I think there needs to be some distinction made between two separate things:
1) arranging individual boards on a fabrication panel to get the best yield
2) designing an array for assembly, which may require v-scores or breakaway
tabs
The IPC was trying to use consistent terminology to avoid confusion by
calling the bare board fabrication material a "panel", and calling an
assembly array a "pallet". Unfortunately, they added another term called
"Delivered Panel" to mean the same thing, which just adds to the confusion
in my opinion (also, some of the other definitions in IPC-T-50 aren't
consistent, like the one for "breakaway" or "multiple printed board". I
never noticed that until just now!)
Anyway, I think the "panel drawing" that Greg is warning against is the
result of a board designer trying to optimize the yield of the fabrication
panel. I agree with him, you shouldn't waste your time (and probably waste
money in the long run) trying to do that.
However, if you need assembly pallets to add rails to a board or to create
an array of boards that will require operations after the assembly to
separate, you should document that. Do not leave that up to the bare board
fabricator.
onward thru the fog,
Jack
On Tue, Feb 12, 2013 at 5:10 PM, Greg Smith <[log in to unmask]> wrote:
> Hello
>
> I'm going to have to respectfully disagree with the need for a panel
> drawing.
>
> It depends...
>
> I have worked for companies that bought their bare boards from outside fab
> shops and did the PCB assembly in house.
> We always did a panel drawing as we knew exactly what our tooling,
> equipment, and design needs were.
>
> I have worked on designs where the PCBA was an assembled panel that did
> not get broken up until final assembly in the end product. That required a
> panel drawing.
>
> Other times the company worked with a specific fab house and a separate
> specific assembly house. We did not supply a panel drawing but asked the
> fab shop to supply a Gerber or pdf of their proposed panel for our approval
> and, more importantly, the assembly shops approval. This allowed both shops
> to negotiate the design that best met their capabilities.
>
> I have also worked on designs where I would not even know what continent
> the fab and assembly shops were located in. The contracted manufacturers
> had locations world wide and would use the appropriate facilities that had
> time available to meet the order. This means the panel size could be
> different for every order placed as the location could change. That means
> the panel could, for instance, be prototyped in a shop using inch
> dimensions, and mass produced in a shop using metric dimensions. A panel
> drawing would then tie the shops to a possibly wasteful or inefficient
> design.
>
> However, if there are specific design needs that require that break-away
> tabs or scoring areas not be located in certain places, then this needs to
> be on the fab drawing. You just don't need a panel drawing to do this.
>
> Greg Smith
>
>
>
>
> On 2/12/2013 1:21 PM, Pete wrote:
>
>> If you don't wish to make panelization drawings as a time savings, you'll
>> spend more time fixing issues. Always make a panel drawing, the fab house
>> doesn't know the board assembly, the CM doesn't know the end product. You
>> know what you need, put it on a drawing so there's no doubt.
>>
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