Franklin is correct.
Refer to IPC 7095 page 66 fig. 7.5 and Table 7.3. This shows how to
dimension the score such that the amount of remaining material desired
is known (dim. A). If you keep this remainder at less than .015" for
standard thicknesses of .062" it will be OK. But it cannot be too small,
or the remaining web will break easily during normal handling. For
thicker boards it should be no more than .015"-.018" remaining, as this
provides sufficient strength but will still singulate easily.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: Wednesday, October 05, 2005 6:11 PM
To: [log in to unmask]
Subject: Re: [TN] PCB Score Depth

You will find it referenced briefly in 6012, it might even be in IPC
2221 but dimensions would not be included.

Typically the user (buyer, customer, assembler, etc) would include their
requirements in the fab drawing or spec.

A v-score of 2/3 board thickness is most common; however, this is most
often used for .049 - .062 thick boards. 2/3 rule would not work well
with a .150 thick board and would cause all sorts of problems on an .030
board.

You can mix score and rout (web cut) and can also skip-score (or jump
score) which is most common on thinner boards.

Score depth like nearly everything board related has many variables
which would control it, for example, will an post-score machine be used,
will the array be in a frame during assembly, individual piece size and
number in the array, are components attached close to the edge, near the
score line, are there through hole components, are components attached
to one side or both.

Those and a myriad of other variables will dictate the type and depth of
score.

If you provide some specific features we would be glad to offer more
insight.

Franklin


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joel Mearig
Sent: Wednesday, October 05, 2005 4:52 PM
To: [log in to unmask]
Subject: [TN] PCB Score Depth

Is there a specification for score depth on PCBs? In other words does
one always leave the same amount of web after scoring regardless of the
board
thickness or is it a percentage of board thickness? Thanks
Joel


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