Surface mount soldering - pins won't attach to pads - Page 1
Forum section: electronics / beginners

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 22, 2017, 08:19:44 am
content: I've been doing thru-hole soldering for very many years and also over the past few years some occassional surface mount soldering (both removing and attaching assorted components). I only have basic equipment (temperature controlled soldering iron and rework/hot air station) but I manage just fine with no problems.However, I've now met my match with a surface mounted connector, a connector type which I successfully removed (a faulty one) and attached (a new one) to a different PCB a few weeks ago. Therefore I've done this procedure before.The board in question is a motherboard from a Nintendo Switch console, the connector is the USB C connector which acts as a charging port and video/audio output to the Switch's docking station.Here are some examples of the USB C connector:https://nl.aliexpress.com/store/product/Replacement-Charging-Port-Type-C-Charger-Socket-for-Nintendo-Switch-NS-Console-10PCS-LOT/1222106_32825690094.htmlhttps://nl.aliexpress.com/item/Original-Charging-Port-Socket-Replacement-for-Nintendo-Switch-NS-Game-Console-Repair/32828938043.htmlAs you can see, it has two rows of pins which means that, once placed, the reflow of the already tinned solder pads must go smoothly as there's no way to directly access the inner row once the connector is in place.In this case, for some unknown reason, I can't get the solder on the pins and pads to reflow AND attach.I clean up the pads on the PCB, re-tin them and also tinned the pins on the connector. I then attach the connector, apply hot air, let the solder flow, apply gentle pressure to make good contact between the connector pins and the PCB ..... but for some reason the pins aren't attaching to the pads on the PCB. They ARE making good contact, there IS solder on the pads and the pins as well as flux. So why won't they attach?I have tried both liquid and gel flux.I CAN get the external row of pads to attach if I manually heat them with my soldering iron and apply more solder, but of course I can't use an iron on the inner row of pads.I will say that the old connector was particularly difficult to remove and I had to use a lot of heat to get the metal mounting lugs to free themselves, but the pads looks fine and, I'll re-state this, they DO tin okay.Any ideas please as to what I'm doing wrong or how I can get this connector to attach?Thank you

author: nicalitz
author_rank: Regular Contributor
timestamp: December 22, 2017, 01:20:02 pm
content: I'm not sure what you mean by the connector wont attach. I'm assuming you're struggling to get the solder to stick. If you say you have no problem tinning the connector, the problem is either with the flux you're using or the amount of heat your're applying.Are you using a decent quality flux? Check the expiry date? Using proper flux would almost always make your life a lot easier.Also, you obviously need enough heat. Maybe see if you can find a spec sheet that tells you what temperatures the plastic used on those connectors can withstand. You can then try to preheat the connector pins to a 'safe temperature'. Might be a bit more successful?

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 22, 2017, 01:29:32 pm
content: What's happening is that the solder is melting and flowing (I can tell because the metal mounting lugs sink into their solder-filled holes) therefore the adjacent pins and their padsshouldalso have molten solder as I'm heating the whole connector. This is the part that has me really stumped as it SHOULD work, but after the heat application and subsequent cooling I can still move the pins with a fine needle.I agree that it seems like I've not heating it enough but I'm positive that I am, hence my extreme puzzlement at the lack of attachment.I don't recall the name of the gel that I've tried but I've used it on other surface mount parts recently without any problems.The Rosin flux pen that I have I've also used recently without any issues; it's a good brand, MG Chemicals.I've also attached one of these connectors to another Nintendo Switch motherboard before without any problems which is yet another reason why I'm really puzzled why this isn't working.

author: nicalitz
author_rank: Regular Contributor
timestamp: December 22, 2017, 01:56:34 pm
content: Maybe just start over then. Clean as much solder of the pads and pins as you can. Get some IPA, clean the pads and pins of any flux residue. Maybe test the flux on some other components, make sure its doing its job. Tin the pads and pins. Would still suggest maybe preheating the connector if possible. Then give the reflow another go.The main reasons for solder not 'sticking' is (a) poor solderability of contacts (dirty, poor materials used), (b) not enough head or (c) poor quality or not enough flux.

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 22, 2017, 03:46:33 pm
content: Thanks. I did clean the pads thoroughly a couple of times but will try again in the next few days using your additional advice too.

author: Teledog
author_rank: Regular Contributor
timestamp: December 22, 2017, 03:52:16 pm
content: You ARE using leaded, rosin core solder, yes?The no-lead is a nightmare!Also if you're pre-heating both sides of the board & there's other heat sensitive components, cover them with shields & /or kapton tape prior to using the hot air.G'Luck!

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 22, 2017, 03:56:49 pm
content: Yup, it's leaded solder.Thanks for the tip as well.

author: nicalitz
author_rank: Regular Contributor
timestamp: December 22, 2017, 09:13:17 pm
content: Also, high quality solder can also make a huge difference. Go proper name brand.

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 22, 2017, 09:19:40 pm
content: It's Henkel / Loctite solder so it should be good quality.

author: Bassman59
author_rank: Super Contributor
timestamp: December 22, 2017, 10:27:56 pm
content: Quote from: SolderSucker on December 22, 2017, 08:19:44 amUse solder paste, something perhaps likethis. (Yes, it's lead-free, but it's also a low-temperature solder paste.) A stencil would help, but dabbing the paste on the pads with a toothpick oughta be sufficient. Then place the connector onto the board and gently heat with the hot-air tool.

author: nanofrog
author_rank: Super Contributor
timestamp: December 22, 2017, 11:10:11 pm
content: Quote from: Bassman59 on December 22, 2017, 10:27:56 pmIf you're going to use leaded solder paste, go with Kester EP256 instead, as it works better than Chip Quik's paste. Stuff works great IME.You can get it fromCML Supplyin both a syringe or jar (35g & 150g respectively).

author: SolderSucker
author_rank: Regular Contributor
timestamp: December 23, 2017, 09:31:11 am
content: I'll grab some solder paste and give that a try, I've never used it before so it'll be a fun experiment (I'll do some tests on an old board first of course). Ta for the tips.