EEVblog #588 - How To Do PCB Production Testing - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: March 09, 2014, 10:46:17 pm
content: Dave shows how the assemblers will production test the µCurrent PCB panels using his new test jigs. And he will does a trial run on 50 µCurrent PCB's to determine the average testing time. What will take the longest - PCB testing, or wrapping, or packaging?!Private video

author: krivx
author_rank: Frequent Contributor
timestamp: March 10, 2014, 12:11:34 am
content: So 2 failures out of 50? Is that typical for a product like this?

author: kony
author_rank: Regular Contributor
timestamp: March 10, 2014, 12:27:18 am
content: Wouldn't be from an perspective of ergonomy more convinient just slap in small micro on the test jig and do test indications via buzzer ?I'm sure i'd be pissed in just an hour by bending my back every single time to check LEDs, not to mention how easy is to overlook indication of bad board once worker slides in stereotype and gets bored.Short beep for in specs board and some longer alarm signal for failed is making much more sense for me

author: TVman
author_rank: Frequent Contributor
timestamp: March 10, 2014, 01:01:03 am
content: Quote from: krivx on March 10, 2014, 12:11:34 amThat seems average for something like A uCurrent.that would be 100 bad out of 1000.At least he tested 50 of the uCurrentsYou can never have to many uCurrents! :-)

author: EEVblog
author_rank: Unknown
timestamp: March 10, 2014, 01:20:25 am
content: Quote from: krivx on March 10, 2014, 12:11:34 amWhen you are still trying to iron out bugs in the assembly process, yes, totally expected.

author: EEVblog
author_rank: Unknown
timestamp: March 10, 2014, 01:21:34 am
content: Quote from: Dawgie on March 10, 2014, 12:33:25 amThat's a risk with any product. That is why you identify these and tweak the production process.

author: EEVblog
author_rank: Unknown
timestamp: March 10, 2014, 01:22:50 am
content: Quote from: kony on March 10, 2014, 12:27:18 amEver worked in production test? Beeps are annoying!

author: TerminalJack505
author_rank: Super Contributor
timestamp: March 10, 2014, 01:39:55 am
content: Quote from: EEVblog on March 10, 2014, 01:22:50 amAnd the production floor can be fairly noisy.

author: BravoV
author_rank: Super Contributor
timestamp: March 10, 2014, 01:50:57 am
content: Talking about loose nut at the banana connector, this reminds me the older ucurrent that I bought, its was out of alignment on the spacing at both input and output banana connectors like below photo.Dave, I guess this time your contractor also aware of the spacing when fastening them right ?

author: Alphatronique
author_rank: Regular Contributor
timestamp: March 10, 2014, 02:32:48 am
content: Hi2 bad on 50 look bit high for such simple board even on first batchif you have >50 0402 part on each PCB that may okbut it look more like 0805 on that board and ok the shunt may pose a bit of challengebut normally that spotted and inspected manually before delivery to customer

author: calexanian
author_rank: Super Contributor
timestamp: March 10, 2014, 03:52:55 am
content: Wow. most of you are way too critical on them. For an assembly house to not really have the test rig yet and be assembling blind on the first runs only having two failures, and those being simple to correct is not bad! Especially with mixed boards like this. This is why you always have an in house re inspection and in most products cases a monitored burn in. Real production problems are things like bad plating and down the road stress failures, Via separation, Thermal shock that leads to latent failure, material incompatibility (Some plastics do not play well with each other!) Solder mask pealing or under oxidation, board washdown or defluxing issues (My current problems) BOM translation failures on a massive scale (Why oh Why don't passive manufactures just put in huge numbers the parts values on the spools. I write them in big sharpie marker numbers on them) The best feeling on earth. 1000 boards with 47K resistors in place of 4.7K and the darn thing still passes test, but eventually will fail..... Honestly I would rather find a few random bugs and mistakes and have to troubleshoot them to get a good feeling of how things are going to shape up and figure out how that particular manufacturer does things.In other words, Stop complaining! You put your pants on one leg at a time too! Unless you somehow drop into them while they are being held open, which would be pretty cool... Testicular torsion might be an issue though if you happen to be male.Looks good Dave! Cleaning a small portion of my bench in anticipation of its arrival! Trying to decide which meter I will use it with first...

author: EEVblog
author_rank: Unknown
timestamp: March 10, 2014, 04:06:09 am
content: Quote from: BravoV on March 10, 2014, 01:50:57 amNo need, the new one is engineered to b a precise spacing. No way to mount out of alignment,

author: SeanB
author_rank: Super Contributor
timestamp: March 10, 2014, 05:07:29 am
content: Whoever gets 261 will know it has been inspected, reworked to reach spec and checked twice. One poor solder on the fist run is pretty good, and better the nut was not tight enough than they strip them. Brass is pretty soft if you have enough torque.

author: Pillager
author_rank: Unknown
timestamp: March 10, 2014, 07:31:19 am
content: Quote from: SeanB on March 10, 2014, 05:07:29 amAgreed. But there are specs for the connectors, and hopefully values for recommended and maximum torque. With the right tools, that shouldn't be a problem.

author: Pillager
author_rank: Unknown
timestamp: March 10, 2014, 07:50:08 am
content: Quote from: kony on March 10, 2014, 12:27:18 amWhen doing repetitive work like this, workers usually listen to music, either on a radio or an ipod or some such device. And that worker won't be sitting in a room all by her-/himself, but at a workspace next to other workers performing similar procedures on other products.If everyone has a buzzer, aside from the noise level, soon you wouldn't know if it was your buzzer going off, or that of your neighbour. Then you would have to recheck that board and that takes time, which in turn costs money.So the visual indicators are really the only pratical way to go on a factory floor or test room. At home, when no one else is around, it might be ok, if you can stand the constant beeping.At as far as bending forward to see the LEDs: The workbenches used in production/testing are adjustable, and there will be a custom or adjustable jig for holding the panel in place and at the right angle to minimize physical stress for the worker. Not just because its nice for the worker, but because it increases productivity

author: Gecko
author_rank: Contributor
timestamp: March 10, 2014, 10:32:42 am
content: @Dave: Will you make a Video of the production and testing at your manufacturer?And can you make an overview over the costs in the end? I think it would be interesting how much such a fairly small size project costs from front to back.I guess a lot of experience goes into it and knowledge from the uCurrent 1, but a video on how to estimate such costs could also be interesting.Thanks for another interesting video :-)

author: Ross_ValuSoft
author_rank: Newbie
timestamp: March 10, 2014, 11:24:05 am
content: Hi Dave.I noticed that you did not (yet) have a "from" address on the packages going to Aust Post. Remembering the hassles with the pcb rulers (I received an empty envelope with no return address), I hope you will be putting your return address this time... please!Cheers,Ross

author: EEVblog
author_rank: Unknown
timestamp: March 10, 2014, 01:08:41 pm
content: Quote from: Ross_ValuSoft on March 10, 2014, 11:24:05 amYes, there is a return address on them. Where did you see otherwise?

author: Excavatoree
author_rank: Frequent Contributor
timestamp: March 10, 2014, 01:26:12 pm
content: The first failure examined on the video was the SMD shunt, which was not soldered properly - Dave pointed it out on the video.The second failed unit was a not tightened binding post/jack, which was also explained on the video.However, the video shows that the second unit's shunt resistor isn't soldered too well either. It looks to me like it could use a touch up as well.I know absolutely nothing about production SMD boards, but would one consider a solder paste stencil or application problem even if most units worked, but the joints were marginal?

author: essbdub
author_rank: Newbie
timestamp: March 10, 2014, 01:55:12 pm
content: To be fair to the assembler, it appears as though the spring washers may bind up slightly on the locating portion of the post before they contact the board. Applying a bit more torque opens up the washer slightly, allowing it to contact the board properly. Might be worth pointing out to an external assembler...

author: Alphatronique
author_rank: Regular Contributor
timestamp: March 10, 2014, 03:15:01 pm
content: Hi calexaniani run myself a assembly house for 10 yearand personally 4% failure on 0805 / 0603 part board whit less that 100 part on each PCB was bit over expected rateeven if assemble "blind" 0805 / 0603 was a 20 year old assembly process so if parameter control was right you have no defectand normally today shop have automated optical inspection system ,and operator manually inspect critical partbut many shop skip or do it fast for final inspection since it very labor intensive ,so cost money ..Qoute"bad plating , Via separation, Thermal shock that leads to latent failure, material incompatibility , Solder mask pealing or under oxidation, board washdown or defluxing issues"all this was trouble that not normal and was clear sing that PCB fab not follow any of the IPC standard and quality controlas example final rinse water must have Resistivity over 1 to 5 M?·cm (cleaning solvent and flux was quite very conductive)so easy to see if still have ionic contamination present on PCB whit a simple TDS meter reading of < 1PPMExcavatoreeon video solder volume look good ,so it likely that it caused by ,wrong pressure on pick place head for push part on the pastand / or bad thermal profile of the reflow oven , for small batch it may bit harder to control the reflow ,put to many cold board on it may change to much it temperature ,so heat become non uniform and one side of the solder may melt before and surface tension twist part so one pad lift a bit and not solder (if part was push well on the part it stick a bit so it help)that a huge issue on smaller part like 0402 that not have big mass so part flip (Tombstoning)normally the guy at inspection find that part whit uneven pad or thermal mass and closely inspect it on every boardp.s. i not tell Dave PCB fail rate was really bad , ONLY a BIT over expected rate for that board ..Best regard

author: squeezebox86
author_rank: Newbie
timestamp: March 10, 2014, 08:21:27 pm
content: Personally I love the testing rigs that Dave created ti test the products. I really like the episodes that showed the creation of the panel edge connector, and the pass/fail rig. I would love to see more about the design of the test rigs (the other two that haven't been covered yet).When those rigs are created I can see they are basically a similar form factor as the uCurrents themselves (for obvious reasons), does that mean you had a whole pannel of those different rigs manufactured as well? Are they hand assembled or assembled at the assembly house?For some really big eevBlog fanboy, getting their hands on these limited production run devices would probably be pretty sweet! (Future kickstarter idea)

author: lewis
author_rank: Frequent Contributor
timestamp: March 10, 2014, 08:50:30 pm
content: Quote from: Alphatronique on March 10, 2014, 03:15:01 pmDude, PLEASE get rid of that music on your website. It plays every time I click a link.

author: Simon
author_rank: Unknown
timestamp: March 10, 2014, 09:35:36 pm
content: The sockets should have a torque on their datasheet and this needs passing to the assembler. Where i work we do mechanical assembly of radiators and everything has to have a torque set on it be it the standard for that bolt size or specific because it's something else. We also expect our electronics subcontractors to tighten panel mount switches etc up to a specific torque to ensure they are well tight (military kit) but not brocken.

author: Alphatronique
author_rank: Regular Contributor
timestamp: March 10, 2014, 10:29:14 pm
content: Hi lewisyup totally agree ,have request it to my webmaster for some time ,still un-fixedsame for got static banner for all page after main one ..will go kick some ass now ..Fix was Done ...

author: ConnorGames
author_rank: Regular Contributor
timestamp: March 11, 2014, 01:38:45 am
content: If you get the boards that failed testing back from the assembler, it would be AWESOME if you could do a video where you identified the faults. It could let many hobbyists who don't have the time or money to make 1800 boards know what failures are common and how to avoid them.

author: Alphatronique
author_rank: Regular Contributor
timestamp: March 11, 2014, 01:54:03 am
content: Hi you what a good starthttp://communities.mentor.com/mgcx/servlet/JiveServlet/download/28883-8838/PCB%20Design%20Optimization%20Starts%20in%20the%20CAD%20Library.pdfthen remain of the serieshttp://blogs.mentor.com/tom-hausherr/blog/2010/09/22/pcb-design-perfection-starts-in-the-cad-library-part-2/and remember to always use thermal relief on copper-pour / planewhit this you cover 90% of the issue ... and make your assembler happybut please use only IPC7351B forgot about the new IPC7351C that was crap for low volumeif you follow this and have defect ,issue was probably on the assembler side or the PCB shopBest regard

author: Stonent
author_rank: Super Contributor
timestamp: March 11, 2014, 06:52:40 am
content: Most hand-held cordless drills have an adjustable torque setting before they click. You could probably just get a drill with a socket end and set it appropriately and just go zip, zip, zip on the nuts and have reasonable certainty that they got torqued well.

author: Simon
author_rank: Unknown
timestamp: March 11, 2014, 07:02:39 am
content: if the drills have known torque points yes, every model of drill may be different

author: merelyuseful
author_rank: Newbie
timestamp: March 11, 2014, 10:40:46 am
content: Hi Dave,The track leading from the bad joint looks pretty wide. Is there a systematic way to work out the trade-off between having good conducting tracks vs too much heat drain from the solder joint?Neil

author: ErikTheNorwegian
author_rank: Frequent Contributor
timestamp: March 11, 2014, 01:23:29 pm
content: I missed out where to buy one of them, cant find it in the shop...

author: Ross_ValuSoft
author_rank: Newbie
timestamp: March 11, 2014, 01:53:29 pm
content: Quote from: EEVblog on March 10, 2014, 01:08:41 pmThis image. But as I said "(yet)". Good to know.Cheers,Ross

author: alter Ratz
author_rank: Contributor
timestamp: March 11, 2014, 05:06:29 pm
content: Hi Dave,In my opinion the current source(s) seems a little unhandy and is IMHO a thing which could be broken easily. I am just wondering what made you choose this design solution instead of a cable based solution which an switch to change the curent (which also would eliminate the need to plug/unplug the current source for each current range change). Also the 1A range also will need a bigger battery.Best Regards,BernhardPS: Like a previous poster already pointed out a video showing the test at the manufacturer would be welcome.

author: SeanB
author_rank: Super Contributor
timestamp: March 11, 2014, 05:15:57 pm
content: Probably based on things to hand, like a lot of those coin cell holders, a component list of common parts and then again a desire to make it simple and match the boards themselves in form factor. Bigger batteries yes, but as the current draw on the low ranges is not going to kill the cells for at least 300 or so 1 second tests not a big issue. I think the 1A version will be bigger and use AA cells or something similar. Even a 12v A23 cell to drive the reference and a single AA cell to provide the current will be usable for thousands of tests.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 11, 2014, 11:57:09 pm
content: I wonder why wasn't the uCurrent (and by extension, the test jigs) designed to use AA or AAA batteries. They're far more common than coin cells and there seems to be enough room to fit them inside the box. That also eliminates the need for the rail splitter.

author: DavidDLC
author_rank: Frequent Contributor
timestamp: March 12, 2014, 01:52:05 am
content: Misleading video title, It should be: How to do PCB production testing for the microcurrent.PCB production testing can be very simple or extremely complicated, when I read the video title I was expecting something else.I have seen the same misleading titles with other videos, my recommendation is to have the title more specific of what exactly the video is.David.

author: EEVblog
author_rank: Unknown
timestamp: March 12, 2014, 02:34:26 am
content: Quote from: DavidDLC on March 12, 2014, 01:52:05 amNo surprises for guessing that I do chose titles that will optimise my SEO. But I don't think it's misleading, it contains tips on production testing, sure, it's using a specific example, but tips none the less. Also, the first line of my description text tells you precisely what the video contains. I also can't make titles that are arbitrarily long, shorter ones work better.

author: EEVblog
author_rank: Unknown
timestamp: March 12, 2014, 02:36:43 am
content: Quote from: NiHaoMike on March 11, 2014, 11:57:09 pmYou can run it off 3 x AAA's (only AAA's fit in the existing box), but you can't do the split supply with them, because you'd need 4 to balance it, and 4 is too high a voltage.Also, split battery supply changes the requirement for how the battery OK LED works.

author: calexanian
author_rank: Super Contributor
timestamp: March 15, 2014, 02:00:02 am
content: #247 arrived today in Fresno California. Also the TSpring shirt arrived as well. Just in time for the mini hamfest tomorrow! I may just have to do a burden voltage demonstration.