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July 2005

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Subject:
From:
"Croslin, Robert" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Croslin, Robert
Date:
Fri, 29 Jul 2005 09:22:44 -0400
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We often use a combination of both V-score and route.  If we have an offending component that may be damaged by breaking off a scrap rail as we recently did on an SMT USB connector, we'll trig out the width needed for a routed slot in front of the part and simply have the V-score pass tangential to the edge of the route.  You can get real creative this way and still make the breakaway process clan.  We also use a routed slot for 45º corners and just pass the score over them.  

We attempt to design our individual boards with the array in mind first, then yield form the fabricators panel second. The idea is to be able to place all the parts in the optimum position so the array appears as a single board during the manufacturing process, but repeat the stepping as much as possible to take advantage of an 18x24 panel.  Since we do the arrays for both of our subcontract manufacturers, we really depend on their feedback during the design process.  On critical layouts, we actually send the initial placement to them for comment and approval before routing the circuitry.  

We'll often have our fabricator, even though our subcontractors use different shops, route a sample panel without plating so we can test things like debris left on edges, ease of breaking it apart and rigidity for handling purposes.  Bottom line, like has been said so many times before is to actively involve both your fabricator and assembly house (internal or external) aggressively in the design process.

By the way, on the USB problem, the connector had no mechanical anchoring and was easily pulled off the board, actually lifting the four anchor pads.  It's a 6 layer board, so we tried several approaches and used a 10 mil blind via to the internal 1 layer with a 30 mil pad on all four pads.  Now, when you try to rip it off, the connector fails long before the pads lift.  I hope this tip helps someone else to avoid the grief this caused us.


Bob Croslin
Nielsen Media Research

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Garry Foskett
Sent: Friday, July 29, 2005 3:01 AM
To: [log in to unmask]
Subject: Re: [TN] Standard panel size?...

Steve,

Just to add comments from my experience. When I was looking into this the response I found most useful from the production guys was that depending on the size of the run they were prepared to set the line up for a different panel that I defined for best space utilization. 
When doing a smaller run I would find out the panel sizes they were set up for and work out a placement strategy that did the best utilization of the space available.
Also a comment on V scoring, this is great for space saving but if your boards have any on board contacts such as buttons it would be best to go for routing, as the V-Scoring can lead to board fibers interfering with the contact operation and providing unreliable contacts. Even washing the boards after separation provided a limited success in stopping the problem

Garry 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lee parker
Sent: 29 July 2005 03:44
To: [log in to unmask]
Subject: Re: [TN] Standard panel size?...

Steve

I agree V-scoring should be a part of the initial design concept not an after thought. I have worked with many designers where cost is the primary consideration and we have found V-scoring to be a primary cost avoidance driver. As you point out though, to achieve the maximum benefit, this technology must be a part of the design process, not an after thought.

Best regards

Lee 

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389
  ----- Original Message -----
  From: stephen gregory<mailto:[log in to unmask]>
  To: TechNet E-Mail Forum<mailto:[log in to unmask]> ; Lee parker<mailto:[log in to unmask]>
  Sent: Thursday, July 28, 2005 8:56 PM
  Subject: Re: [TN] Standard panel size?...


  Hi Bill!

  V-scoring is great for some assemblies, but wreck havoc for others! I will depend on how close components are located to the score line. You can fracture components (especially capacitors) if you're not careful.

  As to what size is better for your assemblers, (I'm sorry for having to use a registered and copyrighted statement), it depends...

  As an example, just today one of our buyers wanted me to look at a panel layout of a board we were about to buy that was recommended by one of the board reps that we deal with. The board is about 2" X 12". Good candidate for panelization, right? Sure.

  Their recomendation was to be a 4-up scored panel, with .5" breakaway rails on the sides. I stopped that as soon as I saw it. It was good for the board house, because they would be able to give us a low price per board...but what we had to do to singulate the individual boards after we assembled them wasn't their problem.

  There was double-sided SMT, and the passives were all on the bottom...some located pretty close to the board edge. On top of that, they were oriented perpendicular to the board edge...just asking for cracked components or solder joints when trying to separate the the boards after assembly.

  As a designer, you need to be in tune with who will be building your boards, and what their capabilities are. 

  -Steve Gregory- 

  Lee parker <[log in to unmask]> wrote:
    Bill

    Have you considered V-scoring your panels as a way of minimizing waste. Most shops have this capability. after assembly you break the boards out of the subpanel along the V-score line.

    Best regards

    Lee

    J. Lee Parker, Ph.D.
    JLP Consultants LLC
    804 779 3389
    ----- Original Message ----- 
    From: Brooks,Bill 
    To: [log in to unmask] 
    Sent: Thursday, July 28, 2005 8:27 PM
    Subject: Re: [TN] Standard panel size?...


    Thanks for responding Lee... 

    After doing some investigation... I'm thinking a 8X10 assembly panel would
    work well for our assembly folks and still be dividable into a 18X24 or
    12X18 panel without difficulty... 
    One shop recommended 8.2 X 11.2 as the maximum assembly panel so it gave
    them room to put a .100 in router bit down the center and ¾ in. all round
    the perimeter... another wants .400 in between the boards... still another
    has many more standard panel sizes to work from and sees no problem with
    many different configurations... it's a bit 'non-standard' if you ask me...
    but that's what makes the challenge interesting... I'm wondering what other
    folks are using for their standard assembly panels...
    :-)

    Bill Brooks - KG6VVP
    PCB Design Engineer, C.I.D.+, C.I.I.
    Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
    Datron World Communications, Inc.
    _______________________________________
    San Diego Chapter of the IPC Designers Council
    Communications Officer, Web Manager
    > http://dcchapters.ipc.org/SanDiego/
    > http://pcbwizards.com 
    -----Original Message-----
    From: Lee parker [mailto:[log in to unmask]] 
    Sent: Thursday, July 28, 2005 5:20 PM
    To: TechNet E-Mail Forum; Brooks,Bill
    Subject: Re: [TN] Standard panel size?...

    Bill

    18x24 is by far the most popular panel size used in the industry.
Most
    Chinese shops, however, often tailor the panel size to the board or subpanel
    to optimize panel utilization. I suggest if you are using a Chinese shop you
    consult with them and take advantage of this benefit. I worked in the AT&T
    Richmond shop from the day it opened till it was shut down and we never
    considered multiple sizes to be manageable. After visiting many of the
    shops in China, I have come to realize that not all knowledge resides in
    North America.

    Best regards

    LeeJ. Lee Parker, Ph.D.
    JLP Consultants LLC
    804 779 3389 
    ----- Original Message ----- 
    From: Brooks,Bill > 
    To: [log in to unmask] > 
    Sent: Thursday, July 28, 2005 6:45 PM
    Subject: [TN] Standard panel size?...

    Hi TechNet...

    We are re-evaluating our board assembly panel sizes and want to get the best
    yields from our vendor's manufacturing panels when we select the final size
    of our 'standard' assembly panel...

    What is your PCB manufacturing 'standard' panel size for glass/epoxy type
    materials??? Some PCB vendors tell me they have a working panel size of
    18x24 inches... what do you use? And why?

    Thanks in advance for your help...

    Bill Brooks - KG6VVP
    PCB Design Engineer, C.I.D.+, C.I.I.
    Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
    Datron World Communications, Inc.
    _______________________________________
    San Diego Chapter of the IPC Designers Council
    Communications Officer, Web Manager
    http://dcchapters.ipc.org/SanDiego/ > 
    http://pcbwizards.com > 

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