How to solder 20pin header onto an unpopulated footprint of an Asus motherboard? - Page 1
Forum section: electronics / projects

author: GotZapped
author_rank: Contributor
timestamp: July 18, 2020, 07:04:08 am
content: Hi,Not sure if this is the right spot for this question. Mod's please move if needed.I plan to install a port of OpenBMC by Raptor Engineering onto a Asus KGPE-D16 Opteron-based motherboardhttps://www.raptorengineering.com/coreboot/kgpe-d16-bmc-port-status.php. However, it requires the installation of a 20-pin ARM debug header in the unpopulated AST_JTAG1 footprint as shown in the picture from Raptor Eng.I've seen suggestions to use pogo pins (e.g.https://www.cfeconn.com/connector/20-pin-pcb-pogo-pin-connector-factory) to interface with the debug header pads, but I'm not sure how to keep them in place.Hence, I'll bite the bullet and install the header. I don't wish to damage the board as I would need to first clear the plated through-holes (eyelets) of solder without damaging surrounding components. I've searched online and not found anything specific to what is a reliable technique for clearing through-holes on motherboards. From what I've read, because motherboards have typically ~16 layers they can absorb a lot of heat so preheating is recommended.Q. What is the suggested technique for clearing solder from eyelets of multi-layer motherboards like the KGPE-D16?Q. Is preheating recommended? If so, how to do it correctly?Once the through holes are cleared I imaging soldering the header into place would be like soldering any other PCB.I have access to a decent Hakko soldering station, solder sucker, solder pot, desolder braid, smd hot air gun, heat gun, etc. I imagine it does not require expensive specialised equipment, just good technique. Your advice and maybe a video of a true master at work would be appreciated.Thank you.

author: zzattack
author_rank: Regular Contributor
timestamp: July 18, 2020, 08:10:18 am
content: I'm not sure how many layers this board has but it's definitely possible. Given its age, the first thing you should do is mix the lead free solder with leaded and remove as much of it as possible. Can do this pin by pin. Pogo pins looks like an option, but they're somewhat weak and you'd need all 20 holes cleaned properly which can be difficult, especially for ground pads on such a thick old board. If that proves difficult, an alternative would be to simply use header pins one by one. Use them with a small diameter like 0.7mm for an easier job. The plastic tab that holds the pins together can be slid off quite easily.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 18, 2020, 08:59:24 am
content: A good electrical desoldering pump will do nicely, i work with multi layer boards, in my case i add flux paste on the solders, while the desolder pump reheat the solder, the flux refresh the solder and bam goes into the pump ... under 3-4 secsCare not to put too much pressure on the pcb pads, you may break them

author: kolbep
author_rank: Frequent Contributor
timestamp: July 18, 2020, 10:00:56 am
content: I wouldn't risk it on a Working MOBO. Especially without a LOT of practice.If they are Plated Throughholes, then with too much force, if you damage the bonding to the internal layers, it will ruin your day.I would put flux on the pads, and then just put some normal Leaded solder on top of the pads. Then Solder some modwires / other small wires to the tops of the pads. Solder the other side of the modwires to a 2x10 Pin header, and superglue the header somewhere close by.That way you are not risking too much damage.

author: GotZapped
author_rank: Contributor
timestamp: July 18, 2020, 11:45:58 am
content: Quote from: zzattack on July 18, 2020, 08:10:18 amThank zzattack,Good point about the need to clean the contacts if using pogo pins, I had not thought of that.Yes, if installing the header, inserting 1 pin at a time looks like a good approach.Quote from: coromonadalix on July 18, 2020, 08:59:24 amThanks coromonadalix,I have a desoldering gun, but the nozzel looks to be a bit large for the space I have available. If I slipped I'd likely melt/damage something elseQuote from: kolbep on July 18, 2020, 10:00:56 amI really like your idea as it certainly reduces the risk of damage. It is a similar technique as attaching breakout boards to SOIC bios chips with small leads as illustrated herehttps://nm-projects.de/2017/08/flashing-coreboot-on-the-t430-with-a-raspberry-pi/.Keep the suggestions coming, but kolbep's idea looks the easiest and lowest risk.Thanks for your suggestions!