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January 2001

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 23 Jan 2001 13:16:15 -0500
Content-Type:
text/plain
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text/plain (130 lines)
Apply the specification to the individual circuit boards.

 Guy Ramsey
American Competitiveness Institute
Senior Lab Technician / Instructor
610 362-1200 ext 107


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Brian Gaynor
Sent: Tuesday, January 23, 2001 9:43 AM
To: [log in to unmask]
Subject: Re: [TN] Bow and twist: Need clarification


 Guy Ramsey writes: Indeed, .75% may be too much.

My question is "Considering an SMT board in panel format, is the figure of
0.75%
for bow and twist a measure of the  complete multiple up SMT panel or is it
a
measure of the single circuit boad within the panel?

Brian Gaynor




Guy Ramsey <[log in to unmask]> on 23/01/2001 13:37:38

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
to
      Guy Ramsey <[log in to unmask]>

To:   [log in to unmask]
cc:    (bcc: Brian Gaynor)

Subject:  Re: [TN] Bow and twist: Need clarification



Methods for measuring Bow and Twist are described in IPC-TM-650 2.4.22 and
can be found in the JSTD-001C. You are esentially correct, without going
into details. However, the IPC-A-610C performance requirement states,
"Consider "Form Fit, and Function" and product reliability. The Defect
Condition for all product classes is reached when bow and twist causes
damage during assembly or end use.

Indeed, .75% may be too much.

 Guy Ramsey
American Competitiveness Institute
Senior Lab Technician / Instructor
610 362-1200 ext 107


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ken Patel
Sent: Monday, January 22, 2001 9:46 PM
To: [log in to unmask]
Subject: [TN] Bow and twist: Need clarification
Importance: High


What is the meaning .75% of maximum bow and twist allowed for SMT? Is it 7.5
mil per 1"? To me it is too much unless I misunderstood it.

Can someone clarify it?

re,
ken patel

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