Boards per Panel Arithmetic before Anyone Argues Unit Price
Calculate usable circuits per master production panel and subtract outer border clearances before negotiating bare board unit prices with fabricators.
Mouse Bite Tab Routing
Depanelization Method
Mechanical singulation of printed circuit board arrays utilizes narrow breakout tabs with closely spaced drill holes. Applying mouse bite tab routing allows individual boards to remain securely connected within a panel during assembly but break away easily during final depanelization. This technique provides a cost-effective alternative to straight V-scoring.
Mechanical Stress
Localized mechanical strain occurs when the breakout tabs are snapped during the singulation of the board. Implementing mouse bite tab routing requires careful placement of the holes to balance panels during surface mount processing while minimizing the force needed to break them. Placing ceramic capacitors too close to these breakable tabs can cause microcracks in the component bodies due to bending forces.
Stencil printing and component placement are also affected if the tabs bend under the pressure of the assembly heads.
Design Rule
Structural dimensions and clearance distances are defined in the fabrication drawing to protect trace routing from tearing. A typical mouse bite tab routing design utilizes a line of five holes of small diameter grouped across a tab of narrow width. The hole centers must sit slightly inside the board edge so that the broken fiber protrusion does not exceed the board’s finished dimensions.
Fabricators and assembly houses negotiate these hole layouts to accommodate the specific fixtures of their production lines.