Barry,
According to my review of IPC-2221, IPC states that tolerance of features "shall" appear on master drawing.
I would interpret this to mean IPC does not recommend a default standard tolerance.
I would recommend that you advise your customer, find out what they would prefer as an acceptable range and hope you do not have a fight on your hands with your supplier.
All that said, I personally feel +/-.005" should be default for a 3 place inch dimension, and think anything greater is not necessarily best practice.
Hope this helps and good luck,
FNK
 

Frank N Kimmey CID+
Sr. PCB Designer
Powerwave Technologies
EDH 916-941-3159
FAX 916-941-3195

-----Original Message-----
From: Barry Gallegos [mailto:[log in to unmask]]
Sent: Thursday, June 05, 2003 7:45 AM
To: [log in to unmask]
Subject: [TN] IPC PCB Dimensioning standard

Good Morning TechNet.

I have sent the following Message to the Designers Counsel forum. And thought I would send here as well.

We have an issue on a customer drawing, where the customer calls out dimensioning on their data, to 3 decimal places, but do not provide a tolerance table or tolerance indication at all. The exact method the customer used to call-out dimensions on their drawing is: 250Mils or 530Mils for example. The pcb shop that built these is saying that, in the absence of having a tolerance call-out, they default to IPC standard tolerance. The customer service person at the pcb shop, cannot tell me which standard he is referring to, nor can he tell me what that default IPC standard tolerance might be. We do not have the 2221 IPC design standard nor do I know if it would cover this issue. We have issue with the dimensions of these pcbs we received, including hole positions.

Can you find out what the IPC default tolerance is for dimensioning of pcbs, in the absence of having a specific tolerance call-out?

Barry

---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------