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From:
"Stadem, Richard D" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D
Date:
Tue, 22 May 2018 13:01:01 +0000
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Au contraire. 

Bow and twist requirements must be met during or after assembly per IPC-A-610 as per figure 10-23, on page 10-13, to be less than 1.5% for PTH, and less than .75% for SMT. IPC-610 also refers you to IPC-TM-650 method 2.4.22, as does the J-STD-001, IPC 6012, and as a condition for fabricated circuit boards, IPC-A-600. They ALL refer you to method 2.4.22, and they ALL have requirements for maximum bow and twist throughout all stages of fabrication and assembly.



-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of Chris Mahanna

Sent: Monday, May 21, 2018 4:24 PM

To: [log in to unmask]

Subject: Re: [TN] Bow and Twist measurements per IPC 650 TM 2.4.22, IPC 600-2.11 Flatness



To my knowledge, there is no IPC standard requirement (or method) for during/post assembly; much to the package manufacturer's chagrin.



Chris





Chris Mahanna

Robisan Laboratory Inc.











-----Original Message-----

From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]

Sent: Wednesday, May 16, 2018 11:04 AM

To: [log in to unmask]

Subject: Re: [TN] Bow and Twist measurements per IPC 650 TM 2.4.22, IPC 600-2.11 Flatness



Folks,



   Is there a consensus, especially from committee (7-11D) members, on the above inquiry regarding Bow & Twist for raw board and PCBAs (populated boards)?



Ref:     IPC-T-50M (May – 2015)  ( Victor’s comments )

            Bow -  (Fabric)   Filing yarn that lies in an arc across the width of a fabric.

            Twist -  The deformation of a rectangular sheet, panel, or printed board, that occur parallel to a diagonal across its surface, such that one of the corners of the sheet is not in the plane

                          that contains the other three corners.



Victor,



From: Jose A Rios [mailto:[log in to unmask]]

Sent: Wednesday, May 16, 2018 8:35 AM

To: TechNet E-Mail Forum; Hernandez, Victor G

Subject: Re: [TN] Bow and Twist measurements per IPC 650 TM 2.4.22, IPC 600-2.11 Flatness



2.4.22 is only for bare (unpopulated) PWB’s, and the rigid portion of rigid-flex PWB's. Section 1 (Scope) explicitly excludes PCBA’s from being evaluated using this method.





José (Joey) Ríos, Sr QA Engineer

Mission Assurance Manager

Kavli Institute for Astrophysics & Space Research Massachusetts Institute of Technology [log in to unmask]<mailto:[log in to unmask]>

(617)324-6272



On May 16, 2018, at 7:17 AM, [log in to unmask]<mailto:[log in to unmask]> wrote:



Fellow TechNetters:



  Is there a separate Bow & Twist Test/documentation for Printed Wire Boards, PWB, and Printed Wire Board Assemblies, PWBAs?   Are they interchangeable......



Victor,




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