Re: de-panelizing scored PCBs

We often manufacture in small quantities, sometimes less than 100
boards at a time. Boards are not assembled in-house, but after
assembly we do all testing in-house. Some products have options which
require final configuration in-house, perhaps programming or component
adjustment. When we do a new design, we know how big our boards are
going to be. We know from past experience which of the assembly subs
we use will best be able to handle this work; we ask those assemblers
to define/specify the size of array (panel) that they want from us,
usually it depends on the size of stencil or paste screen they can
handle with their equipment. At this point, the assembler may need us
to change our pcb design, perhaps alignment fiducials or tooling holes
need to be added to our board design. The tooling used by our
assembler defines how the panel must be scored or cut. Eventually we
have final Gerbers to send out for pcb fab quotes, and now we can
define for our pcb maker any of the special requirements set by the
assemblers. There is still some juggling in the quote process, because
different pcb fab companies will quote setup, NRE, and electrical test
in different ways according to number of boards per panel, meaning you
may go through another quote iteration to find the best panel size for
both pcb fab and assembly. One of our products requires two small
boards that fit in a box-like enclosure, the front panel of the box
incorporates field wiring screw terminals, which interface to the
boards via edge fingers. The boards slide in to extruded slots inside
the enclosure. Plated edge fingers are one of those design features
that will limit the number of boards per panel, as the pcb fab needs
that edge to be outward facing on the panel. The enclosure slots will
not allow any significant amount of roughness on the board edges after
cleaving/cutting, so someone will need to dress each board. Again,
work with your pcb fab and assemblers to figure out how best to
accommodate these requirements. In our case, the best compromise was
to assemble in arrays, the assembler has the tooling to cleave/cut
panels so they do that, then delivers the assembled boards to us. We
do the edge cleanup on the 3 board edges after assembly, it is a very
small operation as the cut edges will only have a few rough spots, we
do this in-house using a belt sander with a vacuum attachment.

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