Design Engineers: Control Costs and Speed Up Production with Panelization

The design layout has been prepared and the components and placement determined. What’s the next step on the way to seeing the final production of your design? Your contract manufacturer is the partner that will move the process along.

What you know about the manufacturing process will improve manufacturability, which can, in turn, help control costs.

Automation in the manufacturing process increases accuracy and quality as well as speed. It’s also one of the chief ways to help keep costs in line. It makes sense that, depending on the design parameters, your contract manufacturer will want to automate the process as much as possible.

In most cases it will be more efficient to panelize boards than to process them individually. The smaller the board size, generally the greater the benefit of panelization. The exact format of panelization in turn, is determined by board requirements, component placement, and board shape, all of which influence the depanelization method that’s best suited to your board.

Let’s take a closer look at some of these options.

Panelization means joining boards together to form a single, larger array. This larger panel travels through the automated assembly process, improving material efficiency and lowering the cost of production. Each panel is made up of several repeats of the same board design. Most often–and preferably–the contract manufacturer will be the one choosing the method of panelization and depanelization based on your performance requirements.

Several factors affect panelization:

• Design characteristics. In particular, how close to the edge do components need to be placed?
• Component characteristics. What specific components will be placed, and what requirements must be met for optimal performance?
• Component density and weight. Heavy components and densely populated board layouts restrict panelization methods, potentially requiring boards to be processed individually rather than in panels.
• Board materials and board thickness. Some substrate materials may be prone to splintering; very thin or very thick boards create depanelization challenges.
• Optimal depanelization process. The method of depanelization (the process of cutting or breaking apart the array into individual finished board assemblies) will influence the panelization process.

Various depanelization techniques are available; each method affects the format of panelization and the structure of the finished board.

Consider the pros and cons of some popular methods of depanelization:

Board Depanelizer aka Pizza Cutter

This depanelization method works best for straight-edge boards. In this application, boards are set into arrays with edges butted together, and a v-score groove is cut between them. The pizza cutter separates the boards along the groove, providing a straight edge cut. This method offers the benefit of being fast and straightforward. It is a comparatively low-cost method for separating boards and typically requires manual operation.

On the downside, there is a risk of the board and components flexing during the separation process, especially any components placed close to the edge. Solder joints may also be stressed. If the board design includes components that hang over the edge, separation using the pizza cutter may not be appropriate. For these and other applications, mouse bites may be a better alternative.

Also, it’s worth noting that the pizza cutter does not produce as clean an edge cut as a router. Often it leaves splinters of fibers or fiberglass resin strands at the edge.

Perforated Tabs aka Mouse Bites

Contrary to the name, no mice are involved in the process. Instead, small perforated tabs connect boards into panels so that later on the completed boards can be broken apart along the perforation. These small tabs allow irregularly shaped boards to be joined into an array for more efficient population. In addition, the flexibility of tab size and placement means that elements overhanging the edge no longer interfere with adjacent boards.

During the process of breaking the boards apart, once again, there is the potential for unwanted stress to the board or its components. Depending on the board and its application, some additional edge smoothing may be required.

CNC Router

An alternative to the pizza cutter and mouse bites is to use a CNC router to depanelize boards. A laser cutter offers similar advantages for producing clean, precise separations and the ability to work with complex shapes. Generally, manufacturers may have either a router or a laser cutter, but not both. Both methods produce a clean cut with little risk of disturbance to the structure or population of the board. The CNC router can be programmed to cut the tabs on the board, and it also does tooling pin placement, so the board stays in place while being cut.

Depanelization using a router produces minimal stress on the boards and precision control, but the equipment cost is substantially higher than that of some other solutions.

Additional factors affect the choice of the depanelization method:

Board thickness. A V-cut won’t work on a very thin board. If the groove penetrates too deeply into the board, the handling benefits of stability are lost, so other panelization methods need to be explored. Likewise, a board that has too many layers will be too thick for the V-cut to be effective.

Sensitivity to bending. Certain boards and components are highly sensitive to stress and will not tolerate bending. These will require special handling and separation using a router.

Component placement. Components need to stay clear of the edge as much as possible so that there is sufficient clearance to allow for smooth separation of the final boards. For every project, the depanelization process must be anticipated so that components don’t interfere with or overhang connecting tabs and so that adequate space is allowed for any components that must be placed near the edge, so that components on nearby boards aren’t burned by selective solder.

Regardless of the panelization option, one of the most important points for design engineers to remember is that to be compatible with automated systems, panels need to have clear rails (borders) around the edges, 600 mils or so, to allow the array to go through the automated systems.

Customer Involvement

As a customer, you may have requirements that necessitate providing your contract manufacturer with boards and/or components. But if you provide your manufacturing partner with those elements to secure cost savings, you might find that that’s not the result you get.

Your best option for efficiency in manufacturing and price is to have the contract manufacturer procure both boards and components and allow them to determine the panelization technique and arrangement that will best suit your project requirements.

Why should you let your contract manufacturer provide the parts and panelization?

Customer-provided boards may not have sufficient clearance at the edges to provide the necessary border to create workable arrays compatible with automated processes. In other cases, depending on the size and shape of the provided boards, custom carriers may need to be developed to allow the boards to go through the pick and place operation, and these carriers may or may not be able to withstand going through the reflow ovens.

When your manufacturing partner makes the selection, they have the freedom to create more efficient arrays that can avoid the need for carriers and ultimately result in cost savings.

We’ve touched on some of the more popular methods for panelization and depanelization, but the specific techniques available may vary from one manufacturer to another, and each will have its own processes and preferred equipment. As you work with new contract manufacturers, it’s worth the time to get to know their overall methods and seek their input as to how to create the optimal design.

Involve your manufacturing partner early in the design process; don’t try to design and source in a vacuum.

The greatest benefits of DFM come to those who bring the contract manufacturer into the process at the beginning because fewer redesigns will be needed. As your designs begin to take shape, let’s get the conversation started early.