out with a pin.