Tom, we have also done this style of design with good results. the issues, the way we
see them are; 1) it's overkill. it drives up costs. why have 2 processes when 1 will
do?
2) many designs don't provide space for blade run-out. (a 4" circular blade needs
approx. .250" beyond the end of score line to retain full depth.) There is also the
issue
of coordinating two NC machines. Lastly...many designs don't allow for a "keep out"
area where half the blade can encroach into the part.
hope this helps,
Mark
Tom Martin wrote:
> Just curious Mark,
>
> What are the problems with "replacing small holes
> with score lines on tab rout designs?" I
> once had a manufacturing engineer request that an
> array panel be done this way and the results appeared satisfactory.
>
> Tom Martin
>
> Date: Thu, 22 Jun 2000 08:58:55 -0700
> From: Mark Simmons <[log in to unmask]>
> Subject: Re: V-score depth
> MIME-Version: 1.0
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
>
> Dennis, Steve, et al....
>
> i suspect the reason this topic keeps coming up is because of our well
> intended desire
> to nail things down. after all, there are so many things to keep track
> of, eh?
>
> By way of review,...there are too many variables to be specific about what
> the
> remaining core thickness (web) should be. the chart that Steve recommended
> from the
> Accusystems web page, takes into consideration the most variables, but
> still makes many
> assumptions. i.e.; the material is FR4, and the score line is not adjacent
> to SMT
> component lands. So this chart will get you into the ball park, but you
> must find your
> own seat. Here at Vscore Central, we deal with these issues on a daily
> basis...over
> the years, we have seen some pretty strange stuff. There is an astonishing
> lack of
> convention. There are a number of mis-applications, including replacing
> small holes
> with score lines on tab rout designs. Simple things like providing solder
> mask
> clearances for the score lines are overlooked. (acrylic masks machine so
> poorly..)
> Generally, the process is an afterthought (at best) for most
> designers...but i
> digress. In summary, be careful with "rules of thumb".
>
> Mark Simmons, V-Score Central, Inc.
>
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