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SMT electronics assembly manufacturing forum.


What is gonna impact boards without silkscreen on quality and mf

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#51441

What is gonna impact boards without silkscreen on quality and mf | 16 August, 2007

What do you think is gonna impact or benefit using board without silkscreen on it, talking about quality and manufacturing methods??.. I mean.. it is an opportunity or bad idea.. specs of assemblies refers always to references on board so schematics, etc...

Thanks

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#51445

What is gonna impact boards without silkscreen on quality and mf | 16 August, 2007

There is limited benefit to silk screen legends. They cost ~$45 a side per batch.

There is benefit to some board users in having reference designator and orientation markings as an aid in test and repair actions. There is no reason these markings cannot be done in etched metal. This etched metal should not: * Violate minimum spacing requirements. * Seperate from laminate causing short circuits.

Why does your company specify silk screen legends?

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#51451

What is gonna impact boards without silkscreen on quality and mf | 17 August, 2007

We usually do Solder reworks, and some components that cannot be installed by SMT Machines or Wave solder due to specs or the technology in our company... aur work methods and instruction are always based on designators and are more illustrated to can make easier to operator.. my question now is...

How can other companies work with operator, they use the schematics or how you indicate the installation of for example 10 cap. on a board.. or a polarity connector.. i think there is a risk of quality..

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#51452

What is gonna impact boards without silkscreen on quality and mf | 17 August, 2007

Good documentation would allow you to make the product without silkscreen. Our operators are trained to use our documentation and not the silkscreen. Silkscreen can be hard to use on many boards and could actually lead to mistakes.

Silkscreen is more useful to someone that troubleshoots a board that does not have access to the production documentation.

Jerry

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FD

#51453

What is gonna impact boards without silkscreen on quality and mf | 17 August, 2007

I agree that the documentation should be used and not necessarily the silk screen. The silk screens can be a first line of defense, but nothing beats the proper documentation.

Years ago I visited a contract manufacturer that a friend was working at and he told me about this situation. It was a large facility with many, many, production lines. They were building the same board on two of their lines.

The QA person on each line noticed that the silk screen showed that there was a cap and resitor (next to each other) that were swapped in placements. The silk screen showed that the cap was placed where the resitor should be and the resitor was placed where the cap was suppose to be placed.

One QA person checked the documentation and was informed that the silk screen was wrong and the placements were actually valid. The QA person for the other line simply told the operators to change the program for his line to match the silk screen.

Now since the silk screen was wrong they were building 50% bad boards for many weeks. Oddly enough the boards would pass the functional tests, so all the boards were being sent to the customer. But once the completed assembly was installed in the field they started getting many failures and the customer was quite upset that so many bad boards were made from a QA person that didn't do his job properly.

That QA person that told the operators to change the program was quickly looking for another job.

Lesson: Don't trust silk screens.

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