I have a friend who loves to help people when they are moving. He makes it his personal goal in life to carry as many items at once in order to get the job done more quickly. While his desire to help is commendable, I do worry about the box of glass decorations balancing precariously on top of all of the other boxes in his arms. Even though he takes some chances, my friend is on the right track. By consolidating work into one load, he can get a lot more done in less time.
When printed circuit boards are manufactured, the same principle applies. To increase the productivity of the manufacturing process, multiple instances of a smaller board will be placed into a manufacturing panel. This is a much more efficient way to fabricate and assemble these boards instead of building them one at a time. Let’s take a closer look at some helpful layout tips for PCB panelization to see how we can increase the productivity of PCB manufacturing.
Layout Tips for PCB Panelization that are Essential for Success
To go through the different fabrication and assembly processes, a printed circuit board will be manufactured in a panel. This panel will be composed of the same materials and layer stackup configuration as the board, and the size of the panel will be chosen to best fit the needs of the board and the different processes used during manufacturing. Panel sizes can vary from small to large, with 18 X 24 inches being one of the more common sizes. Panels are typically designed with the boards being spaced 0.100 inches apart, with a clearance perimeter around the boards of half an inch or more.
The circuit board designs are arranged within the panel to utilize the most usable panel space as possible. Typically the more boards that can be fit into a panel, the more the manufacturing efficiency will be increased while decreasing the amount of unused panel material. To maximize the panel space, panel designers will look at all the arrangement options when placing the PCB designs within the panel, including rotating the designs if possible. The PCB designer can help with this process by altering and optimizing the design to make the most efficient use of the panel space. By cutting back on the size of the board or slightly changing its shape, can potentially help create a more efficient panel design.
Another important detail in PCB design are the board edge clearances needed to protect copper and components from being damaged when a board is removed from a panel. PCBs are extracted by either cutting pre-scored marks along the edges of the board called V-grooves, or by breaking out tabs that hold the board in place where it has been milled out around its edge. For V-grooves the components should be a minimum of 0.050 inches back from the edge, while copper should have a 0.020 inches clearance. For breakout tabs, both the components and the copper should have a minimum of 0.125 inches from a tab in case the broken tab splinters.
Two different boards are rotated and arranged on this panel for the most efficient layout
Making the Panelization Process Even Better
The usual method of panelizing a board is to replicate copies of the PCB design to fill up all of the panel spacel. There is another option though that can improve the efficiency of the panel even more. By putting instances of different boards into one panel, you may be able to salvage unused panel space. Consider a large “L” shaped board and a small rectangular board. Both of these boards could be combined in one panel as long as their materials and layer stackup configurations matched. In some cases, simple boards will be purposely designed with multiple layers that it doesn’t need in order to be panelized along with larger more complicated boards.
Here are some other panelization details that PCB designers should consider:
Overhanging Components: Components like connectors that overhang the board will require extra clearance room around the board outline in the panel. This could impact the design of the panel, and you should consult with your manufacturer to explore all the options first.
Tooling Holes and Fiducial Marks: Your manufacturer will be including these features in the panel, and you will want to make sure that your placement doesn’t cause any problems.
Component Weight: Large concentrations of components can cause the panel to bend, which would necessitate additional support. By first consulting with your manufacturer, you can find out if there are any PCB layout options that can help.
PCB Width: In the same way, thin circuit boards could also cause a panel to bend. This can lead to problems such as solder coming over the top of some of the boards as the panel bends going through the wave. This may result in your manufacturer having to brace the board or use a pallet, which could have an impact on how you place your components.
The key to all of this is for you to work early with your manufacturers to make sure that there won’t be any surprises when they create the panel from your PCB design. By consulting with them early, you can avoid annoying and costly redesigns to fix these manufacturing problems, as well as getting the most efficient panel design possible.
With advanced PCB design tools, you can easily see how your layout will affect the panel
Put Your PCB Design Tools to Work
To help you to design boards that can be panelized efficiently, make sure to use the full capabilities of your PCB design tools. Set up your design rules to give you the appropriate amount of board edge to component and copper clearances for the panels that you will be working with.
Also, be sure to get your manufacturer’s recommendations on PCB materials and layer stackup configuration, and your design tools can help you with this as well. Many PCB design tools today have the ability to import and export design data through open standard formats like IPC 2581. With this format, your manufacturer can send you the design data that you need, and you can send back the entire set of fabrication and assembly data all in one simple file format.
One of the most advanced PCB design tools available for doing work like this is from the Cadence line of high performance EDA tools. OrCAD PCB Designer has a full and comprehensive set of rules and constraints that you can configure for specific design and manufacturing conditions, as well as the bi-directional IPC 2581 interface. With these capabilities, plus many more, you will be able to design printed circuit boards that are optimized for panelization in order to be manufactured efficiently and as error free as possible.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.
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