We moved from silkscreen layers being used for the assembly for a variety of reason, size being a major driver and it limits flexibility considerably when it comes to doing documentation.  But I do see it being more common now to have them as separate layers.

Typically we have a layer for
-Silkscreen (outline, ref-des and pin1/other indicators)
-Assembly (component physical outline, ref-des and pin1/other indicators)
-3D part outline (usually same outline as the assembly layer)
-Placement outline (outline plus manufacturing allowances)

The "PCB Librarian" LP Wizard tool  made doing this for PADS a snap, so it's been pretty easy to follow and keep moving forward.

-Jeffrey

Jeffrey A. Jenkins CID+,CIT
Senior PCB Staff Designer || L-3  Linkabit || Ph: 858-552-9832 || [log in to unmask]


-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Pete
Sent: Tuesday, April 01, 2014 1:18 PM
To: [log in to unmask]
Subject: Re: [DC] Assembly standard + best practices

You really can't depend on silkscreen layers for assembly anymore, with the size of the parts and limited room for silk.

We use one layer for silk, another for MMC part outlines, and another to add additional placement clearance for parts that need it.  One layer for silkscreen legends, another for assembly legends.

But we do assembly drawings in our 3D modeling software.  We need the 3D model for higher level assemblies anyway, assembly drawings in PCB CAD programs are pretty clunky.

Pete

---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 16.0.
To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL) For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________




---------------------------------------------------------------------------------

DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 16.0.

To unsubscribe, send a message to [log in to unmask] with following text in

the BODY (NOT the subject field): SIGNOFF DesignerCouncil.

To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)

For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815

---------------------------------------------------------------------------------