Soldering Two PCBs Together - Looking for Ideas

Status
Not open for further replies.

JonSea

Well-Known Member
I have a circuit board with 12mm tactile switches and caps that extend through a 3mm acrylic panel. I want to add a piezo beeper that will be flush against the back of the panel, but the beepers are slightly too thick to match the switch height. If I make a sub-board to mount the beepers through a hole in the main board, the elevation is almost perfect, and I can mount the beeper just a bit off the sub board to fit exactly right.

I'm trying to figure out the best way to solder the sub board to the back of the main board. I want minimal thickness between the 2 boards. I guess castellated holes would be the usual approach, but this increases board costs significantly. The main board is mostly surface mount, so one way to do it would be some matching pads on the two boards with solderpaste. Or maybe some large-ish plated through holes soldered with paste or by hand. I could also just insert a screw through each hole and depend on the annular rings making good-enough contact.

Anybody done anything like this? Suggestions?

JonSea

Well-Known Member
A picture may make this more clear....

ronsimpson

Well-Known Member
piezo beeper
What is the part number? Data sheet?
Are the other parts through hole or surface mount?

I moved the PCB back one step to make the beeper work. Then added a PCB spacer to keep the switches at the right place. The switch spacers are a simple blank PCB with holes for the switch wires to pass through. (assuming the legs on the switches are long)

Last edited:

JonSea

Well-Known Member
The beepers are actually magnetic rather than piezo - they work well in my application and have a not-unpleasant tone. There are a couple pics from an ebay listing below.

The ideal spacing between panel and pcb is 8mm + a nylon washer to get the switch elevation right - yes, that's probably 9mm, but standoffs typically don't come in 9mm length. The beepers are 9.6mm tall, which works ok with an 8mm standoff and 2 washers, but then the switches are very nearly flush with the panel. That might be ok or even desirable for some applications, but it's less than ideal for mine.

I had thought about spacers behind the switches, but there are 5 switches, and the legs are..um...crimped...to snap into a standard thickness board. The position of the switches in critical to fit the panel. the position of the beeper not so much.

ronsimpson

Well-Known Member
I think these type of switchs are made in any height in 1mm increments. Trying to say get a switch that matches your piezo.

JonSea

Well-Known Member
Those switches don't have the type of caps I want to use. 12mm tact switches don't come in (meaningly( different shaft lengths.

Offsetting the beeper makes everything else work perfectly.

Pommie

Well-Known Member
Can you mount the sounder on the back of the board?

Mike.

JonSea

Well-Known Member
No, the panel has a hole for the sound to emerge.

Pommie

Well-Known Member
If you can get copper to the edge of the daughter board then can't it be mounted like any other smd?

Mike.