Depends how much investment your CM is prepared to make - we use a $ 270K machine which is fully CNC controlled which can either rout out the boards OR saw the boards out of a panel depending on the requirement and also has program controlled auto tooling set up.. Best regards John Burke General Manager Zollner Electronics Inc. From: Bob Landman <[log in to unmask]> To: <[log in to unmask]> Date: 02/20/2012 03:00 PM Subject: Re: [TN] Sanding board edges after reflow Sent by: TechNet <[log in to unmask]> Thanks Graham, Phil & Ted. The CM says ESD isn't a problem because his employee wears a wrist strap and the sander is grounded... I gave up - no point trying to explain how friction generates charges. He refused to take Amol's advice, said the pizza cutters he looked at were NG. Looks like its time to find a new CM. Bob Sent from my iPhone On Feb 20, 2012, at 1:46 PM, Bob Landman <[log in to unmask]> wrote: > 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 >> >> ______________________________________________________________________ >> This email has been scanned by the Symantec Email Security.cloud >> service. >> For more information please contact helpdesk at x2960 or >> [log in to unmask] >> ______________________________________________________________________ >> >> ______________________________________________________________________ >> This email has been scanned by the Symantec Email Security.cloud service. >> For more information please contact helpdesk at x2960 or [log in to unmask] >> ______________________________________________________________________ >> > > ______________________________________________________________________ > This email has been scanned by the Symantec Email Security.cloud service. > For more information please contact helpdesk at x2960 or [log in to unmask] > ______________________________________________________________________ > ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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