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,