Yarns PCB assembly


#1

Hi, first timer here. I’m working on a module, and due to size constraints, I’ve had to place all my SMT components on the back side of the PCB. Then there are some jacks and pin headers on the top side. This leaves SMT and THT pads on the same side. I’m curious as to how much this complicates the PCB assembly.

I see that a similar approach was taken with the Yarns module. Did you have to solder the THT components by hand after reflowing or is there a more cost-effective method to this?


#2

For Yarns and Stages, a part like this is made (milled from a composite material).

It masks every SMT component and only exposes areas with through-hole components. The board can be wave soldered.

Constraints:

  • There must be some minimal distance between the THT pins and the closest SMT component.
  • The SMT components shouldn’t be taller than 4 or 5 mm (that’s why the crystal and electrolytic caps on Yarns are on the other side of the board).

It’s costly, too (about 1.5k€).


#3

Another option is to use a selective soldering machine. But these things are slow (and you still need to enforce similar distance constraints between THT pads and nearest SMT components).


#4

Wow, that’s something new! Thanks for the info. I guess we’ll just have to see if it makes sense for the quantities we’re expecting. We might just hand solder the THT components after all.