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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Chip on board - board metalization

jvasconcelos

#2060

Chip on board - board metalization | 8 January, 2001

Hello everybody ! I�ve known thickness of gold over nickel board of chip on board (COB) boards are between 5 �n 15 microinches. A supplier suggested 1 to 4 microinches of gold over nickel ! Have someone any expierince about it ? I�m glad if you help me !

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#2061

Re: Chip on board - board metalization | 8 January, 2001

Ask your supplier if he will guarantee to cover rework, warranty, and lost business costs, if he's incorrect.

Below 2uinch gold is very pourous and not worth anything in preventing corrosion of your nickel undercoat. 3 uinch has to be the absolute minimum gold thickness.

Further, that minimum has to be counter balanced by a maximum thickness of gold so to not form excessive gold-tin intermetallics that could affect the LT reliability of your product. From that perspective, your 15 uinches is far too high, especially when thinking about the relatively small pad size of your component.

Consider 3 to 8 uinches as your specification.

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#2062

Re: Chip on board - board metalization | 8 January, 2001

Consider the recommendations of J-STD-012 as the baseline for your efforts.

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Rob K

#2063

Re: Chip on board - board metalization | 9 January, 2001

Anyone want to convert to microns rather than micro inches?

.... or would furlongs be better?

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#2064

Re: Chip on board - board metalization | 9 January, 2001

So true!!!! I'm with you 100%.

I get so tired of those people with their metric this and that. You know what I do? If someone talks centimeters, I just mutiply it times 0.4 to get inches!!! And another thing, if I ever wanted to convert inches to centimeters, just divide it by 0.4. Cool, eh? ;-)

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Michael Parker

#2065

Re: Chip on board - board metalization | 10 January, 2001

Furlongs? won't that be confusing and leave a lot to interpretation?

Question: How long do you want it fur? Answer: 6 months, the unit will be obolete by then.

and let's not forget the Animal Rights activists, they will have a field day if they begin to suspect this industry advocates the senseless killing just to get long fur.

Ay, chihuahua

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Michael Parker

#2066

Re: Chip on board - board metalization | 10 January, 2001

Furlongs? won't that be confusing and leave a lot to interpretation?

Question: How long do you want it fur? Answer: 6 months, the unit will be obolete by then.

and let's not forget the Animal Rights activists, they will have a field day if they begin to suspect this industry advocates the senseless killing just to get long fur.

Ay, chihuahua

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