Several approaches are practiced for depaneling printed circuit boards. They consist of:
Punching/die cutting. This method demands a different die for PCB Depaneling, which is not just a practical solution for small production runs. The action could be either a shearing or crushing method, but either can leave the board edges somewhat deformed. To lower damage care must be come to maintain sharp die edges.
V-scoring. Often the panel is scored on sides to a depth of around 30% in the board thickness. After assembly the boards could be manually broken out of the panel. This puts bending strain on the boards which can be damaging to a few of the components, especially those near the board edge.
Wheel cutting/pizza cutter. Another approach to manually breaking the net after V-scoring is to use a “pizza cutter” to slice the remaining web. This requires careful alignment in between the V-score and the cutter wheels. It also induces stresses in the board which can affect some components.
Sawing. Typically machines that are used to saw boards out of a panel use a single rotating saw blade that cuts the panel from either the top or even the bottom.
All these methods is limited to straight line operations, thus simply for rectangular boards, and each one to some degree crushes and cuts the board edge. Other methods are definitely more expansive and include the following:
Water jet. Some say this technology can be carried out; however, the authors have discovered no actual users of this. Cutting is conducted having a high-speed stream of slurry, which can be water with an abrasive. We expect it will require careful cleaning right after the fact to remove the abrasive portion of the slurry.
Routing ( nibbling). Most of the time boards are partially routed prior to assembly. The rest of the attaching points are drilled with a small drill size, making it easier to get rid of the boards from the panel after assembly, leaving the so-called mouse bites. A disadvantage could be a significant loss in panel area towards the routing space, since the kerf width normally takes approximately 1.5 to 3mm (1/16 to 1/8″) plus some additional space for inaccuracies. This implies a significant amount of panel space will be required for the routed traces.
Laser routing. Laser routing supplies a space advantage, as the kerf width is simply a few micrometers. As an example, the tiny boards in FIGURE 2 were initially presented in anticipation the panel would be routed. In this way the panel yielded 124 boards. After designing the design for laser Laser PCB Cutting Machine, the number of boards per panel increased to 368. So for each 368 boards needed, only one panel needs to be produced as opposed to three.
Routing can also reduce panel stiffness to the point which a pallet may be needed for support throughout the earlier steps within the assembly process. But unlike the earlier methods, routing is not limited to cutting straight line paths only.
The majority of these methods exert some extent of mechanical stress on the board edges, which can lead to delamination or cause space to build up across the glass fibers. This can lead to moisture ingress, which in turn is effective in reducing the long-term reliability of the circuitry.
Additionally, when finishing placement of components on the board and after soldering, the last connections between the boards and panel have to be removed. Often this can be accomplished by breaking these final bridges, causing some mechanical and bending stress on the boards. Again, such bending stress can be damaging to components placed near areas that ought to be broken to be able to remove the board through the panel. It is actually therefore imperative to accept the production methods into account during board layout and then for panelization in order that certain parts and traces usually are not put into areas considered to be susceptible to stress when depaneling.
Room is additionally needed to permit the precision (or lack thereof) that the tool path can be put and to take into consideration any non-precision in the board pattern.
Laser cutting. The most recently added tool to delaminate flex and rigid boards is actually a laser. Within the SMT industry various kinds lasers are being employed. CO2 lasers (~10µm wavelength) provides very high power levels and cut through thick steel sheets and also through circuit boards. Neodymium:Yag lasers and fiber lasers (~1µm wavelength) typically provide lower power levels at smaller beam sizes. These two laser types produce infrared light and could be called “hot” lasers because they burn or melt the fabric being cut. (As being an aside, they are the laser types, specially the Nd:Yag lasers, typically employed to produce stainless stencils for solder paste printing.)
UV lasers (typical wavelength ~355nm), on the contrary, are employed to ablate the fabric. A localized short pulse of high energy enters the best layer from the material being processed and essentially vaporizes and removes this top layer explosively, turning it to dust.
The choice of a 355nm laser is based on the compromise between performance and cost. In order for ablation to take place, the laser light needs to be absorbed from the materials to become cut. Inside the circuit board industry they are mainly FR-4, glass fibers and copper. When looking at the absorption rates for these materials, the shorter wavelength lasers are the most appropriate ones for your ablation process. However, the laser cost increases very rapidly for models with wavelengths shorter than 355nm.
The laser beam includes a tapered shape, because it is focused coming from a relatively wide beam with an extremely narrow beam and after that continuous in a reverse taper to widen again. This small area where the beam reaches its most narrow is known as the throat. The optimal ablation occurs when the energy density placed on the content is maximized, which occurs when the throat of the beam is simply inside the material being cut. By repeatedly exceeding the identical cutting track, thin layers of the material will be vboqdt till the beam has cut all the way through.
In thicker material it could be necessary to adjust the main focus from the beam, because the ablation occurs deeper to the kerf being cut to the material. The ablation process causes some heating in the material but can be optimized to go out of no burned or carbonized residue. Because cutting is done gradually, heating is minimized.
The earliest versions of UV laser systems had enough capacity to Pneumatic PCB Depaneling. Present machines get more power and may also be used to depanel circuit boards up to 1.6mm (63 mils) in thickness.
Temperature. The temperature surge in the material being cut depends on the beam power, beam speed, focus, laser pulse rate and repetition rate. The repetition rate (how quickly the beam returns to the same location) is dependent upon the way length, beam speed and whether a pause is added between passes.
A knowledgeable and experienced system operator can choose the optimum combination of settings to make certain a clean cut free of burn marks. There is absolutely no straightforward formula to figure out machine settings; these are relying on material type, thickness and condition. Depending on the board along with its application, the operator can select fast depaneling by permitting some discoloring or even some carbonization, versus a somewhat slower but completely “clean” cut.