Recently, we processed a job that was what I refer to as "ghetto panelized." Basically, rather than having the PCB fab shop create a panelization for you, ghetto panelization refers to creating your own large panel and separating all the different boards with lines of holes (see image).
- 3" x 4"
- 2 layer
- Tin Lead Finish; non-RoHS
- Electrical Tested
- 4 day processing time
- 100 boards needed
Taking this same board, ghetto panelizing yourself to a 3 x 3 panel (Total dimensions of your single board are now 9 x 12), the price for 15 panels (135 boards) drops to the price to $4.61 per unit. That is a pretty big difference in price. Overall, you would save $967. It's safe to say that someone would do this for price reasons, not convenience; unless of course you find using a band saw to cut apart PCBs more convenient.
So, why wouldn't everyone want to ghetto panelize boards? First, it is near impossible to get a precise cut, so each board is has a unique shape (and rough edges). This will negate any machine assembly house from being able to assemble them post breakout. You would therefor need to do hand assembly, or have them assembled before you break them apart.
Secondly, reliability is a concern. Depending on your method, you can damage the board functionally. This is especially applicable to boards that have been assembled, where certain solder joints can crack. You are introducing a lot of vibration and force to the board. A joint that is already weak can snap.
However, if you need a few simple connector boards, ghetto panelizing your PCBs can be a cost effective way to get a few extra boards for a better price.