The most cost-effective method of producing circuit boards is by printing multiple circuit boards onto a panel. These panels must then be separated into the smaller, individual boards the customer ordered. This process is called depaneling. Years ago, this process was painstakingly done by hand, but as circuit boards got thinner and more fragile, these manual methods quickly became impossible and unaffordable. Today, there are a slew of different technologies available to depanel circuit boards, each with their strengths and weaknesses. In this article, we will explore those differences.
There is an inherent problem in depaneling: it’s a violent activity that can damage circuits’ highly sensitive components. Because not all circuit board manufacturers have multiple depaneling methods available at their disposal, circuit board designers need to know which method their manufacturer will use. If a board’s design is incompatible with the manufacturer’s depaneling process, it could create a long series of setbacks. Designers working with flexible or extremely thin boards should be especially concerned.
Bending is simply the mechanized form of a manual break. Usually used for boards connected by small tabs, one end of the circuit board is placed in a slot against a fixed plane and a lever snaps the pieces in two. Obviously because of its rough physical nature, bending should only be used for thick circuits with durable components.
The punching method requires a tabbed circuit board and, because less material needs to be removed, it is one of the quickest depaneling methods. A typical tabbed board will have anywhere from three to five tabs depending on the weight of the components. The board will then be placed on a flat surface, and a punch die will then be lowered to completely remove the tabs. But be warned, punching puts significant stress on the circuit because the force is concentrated on a small surface area.
“Pizza Cutting” involves two spinning saw blades that meet at a fixed point or one blade that meets with a fixed ridge. Typically, the board itself will have “v-scored” schannels which are pre-routed, where the blades will eventually make the full through-cut. This limits the amount of material that the blades have to cut through. This method produces less stress on the circuit board because it’s not cutting through the full thickness of the board. However, V-cutting cannot be done on boards with overhanging components. Furthermore, all components must be at least a quarter inch from the edge of the circuit, making the board bigger than needed.
Mechanical routing is a common PCB depaneling method. Essentially, a router is a small, quickly spinning tool that plunges through and cuts the board’s outline. Mechanical stress to the board’s components and solder joints, caused by the vibration of the routing tool can still negatively affect yields. However, routing creates vast amounts of residual dust from the grinding. While a built in vacuum will quickly remove the dust, but some particles may still be left behind and interfere with the circuit’s operation.
Lasers are the latest technology to hit the depaneling industry and come in two varieties: CO2 and UV. Laser depaneling eliminates the issue of physical stress on the boards because there is no contact during the process. For this reason, lasers are perfect for flexible and highly sensitive circuit boards. Designers can also create endlessly intricate cuts by utilizing laser technology. The size of the cut itself can usually be changed as well, depending on the job.
Lasers, however, have downfalls of their own. First, they take longer to cut than the mechanical options. This means that lasers may not be the best option for mass produced boards with simple cuts. Second, while there is no mechanical stress being placed on the board, CO2 lasers exert thermal stress. This is because CO2 lasers use heat to burn away the board material. However, this heat will also burn the edges of the board at a variable rate, making a few millimeters around the edge of the board useless.
UV lasers, on the other hand, use “cold” cutting technology. In reality, they utilize high powered UV light to cut the boards, which creates relatively insignificant thermal stress. Cuts with a UV laser will be consistent and cause virtually no damage to the end of the board.
Know Which Depaneling Method is Best for Your Circuit Design
As you can see, a number of methods have been developed over the years. While they all essentially do the same job, each method has its own flaws and benefits. Mechanical methods create various degrees of stress that may damage the boards while laser options exert no mechanical stress but are slower.
Laser technology is quickly developing and UV lasers will most likely be the preferred depaneling method of the future. For now, the most important thing to remember is that you ensure your manufacturer utilizes a depaneling method that is compatible with your circuit’s design.