I agree with Bob. The bow/twist in the individual pwb in the panel is relevant to the stress
on the nonleaded SMDs when the assembly is unbowed or untwisted upon installation to the
console.
The bow/twist of the panel is significant to the assembly processes, possibly effecting
conveying, printing and placement.
Gary Camac
bbarr wrote:
> But how does one measure bow and twist of an individual board in a panel?
> Aren't I really concerned with the bow or twist of the entire panel since
> that is what is going through the assembly line?
>
> Bob
>
> Robert Barr
> Manufacturing Engineering
> Formation, Inc.
> Voice: 856-234-5020 x3035
> Fax: 856-234-6679
> email: [log in to unmask]
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Guy Ramsey
> Sent: Tuesday, January 23, 2001 1:16 PM
> To: [log in to unmask]
> Subject: Re: [TN] Bow and twist: Need clarification
>
> 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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