When using break-routing keep your overall panel size small : don't put too many small PCB's in a panel
The more small PCB's you put in a panel, the more material will be cut away from the panel. This makes your panel increasingly weak. Typically large break-routed panels made up of small PCB's tend to bend through when held horizontally.
To prevent this sagging, and to increase the overall mechanical stabiltiy, add extra material between the PCB's.
Also consider that the cutting tool has a width of 2 mm. – A bigger clearance then 2 mm will not necessarily increase the stability. For instance a clearance of 5 mm results in 2 x 2 mm from this clearance cut away, so only 1 mm is left. This is not helping the panel stability at all.
We recommend a minimum clearance between small break-routed PCB's of 10.00 mm.
Choose a wider panel border for extra strength.
Remember also that when using break-routing we need to place break-out-tabs on the PCB in both X and Y direction. Defining the routing tabs on smaller PCB's can be problematic or even impossible as the routing tabs require a minimum accessible length of 5.00 mm for proper placement.
In many cases the best solution for the panelization of small PCB's to ensure good mechanical stability is to use V-cut ( scoring) as the board separation method.