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I am trying to solder Type-C SMD USB connectors but I can't do it properly. Despite using an SMT stencil for soldering, each time I am having an issue and I can not solder it properly. Sometimes pins are shorted, sometimes pins are not soldered. I have to check it under the microscope every time.

After that I give an order to JLCPCB for SMT assembly for this part. They also give a warning:

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After that I have received my SMT assembly order and when I checked, I saw that all the USB connectors were soldered correctly. At that time I thought there was definitely a different technique to this. Only stencil is not enough. I should do something different?

Can you show me a video or what should I do for soldering properly the Type-C SMD USB connectors?

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My PCB's soldered state by JLCPCB

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    \$\begingroup\$ I would guess that attachment of the mechanical pads is what they refer to, more so than the actual soldering. Manually applied components are more expensive to assemble than those that the pick & place can handle. I'd expect the assembly contractor to charge extra for such - same deal with various RF connectors like SMA. For the soldering part, I have no experience of these specifically. But generally, bad PCB layouts are often causing problems, in case pins/pads are directly connected to large copper pour ground areas without "thermal relief". \$\endgroup\$
    – Lundin
    Mar 25 at 8:41
  • \$\begingroup\$ If you’re hand soldering these items then you need some flux gel. You can buy it in a 10cc syringe. You’ll also need a needle point tip on the soldering iron. \$\endgroup\$
    – Kartman
    Mar 25 at 9:08
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    \$\begingroup\$ "Sometimes pins are shorted", I've been doing this for quite a while, what I did is to use a twizzer to lightly tap the USB a couple of times (or lift it up slightly) during the reflow stage (I use hot plate), this usually break out the short circuit. "sometimes pins are not soldered", I never has this problem, but this usually means that the temperature is not right, check the solder paste temperature profile and make sure it match the reflow profile. The extra charge from JLCPCB is the labor charge for hand-soldering the 4 mechanical pads. \$\endgroup\$
    – hcheung
    Mar 25 at 9:16
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    \$\begingroup\$ Check out the "TronicsFix" YouTube channel, he often does USB-C port swaps on Nintendo Switch consoles and shows the entire soldering process. You might also have better luck by tinning the pads with a soldering iron, rather than using solder paste. \$\endgroup\$ Mar 25 at 11:49
  • \$\begingroup\$ @Lundin I have attached images of my pcb last state \$\endgroup\$
    – mehmet
    Mar 25 at 11:55

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It's very difficult to accurately apply paste on small pads with a stencil without a "paste printer" (device to do that mechanically)

To solder this type of component manually, you should create extra longer pads. Like 3 to 5mm longer. Before putting the component, apply solder on the external end of the pads (the end far from where the pin will be). Put the component on the its pads. Apply the solder iron on the external end of the pad, not on the pin. The solder will naturally climb up the pin. If you see that a short was forming, move the iron from the pin toward the external end of the pad.

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Looking at the datasheet, the through-hole pins are 1.20mm long. As such, they can be problematic with standard (1.6mm) PCB thickness.

I'd suggest looking for a part with longer pins, or using a thinner PCB. Eiter way, I'd assume JLCPCB adds some cost as they have to either wave-solder or manually solder the pins, adding to the manufacturing process.

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Reduce the paste aperture a bit to resolve shorts

The pads have a relatively large area, of which most is covered by the pins. This causes too much solder paste on the pads, which flows over and shorts pins.

Adjust the paste aperture -20 % in PCB tool and that should solve the issue with shorts.

If you are getting unsoldered pins in a reflow process, either your paste spreading is very uneven, or the heating profile is off. A slower rate of heating around 150-200°C is important so that larger parts such as connectors get time to preheat sufficiently.

I think the JLCPCB note about difficult processing is not necessarily due to pins shorting, but for accurately installing the connector into the through-holes. In particular the small plastic pins can be tricky to align in an automated process.

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I also often find it difficult to gauge the right quantity of paste to use, and with USB connectors, it can often be particularly annoying to rework as the pins extend under the connector. What you can try instead is soldering it by hand with an iron.

You can use a small tip for this. Heat up one of the end pads, and melt some solder onto it. Then place your connector over it, lining up the pins, and tack it onto that pad. Add lots of flux, and start soldering each pad from the opposite end. You can try either pin by pin, or dragging your iron along (faster and arguably easier, but you run the risk of having too much solder and, again, that's annoying for these kinds of components).

Also, you should plug in a USB cable when soldering it to avoid solder getting into the connector and ruining it.

Finally, solder the mounting pins with a larger tip.

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