Quite a few solutions are applied for depaneling printed circuit boards. They include:
Punching/die cutting. This process requires a different die for PCB Depaneling, which can be not a practical solution for small production runs. The action can 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 both sides to a depth of approximately 30% of the board thickness. After assembly the boards could be manually broken out from the panel. This puts bending strain on the boards that can be damaging to a number of the components, in particular those near to the board edge.
Wheel cutting/pizza cutter. A different method to manually breaking the internet after V-scoring is by using a “pizza cutter” to slice the remaining web. This requires careful alignment involving the V-score and also the cutter wheels. It also induces stresses within the board which may affect some components.
Sawing. Typically machines that are utilized to saw boards from a panel utilize a single rotating saw blade that cuts the panel from either the very best or perhaps the bottom.
Each one of these methods has limitations to straight line operations, thus just for rectangular boards, and all of them to some degree crushes or cuts the board edge. Other methods are definitely more expansive and can include the following:
Water jet. Some say this technology can be achieved; however, the authors have discovered no actual users of this. Cutting is carried out with a high-speed stream of slurry, which is water having an abrasive. We expect it will need careful cleaning right after the fact to remove the abrasive part of the slurry.
Routing ( nibbling). Usually boards are partially routed before assembly. The rest of the attaching points are drilled using a small drill size, making it simpler to get rid of the boards from the panel after assembly, leaving the so-called mouse bites. A disadvantage could be a significant loss of panel area for the routing space, because the kerf width normally takes approximately 1.5 to 3mm (1/16 to 1/8″) plus some additional space for inaccuracies. This implies lots of panel space will likely be needed for the routed traces.
Laser routing. Laser routing supplies a space advantage, as the kerf width is only a few micrometers. For example, the little boards in FIGURE 2 were initially laid out in anticipation the panel will be routed. In this way the panel yielded 124 boards. After designing the layout for laser Laser PCB Depaneling, the quantity of boards per panel increased to 368. So for every 368 boards needed, only one panel needs to be produced rather than three.
Routing could also reduce panel stiffness to the stage that a pallet may be needed for support during the earlier steps within the assembly process. But unlike the previous methods, routing will not be restricted to cutting straight line paths only.
Many of these methods exert some extent of mechanical stress on the board edges, which can lead to delamination or cause space to develop across the glass fibers. This can lead to moisture ingress, which is able to reduce the long-term longevity of the circuitry.
Additionally, when finishing placement of components on the board and after soldering, the ultimate connections in between the boards and panel have to be removed. Often this really is accomplished by breaking these final bridges, causing some mechanical and bending stress on the boards. Again, such bending stress could be damaging to components placed near to areas that should be broken to be able to eliminate the board through the panel. It is actually therefore imperative to accept the production methods into consideration during board layout and then for panelization so that certain parts and traces are not positioned in areas considered to be susceptible to stress when depaneling.
Room can also be necessary to permit the precision (or lack thereof) in which the tool path can be put and to take into account any non-precision in the board pattern.
Laser cutting. The most recently added tool to delaminate flex and rigid boards is a laser. Inside the SMT industry various kinds lasers are being employed. CO2 lasers (~10µm wavelength) provides 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 may be called “hot” lasers because they burn or melt the fabric being cut. (As an aside, they are the laser types, especially the Nd:Yag lasers, typically employed to produce stainless stencils for solder paste printing.)
UV lasers (typical wavelength ~355nm), on the other hand, are used to ablate the fabric. A localized short pulse of high energy enters the top layer of the material being processed and essentially vaporizes and removes this top layer explosively, turning it to dust.
The choice of a 355nm laser is situated on the compromise between performance and expense. To ensure ablation to happen, the laser light needs to be absorbed by the materials to get cut. Inside the circuit board industry they are mainly FR-4, glass fibers and copper. When thinking about the absorption rates for these particular materials, the shorter wavelength lasers are the best ones for the ablation process. However, the laser cost increases very rapidly for models with wavelengths shorter than 355nm.
The laser beam features a tapered shape, as it is focused from a relatively wide beam for an extremely narrow beam then continuous in a reverse taper to widen again. This small area where beam are at its most narrow is referred to as the throat. The ideal ablation happens when the energy density placed on the fabric is maximized, which occurs when the throat from the beam is merely inside the material being cut. By repeatedly exceeding the same cutting track, thin layers in the material is going to be vboqdt till the beam has cut right through.
In thicker material it may be required to adjust the main focus of the beam, as the ablation occurs deeper into the kerf being cut into the material. The ablation process causes some heating from the material but could be optimized to go out of no burned or carbonized residue. Because cutting is carried out gradually, heating is minimized.
The earliest versions of UV laser systems had enough capacity to Pneumatic PCB Depaneling. Present machines acquire more power and may also be used to depanel circuit boards as much as 1.6mm (63 mils) in thickness.
Temperature. The temperature increase 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 towards the same location) depends on the road length, beam speed and whether a pause is added between passes.
An experienced and experienced system operator will be able to select the optimum blend of settings to ensure a clean cut free of burn marks. There is not any straightforward formula to figure out machine settings; they are affected by material type, thickness and condition. Depending on the board and its application, the operator can select fast depaneling by permitting some discoloring or perhaps some carbonization, versus a somewhat slower but completely “clean” cut.