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What are Mouse Bites in PCB?

Mice are pretty small. Whenever they bite on anything, they leave some tiny marks behind as evidence. On your printed circuit board, you may find some “mouse bites”. Now, don’t get scared. These mouse bites don’t indicate rodent infestation.

Rather, these tiny holes assist in breaking out a circuit board from the manufacturing panel. Now, the locations of these holes are precise and dimensioned. Of course, they are similar to those nibbling you may find left behind by a mouse.

So, there’s no need to get your traps and cheese ready because our topic linking “mouse bites” to printed circuit boards has nothing to do with real mice. Rather, we will focus on mouse bites PCB and its dimensions to ensure you comprehend the manufacturing or circuit boards better.

What are Mouse Bites in PCBs?

Mouse bites circuit board

 Mouse bites in printed circuit boards are sections of the manufacturing panel that helps in assembling and fabricating circuit boards. Some individuals utilize the “mouse bite” term to describe and explain the over-etching of copper. However, what we mean here is different.

PCB manufacturers lay out circuit boards in a panel making use of CAM – Computer Aided Manufacturing systems. This panel ensures that the assembler and fabricator is given additional board material for any handling during all processes involved in manufacturing, which is very critical for the smaller boards.

Normally, panels have a uniform size, and you can lay out multiple instances of your printed circuit board design within the panel’s outline. The panel will not just make board manufacturing easier. It also allows the processing or multiple boards in panels for a similar cost as one board.

Once the fabrication, as well as assembly processes of these circuit boards, has been completed, then you must separate them from their panels. The process of separating them is known as depanelization. You can achieve the depanelization process either by breaking out the boards along the “V-grooves” or pre-scored lines, or cut them out.

The boards you have to break out have to be routed already around its outlines. This will help in bringing a separation between them and the panel, which are held by just small material tabs. The removal of the “breakout tabs” takes place, thereby making the board free from the manufacturing panel.

These tabs also feature small holes, which ensure the easy breaking of the PCB, and reduce the stress of the boards. With each of the tabs broken along the holes’ lines, the material remaining will have the appearance of a “mouse bite” until you have smoothed it out.

Mouse Bite PCB: Locations, Dimensions and Sizes

The holes utilized for breakout tabs may vary. However, majority of manufacturers utilize five holes in breakout tabs having these dimensions.

The hole size is usually 0.5 mm or 0.020 inch in diameter. Concerning the spacing, they are 0.76 mm or 0.030 inches apart.

The spacings and sizes of the mouse bite PCB holes appear random. This reduces the cleanup needed after the breaking out of the board from the panel. Though, it takes less effort for a smaller hole to smoothen out, it will also need more holes to be drilled and leave out much bulk material.

However, if there are too big holes, the board will end up having mouse bites that are larger and will need smoothening out. The hole placement within this breakout tab is important as well. The goal here is drilling them nearer to the PCB edge. This helps in reducing the tab material leftover that needs to be removed.

Constraints to consider during placement of breakaway Tab PCBs

There are some constraints to consider while performing the breakout tabs’ placement around the outline of the board.

  • Don’t make use of many tabs in order to save wear, effort, and time on its router bits.
  • Have enough tabs that can support the PCB board fully in its panel throughout the operations of PCB assembly.
  • Tabs having a minimum clearance of 0.125 inches should be located to the closest components.
  • Don’t place the tabs close to circuitry or sensitive components areas. This could cause the board to experience more breakout stresses.

At times, stress damages coming to the circuitry or components due to the tabs breaking may not be seen till later. It may also cause intermittent issues that won’t be debugged easily. This is why the location of breakout tabs, a distance away from any sensitive area, is very important to the circuit board’s success.

Also, if you don’t use enough tabs, and you don’t place them strategically to support your board during the manufacturing process, your board may end up flexing too much. This will prevent a reliable assembly. Now, this is the point where the experience and knowledge of your PCB manufacturer comes in.

What is V Groove PCB?

Breakaway tab pcb

The V groove PCB results after the splitting of circuit boards. This requires the cutting of the circuit board, and leaving a little material to help hold these boards. The final stages involved in the production is profiling the v groove pcb and cutting them from the manufacturing panel. This is either done by routing or v-cut scoring. There are some rules to adhere to when manufacturing V Groove PCB.

Rules When Manufacturing V Groove PCB

  • Ensure that the board’s spacing is 0mm
  • The spacing found between the outline and V-scoring line stays at 0.35mm
  • The line for V-scoring has to be straight. Also, it must be a horizontal and vertical line.
  • The minimum size of the v groove PCB should be 75 x 75 mm, while the maximum size of the v groove PCB should be 450 x 1245 mm.

Breakaway Tab PCB: Panelization Methods

There are multiple methods for Panelization of breakaway tab pcbs. Each of these comes with their own benefits and drawbacks. The board’s design present on the panel, as well as the panel, usually plays a big role in whatever method of Panelization will suit the application best. Let’s consider these factors.

Components: The importance of the component utilized on the board is just the same as its placement. Connectors and components that are sensitive may play a huge role in the most effective Panelization and breakout method.

Design: The board’s design plays the most significant role when determining the best method for Panelization. The clearance amount between the board’s edge and the components may make some of the methods less appropriate compared to the others.

Materials: Materials utilized in mouse bites PCB may end up limiting the Panelization method type that is best. This is because some of the materials can splinter easily during the breakaway process. Another factor is the thickness of the board. Particularly, all thin boards have a higher chance of breaking while assembly is on. Thick boards on the other hand, may give more problems during this breaking out as well.

These factors explained above limit the available choices to any given application. Many companies handling the assembly may combine different methods on a specific project. This is to ensure the array’s structural integrity coupled with mitigating the issues encountered while the breakout was on.

PCB Breakaway: Panelization Techniques

For breakaway tab pcbs, there are three techniques for Panelization. However, most of the time, just two are practiced.

Tab Routing Panelization

Here, mouse bites pcbs are usually pre-cut from the arrays and then held properly on the board. Most times, about 3-5 holes are utilized in the perforation patterns. With this method, you are sure to get some benefits due to its design support ability. You can also break them with your hands rather than using tools.

V Groove Panelization 

This technique for Panelization is very common. This uses V-shaped grooves in separating individual printed circuit boards. About 33% of the thickness of the board is removed by these grooves from the bottom and top of the board using a blade.

Most times, a machine is used in finishing the PCB breakaway process. This it does considering that the third left of the bard in-between your grooves is strong and stress can be put on the mouse bites pcb as well as its surrounding components through hand-breaking.

Solid Tab Panelization

You can design arrays using solid tabs between the boards, thereby improving the strength overall. However, the method for depaneling this panel type needs either a laser-cutting machine, a depaneling router, or a blade tool (hook-shaped).

The laser-cutter is very expensive. Also, they usually don’t work on boards that are more than 1mm thick. The router can cause vibration and dust. The blade tool with a hook shape is a less expensive option. However, they usually experience blade rotation, and are inefficient. Compared to the first two methods, this method is less common.

For majority of applications, the preferred method of panelization is Tab Routing and V-Score. One good thing that a PCB designer must understand is which of both methods works best for the application. Now the next step is designing their array to ensure breakout success and maximal strength.

Many people prefer using the V-groove method due to its surface stress reduction and efficiency. This array’s depaneling machines are also cost-efficient and relatively inexpensive. Better still, they require less maintenance, and they are portable. Though this method usually results in board edges that are rougher, this concern is rare for applications utilizing V-groove panelization.

Tab Routing Vs V Groove PCB Panels

Making a choice if you should use tab routing or v groove methods in the panel largely depends on your PCB design. These are some factors to consider before you make a decision.

Edge components

It is possible that your breakaway tab PCB relies on components attached near an edge, it could be very appropriate using some tab routing variation, rather than v groove pcb panels. Just make sure that you don’t locate the tabs close to the edge components.

Board Shapes

Mouse bites PCB shapes that are added to any array usually play a significant role in panelization. For rectangular and square boards, v groove PCB panels work very fine. When dealing with unusual shapes, the better is tab routing.

Time Expense

Setting up tab routing takes more time. This is because the router requires much time. V groove, while under machines requires lesser time.

Edge Quality

The fact is, if the edge quality stands as a factor then tab routing may be more preferred to v grooving. Although, working with this process leaves back small rough laminate rubs, you can easily sand them off. Then the edges remaining are smooth. V grooving causes rough edges around. If you require smooth edges, this may need more sanding.

Waste

If you are concerned about material waste, then the best benefit will be provided by v grooving. Compared to tab routing, this method wastes less material. This means the overall cost for each board will be much lesser.

Mouse Bites PCB Manufacturer

When setting the manufacturing panel up for printed circuit boards, there are lots of variables to work with. This is why your mouse bites PCB manufacturer must have much experience in this.

Your manufacturer will tell if a breakout panel or V-groove will suit your design best based on the design criteria and the specific needs of the board. Also, they understand the needs of your business and also tailor the creation of the panel in line with your expected volumes of production, as well as the specific requirements of the board.

At RayMing PCB, we help in designing our client’s PCB panels. This is part of our usual manufacturing workflow. We have reliable manufacturing and engineering teams that have vast experience in working with several panel requirements. Choose us today and be sure of top quality creation of your application’s panels.

Conclusion

By now, you should have gained vast experience about mouse bites PCB, breakaway tab pcb, pcb breakaway, and v groove pcb. Remember that you should always work with top manufacturers to bet the best panels that also meet your requirements.