Pcb Cutting

[asti]

Dear collegues,

Ive seen before a single PCB panel that consist of multiple designs(different designs) in it. it has slots where you can just snap the boards.

As of now i have six designs (prototypes) and i have to combine the designs to a single board hopefully to minimize fabrication cost. I need to know what are the rules in making the cutting pattern for the individual boards. I will greatly appreciate your inputs. =)

Best regards,
asti

[randychase]

There are different ways to panelize and different methods.

A common method I used to use, was to create the separate Gerber files in the CAD program and then import them into CAM-350. You could offset the files using snap to object and coordinates. To make this easy, I would use a common origin point.. or I guess if you are clever, you could create the offsets in your CAD program.

Then you have some options for how to panelize. One method is scoring, which is a V shaped cutting line on either side of the PCB and it allows you to snap the boards apart. Be aware that this does not make sense for smaller runs, and it does use a little bit of real estate. And the lines need to be straight.

Another method is from pressing out the boards and then pressing them back into. The friction holds them in. This makes more sense for large numbers of smaller boards.

One common method is to route out the boards, and leave webbing to keep them attached. This method can make sense for smaller runs, and for odd shaped boards. Use a standard routing mill to determine the size of the routed out section. I used to actually place these end points of the mill using pads and drill hits. To make the webs more breakable, people place "rat bites" on the webs, which are a series of small holes designed to reduce the overall material connecting the boards.... and these holes also create a break line along them... so you can control how the boards break away.

The size of the web, size of the holes, numbers of holes, locations of the webs.. are all part of the art form.

[asti]

thanks so much and i really appreciate your reply. now things got clearer for me. i need to include a cutting layer for my design where i need to leave web(with rat bite as you mentioned) to allow the boards to be attached to each other.

is is ok if one routing is just exact to divide two boards (i mean one passing of the routher will devide the two boards). or i need to put the designs apart such that individual boards will have individual routing? another question is how long will be the web. we will be using two layered fr4 laminate.

regards

[randychase]

You can use one route to separate two different boards. So the edges of the boards are going to be 0.094" apart, if using a 0.094" mill.

One example of a common ratbite I use, is 0.035" dia non-plated holes, set 0.050" apart, in a row of 5 holes. That leaves only 0.015" between holes (4 places plus ends) or a total web of about 0.090"

[Skip Yutkus]

That's pretty much how it's done, just a comment, I've been down this path a couple of times and usually, although it sounds great in theory, especially if you have asystem that uses 5 different boards per and you can get them all on one panel, what happens is if you get 1 bad board on a panel you have to make 5 more to get a good one, very difficult to get a handle on inventory, unless you can work some sort of deal with the board shop, (which will usually involve paying a little more), just something to consider.

Skip