Printed circuit board uniformity is a key concern in many PCBA-related projects. Non-uniform boards are discarded because manufacturers consider them to be unsuitable for supporting an intended application. Fortunately, manufacturers can prevent some waste by ensuring uniformity of small circuit boards through PCB panelization.
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What is PCB Panelization?
PCB panelization allows you to connect various smaller circuit boards to form a single, large array, which allows designers to receive high-quality boards in large volumes. Panelization also helps where a product enclosure doesn’t have room to expand the width of the board. The vendor performing panelization can easily remove or depanelize the array for insertion or packaging into a product. Depanelization is often used to increase the “throughput” of a PCB.
Factors to Consider for PCB Panelization
Before panelizing a PCB, it’s important to consider that the design of the panel, as well as the boards, will affect the choice of the panelization method. That’s because the clearance between the board’s edge and its components can make certain methods less effective than others. The presence of edge-hanging components may also influence the final choice.
Besides design, it’s also important to consider:
Components – The component types are just as critical as the areas designated for them on the board. Sensitive connectors and components play an essential role in appropriate panelization and breakout techniques.
Materials – The type of materials used on the board can also determine which panelization technique is the most suitable. Some materials are susceptible to splintering during breakouts. Thick boards may also cause issues as manufacturers try to ensure the structural integrity of the board.
Shape – The board’s shape can also complicate the choice of panelization. For example, alternating images 90 degrees to 180 degrees can play a significant role in expanding panel space if the board’s shape is complex. While rectangles are preferred, manufacturers can fit uniquely designed PCBs into an array with the help of CAD software.
PCB Panelization Methods
The following are the three main PCB panelization methods:
- V-groove panelization
- Tab routing panelization
- Perforated tabs routing
Here’s a bit more detail on each method.
What is v-groove panelization?
Also known as v-scoring, v-groove panelization involves separating individual boards housing V-shaped grooves. This enables the manufacturer to remove 1/3 of the board’s thickness from the bottom and top. The cutting is typically performed at an angle of 30 or 45 degrees with the help of a machine. Hand-breaking isn’t recommended as manual panelization can place stress on the board and its surrounding components.
In terms of design, the individual performing panelization needs to attain a 0.05 inch clearance from the components to the groove’s center. And suppose the manufacturing process requires the unprinted edges of the board to be completely intact. In that case, the manufacturer may also use “jump-scoring” to prevent the v-score from damaging the array. This means they’ll leave half an inch or more at the end of the panels.
V-groove panelization is most suitable for scoring square and rectangular-shaped boards. However, you can’t use it to cut straight lines through the array.
What is tab routing panelization?
In tab routing panelization, the manufacturer leaves space between the perforated tabs, traces, and surface mounted components. This technique is used for boards of the same or varying designs to avoid the risk of splintering. The panels need to have around 1.8-in clearance away from the other parts to minimize surface stress. Those planning to place perforations should fix it on the sides of the tab rather than through the middle to minimize the size of the protrusions.
When it comes to array arrangements, try keeping the tabs and movements to a minimum. PCB panelization is the most efficient when minimal processing is needed. The right technique allows manufacturers to utilize almost every inch of space present on the board.
However, tab routing isn’t suitable for heavy components, such as large transformers and relays. Tiny laminate nubs might remain during the tab separation process (these need to be sanded if you want to get smooth board edges). Solid tab panelization can be used as an alternative, but it isn’t popular due to the difficulty and cost of cutting thick tabs in the latter stage of the process.
What is perforated tab routing?
This panelization technique involves drilling small perforated holes (mouse bites) in tabs. The manufacturer pre-cuts the boards on the array and holds it in place on the PCB with perforated tabs. Most perforation patterns include three to five holds.
Tab routing panelization isn’t recommended for heavy components, but the small perforated holes make depanelization of small PCBs a whole lot more convenient. It is especially popular for its ability to support edge-hanging component designs.
However, perforated tab routing leaves some material on the edges that the manufacturer can address through sanding. Also, a placeholder or knockout might be required for holes more than 0.6 inches. This is done to avoid problems during the wave-solder stage.
A word on array arrangement: As you arrange the boards, make sure to break all tabs “one at a time” (keeping them collinear) so that consistent break-lines are formed throughout the array. This is done to ensure that individual tabs don’t break or tear the lamination by pulling perpendicularly to the PCB’s surface. Remember, array designs can make or break the success of different components and the overall project – do your best to get it right.
How to do PCB depanelization?
You can use any of the following methods to depanelize a PCB:
- Pizza cutter-shaped blade: This is ideal for converting large panels into smaller ones. It’s commonly used on V-grooves.
- Punching: Single PCBs get punched out by a 2-part fixture. This costs more than using a pizza cutter.
- Hand breaking: The technique is only applicable to strain-resistant circuits.
- Laser: Best for achieving precise tolerances and low stress. However, it requires a higher initial investment.
In conclusion…
PCB panelization used to be an optional step, but now it has become a necessity in PCB manufacturing and PCB assembly. Using the guidelines mentioned above, you can minimize the occurrence of costly delays and redesigns.