Many approaches are applied for depaneling printed circuit boards. They include:
Punching/die cutting. This process needs a different die for PCB Depaneling, which is not 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 minimize damage care has to be come to maintain sharp die edges.
V-scoring. Often the panel is scored on both sides to your depth of around 30% of the board thickness. After assembly the boards could be manually broken from the panel. This puts bending strain on the boards that may be damaging to some of the components, especially those near the board edge.
Wheel cutting/pizza cutter. An alternate method to manually breaking the internet after V-scoring is by using a “pizza cutter” to cut the remaining web. This calls for careful alignment between the V-score and also the cutter wheels. Additionally, it induces stresses in the board which may affect some components.
Sawing. Typically machines that are employed to saw boards away from a panel use a single rotating saw blade that cuts the panel from either the best or the bottom.
Each one of these methods is restricted to straight line operations, thus simply for rectangular boards, and each of them for some degree crushes or cuts the board edge. Other methods are more expansive and can include the subsequent:
Water jet. Some say this technology can be achieved; however, the authors have discovered no actual users of this. Cutting is carried out having a high-speed stream of slurry, which can be water with the abrasive. We expect it should take careful cleaning following the fact to eliminate the abrasive portion of the slurry.
Routing ( nibbling). Most of the time boards are partially routed prior to assembly. The other attaching points are drilled having a small drill size, making it easier to interrupt the boards out of the panel after assembly, leaving the so-called mouse bites. A disadvantage can be a significant loss of panel area to the routing space, because the kerf width often takes approximately 1.5 to 3mm (1/16 to 1/8″) plus some additional space for inaccuracies. This means a significant amount of panel space will be required for the routed traces.
Laser routing. Laser routing provides a space advantage, since the kerf width is just a few micrometers. For instance, the little boards in FIGURE 2 were initially laid out in anticipation that the panel could be routed. In this manner the panel yielded 124 boards. After designing the design for laser Laser PCB Cutting Machine, the quantity of boards per panel increased to 368. So for each 368 boards needed, just one single panel has to be produced instead of three.
Routing can also reduce panel stiffness to the point that a pallet may be needed for support during the earlier steps in the assembly process. But unlike the earlier methods, routing is not restricted to cutting straight line paths only.
Many of these methods exert some degree of mechanical stress on the board edges, which can lead to delamination or cause space to produce around the glass fibers. This may lead to moisture ingress, which can reduce the long-term longevity of the circuitry.
Additionally, when finishing placement of components on the board and after soldering, the last connections in 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 may be damaging to components placed close to areas that ought to be broken so that you can take away the board from your panel. It is actually therefore imperative to take the production methods into consideration during board layout and for panelization so that certain parts and traces are not placed in areas considered to be subjected to stress when depaneling.
Room can also be necessary to permit the precision (or lack thereof) that the tool path can be put and to take into account any non-precision in the board pattern.
Laser cutting. By far the most recently added tool to delaminate flex and rigid boards is really a laser. Within the SMT industry several kinds of lasers are employed. CO2 lasers (~10µm wavelength) can provide very high power levels and cut through thick steel sheets and in addition through circuit boards. Neodymium:Yag lasers and fiber lasers (~1µm wavelength) typically provide lower power levels at smaller beam sizes. Both these laser types produce infrared light and can be called “hot” lasers because they burn or melt the fabric being cut. (Being an aside, these are the basic laser types, specially the Nd:Yag lasers, typically used to produce stainless-steel 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 in the material being processed and essentially vaporizes and removes this top layer explosively, turning it to dust.
The option of a 355nm laser relies on the compromise between performance and expense. To ensure ablation to occur, the laser light has to be absorbed by the materials to be cut. In the circuit board industry these are generally mainly FR-4, glass fibers and copper. When thinking about the absorption rates for these particular 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, as it is focused from the relatively wide beam to an extremely narrow beam and then continuous in a reverse taper to widen again. This small area where the beam reaches its most narrow is referred to as the throat. The perfect ablation takes place when the energy density put on the content is maximized, which takes place when the throat from the beam is just within the material being cut. By repeatedly groing through the identical cutting track, thin layers in the material will be vboqdt till the beam has cut right through.
In thicker material it might be necessary to adjust the focus from the beam, since the ablation occurs deeper to the kerf being cut into the material. The ablation process causes some heating of the material but could be optimized to leave no burned or carbonized residue. Because cutting is done gradually, heating is minimized.
The earliest versions of UV laser systems had enough capacity to Motorized PCB Depaneling. Present machines get more power and may also be used to depanel circuit boards approximately 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 fast the beam returns towards the same location) is determined by the path length, beam speed and whether a pause is added between passes.
An educated and experienced system operator can choose the optimum combination of settings to ensure a clean cut free from burn marks. There is not any straightforward formula to find out machine settings; they are relying on material type, thickness and condition. Depending on the board as well as its application, the operator can choose fast depaneling by permitting some discoloring or perhaps some carbonization, versus a somewhat slower but completely “clean” cut.