# Surface mount soldering - pins won't attach to pads

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 without any 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.html

https://nl.aliexpress.com/item/Original-Charging-Port-Socket-Replacement-for-Nintendo-Switch-NS-Game-Console-Repair/32828938043.html

As 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. The heat that I'm applying IS sufficient.

I cleaned up the pads on the PCB, re-tinned them and also tinned the pins on the connector. I then attached the connector, applied hot air, let the solder flow, applied 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

• Is it all the pads not soldering properly? I would hazard a guess at it being the GND pins that aren't attaching properly – MCG Dec 22 '17 at 11:19
• Multilayer boards with internal planes can take a lot of heat to get them to reflow. Sounds like your equipment isn't up to the task. – Spehro Pefhany Dec 22 '17 at 13:24
• GND pins definitely attaching properly (the GND lugs sink into the solder filled holes when heated, therefore the smaller adjacent comms pins should also be getting plenty hot enough as I'm heating the whole connector - yet those surface mounted comms pins aren't attaching). I'm sure I'm applying enough heat. As for my equipment perhaps not being up to the task, I've done this before on another Switch motherboard with the same type of connector - that went fine and I was using the exact same equipment, same solder, same flux, etc hence my extreme puzzlement why it's not working this time. – user172636 Dec 22 '17 at 13:32

For that kind of connector, USB-C dual row, you really need a stencil and some solder paste if you expect this to work. It's not enough to tin the pads and press down. I'd also suggest a pre-heater underneath if you have one. A stencil can be had for as little as $20 but you need the artwork to send to them. You could build the footprint from the datasheet easily enough and send it off to them. Then just apply the solder paste through the stencil, place your connector carefully, and reflow. • Solder paste, yes. But with care you can do it without the stencil, at least if you're willing to test for shorts and if necessary do it again. Surface tension is a wonderful thing, so often if you have a well designed PCB footprint and about the right amount of paste in an area, it will aggregate onto the pads and pins and not bridge the gap in between. But not always, so this is of course not relied on in production. Stencils laser cut from kapton can be quite inexpensive, probably around$5 for a small one at a place like oshstencil. Clearance on a populated board will be a challenge. – Chris Stratton Dec 22 '17 at 14:27