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February 2012

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Subject:
From:
Graham Collins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Mon, 20 Feb 2012 14:51:38 -0400
Content-Type:
text/plain
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text/plain (120 lines)
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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