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SMT electronics assembly manufacturing forum.


Identifying Caps

Tony

#22354

Identifying Caps | 9 November, 2002

I recently took over a small SMT department where not only was organization not a prioreity, they didn't even know what the word means. I am preparing for year end inventory and I am finding a lot of loose parts to identify. Is there any way to find the values of chip capasitors with no markings?

Thanks for any input.

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#22356

Identifying Caps | 10 November, 2002

Organized or not, it is very easy to end-up with a bag of "fly shit" after sweeping the floor.

Making measurements: * Search the net on "capacitance meter" to find an equipment supplier. HP [Aligent?] and IEC make very good meters. [We just use a Fluke volt-ohm meter with a blue function button.] * Look in the SMTnet Equipment Mart for someone selling a meter.

Taking this from a different angle: * Is the value of these components worth the time you plan to spend putzing around with them? [For discussion purposes, say your burdened labor rate is $36/hour. Say the caps cost $0.02. Then, you can spend a total of 2 seconds working on each capacitor, before you start loosing money for your company. Assuming, of course, you have something better to do.] * After you determine the value of these components, what do you plan to do with them?

Finally, I hate doing "physicals".

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RDR

#22360

Identifying Caps | 11 November, 2002

I agree with Dave, Identifying chip components is not worth the time or effort. I believe that you can only tell what the value is and not the voltage,temp rating tolerance, etc...anyway. You will need to then put them back into tape to make them useable (again more cost). I would recommend that you throw them away (take the loss)and start looking at your placement management data and correct the package types that are being rejected at a rate of greater than 1%. OR you can give these parts to your techs and have them measure and use them in De-Bug operation(s).

That's my .02 cents worth

Russ

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Tony

#22366

Identifying Caps | 11 November, 2002

Thanks for the suggestions. I should have been more clear when I said "loose parts". Along with the truly loose parts I have many strips of 50 to 1000 on reels (not marked) and in bags (not marked). I guess if I cannot determine all of the tolerance information it would be pointless.

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Daan

#22367

Identifying Caps | 11 November, 2002

Perhaps you can benefit from the "SMD Codebook" at http://www.marsport.demon.co.uk/smd/mainframe.htm It has a section about capacitors that might help.

Daan Terstegge http://www.smtinfo.net

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dragonslayr

#22380

Identifying Caps | 12 November, 2002

Use an "LCR" (L= inductance, C= capacitance, R= Resistance)meter. There are several name brands to choose from (Fluke, etc.) Hand held units are relatively inexpensive. In fact, you may consider having more than one available. Receiving inspection should have one to validate each reel. SMT operators should have one to validate each reel before loading. Capacitors have a wide (and forgiving)range of tolerances. A bit of research on your end to determine what ranges may have been purchased will help. Then consider all unknown to be of the widest tolerance type and inventory them under that part number only. For example, if you have 16V, 50V devices, store them all as 16V parts. (A 50V chip will work in a 16V circuit but not vice versa). With 5%, 10% and 20% tolerances, make them all 20%. This will keep you safe and regardless of actual tolerance, the chips will function in the circuit. Be sure that you consider the volts and range tolerance together. (Lowest volts, highest tolerance) This sort and guess method works best with capacitors as they are the most forgiving of devices. For resistors, consider them of the highest % tolerance.

good luck

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