PCB Serialization for Manufacturing Tracking - Page 1
Forum section: electronics / general

author: forrestc
author_rank: Unknown
timestamp: December 31, 2018, 06:26:06 am
content: I'm looking at options for applying a serial number to each PCB which we assemble so we can track things like test results, operator, specific component reels, etc., to a specific board. This is an internal manufacturing serial number, and won't be used/seen by customers.The current thought is to apply 2-3 datamatrix barcodes to the board (unique number per board, all barcodes coded the same on a board). At least one per side, maybe 2 on the top, 1 on the bottom. These would be small - probably around 6mm square including the label. Or, perhaps some other symbology (like a 5mm x 15mm code39 2d barcode, etc). Regardless, I'd use a polyimide label which is rated to survive the reflow oven. We're about done using the wave solder machine, so that probably isn't a concern.Of course then you have the cost of the label and the cost to apply to the board.The other thought I've had was to laser or otherwise print these on the board. Or even better is if I could find a reasonably priced PCB house which will do the serialization for me in some way.Curious what others are doing or have seen done?

author: mrpackethead
author_rank: Super Contributor
timestamp: December 31, 2018, 10:02:10 am
content: something that becomes painful wiht labels, is when to put them on. Putting them on before you stencil can mean your board has a a high spot.. ( have learned this the hard way ).

author: Karel
author_rank: Super Contributor
timestamp: December 31, 2018, 11:35:04 am
content: There are companies specialized in board assembling who use lasermarking to apply unique serial numbers to the boards.

author: xdave
author_rank: Contributor
timestamp: December 31, 2018, 04:17:36 pm
content: We use data matrix codes on all our PCBs (some are panelised at 50+ per panel). Only on one side.We tried manually applying labels to the bare PCBs when loading up the magazines. It was taking too long though and had a lot of wastage. We had to print 3 labels for every 2 that were needed because if one was misapplied it had to be scrapped as they were non-repositionable (easy to do when they all look the same and you have brain fatigue after 2 hours of sticking tiny labels onto identical boards). We also had to scan back each panel to confirm correct placement.That was always going to be a temporary method while we found an automated way to apply the labels, but as with all temporary processes it ended up lasting 3 months and was horrible.The issue we faced with automatically applying the labels was because we wanted variability in 2 degrees the cost was prohibitive for our budget. We were looking at around $30k for a machine that could print on demand and was basically a vacuum pick and place machine for labels.We also faced the issue of stencils not sitting perfectly flush unless there was around 10mm border around the label which is not always possible. Our solution during testing was to have the label position cut out of the stencil and apply kapton tape to the squeegee-side, then remove the exposed adhesive with alcohol. It worked pretty well – I can only recall one repair where it snagged the blade. If we had kept going with labels we would have had the stencils only partially etched through, although those are expensive to produce.We ended up using one of those 20W portable marking lasers you can pick up on any Chinese trade site to etch the codes directly onto the PCBs (we added a 7mm square white box to the screen-printing layer, and tweaked the laser so it produced a nice crisp almost black image). We modified an inspection conveyor to add a simple pneumatic board stop and a proximity sensor and used those to feed the laser software (it came with a Windows XP machine). Total external cost was around $6k.It now just reads a single manually-applied barcode on the side bar of each panel which has the panel and design number encoded in it, looks up a CSV containing the centroids for the screen-printed boxes, and etches the panel, design and individual board number across an entire 300x220mm panel in about 2 seconds. No consumables, no waste, and it fits right after the magazine unloader so you can pull a panel at any stage of production and read off the tracking data. Once the panel is etched the tracking numbers are recorded in a database that are linked up when the final products are assembled and let us drill down into data such as which supplier provided a component, when it was checked into stock, which feeder and which machine applied it, even which batch of solder paste and the reflow profile that was used.Note if using a fixed laser you need to consider the focal length as that determines the area you can etch onto. If you increase the distance to the board you increase the area it covers but you lose resolution. Our laser is about 350mm from the board and provides about 200dpi. Not as crisp as the labels were, but still scannable for our needs. If we needed to encode more data we would just make the barcode bigger.

author: mrpackethead
author_rank: Super Contributor
timestamp: December 31, 2018, 07:45:40 pm
content: would a 40W CO2 laser etch FR4? Or , maybe burn of silk screen.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 31, 2018, 08:38:31 pm
content: Just a crazy idea:I know there are serial number chips that are read electrical.Maybe there are also optical readable ones, e.g. like QR codes on a dummy SO8.

author: ataradov
author_rank: Super Contributor
timestamp: December 31, 2018, 08:41:29 pm
content: Quote from: Kleinstein on December 31, 2018, 08:38:31 pmThere are actually chips like that. I've seen that somewhere recently, but I can't find where. But this does not help before the soldering and probably adds quite a bit to the cost.

author: mrpackethead
author_rank: Super Contributor
timestamp: December 31, 2018, 10:58:10 pm
content: Quote from: mrpackethead on December 31, 2018, 07:45:40 pmThe internet says, yes. You can actually cut it. but it burns.

author: nisma
author_rank: Regular Contributor
timestamp: January 01, 2019, 08:40:56 pm
content: Digikey sells tracking pads, 0.1342 Euro here in inventory.This are 2x3mm solderable ceramics with emailed barcode.Lasering is cheaper but require approx 2000 euro investment.This parts from molex costs 1074 Eur for 8000 PC reel.Label feeder costs start from 2500 for preprinted labels, at least at time I have searched for it.

author: ataradov
author_rank: Super Contributor
timestamp: January 01, 2019, 09:44:38 pm
content: Quote from: nisma on January 01, 2019, 08:40:56 pmYea, I remember where I saw them. In the last DigiKey mailer brochure. But I can't find it now, nor can I fins the actual component. Do you have a link?

author: mrpackethead
author_rank: Super Contributor
timestamp: January 01, 2019, 10:33:37 pm
content: Quote from: ataradov on January 01, 2019, 09:44:38 pmhttps://www.digikey.co.uk/en/product-highlight/m/molex-connector/track-it-traceability-pad

author: forrestc
author_rank: Unknown
timestamp: January 02, 2019, 10:41:27 pm
content: Quote from: nisma on January 01, 2019, 08:40:56 pmI think we may have a winner here... This molex part seems to be perfect for our volumes. The cost + labor of the laser solution is much more than this, and hand applying labels seems like a nightmare (and the labels aren't cheap either). Plus this is small enough it will fit pretty much anywhere. I *think* I can even get the P&P to scan this in one way or another during production which helps even more with traceability.I've got some coming for engineering purposes at this point. If anyone knows of a different manufacturer/type I'm open to evaluating them.

author: Geoff_S
author_rank: Regular Contributor
timestamp: January 03, 2019, 11:41:49 pm
content: Cool little devices for visual serialisation. What would be really neat would be to include a simple ROM with electrical interface (eg I2C) to allow a microprocessor to read the assigned ID also. Does such a thing already exist ??

author: ataradov
author_rank: Super Contributor
timestamp: January 03, 2019, 11:43:45 pm
content: There are unique ID chips. But I don't think there are combined devices. I'm not even sure there is a second vendor for those SMD passive labels.

author: ar__systems
author_rank: Frequent Contributor
timestamp: January 07, 2019, 02:31:41 pm
content: Many MCUs can be ordered from supplier with pre-programmed unique IDs. Microchip for example, I'm sure others have the same capability.