When cooking for a group of people on a camping trip, I like to throw some chicken in a pan along with some lemon marinade, cover it with foil, and then slow cook it over a low flame. For the best results, the marinade needs to evenly cover the chicken, which requires that each piece be carefully arranged, making the best use of the space. So what do roasted chicken and PCB panels have in common? Printed circuit boards also need to be organized expediently on a panel to make the best use of space, but admittedly I’m thinking more about the chicken now.
If we can all just ignore our growling stomachs for a few minutes, there are some important points about PCB panels that you should be aware of when you’re laying out a board. While we may think in terms of an individual printed circuit board when designing them, the reality is that circuit boards are often laid out in a panel to help lower production costs. Let’s take a look at what a PCB panel is, and then the eight PCB panelization guidelines that you should know for circuit board design.
The Basics of a PCB Panel
A PCB panel, or array, is a large sheet of circuit board material that holds multiple instances of individual circuit boards. By panelizing multiple PCBs at once, the fabricator and assembler can reduce overall manufacturing costs to the customer. Another benefit is that the size of the panel is better suited to the manufacturing operations, and will help in the reduction of fabrication and assembly defects. When you consider just how small some PCBs are, it makes more sense to panelize them instead of trying to handle each tiny individual board.
The panelization process starts in fabrication where the images for the individual boards are replicated to fit a standard panel size. Once the panels are fabricated, they will then be sent to the assembler where parts will be installed and soldered. When the manufacturing of the panels is complete, the circuit boards are depanelized, which means they are broken out into individual PCB assemblies. Panels are a normal part of the circuit board manufacturing process, but there are some details that designers should be aware of that will help with the panelization of their PCB designs.
The Top Eight PCB Panelization Guidelines You Should Know
Here are some guidelines that will help PCB designers to layout their boards in a way that will be more conducive to them being panelized for manufacturing:
- Panel size: There are different sizes of panels that are used by manufacturers, with some that are more common than others. The size of your circuit board will have a big influence on what panel size is ultimately chosen due to how it will be laid out in the panel. It is a good idea to work ahead with your PCB contract manufacturer in case the board size can be altered to fit more instances into the panel.
- Layer stackup: One advantage of a panel is that multiple circuit boards can be laid out in it, but the layer stackup has to be uniform for all boards. If you are planning on panelizing multiple boards, make sure that they have identical layer stackups.
- Panel structure: The instances of boards will need specific clearances to each other and to the edge of the panel, and will usually include alignment holes and other features. Once again, working ahead with your CM will help you in the end to have a finished board size that can be easily panelized.
- Panel layout: The boards are typically placed to maximize the usable space in the panel, however, this is all contingent on the direction the board will take through the soldering process. In some cases, the boards have to be arranged for the best solderability. Here is where working ahead with the CM to determine the board’s direction through soldering can enhance its ability to be efficiently panelized.
- Breakouts: In order to depanelize the finished boards, the board edges will be configured either with a V-groove or breakout tabs. The designer needs to know which will be used to place the components correctly. There needs to be a minimum of 0.075 inches between the edges of the board and components when a V-groove is being used, while a breakout tab needs 0.125 inches. These clearances are necessary to protect solder joints from fracturing during depanelization.
- Component clearances: The breakouts aren’t the only component clearance concerns that designers need to be aware of. Components that overhang the edge of the board also need additional clearance depending on the needs of the manufacturing processes. Larger components will also need additional clearances to the edge of the board than the minimums already specified for V-grooves and breakout tabs.
- Panel tooling: The panels will need their own tooling holes and fiducial marks that should match what is on the board. Here again, is where coordinating with the CM can prove very helpful.
- Physical support: Due to their thickness and overall size, some PCBs may need additional support to prevent sagging during manufacturing. This is done by adding a brace to the panel, which could be affected depending on the layout of the board.
Working together with your PCB contract manufacturer on these guidelines can help you in avoiding problems when the board is panelized for manufacturing.
Should PCB Designers Layout Their Own Panels?
While PCB designers can do their own panels, it is generally advisable for the contract manufacturer to do this work. Ordinarily, the PCB CM is already working with the fabricator on the build and designing the panel based on the size, shape, assembly criteria, and expected volume of production. The CM also has a lot of experience in panelizing boards and understands the different requirements needed such as location, the spacing of breakouts, and other panel features.
At VSE our engineering team not only has the technical expertise in creating a panel that will work best for your circuit board design but also understands what works best for your production needs. We’ll optimize the panel so you get the highest quality of circuit board manufacturing and the greatest return on your investment.
