In cases like this (the joys of contract manufacturing) we have had
carrying pallets made, for more like $250 each. We had one board that
was donut shaped, can't do much with that!
Using a carrying pallet will increase the handling time, but is likely
cheaper than re-spinning the PWB.
regards,
- Graham
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Monday, February 20, 2012 2:47 PM
To: [log in to unmask]
Subject: Re: [TN] Sanding board edges after reflow
Thanks Amol. The CM just told me that he can get a custom fixture made
to grip the boards but it costs $850 (I guess thats an "each" cost) so
I'll pass to him your suggestion.
Bob
Sent from my iPhone
On Feb 20, 2012, at 11:40 AM, "Amol Kane (Asteelflash,US)"
<[log in to unmask]> wrote:
> Hi Bob,
> While your CM is doing what is very common in the industry (adding SMT
> rails for manufacturability), I would be concerned with the ESD
> implications of sanding, as well as FOD on the assembled product.
> Furthermore, We do not prefer tab routing (mouse bites) due to the
> shock/impact to the board during de-paneling.
>
> I would recommend you investigate a scored/routed rail that can be
> de-paneled on a pizza cutter. If there are overhanging components on
> the assembly, you may not have a choice. But, careful design of the
> mouse bites, and the tooling thickness can still eliminate the need to
> sand the edges after de-paneling
>
> Regards,
> Amol
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
> Sent: Saturday, February 18, 2012 2:23 PM
> To: [log in to unmask]
> Subject: [TN] Sanding board edges after reflow
>
> Our contract assembler just sent us the following message for a short
> prototype run on a modified design:
>
> -------
>
> "I asked the board house to add a 1/4" tab routed strip on the long
> side of the board that P1 is on so that we can put solder paste and
> place all of the top side SMT parts. We need at least 4mm (0.160")
> for the clamping rails on the machines. C180, C181, D1, R19 and C27
> are to close to the edge of the board.
>
> We will remove the strip and sand the tabs."
>
> ------------
>
> It's a 6" x 8" 6 layer board (Sn63 soldered) with SMT parts (including
> a
> 256 ball BGA and a number of tiny QFN parts). Apparently the EE who
> designed the changes and the PCB layout person were very tight on
> space so extended circuitry into the area reserved for the reflow
> oven's grippers.
>
> Should I not be concerned that sanding could cause cracks in the
solder?
> The EE told me, as did the assembler, there was nothing to worry
about.
>
> This is the first time this problem has occurred since we began making
> products in 1980.
>
> Should I pull the job (which is a 5 day turn) on Monday and have the
> artwork fixed to provide gripping areas (which used to be there) ?
>
> Or is it safe to do what the assembler had told the board fabricator
> to do?
>
> Bob Landman
>
> Sent from my iPhone
>
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