In the dynamic world of PCB manufacture, accuracy, price, and efficiency are paramount. One aspect that is crucial but often overlooked in this industry is the use of mouse bites. These microscopic perforating holes along the edges of a PCB facilitate simple board separation from a panel during assembly. This article explains what mouse bites are, why they are beneficial, design rules, and how they differ from other depanelization processes like V-scoring.
What Are Mouse Bites in PCBs?
Mouse bites or perforated breakaway tabs are collections of tiny holes drilled into a PCB, just like the perforation present in a postage stamp. In the process of manufacturing PCBs, especially when break-routing methods are employed, these perforations assist in the assembly of small PCBs in arrays and facilitate them to be separated easily later. The impressions created by these perforations resemble the mouse bite marks, and hence the name. Even though commonly utilized with FR4 panels, mouse bites can also be employed with other materials like aluminum PCB boards, but with caution as the rigidity and thickness of metal-core materials make them more durable.
Why Are Mouse Bites Used?
Ease of Separation
Mouse bites allow individual boards to be separated out of a larger panel without using intricate tools. This is especially valuable in hand-assembled prototypes, low-production runs, and surface mount technology (SMT) assembly where simplicity is an important consideration.
Cost-Effectiveness
Mouse bites are cost-saving and labor-saving as the boards can be hand-separating easily. Special equipment is not needed, so they are cost-friendly for organizations that want to optimize resources.
Design Flexibility
These perforations are ideal for one-off or non-rectangular board shapes where V-scoring is impossible. They give flexibility and flexibility, so ideal for boards having intricate designs and unusual shapes.
Better Grip
Where a board must be screwed or forced into a tight space, mouse bites allow for the formation of a rough edge that provides a stronger grip than smooth finished edges.
How Mouse Bites Work in Panelization
Mouse bites come in handy at panelization when several PCBs are processed as a group. Here is how they work:
Panel Arrangement: Several PCBs are assembled in one panel with breakaway narrow tabs linking them.
Hole Drilling: Drilled holes (mouse bites) are added to these tabs, loosening the connections to permit easy separation upon assembly.
Post-Assembly Separation: Assembly and soldering are completed, and boards then are snapped off by hand or by basic tools like pliers.
These hole-drilled weakened connections are sufficient only to provide easy separation without compromising panel strength during manufacture.
Mouse Bites vs. V-Scoring
Both V-scoring and mouse bites are used on depanelization, but both are used to fulfill different needs:
Mouse Bites: Comprised of microscopic perforated holes with an irregular edge. They are ideal for curved edges or irregular borders, allowing design flexibility for complex board shapes. The edges, however, may require post-processing in the form of sanding for a smooth finish.
V-Scoring: V-shaped groove cutting on the panel for simple edge separation. This process is suitable for standard rectangular boards with smooth edges but not as flexible for irregularly shaped handling.
Mouse bites are especially useful when utilizing precise imaging processes such as laser direct imaging (LDI) for making highly detailed and dense circuitry designs.
Design Considerations for Mouse Bites
Including mouse bites in a PCB design requires careful detail consideration:
Perforation Inset: A small inset of perforations is preferable because it reduces the amount of post-separation cleanup, producing an edge that needs little or no additional labor.
Tab Spacing: Typical spacing between breakaway tabs is from 60 mm to 90 mm, with 77 mm being a benchmark to provide even spacing without compromising structural strength of the panel.
Material Compatibility: While mouse bites are typical with FR4 boards, extra caution must be exercised in the case of materials like aluminum, due to their brittleness and potential for making separation more difficult.
Cost-Saving Benefits
Use of mouse bites can also cut manufacturing expenses quite substantially:
No Special Tooling Required: Unlike V-scoring or routing, mouse bites are naturally created using standard CNC drill tools, eliminating the need for specialty cutting tools.
Less Labor Cost: Boards separated manually imply no requirement for expensive equipment, thereby less labor cost.
Maximum Panel Utilization: Mouse bites enable us to design arrays in a flexible way, keeping panel losses at the least and making them optimum for prototype and low-volume runs where tool cost is usually kept to a minimum.
Usage of Hand-Assembly PCBs
In small-volume, hand-assembly PCBs for applications in environments like research labs or startups, mouse bites are a low-cost, efficient option. They obviate the requirement for special depaneling equipment, which is a relief during early stages of development when cost control and speed are critical. The method can also be combined with fiducials for alignment, contributing to practical application.
Strength and Reliability Considerations
While mouse bites are preceded by numerous advantages, they also possess concerns with regard to the structural strength of the PCB after depaneling:
Rough Edges: The snap effect can produce rough edges, which can be smoothed.
Potential Microcracks: Improper care when splitting can lead to microcracks, which compromise the board strength.
Weak Corner Strength: Compared to routed or scored boards, break tab separation can provide relatively weaker corner strength.
These issues can be mitigated by designing with maximum tab width, reduced mouse bites per tab, and post-break sanding at design time.
Mouse bites in the course of PCB manufacturing are an inexpensive and flexible solution for depaneling and finding application on projects from one-off prototypes to production runs. They are inexpensive, simple to use, and very versatile in design, function, and use.
At PCBCart, we specialize in high-precision PCB manufacturing with precisely designed mouse bite structures for optimal panelization and depaneling. From rigid-flex PCBs, durable aluminum boards, to advanced HDI solutions using laser direct imaging (LDI), our experts guarantee precision work on your boards. Partner with us to maximize your product's performance, reduce lead times, and control costs with the highest manufacturing standards.
Request for High-quality PCB Assembly & Fabrication Quote Now
