EEVblog #552 - DFM Automated PCB Panel Testing

[kaindub]

Dave, you have connected all the negative output terminals together. Is this correct? The negative output terminal is your virtual ground derived via an op amp from the battery. There may be a small potential difference between the 10different circuits, which will show up as an offset on the output. Since your current is a precision measures, won,t the offsets upset your tests?
Robert

[SeanB]

Simple multipoint test jig is to use a unmilled panel and populate the current points with banana plugs that fit the test panel holes, along with a relay bank or switch to select the unit under test for current source. That way you place it on a bed of pins, plug in the test connector and start testing using the switch to select the device under test for current. when finished testing simply pull off the test jig. Using an unmilled panel and cutting unnedded traces saves spinning a test board specially for this, you only need one unmilled panel.

Sure there will be a market for those panels unmilled as wall art. Might be a good funding project there for excess boards. I would take one or two for $20 each.

[rs20]

Hey, awesome video, I'm really looking forward to seeing this working in the flesh.

One little potential bug spotted by a guy on YouTube though -- you've got all the virtual grounds commoned, which means that if (for example) one board's virtual ground op amp output pin was not soldered down (or basically any other problem with the virtual ground section of the circuit, really), that board would still pass the test because its virtual ground would be overruled to a correct value by the other nine circuits. Once the boards are broken out, it'd become dud.

Probably a very pedantic corner case, but kinda worth being aware of?

[EEVblog]

Probably a very pedantic corner case, but kinda worth being aware of?

Yes, I realised this potential issue myself after I sent the board away, which is always the case.

[rs20]

Probably a very pedantic corner case, but kinda worth being aware of?

Yes, I realised this potential issue myself after I sent the board away, which is always the case.

Bloody Murphy!

[centon1]

Could someone please provide a link or IC number to Dave's 'window detector' reference so I may understand it better.

Thanks.

[RobbieC]

For the test jig interconnect, this may also be an option:

https://www.phoenixcontact.com/online/portal/us?1dmy&urile=wcm:path:/usen/web/main/products/subcategory_pages/pcb_terminal_blocks_and_pcb_plug-in_connectors_p-11/495ba453-0024-4c4a-bf61-897a8daa650e/495ba453-0024-4c4a-bf61-897a8daa650e

I was speaking with our rep yesterday morning and he was showing me some various solutions they may have for one of the test jugs I'm currently working on.

Unfortunately I think the pad size requirement may be a bit too long for your needs. If the connector life and cost is good enough I may use it to reduce our interconnect replacement costs.

That being said, those right angle headers are cheap enough for your test volumes and if you've soldered as many as I have, they're pretty quick!

Cheers!
-Rob

[TheWelly888]

Ah! You made me feel dirty when you used heavy pixellation on that potential nerd porn!

 

Actually, I understand that particular board is commercially sensitive so fair dos.

Informative video as usual, Dave! 

Yeah G+ really felches indeed!

[nitro2k01]

Could someone please provide a link or IC number to Dave's 'window detector' reference so I may understand it better.

Thanks.

You may be interested in watching this:

[centon1]

Thanks Nitro...

I misunderstood the context of the 'window detector' reference in the PCB video but it is 'clear' now.

[mfeinstein]

Hey Dave,

Any reasons for doing this routing with the trace? I mean, why didn't you just continued it straight until the board edge and then turned it 45º down?

[jolshefsky]

 I just wanted to chime in and say this video is extra helpful for me right now. I'm working on redesigning a board for our product and wanted to add test functionality. Our production is incredibly low (specialized industry equipment; <100 per year) but it's a pain to debug a board without adequate test connections. When I say I'm redesigning it, I mean literally right now — to be completed in a month or so. So it was extra helpful to reconsider a card-edge break-out of test pins, and the suggestion to add power and current test/limiting to the test bench.

Excellent work, and thanks!

(By the way, your worry about the virtual ground may be alleviated some in the case that only one board would be powered at a time. I'm not sure what happens to the output pin of an unpowered op-amp, but I believe it floats, so with only one board powered at a time, you could actually test every board. Maybe once verifying the virtual ground on the most-likely-test to cause an error, power them all and run through quick.)

[majbthrd]

When using discrete pogo pins, what works for me to ensure they are mechanically aligned is to use through-hole variants of the pogo pins and order at least one more PCB than I plan to build.

The PCB will likely have some sort of mechanical holes for alignment to the DUT.  I use said mechanical holes to clamp two PCBs together (one PCB is the one being built; the second is the unpopulated spare).  Before tightening the screws between the PCBs, I add the pogo pins.  The through-holes on the unpopulated PCB act to align the pogo pins.  I tighten the screws, making sure the pogo pins have seated properly.  Then, I solder them in.  The PCB sandwich can then be taken apart, and the pogo pins should all be nicely aligned.


There was seemingly another feature of the test fixture (with PCI card-edge connector) that Dave showed but didn't mention.  He explained that the PCI connectors had adapter PCBs to 0.1" connectors.

Surely, a benefit of using the adapter PCBs (0.1" or otherwise) is that the PCI connectors can be swapped out (and the insertion counter reset) without having to scrap the entire test fixture PCB?

[EEVblog]

There was seemingly another feature of the test fixture (with PCI card-edge connector) that Dave showed but didn't mention.  He explained that the PCI connectors had adapter PCBs to 0.1" connectors.
Surely, a benefit of using the adapter PCBs (0.1" or otherwise) is that the PCI connectors can be swapped out (and the insertion counter reset) without having to scrap the entire test fixture PCB?

Yes, that was the idea, I should have explained that. Obviously if you know your test connector has finite life then you desing it to be easy and cheap to replace. In this case a simple adapter board you swap out in a few minutes. "Connector saver" gender changers also work a treat in those situations where you can use them.