JLCPCB BBT (Not?) - Page 1
Forum section: electronics / general

author: devonnije
author_rank: Contributor
timestamp: June 23, 2021, 03:03:56 pm
content: Attached. FYI.Bridge was a dead short, needed scalpel to clear it.Board also has features not on the films, and not on the other PCBs in the batch.

author: Mangozac
author_rank: Frequent Contributor
timestamp: June 23, 2021, 10:27:21 pm
content: Did you pay for 100% testing?

author: devonnije
author_rank: Contributor
timestamp: June 23, 2021, 11:48:21 pm
content: It (BBT) always shows as included by default on all the jobs I've placed with them. I'm not unhappy with they quality generally.When I had a PCB co, we did BBT on a rig that looked for all boards to test out the same (and any that were different would fail, same fault on all boards would pass!) - I guess that modern systems check against the films?In any scenario, the board I found today should fail, and therefore one can't assume that JLCPCB BBT can be relied upon. I've not tried them with Multi-layer, but was starting to consider it ... less enthusiastic about that now.

author: Mangozac
author_rank: Frequent Contributor
timestamp: June 24, 2021, 03:07:17 am
content: For prototyping the default is 100% test but for production quantities 100% testing is optional - the default is just random test.It's a surprising error. We've done many thousands of boards with JLC and I'm honestly not aware of any failures.

author: 48X24X48X
author_rank: Frequent Contributor
timestamp: June 24, 2021, 05:20:27 am
content: Just look at the SMD pads for needle poke marks. The marker pen marking on the edge of PCB could sometimes be misleading to conclude that the boards has been tested.

author: IconicPCB
author_rank: Super Contributor
timestamp: June 24, 2021, 06:36:39 am
content: It depends on the test method. Flying probe or universal grid with product specific fixture.Each has problems.The fixture test may be a comparison to "golden board" in which case you better have real gold rather than fools gold.Flying probe testing may be a combination of resistive con5inuity and charge / discharge times based on Gerber information.Charge discharge component is susceptible to misinterpretation and is often times marred by operators inability to set the parameters correctly.

author: Deni
author_rank: Regular Contributor
timestamp: June 24, 2021, 06:22:13 pm
content: We are using JLCPCB A LOT - and I must say that generally quality deteriorated in the last 10-12 months. Initially no PCB errors were found (and we use batches up to 2000 pcs.) now it is not so uncommon. On one ocassion we re-ordered same PCB (batch of 500) and they did not route it correcly - how can that happen if you re-use old set of documentation, beats me. On the other hand, all complaints were resolved without too much hassle. It looks like their business grew too fast...

author: Lusu
author_rank: Contributor
timestamp: June 25, 2021, 07:06:21 am
content: I also use JLC (including SMT and THT assembly services) and never had issues with them. The only thing "added" is the tracker number, which, if I don't mind placed randomly, I leave it as is, or I just place a marker (as instructed) somewhere where it does not bother me and they place it there.You also have to check if you are within the specified limits for clearances! The automatic tests may not catch a violation or two and that may cause the "shorts". Full flying probe test option (which is for free, as far as I see) should help.Even if all fails and you have a faulty board, contact them and report a quality issue, I'm almost 100% sure they will help you solve it (by issuing new boards). I had the experience in contacting them with some silly questions (some questions for very small boards assembly way under their minimum limits) and they did replied promptly and on subject. They really tried to help me, even if I didn't ordered anything yet for that particular case.JLC is quite big and they don't mock around, if they did, then they would be out of business in no time. But they are not the best on the market, there are some way better, with better or more advanced services offered. But for the price, I would not complain too much.I'm not advertising for them, this is just my experience with them...

author: devonnije
author_rank: Contributor
timestamp: June 25, 2021, 07:18:24 am
content: One faulty board in a batch. Clear fault on one, dead short that was happy to pass an amp and more. How did it pass BBT?Faulty board now fixed, made good and into our finished stock.Clearances all well in excess of their minima, and satisfied all of their analysis pre-manufacturing. Other anomalies on same board looked like the films were distorted. Do they do their photo-mech from films, or some kind of direct (laser?) digital exposure ?? - I don't know, but the short looked like a bit of "crap", or perhaps a copper fault/impurity in the raw laminate?It's all OK for now, but we can't sit back and enjoy the idea of "all good, everything is BBT'ed".

author: true
author_rank: Frequent Contributor
timestamp: June 25, 2021, 12:45:32 pm
content: I've had boards come back with shorts even with quoted 100% test. If it comes from China I just assume it's luck and get on with it.That said it's not like the failures have been all that common - maybe half a dozen boards over the last 5 years.I don't know how they test so that it can pass. Probably just continuity on the net, not extensive testing between nets.

author: devonnije
author_rank: Contributor
timestamp: June 25, 2021, 12:48:03 pm
content: OK - so perhaps (1/#nets)%age BBT

author: IconicPCB
author_rank: Super Contributor
timestamp: June 25, 2021, 01:47:55 pm
content: Flying probe testing can be unreliable since it is based on charge.discharge time measurements and then analysis of the measurements is deployed to determine shorts / 0p3ns. If the analysis parameters are not set correctly for the board build iy may cause problems.The only safe way is a much longer deeper approach to testing by using the continuity measurements to confirm suspected faults.That takes time .

author: phil from seattle
author_rank: Super Contributor
timestamp: June 25, 2021, 10:57:07 pm
content: At this point, I have had over 600 boards made by JLCPCB. 4 failures that I know of. This includes assembly errors (2 PCBs).For what it's worth, I used their complaint form and never heard back from them. Not that I'm going to start a Jihad or anything, just but it is annoying.