de-panelizing scored PCBs

On Tue, 13 Jun 2006 11:20:02 -0700, "Walter Harley" Gave us:

One must remember, however, to place in enough "stitches" so that the overall card is still fairly sturdy. The pick and place machine has to be able to shove a part down onto the cream. This would depend on how big your PCB is though.

The board house is likely familiar with the practice. I can't imagine them not being so. Most can replicate the traces and panelize your PCB for you. Were it me, I would prefer to design the panel, but that is high dollar engineer labor intensive work. The PCB fab house has software that will take your gerber data and plot out a panel, add fiduciary marks, etc. (So do most good EDA suites these days).

On Tue, 13 Jun 2006 18:58:11 GMT, "Genome" Gave us:

Slots are cheap.

Nearly ALL good HV multiplier designs have slot milled in the pcb layout to allow potting compound to build barriers between parts. Shouldn't increase a quote by much to have a few or even several lineal inches of slotwork on a PCB.

I have even had fabbers say they can make me layered, non thru cut steps in my layouts (troughs)... A lot of interesting ideas come to mind.

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.

I think Genome is talking about a slot in the front panel of the enclosure, not in the PCB. And he's right, I don't like it :-)

My assembly house claims that they can depanelize these things (for a price). I haven't had a chance to ask 'em yet how they do it, but I imagine with one of those pizza cutters. I guess for the small number (prototypes and special orders) that I continue to do in-house I'll just be Very Careful.

Thanks, all.

Thanks for the nice summary of your operation!