Bottom ported MEMS soldering

[davegravy]

I'm looking for suggestions regarding soldering technique.

I'm wanting to do some prototyping with the IM72D128V01 bottom-ported MEMS microphone.

I'm on a fairly narrow budget and am hoping to avoid PCBA and to do my own assembly. I haven't found much online in terms of guidance on how to approach DIY soldering of bottom ported MEMS. I expect this will be a pretty delicate operation since the sound port filling with solder/flux will impact performance as will hole alignment.

I have a soldering iron with a fine tip and hot air gun but no proper reflow oven (except a cheap toaster oven).

The selected IC has integrated IP-57 protection which I expect helps. I have to imagine that even if debris isn't physically sitting on the diaphragm but is within the sound channel it's still going to impact performance to some degree.

My current plan:

• Don't use a stencil+paste (has failed me for things like QFN previously).
• Hand tin the ring pad on the board and sensor side with a small amount of solder from the iron and then apply heat gun - with little to no flux.
• Inspect hole alignment with microscope, reheat and nudge the IC if it's off, and re-inspect, etc.

Please let me know if this is doomed to fail!

Another thought I had was to design the PCB such that the ring pad extends beyond the chip so I can use the soldering iron to conduct heat to the hidden pad.

Open to suggestions!

[TC]

I have used a mini hot plate... MHP30 from seeed studio... successfully. But you can cook the mic if you aren't careful.

I've used it with paste and paste screen and also rework scenarios where there was solder on the pads with plenty of good flux. Be careful not to get paste in the port hole.