On 18 December, James wrote:

>> We presently route out multi-ups but would like to get away from the
>> router on some designs if possible.
>> Could anyone supply design guidelines or rules/equations to allow a
>> "breakaway" process (seperate multi-ups by snapping them apart)?
>> Thanks in advance!

>> I just learned of this TechNet, and it's A GREAT THING!!


Hey there James!

     Ahhhh scoring, such a wonderful thing. It saves time, the PCB's can be 
singulated from a panel in probably half the time it takes on a router, and ya' 
don't need a fixture to do it...no broken router bits, and ya' don't get router 
dust on the assemblies either. It saves space on the panel too! Ya' can butt one
PCB right next to the other one without having to have a gap of clearance 
between each PCB for the router bit to cut them out. _BUT_ (notice the heavy 
emphasis on the "_BUT_"), it absolutely, positively, _HAS_ to be done RIGHT!

     It's been my experience that a fab vendor that does a good job scoring is 
hard to find...there's a few out there, but very few. The problem that I've seen
is that it's either scored too way too deep and the panel falls apart when yer' 
trying to build it, or it's not deep enough and the operators wind-up fracturing
solder joints on the assembly because it takes so much darned force to snap the 
dad-blamed thing apart, or delaminating it because ya' can't get a clean break 
of the fiberglass filaments in the laminate.

     I've asked a few of my peers why it seems that scoring is something that 
many fab vendors never get real good at. They tell me that scoring is something 
that fab vendors hardly ever start out in the business doing from the beginning.
The typical fab vendor ALWAYS starts-up the business with a router, and they'll 
start getting customers and getting busy, then a customer comes along and has a 
board that they want to get scored. Well, it's the only board that anybody has 
asked them to score so far, but they don't want to lose the business so they go 
out and buy some low-end machine and give one of their operators a 15-minute: 
"Here's where ya' put the panel, press this button and when it comes out the 
other side put it in the box and ship it." and that's why ya' see way too many 
bad score jobs coming from a fab vendor...at least I have anyway.

    But when it's done right, what a throughput enhancer!! At a past employer 
where we did memory products (SIMM's, DIMM's, FLASH Cards, and PCMCIA product) 
we were always "bottle-necked" at the router. We had two 4-head Kennards and two
dual-heads and could never catch-up. We started getting all our PCMCIA product 
scored and it helped...at least we could keep from getting buried, and it gave 
us some time to at least PM the routers. When ya' run em' that much ya' gotta' 
take care of them!

    I was given a score depth guideline chart back in the past that I can't 
remember where I got it from, but I still use it and it's pretty good as far as 
getting ya' in the ball-park for a proper score depth...ya' know, so yer' panels
don't fall apart on ya' trying to build the darn things, and being able to break
it apart when ya' need to. It's for FR-4 and for yer' standard PCB laminate 
thicknesses....015", .020", .031", .062", and .093".

    Ya' know, I was trying to depict the chart here in ascii...but I can't 
really get the kind of information that needs to be shown just by ascii 
characters. If ya' would like a copy of the chart, email me and I'll send ya' 
email with it attached in *.BMP, *.GIF, *.JPG, or *.PPT format whatever you 
prefer seeing how we're not supposed to attach anything to our posts to the 
TechNet...
         
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