TECHNET Archives

March 1998

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Ed Cosper <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 5 Mar 1998 16:10:07 -0600
Content-Type:
text/plain
Parts/Attachments:
text/plain (71 lines)
Gregg,

I have been reading several of the responses to you. Some I agree with and some I don't.
Basically it sounds like the board supplier was given data without the thermal connects.
I agree that an experienced cam operation should have question this, unfortunately I would not recommend you rely on that. Despite the fact that there a many who will want to lay the responsibility on the cam operator, the fact is these people are only human. It think you would be surprised if you know just how many errors most cam departments find in the supplied data. Most of these error are detected and addressed but I can assure they will miss some. Even something as obvious as missing thermals.  If this shop is like most I am familiar with, the cam department is typically loaded with data that needs panelizing and manufacturing is usually nipping at their heels to get those tools to the floor! Mistakes will be made. After all,  wasn't it someone who made the original mistake when they sent the data to the shop without the correct apertures?   

A third party review is a great idea.... If you have the time. Unfortunately I doubt this would be 100% accurate 100% of the time. Especially if your data requires someone to manually enter the apertures. 

You would think Net list testing certainly would have caught the design error except I understand the net list is derived after the apertures are entered. Even if a net list would have been extracted
from the supplied gerbers, the supplied gerbers didn't show a connection and the net list would not have reflected those connections. Now if you provide a net list that was extracted from the data that had the apertures in accordance with the ipc standards, this would have worked. However, I doubt the board shop would have felt better since all of their costs would have already been incurred and scrap would have resulted from the supplied data. I suspect it would have only resulted in the expected debate as to who's going to pay for the parts. 

I strongly agree with and recommend the use of extended gerber (274X). This eliminates the potential of  aperture input error by the operator. I only wish all of my customers used this! 
 Typically we like to plot a one up image of the supplied data, fax it back to our customers and have them approve the plots. This has caught many mistakes made by the designers that on the screen did not look like a problem to us. But then again, cam operators in a board shops are not designers.  People may take exception to my thinking but the cam operators function is to panelize the data received, run a DRC for manufacturing tolerances and get the job to the floor. I'm sure we all try to provide that little extra customer support by reviewing your designs for things that "don't look right"  but I feel very strongly that a customer has the primary responsibly to  provide the board shop with data that reflects what is wanted in the finished product.

Just my thoughts.

Ed Cosper
Director of Quality Assurance and Engineering
Graphic Electronics Inc.  

----------
From:  Gregg Klawson[SMTP:[log in to unmask]]
Sent:  Thursday, March 05, 1998 11:34 AM
To:  [log in to unmask]
Subject:  [TN] FAB/DES: Electronic data interchange (EDI)

We just had a couple of PWB types built incorrectly due to bad electronic
data being sent to our board houses.  Unfortunately we did not catch either
problem until we had fully assembled the boards.

Problem A was due to the wrong aperture file being sent out resulting in no
power plane connections.   Problem B was due to an old design tool which
did not show a "filled in" power plane which was required.  No netlist data
was available for either design.

We would like to continue with an all electronic process but need some
fool-proof checks that will detect if we send some incorrect file(s)/data
or our board house does something wrong.  I'm sure companies are doing this
sucessfully all the time (and all electronic).  How are people making this
process work well for them?
---
Gregg Klawson
GTE Government Systems Corp, Taunton, Massachusetts, USA
[log in to unmask], telephone +1.508.880.1822

The views expressed are the author's and do not necessarily reflect the
official position of GTE or any of its subsidiaries.

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
################################################################


ATOM RSS1 RSS2