Electronics > Manufacturing & Assembly

Another PCB FAIL!

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Rufus:
The result of poor process control followed by lack of inspection and test. They didn't etch long enough and/or the etch was weak. The etch isn't completely uniform so when you don't etch enough some areas of the panel being OK and others bad is to be expected.

Couldn't see the track defect well enough to say if it is the same problem or dirty/damaged artwork or materials.

metalphreak:
Do any of the faulty boards have a black marker line on the PCB edge? The 50% that they e-test will have marks on them (and that's 50% of the ten specified, so 5 out of 12 should have been tested).

If you aren't going to use all the boards, then make a habit of using all the tested ones first :)


Also, they charge $8.25 for 100% e-test on the basic 10board 5x5cm package, which is only $9.90... You're better off just buying two batches of 10, getting 10 tested boards as well as 10 untested ones for like $1 more... ?!

ejeffrey:
The drill registration doesn't look so great either.  The drills are all over the pads, and not all in the same direction. 

DrGeoff:

--- Quote from: metalphreak on August 23, 2011, 03:14:34 pm ---Do any of the faulty boards have a black marker line on the PCB edge? The 50% that they e-test will have marks on them (and that's 50% of the ten specified, so 5 out of 12 should have been tested).

If you aren't going to use all the boards, then make a habit of using all the tested ones first :)

--- End quote ---

I should have checked, and yes should have used the tested one for assembly. My mistake, I got used to these fairly low density and large clearance boards being free of defects.

All is not lost, so far testing has not revealed any other shorts or problems.

BTW, I got another batch of 24 other boards back from Itead today and they have perfect registration and no apparent defects.

IanB:

--- Quote from: FreeThinker on August 23, 2011, 01:24:47 pm ---This thread has stated me thinking ( :o ) .Just exactly how does a pcb get made? Do they use the same techniques as home made ones? ie sensitised boards and masks or a litho process or something else? Looking at the faults on the board I would suspect the former ( exposure ) technique as this would explain nicely the random faults (dirt or debis on mask or copper board blocking exposure) Any one any info /links on the process? I think it would be interesting and informative to see exactly how these are made in a production environment.

--- End quote ---
There is an article on Wikipedia about this. For run of the mill boards I believe they start with a blank copper clad board, drill the holes first, plate through the holes using the copper cladding to conduct electricity to the holes, print the etch resist using a screen printing process, etch using a temperature and time controlled spray jet system, then lastly print the solder mask using a further screen printing process. Or something like that. I've often wondered myself exactly how they do it.

I was coincidentally reading that a similar printing technique can be used by the home fabricator using an ink jet printer and a CD printing tray. Some Epson inks contain microscopic plastic particles that will melt into an etch resist layer upon heating gently in an oven. So you basically print your design on the copper clad board using the ink jet printer, fix it in place by heating, etch it, clean off the etch resist using acetone, then drill the holes. You can even put the board back through the same printer and print the silk screen on top. For a finishing touch you could probably silver the copper traces using some of that rub-on silver plating compound?

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