The size of a Printed Circuit Board (PCB)’s panel can impact the outcome of the design. It is all a part of the broader panelization method. In this article, you will find out what the ideal size of a circuit board panel is.
What is PCB Panel?
The panel refers to the platform where the circuit board is fixed for full production. In another perspective, it has to do with panelization – the process of fixing several circuit boards on the same panel.
How Important is PCB Panelization?
The panelization of a circuit board is important for these reasons:
- It helps the circuit board designer to determine the number of panels that are required for the board.
- With panelization, multiple circuit boards can be fixed to form a single array.
- You can also use panelization to determine the amount of waste to be realized per panel.
- PCB panelization could aid in streamlining the production process, especially with the formation of a larger panel and the placement of individual, smaller circuit boards on the top.
Common PCB Panel Sizes
You will find an array of options when measuring the size of a circuit board panel. The common measurements include:
- 18 by 24 inches
- 18 by 12 inches
- 9 by 12 inches and;
- 9 by 24 inches
There is also a need to have a space between the boards on the panel. This is essential for automated routing and allowing for manual removal. The space given often differs by the PCB manufacturer – while some go with the standard 0.5-inch or ½, others would prefer 1-inch.
Nevertheless, the 0.5-inch spacing is prioritized for the double-sided circuit boards. If it is a single-sided circuit board, then using the 1-inch clearance around the panel border is recommended.
The space between the boards and which is positioned near the panel border is not the only one given. You can also use a routing space of 0.1-inches, which would be given between individual circuit boards on the panel and not used for any other purpose.
Balancing the Space Constraints in PCBs
The spaces left in a circuit board might be limited or multiple, depending on the PCB panel size standard used. While the aforementioned are the common sizes, you can also make modifications if the panel is meant to occupy more boards.
Here are some of the important points to note:
1. Take Cognizance of the Size from the Onset
By recognizing the size availabilities at the onset, you can determine if the panel has enough spaces to hold the circuit boards. Look over the horizontal length and width to see if these would provide enough surface area for matching the clearance requirements, the numbers of circuit board components, and the traces and connections.
2. Be Selective with the Board Sizes
You also need to be choosy with the size of the panel. As a rule of thumb, do not use board sizes below 75 mil by 75 mil. This will give enough space to fit the components and make other modifications to the panel.
3. Using the Panel Sizes is Recommended
Your Contract Manufacturer (CM) can also determine what’s best for the device, make the necessary variations and determining the best panel size to use.
However, sticking to any of the standard PCB panel sizes is ideal because it will help you maximize the yield (the number of circuit boards) placed on the panel. The manufacturer can also make additional changes that reflect on reducing the overall costs and producing a few extra boards per panel.
4. PCB Dimensional Adjustment
Looking to get more circuit boards produced per panel? Besides relying on a manufacturer, you can also rotate the boards or make a slight modification to the board’s dimensions.
5. Consider Combining Different Circuit Boards
It is also possible to place several circuit boards of different sizes, but with the same thickness, on a PCB panel.
There is also a possibility of placing a series of PCBs with different arrangements on the same panel.
With any of those two options, you can be sure of getting more circuit boards produced on the same platform, just by reordering the placements and using different PCB panel sizes.
What You Need to Know About a PCB’s “Usable Area”
A usable area in a PCB panel refers to the part or section where most of the panelization processes can be fully-implemented. Hence, any actions taken out of this space might result in a lower yield.
On this ground, the following facts are worth noting:
a. Larger Process Area is Ideal
A large process area or more space is recommended, because it helps you to fit more boards into the panel. Besides, a larger process area is cost-effective, as it drastically reduces the efforts and numbers of boards to be produced with difficulties.
b. Use Tabs on the Panel
There may be a need to use tabs on the circuit board panel. This is the case when the space is limited. With the tabs, you can have Through-Hole (THT) parts passing through.
This is highly-recommended when the client asks the Contract Manufacturer (CM) to deliver a complete panel.
Hence, by using tabs or holes for locating, the easy breakaway for the insertion of THT parts will be realized. This can as well, be extended beyond the usable area of the PCB panel.
Optimizing the Standard PCB Panel Size via Panelization Methods
Several panelization methods can be used to further optimize the numbers of circuit boards that can be fitted onto a panel. Find out more in the next paragraphs.
a. V-Score
The V-scoring method of panelization has to do with the use of V-shaped grooves to differentiate the circuit boards. By using a machine to complete the breakout process, the depanelization process is simpler and reducing the thickness of the board is realized by using an angled blade.
b. Solid Tab
The solid tab panelization method deals with the use of solid tabs to design arrays between the circuit boards. This process also boosts the overall strength of the boards.
A wide range of options can be explored for depanelization. Examples are:
- Depaneling Router: this is not always used because of the dust and vibration it causes.
- Laser-Cutting Machine and;
- Hook-Shaped Blade: although this depanelization method is affordable, it is not efficient.
c. Tab Routing
This is recommended as an option when the V-scoring panelization method doesn’t work. Tab routing a PCB means pre-cutting the board at the array and using perforated tabs to hold it.
Out of those three options, the V-scoring panelization method is recommended for these reasons:
- It reduces surface stress.
- In addition to being affordable, the method is also easy to depanel.
- It increases material utilization.
- The V-scoring panelization method enables an easy removal of the circuit boards from a single panel. As such, spaces can be created for placing more boards, in place of the open space, initially designed for creating a route path.
The Correlation between PCB Panel Size and Board Thickness
The standard PCB panel size can, sometimes, not make do without the thickness. The standardization of the circuit board’s thickness can be dated back to the days of commercialized Integrated Circuits (ICs), but that is a story for another day.
Currently, there is a relationship or synergy between the size and thickness of a PCB. On one hand, using the right thickness and combining it with the ideal PCB panel size aids the realization of a perfect circuit board.
The question then is, “what is the ideal PCB thickness?” While there are ranges to this, the standard PCB thickness is 0.06-inch or 1.57mm. This is recognized as the standard, because it can fit into different applications and meet your needs.
However, this is not ruling out the possibility of “stepping down” to smaller options, especially if your applications require so. In that case, you can explore from any of the following:
- 0.031-inch or 0.78mm: for smaller applications and;
- 0.093-inch or 2.36mm: for larger applications.
The PCB thickness is important for these reasons:
- It plays a crucial role in the upgrade of a circuit board’s core. For example, the 2.36mm or 0.093-inch or thickness can be used to extend a four-layered circuit board stackup, up to 6 layers.
- If you are extending the four-layer stackup to 8 layers, you would need to use the PCB thickness of 3.18mm. In addition, you will add new core/prepreg layers to the original stackup.
Although the thickness is important and can help the PCB designer make an excellent design, it should be used with moderation. Here are some precautions to take:
- The focus should not only be based on the circuit board’s thickness, but also on the standard panel sizes.
- Use a thickness value of 0.063-inches for an average PCB.
- Avoid using a prepreg dielectric layer thickness that is below 3 mil.
Conclusion
Using the ideal PCB standard panel size can save you the headaches of not placing more boards on a panel and optimizing the same for the best performance. As a general rule, the panel size and the PCB thickness should match for optimum performance.
