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Assembly Reference Designator IPC Location

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AGONZ67 View Drop Down
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    Posted: 31 Jul 2019 at 10:46am

Is there a specific IPC specification that specifies the location of the assembly reference designator?

Typically I have placed assembly ref des in the center of the component outline, which seems to be industry standard. 

Is there a specific IPC specification that I can refer to which states something to the effect of "Assembly ref des shall be placed in the center of component outline"?


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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2019 at 11:05am
There is no standard for the placement of the Assembly reference designator. 

The assembly outline should be a closed polygon and the assembly ref des should be placed anywhere inside that polygon. 

This way, the assembly shop has clean data to work with and the chance of making a mistake is greatly reduced. 

When the ref des is placed outside the polygon, it can get confused with another part close by. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote AGONZ67 Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2019 at 2:59pm
Thanks for the confirmation of that. 

This is how I have been using them, but we are working with someone who wants assembly ref des to match the silkscreen ref des, which defeats the purpose of the assembly ref des.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jul 2019 at 3:07pm
If the customer wants to use the Silkscreen Legend Ref Des as the Assembly Ref Des then they are potentially creating a situation where two similar parts could get swapped. 

We did that at a company I worked for and sure enough, the assembly shop swapped two same size resistors by mistake and the PCB did not function properly and it took the EE engineer a couple of days to track down the problem. Very costly mistake. 

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