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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