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Why Bar Code?

John O'Brien

#10631

Why Bar Code? | 14 July, 1999

I'm doing some basic research in trying to understand the purpose and drivers that cause bar code (or other) marking of PCBs. I would appreciate any knowledgable volunteers willing to speak with me -your name, number, the best time for the call- or reply directly to jsbobrien@earthlink.net

Basic Questions: What are you encoding (part No., Serial #., etc.) Who establishes the requirement? (Designer, customer,internal use?) How is the information used? Who uses the information? Are there any in-process uses? I assume space is a limitation - if you could overcome that, what other information would you encode? Why? How could it help you? Who would use it? How?

This request is driven, in part, by the article in Quality Digest I have linked to below:

Any and all help from the PCB experts would be appreciated!

-John O'Brien

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JohnW

#10632

Re: Why Bar Code? | 14 July, 1999

| I'm doing some basic research in trying to understand the purpose | and drivers that cause bar code (or other) marking of PCBs. I would appreciate any knowledgable volunteers willing to speak with me -your name, number, the best time for the call- or reply directly to jsbobrien@earthlink.net | | Basic Questions: | What are you encoding (part No., Serial #., etc.) | Who establishes the requirement? (Designer, customer,internal use?) | How is the information used? | Who uses the information? Are there any in-process uses? | I assume space is a limitation - if you could overcome that, what | other information would you encode? Why? How could it help you? | Who would use it? How? | | This request is driven, in part, by the article in Quality Digest I have linked to below: | | Any and all help from the PCB experts would be appreciated! | | -John O'Brien | John,

The barcode is a wonderful thing, you can use it for WIP tracking, quality data, machine settings and basically what ever your imagination can think of. We apply barcodes to all PCB's we build, for 1 it identify's and individual board and using PC based tracking system's let's you see where it's been what's been done to it, when and by who. That's really important information when your driving quality in production, if you can automat the recording of the data and release it real time then you can not only use historical data to refine the process but you can see when problem's are happening and hit them before it becomes a big issue. Also the ability to know exactly where the WIP is positioned via the tracking system make's scheduling simpler and done correctly can drive your MPS ( master Production Schedule) and hence your material...but your system's have to be slick and your integrety good.You can even use them to set recipies on machines. What goes on a barcode...well it kind of depend's what you need doesn't it ... you need to identify the board as being unique so it'll need a rolling sequencial number of some sort, decimal / hex what ever, if your building lot's of diferent product's then you'll need and individual product identifyer and so it goes on. The amount of info you actually need on a barcode is driven by who uses them and how good your system's are..it's a pretty big subject all on it's own. Who uses them, well I do as a process engineer to look at yeilds and trend's as do quality engineer's, production again it's all dependant on what you need so there is no stock answer. Size on any PCB is a real premium so trying to use the smallest barcode you can is alway's usefull but again it depend's onthe technology your using to scan the code and who else uses the code e.g. an end customer..it amy need to be compatible with what they do. Basically you can change the size of the code by changing thing's like the dot's used / aspect ratio's or just changine the code your using, e.g. code 39 ( or 3 of 9) give's pretty big barcodes but a code 128 barcode is nice n small. The other thing that's hitting the market is 2d barcodes that can handle massive amount's of info in a very compact area, the down side is the equipment is still quiet pricy. One of the question's you also need to think about is the materials. The base material of the label is important, you need to match it to the environment - is it going to see reflow temp's and will it stand up to them, can it take getting soaked in flux from a wave solder..can it with stand wave solder. Do I need a paper label for packing or do I need a laminate and so on, then you've got to match the ink to the label and look at the same issues, will the chemical's your using remove the ink ? The other this is how the heck to I generate the barcode to start with ..do I use a zebra printer - thermal transfer or an inkjet type and then there's the software to drive the printer and the code generation. There are load's of topic's here and it's not as simple as what can I do with a barcode..it's really just simpler to ask how good is my imagination....

Hope this is a start but if you want to talk more email me at the address on the profile.

JohnW

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