4
\$\begingroup\$

Is it a problem to integrate an SMD pad into a large copper pour area? In this case, the packages are 1206. I am wondering if I need to be concerned about thermal issues and interfering with standard soldering processes at assembly shops.

An example of what I have in mind is below.

enter image description here

\$\endgroup\$
3
  • \$\begingroup\$ I see it done all the time (without major issues) but I prefer to use thermal relief around the pads. (unless there's a really good reason not to.) It certainly makes the soldering process and rework easier. Check with your assembly house to get their input. \$\endgroup\$
    – John D
    Commented Jan 5, 2023 at 17:16
  • 1
    \$\begingroup\$ If it is reflowed in an oven, I don’t see any trouble. Also the plane is heated, so it will be balanced. If you solder it by hot air or soldering iron, you could have trouble. Copper has a square resistance of 0,5m Ω, with 3 squared thermal relieve points that is a parallel resistance of less than 0,2 m Ω. So don’t worry about that. \$\endgroup\$
    – RemyHx
    Commented Jan 5, 2023 at 17:30
  • \$\begingroup\$ I do it all the time. \$\endgroup\$
    – DKNguyen
    Commented Jan 5, 2023 at 17:38

3 Answers 3

Reset to default
9
\$\begingroup\$

If the board is processed at an assembly house, there is no problem with flooded pads since the whole board is heated up during the reflow process.

The main problem if you do not use thermal reliefs is performing hand-work. If hand-work is required and you don't have thermal reliefs, preheating the board to at least 180°C is very helpful.

\$\endgroup\$
2
  • 6
    \$\begingroup\$ It should be noted: even with reflow, if there's a significant difference between the two pads, you do run the risk of tombstoning, but the configuration shown in the question is unlikely to have that problem. That's more a risk if, for instance, one pad has a large copper pour and the other pad has just a thin trace. \$\endgroup\$
    – Hearth
    Commented Jan 6, 2023 at 2:30
  • \$\begingroup\$ @Hearth That's a good comment, you could convert it to an answer. Assembly companies have a tendency to work with what is given to them (and curse in silence) - the better the layout, the better the quality of the soldering. \$\endgroup\$
    – Lundin
    Commented Jan 9, 2023 at 14:49
7
\$\begingroup\$

You probably get the best answer by asking your (or a) assembly shop directly.

But from my experience no halfway decent assembly shop should have any problems with such a connection pattern.

However, I'd suggest to use thermal reliefs as a default choice unless you have strong compelling reasons to do otherwise as manual soldering (debugging, repair, ...) is significantly easier with thermal reliefs most of the time.

\$\endgroup\$
5
\$\begingroup\$

You can do it. It might work.

But this is what thermal relief is for. Every PCB CAD software I've ever used makes thermal relief pads easy to implement.

KiCad, for example, allows you to choose if a pad has thermal relief by simply right-clicking on the pad, selecting Properties, going to the Load Clearance and Settings tab and selecting Pad connection. Spoke width and spoke gap can then be set as necessary, particularly for high-current connections.

\$\endgroup\$

Not the answer you're looking for? Browse other questions tagged or ask your own question.