If you’ve ever lived in a high-rise building, then you can probably still hear a parent or some concerned citizen warning you not to get too close to the edge of the roof. Whether or not they explicitly expressed the potential danger, you knew by their warnings that doing so could end tragically. The fact that you are reading this means that you heeded their warnings. Believe it or not, there is a similar admonition when designing PCBs.
The most important aspect of PCB design is probably the board layout, which defines where the components will be mounted, traces run and holes drilled. These specifications and spacing determine whether your layout can be fabricated. Another important layout specification, board edge clearance, determines your PCB panelization for fabrication and assembly. Just like being on the roof, having elements too close to the edge is bad and can even be fatal for the manufacture of your boards, at least until the layout is redesigned. On the other hand, considering board edge clearances and panelization during design can aid your board’s manufacture and may even lower cost. First, let’s define PCB panelization and then consider whether to include it as a part of the board design stage.
What is PCB Panelization?
PCB panel for assembly
When you receive your boards from a fabrication house or fully assembled, they are usually individual units. However, they are actually processed through the PCB manufacturing steps as part of a larger sheet or panel. For example, the figure above illustrates a fabricated panel ready to have the components attached. Obviously, PCB panelization is more efficient than single board processing yet it comes with a cost. Typically, when the boards are separated into single units after assembly, depanelization, there is wasted material left over. The cost significance of the waste is proportional to the number of PCBs manufactured and also determined by your depanelization method as well as the shape of your boards.
PCB Depanelization Methods
There are two methods for depanelizing PCBs: scoring and routing. These methods may be implemented individually or jointly by your CM depending upon board shape and component weights, locations, orientations and soldering techniques used.
Routing – this most flexible method is used for odd-shaped boards and consists of using a router bit to create three or five-hole breakaway tabs.
Scoring – consists of cutting a straight-line V-shaped groove into the board ⅓ of the thickness from the top and bottom, as shown in the figure below.
PCB panel with V-scoring cut
When choosing a PCB depanelization method, the main objective should be to determine how to maximize the number of boards that can be simultaneously processed while minimizing the amount of wasted material, and therefore, cost. This may involve a single design or multiple designs.
More often than not, your boards are fabricated and assembled at separate facilities. It is important to know whether your CM outsources assembly or fabrication and packaging panels to facilitate assembly. One concern is the need to keep copper levels even to reduce stress, which may be done by adding copper dots to the panel. Stress is also a major factor when separating boards into individual units. If excessive stress is placed on the PCB, there is potential for breakage. Another issue is whether there are components overhanging the board edge, which prevent the use of machine depanelization.
Should PCB Panelization be a Design Step?
As shown above, PCB panelization is important to the manufacturing stage of PCB development and is of considerable concern for your CM. It is not atypical for your CM to use your design’s CAD file to make multiple panel layouts before settling on the best version for manufacturing. This process may yield suggested changes to your PCB layout, which can extend board turnaround time and increase development costs due to redesign. PCB panelization is not an optional activity; it is required. However, the choice of whether to incorporate this activity into your initial design rests with you. To help you decide, let’s look at a comparison between panelization attributes when each is performed as an isolated task by the designer or CM.
PCB PANELIZATION DESIGN COMPARISON
|Attributes||Engineer Designs Panelization||CM Designs Panelization|
|Based on a greater PCB layout intent understanding||Yes||No|
|Based on a greater depanelization requirement understanding||No||Yes|
|May require PCB layout redesign||Yes||Yes|
|May increase turnaround time||Yes||Yes|
|May increase development costs||Yes||Yes|
As the table above demonstrates, when the panel layout design is performed by the designer or CM in isolation, panelization is guided by different concerns. These varying perspectives may lead to similar results, including increased turnaround time due to redesign requirements or additional costs due to excessive waste material.
Although often excluded from the design file package, PCB panelization is an essential part of your board fabrication and PCB assembly. It presents an opportunity for you to assist your CM in providing you with the most efficient manufacturing of your boards. However, this does require you to use a design tool like Altium Designer with panelization design capability and consult with your CM to ensure that your design decisions are tailored to your CM’s capabilities and equipment.
|Tempo‘s Custom PCB Manufacturing Service|
Tempo Automation is the industry leader in fast, precise and high-quality PCB manufacturing for prototyping and low-volume production. We include panelization as a standard part of our service; however, we will partner with you and provide whatever support you need to include panelization as part of your design.
And to help you get started, we furnish information for your DFM and enable you to easily view and download DRC files. If you’re an Altium user, you can simply add these files to your PCB design software.
If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on PCB panelization or guidance on creating panels during design, contact us.