Here at SparkFun, we have long prided ourselves on implementing uncommon solutions to common problems. Our hotplate reflow skillet method is one (in)famous example. Another is our pogo bed test jigs that we use to test every one of our designs.
An array of pogo test jigs.
Which brings us to today's post - how does SparkFun work to ensure quality control on our unique designs? Well - in this tutorial from QC Guru Pete Lewis, you'll learn how SparkFun is constantly trying to innovate to keep the performance of our designs at peak levels. Check it out! What else could we be doing differently? What do you think is a great idea? Let us know in the comments section below!
I know I'm late, but I didn't see anything on equipment calibration. Keeping equipment like digital volt meter (DVM), oscilloscope, function generators, etc. calibrated is important. Adjustable power supplies are typically "no calibration required" since you can adjust them using a calibrated DVM (never trust the power supply meter).
Another trick for bed-of-nails I've used is with compressed air rather than a vacuum. If the board has mounting holes you could use them as a guide for your fixture. Place guide pins on the fixture and have the compressed air raise or lower a plate that will hold the board against the pogos.
"This slight difference effects the way the solder flows."
I think you mean "Affects". Your english checker needs some tweaking. Proofreading is qc for words.
Thanks tz. Fixed! We do our best to have a few people proofread our articles before we post, but occasionally some grammar or spelling mistakes slip through. I haven't heard of a good checker to catch these sorts of errors. Do you know of one?
I suppose I'm part of the generation that greatly relies on checker tools, but I am doing my best to remember the rules as I write. A couple articles from The Oatmeal have helped me improve. http://theoatmeal.com/comics/misspelling http://theoatmeal.com/comics/semicolon
I will shoot an email to our IT guys and see what they think. If I was going to design a tool, I might have something that finds all the commonly misspelled words in the entire article and then requires a human approval for each one. This would really just be a double check, but I think it could help. Thanks again!
I wish I knew of one. The best I can think of is something to highlight correctly spelled but often wrong words. Loose for lose is probably the worst offender. I should note I'm probably exceptionally good at proofreading. And finding errors in code and designs just on paper.
It would probably take something like google translate with a large contextual knowledge. Affect v.s. effect is particularly hard since the meaning is similar but the grammar and part of speech is different.
The other problem is engineering terms and usage will create a lot of false positives.
A PCB was being calibrated on a pogo-pin vacuum tester, but was not repeatable and passed PCBs failed in system. It turned out unequal forces on the (large) board could generate piezoelectric currents in a high-impedance node, sufficient to swamp the cal. This could show up today testing designs using modern accelerometers or cap sensors. (The solution at the time was foam pads under the unsupported areas).
Hey Geoff, That's amazing that slight flexing of the PCB could cause and error like that! What amount of current was being created? How did you eventually pinpoint the problem and were you able to measure it?
I suppose the majority of our products do not deal with high-impedance nodes, so it would be unlikely for us come across a situation like that. It's still a good idea to keep the possibility in mind though. Strange things happen on the production floor! It sounds like some sort of foam below the board under test is necessary with the vacuum approach. When we prototype this method, we will definitely include it.
Not sure if you do this, but equally important is the regular testing and validation of your test equipment. We make low risk medical products, all test jigs etc are serialized, and a log made of their testing regime. At least, a test fixture must be tested yearly, unless it is classified as "obvious to user when not working", such as a mouse or keyboard. This regular testing, as well as your production batch logs, would then provide traceability, if you discovered during regular testing of a jig, that it was out of tolerance, or had a fault that meant that a faulty board could pass. The length of time between validation or a test fixture, must be less than expected failures, or for parts to go out of tolerance. All fixtures get a tag indication when they were last tested, and date of next testing, and any user should check them before use.
Hi Andy, This is a really smart idea. I believe we are getting to the size now that a system like you are suggesting will soon be necessary. Luckily, most of our test equipment would fall under the category of "obvious to user when not working". I'm not sure about some of the really old test equipment, but with our more recent designs, we always include some sort of indication (an LED or status message) that the jig is alive and working properly. But self-tests only go so far, and I agree that a regular schedule of re-testing would be a smart thing for us to do.
We currently have over 400 pieces of test equipment, and I imagine it would take at least 15 minutes to test each one. So we're looking at about 100 hours of work to test them all. I think we could justify doing this every 6-12 months. How often do you guys re-test your equipment?
Last March we implemented a system to track any testing problems on the production floor, and this has helped us to see reoccurring failures and/or problematic test equipment. When a technician has a problem during a build, we usually hear about it quickly. If the problematic equipment is old enough (6 months or more), then this usually leads to redesigning the equipment to include all of our recent innovations. This is the trouble with coming up with new ideas: eventually, you have to go back and update the old designs too :)
A toggle clamp is a handy tool for these sorts of fixtures; here are some examples from McMaster-Carr: http://www.mcmaster.com/#toggle-clamps/=q19bqy
Thanks for the tip! Those clamps look like some smart pieces of hardware. We're gonna have to order a few and try 'em out.