Tester for castellation board

MacTuxLin

How would one design a tester for a castellation board (but only 2 sides needed contact)? Pogo pins doesn't seems to "catch" it right since there are only half the pads.

Phil Pilgrim (PhiPi)

Frist, for those of us who don't know: what's a castellation board? Do you have a photo that you can post?

Thanks,
-Phil

MacTuxLin

That's right, my bad. I don't have the board fabricated yet but below picture is an example.

I planned to have them on all 4 sides but only 2 sides are needed for programming & testing.

Phil Pilgrim (PhiPi)

Okay, I get it now, and I see the problem. You can use pogo pins, but what you need is a frame in your test fixture that exactly surrounds the board -- maybe with complementary castellations -- so that the pogo pins do not spread outward.

-Phil

MacTuxLin

Umph...(slap on the head), why didn't I think of that...

Thanks Phil

kwinn

Perhaps a board with square pins turned 45 degrees so the corners mate with the castellations could be used instead. The pins have enough spring to make a good contact as long as they only bend slightly when the board is inserted. They may not last as long as pogo pins but they cost much less and are usually good for testing several dozen boards.

MacTuxLin

That's a good option, kwinn. Unfortunately, my first batch is 100pcs so reliability would probably be what I need the most as intermittent contact failure would cost me a lot more (my hair I mean...)

WBA Consulting

Castellations are a semi-circle method of edge plating. It has become quite common for low cost, SMT modules because it creates an SMT mountable module using standard PCB manufacturing techniques.

There are a few methods that I am aware of:

1. Spring probes (pogo pins) mounted horizontally on cantilever plates on the test fixture so that after the module is placed onto the test bed, the spring pins hit the castellations from the side.
2. Depending on your pitch and size, PLCC sockets can be modified to make custom adapters.
3. Using the contacts from a PLCC socket, design a custom holder for the pins that will present them in the required position. The holder would be laser cut or 3D printed I would assume.
4. Extend the bottomside pad area of the castellated pin so that you have a larger target to hit with a standard spring probe from the bottom side.

erco

But if your testers get castellated, won't you become a Unix?

Tubular

Depending on your pitch 3M IC test clips may help too (might have to insert a solid spreader in the middle and have 2 pivot points to accommodate your board width
http://media.digikey.com/photos/3M%20Photos/923655-14.jpg

I didn't previously know they a 0.8mm QFP clip existed (no P2 0.4mm there):-
http://www.pomonaelectronics.com/pdf/d5961_61-2_1_01.pdf

(Lol, Erco...)

MacTuxLin

WBA Consulting wrote: »

Spring probes (pogo pins) mounted horizontally on cantilever plates on the test fixture so that after the module is placed onto the test bed, the spring pins hit the castellations from the side

Good idea. I'll see if I could fit the the pogo pins to avoid the length from sticking out of the tester.

MacTuxLin

Tubular wrote: »

Depending on your pitch 3M IC test clips may help too (might have to insert a solid spreader in the middle and have 2 pivot points to accommodate your board width
http://media.digikey.com/photos/3M Photos/923655-14.jpg

Thanks Lachlan. Didn't know there's such a part but I'll KIV on this one.

Circuitsoft

If you get pogo pins that don't have ends on them but are just straight pins, lay them down and solder them to surface pads. Then, to insert a device, put one side down and slide it sideways then lay the other side down. It will spring back to the middle with good contact on both sides. I saw this on a dev board once - I think it may have been a MediaTek GPS board, but I'm not sure.

kwinn

MacTuxLin wrote: »

That's a good option, kwinn. Unfortunately, my first batch is 100pcs so reliability would probably be what I need the most as intermittent contact failure would cost me a lot more (my hair I mean...)

I agree. Poor contacts and cold solder joints are two of the most common problems I have found in the field. Worth paying a little extra to avoid that kind of problem.

On the other hand using square pins allows you to make a simple inexpensive test fixture using an un-populated board that is good for testing a small batch. So far the maximum batch size is 48. That's not really enough of a test to judge long term reliability but the pins look like they could be used to run another batch of 48 if needed.