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Assembly Reference Designator IPC Location

Printed From: PCB Libraries Forum
Category: Libraries
Forum Name: Footprints / Land Patterns
Forum Description: [General or a CAD specific issues / discussions]
URL: http://www.PCBLibraries.com/forum/forum_posts.asp?TID=2515
Printed Date: 23 Apr 2021 at 12:35am


Topic: Assembly Reference Designator IPC Location
Posted By: AGONZ67
Subject: Assembly Reference Designator IPC Location
Date 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"?





Replies:
Posted By: Tom H
Date 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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Posted By: AGONZ67
Date 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.


Posted By: Tom H
Date 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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