2
\$\begingroup\$

As a PCB designer, is there a known list of advantages and disadvantages to using BGA vs. QFN packages?

Here is the list I have discovered (please correct me if they are incorrect):

BGA

Pros:

  • Smaller footprint

Cons:

  • X-ray needed for inspection
  • Microvias may be needed
  • Multiple layers may be needed for breakout

QFN

Pros:

  • Pins accessible by probe
  • 1 layer needed for breakout

Cons:

  • Larger footprint

When a component is available in both BGA and QFN packages, what factors govern which package should be used?

Thanks in advance!

\$\endgroup\$
  • 1
    \$\begingroup\$ Number of pins in total sticks out like a sore thumb to me. That seems to be more about what decides a choice. If you can meet your total package size with QFN, then why bother with BGA. But if you can't, or if it makes a significant competitive advantage to go BGA and shrink the size enough, then go with BGA. I would imagine that there isn't much of a difference in cost -- pins are the determining factor and if the pin count is the same then the cost factor should be similar, I'd imagine. \$\endgroup\$ – jonk Sep 24 '20 at 4:09
  • \$\begingroup\$ Honestly, I think first and foremost is whether you can actually mount a BGA or not. If you can't, everything else is moot. If you're working for a company or can afford to mount BGAs out of your own pocket, then surface area. BGAs have better parasitics. \$\endgroup\$ – DKNguyen Sep 24 '20 at 4:47
  • 1
    \$\begingroup\$ @DKNguyen, BGAs often have whole internal traces to muck up signal integrity. Lots of high frequency (20 GHz and up) parts are available in QFN (and also in BGA). \$\endgroup\$ – The Photon Sep 24 '20 at 4:50
  • \$\begingroup\$ @ThePhoton Isn't there a dependency on number of IO there? Are you comparing 20 pin QFNs to 20 ball BGAs? Or 20 ball BGAs to 767 ball BGAs? I think that as pin count increases, the QFN increases in size much faster than the BGA and eventually the QFN is massive for far fewer pins. \$\endgroup\$ – DKNguyen Sep 24 '20 at 4:53
  • \$\begingroup\$ Don't use BGA, unless there's no other option. That would be my practical [albeit closed form] answer to this question. \$\endgroup\$ – Nick Alexeev Sep 24 '20 at 4:54
1
\$\begingroup\$

Beside what is already said in comments,

BGA has the disadvantage, its hard to replace the IC by hand (but possible)

Advantage is, HF Signals like High speed busses can be guided directly from under the pin by special vias into the inner layers, which from impedance is much better than with QFN. Its a good Idea to do a raw routing concept for both and see if BGA is an advantage in your application.

In any case you can place critical components with less distance to an BGA than a QFN (the drawback is, you need more testpoints on your PCB to have chances for production tests or you need a good boundary scan concept)

In projects I participated the point to switch from QFN to BGA was around 80-100 pins...

BGA also normally has a PCB inside to map from your die to the balls, which costs some impedance and don't expect the manufacturer to get it right at the first shot. Advantage is, its possible to bond two die's with no real more effort.

I cant remember which is better, but heat dissipation also is a point to consider

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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