It's a fair comment but you have to set your own standard to be able to set
any automated process?
If a standard is required IPC, SMTA and Automated Learning offers a photo
CDs that has lots of print defects and reference prints. There are also some
reference standards for printing.
I have recommended in the past that IPC have criteria for printing and
adhesive deposits to make the us of the DPMO documents and data collection
easier to use.
Many thanks
Bob Willis
2 Fourth Ave, Chelmsford, Essex, CM1 4HA England
Tel: (44) 1245 351502
Fax: (44) 1245 496123
Mobile: 07860 775858
www.ASKbobwillis.com
New Bob Willis "Printed Board Inspection & Quality Control Workshop" 24th
March www.ASKbobwillis.com/faworkshops.pdf
"Troubleshooting Your Assembly Yields Workshop" 25th March
www.ASKbobwillis.com/faworkshops.pdf
Book Bob's "Step by Step Failure Analysis Workshop" 22nd April
www.ASKbobwillis.com/faworkshops.pdf
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Andy Ng
Sent: 24 November 2008 03:41
To: [log in to unmask]
Subject: Re: [TN] Screen printing
There're no standards on misprinting as this is not a final
workmanship/quality issue...rather a process issue...I'm sure
engineers do set their own guidelines if you utilize an AOI or
automated printing inspection system, depending on what type of
component you're looking at...say, a 20-mil vs a 40-mil pitch QFP. But
you're right, especially for high volume runs, controlling the
printing can reduce a large portion of your defects and time lost.
Andy
Quoting John Goulet <[log in to unmask]>:
> I've never heard of one. The IPC standard is for component
> placement. Occassionally we may have the aperatures longer to print
> off the pad on purpose to have more paste flow up the leads.
> I put in a 1st peice inspection sheet for print, placement and the
> paste used to assure at each changeover the process was good. This
> prevents most of the misprints unless I get my finger in it during
> inspection. Now that the operators know we are watching, the quality
> has gone up substantially. If the camera gets out of calibration
> then the prints can go off. The manaul printers are doing better and
> stencil issues are caught much sooner before they cause a stop
> process.
>
>
> -------------- Original message --------------
> From: Yannick Brisson <[log in to unmask]>
>
>> Hi everyone!!
>>
>> Is anybody have a chart or rule or standard for misprint. What I mean is
if
>> there is a way of saying if my print for some reason a switch 1%,
>> 5%, 10%, etc,
>> off the pad that is not acceptable.
>>
>> Thank you
>> Yannick
>>
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