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January 2013

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Subject:
From:
Steven Kelly <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steven Kelly <[log in to unmask]>
Date:
Wed, 16 Jan 2013 16:34:02 -0500
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Hi Pradeep,
Mr. Gregory's method is best. We have had some success V-scoring through the kapton but that means most times you have to obviously go deeper from one side than the other. You also have to use a newer machine that has these capabilities and you have to make sure you use the correct materials in the flex that can handle scoring. Leaving break-offs on the flex layer only means you have to control pre-preg flow or whatever bonding material you are using to the nth degree - too much and you are cutting through bonding material - too little and you will have de-lam or non-lam issues.
Good Luck.
Steve Kelly

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: January-16-13 1:25 PM
To: [log in to unmask]
Subject: Re: [TN] V scoring of Rigid flex PCB

Hi Pradeep,

I think maybe it is better to design your rigid flex with reinforcing tabs and breakaways to keep everything rigid so that you can build it, and relieve the flex from the edges and place tabs and mouse-bites at strategic locations. Below is a photo of a rigid-flex assembly I was involved in building some time ago that illustrates what I mean. The whole thing was de-panelized and folded up into a cube more or less:

http://stevezeva.homestead.com/files/RigidFlexAssy.jpg

Steve



-----Original Message-----
From: Glidden, Kevin
Sent: Wednesday, January 16, 2013 12:03 PM
To: [log in to unmask]
Subject: Re: [TN] V scoring of Rigid flex PCB

Fully route the rigid portions, and leave small connecting tabs on only the inner layer flex layers.  Then you can simply use an xacto or other type blade to separate the flex-rigid simply by cutting the flex tabs.

-----Original Message-----
From: Pradeep Menon [mailto:[log in to unmask]]
Sent: Wednesday, January 16, 2013 10:53 AM
To: [log in to unmask]
Subject: Re: [TN] V scoring of Rigid flex PCB

Thanks for the inputs. But my query is more specific on Rigid flex V scoring. We do V scoring at our end as well.

The issue is with Rigid flex ( or flex rigid) PCBs wherein there will be flex polyimide layers ( mostly at the center,  with the rigid portion towards the outer layers. For a 1.6mm thick rigid PCB, we usually do a 0.6mm depth V cut on either side which means there is a web of 0.4mm. This is easily 'breakable' since it is rigid. But if we have a flex in the remaining web portion, it is not breakable. Hence the doubt on any accepted practice or method for Rigid flex V scoring.

Rgds

Pradeep


-----Original Message-----
From: Nutting, Phil [mailto:[log in to unmask]]
Sent: Wednesday, January 16, 2013 8:35 PM
To: TechNet E-Mail Forum; Pradeep Menon
Subject: RE: V scoring of Rigid flex PCB

Pradeep,

You will find several discussions on V-scoring in the Technet Archives. 
V-scoring is discussed in IPC 2222.

The Internet has many locations that discuss it, for example: 
http://www.pcbstandards.com/forums/showthread.php?t=2261

To separate the boards at the V-score typically a sharp wheeled device (like a pizza cutter) is drawn over the V-score and does a very nice job of cutting the boards apart.  Bending the boards so they break at the v-score works but is a VERY BAD PRACTICE as it puts large stress on components near the edges which possibly causes failures of the circuit with broken components or cracked etches.

See http://www.cab.de/en/electronics/pcb-separators/ for pcb separators.

Good luck,

Phil Nutting

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Pradeep Menon
Sent: Wednesday, January 16, 2013 8:19 AM
To: [log in to unmask]
Subject: [TN] V scoring of Rigid flex PCB
Importance: High

Sir/Madam,

We have a customer who has asked for v scoring of rigid flex pcb. We are wondering how the PCB will be separated later, once we supply to them. Our customer has a drawing which calls for it, but they are also not very clear on this. We wanted to know whether there is a separate IPC standard or guidelines for V-scoring of rigid flex PCBs.

Tgds

Pradeep



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