Components and printed circuit boards are becoming smaller and more sensitive. When unassembled or assembled separate boards are de-paneled from a multi-image board, it is very important to reduce the forces acting on the board to a minimum. The criteria for precision and cleanliness are also becoming more and more stringent at the same time. Laser systems cut any shape of contour without exerting any mechanical stress – and do so much more precisely than conventional tools such as saws, routers or punches. The laser cuts virtually any shape with minimal spaces between the single PCBs. Densely populated boards and closely arranged panels provide for an increased net usable surface. In the case of flexible and very thin substrates in particular, lasers open up new options for the production of sensitive printed circuit boards. Contract manufacturer’s De-paneling methods impact on OEMs PCB assembly costs and quality, especially if company is trying to create smaller products. PCBs smaller than about six inches are typically fabricated in arrays, after PCB were done assembly process the individual boards are separated or “de-paneled.” The methods manufacturer uses for this seemingly simple step will affect costs and quality. By understanding the different methods available and talking with the contract manufacturer before finalizing a design, buyers and board designers can avoid expensive problems later. De-paneling methods can impact a variety of factors, including:
- Material cost By fitting as many boards as possible into a standard panel, you can reduce waste and minimize material costs.
- Labor cost and throughput Cutters and punches are manual operations, but faster than laser cutting. If you require edge sanding, that adds cost and time.
- Tooling costs Punches may require custom tooling to fit the board design. Laser cutting systems are programmable with low setup time. Cutters may or may not require tooling.
- Tolerances If your tolerances on board dimensions are tight, or you need to place components very close to the edge of the board, you should look for a manufacturer with laser cutting capabilities.
Board designers can create both the layout and the array drawing to meet the constraints of the process to be used. It is especially critical to keep surface mount (SMT) components a safe distance from the edge of the board to avoid damage from the De-paneling tool. If engineers don’t know what tool will be used, they need to error the side of safety – perhaps making the board bigger than it needs to be. For rectangular boards, PCB panels are usually fabricated with a v-score between boards. After components are placed and soldered, we use specialized tools to separate the boards along the score with minimal bending stress. A guillotine type cutter is suitable for thin boards, and a wheel cutter is used for thicker boards. For boards with curves and other shapes, the bare board panels will usually come pre-routed with tabs or drilled perforations to hold the panel together during assembly. We separate the pre-routed boards at the tabs using a hook tool or a punch. The tool or punch will leave a rough edge, called “mouse bites,” at the tab locations. If the board has a tight fit or needs to have smooth edges when installed in your product, these may need to be sanded off – an extra step and expense. Some manufacturers use a mechanical router to de-panel curves and other shapes. The router creates less bending stress, but more vibration stress. It also produces a lot of dust, so you should verify that your manufacturer has systems in place to control the dust and keep it off your boards. All of these methods reduce but do not eliminate bending stresses on the board during De-paneling. Ceramic capacitors are particularly susceptible to cracking from bending stress, as are end caps on resistors. Observing the safe distance from the edge of the board helps prevent this damage.
As with many applications, there is a tradeoff between throughput and quality. For high throughput, continuous rapid scanning cuts through the material are performed in few seconds, but with slightly higher carbonization.
On the other hand for excellent quality cuts the process speed is reduced by introducing cooling delays between scans, yielding a reduced output but lower carbonization.
De-paneling doesn’t stand out in the crowd compared to PCB design, circuit etching, and component placement. But De-paneling is really an overlooked potential superhero in the PCB manufacturing process. Does it right, and you can meet or even increase production yield goals and rule the plant floor. Do it wrong, or do it with the wrong tools or process, and you could end up being the villain with damaged components, too much waste, and not enough production yield.
Commercial Methods V/S Laser Cutting
PCB De-paneling laser machines and systems have been gaining popularity over recent years. Mechanical de-paneling is done with routing, die cutting, and dicing saw methods. However, as the boards get smaller, thinner, flexible, and more sophisticated, those methods produce even more exaggerated mechanical stress to the parts. Large boards with heavy substrates absorb these stresses better, while these methods used on ever-shrinking and complex boards can result in breakage. This brings lower throughput, along with the added costs of tooling and waste removal associated with mechanical methods. Increasingly, flexible circuits are found in the PCB industry, and they also present challenges to the old methods. Delicate systems reside on these boards and non-laser methods struggle to cut them without damaging the sensitive circuitry. A non-contact De-paneling method is required and lasers provide a highly precise way of job without any risk of harming them, regardless of substrate.
Super powers of UV Laser De-paneling
- No mechanical stress – No tool or saw ever touches the PCB panel, so sensitive components are protected.
- No thermal stress – UV lasers produce cold ablation unlike other laser wavelengths, which can cause charring and carbonization of the substrate.
- Cleanliness – No dust. No contaminants. No damage to sensitive components, which is a common problem with saws and routers.
- High precision cuts on arbitrary designs – Cut any design, no matter how small, intricate, and creative with higher yields.
Challenges of de-paneling using routing/die cutting/dicing saws
- Damages and fractures to substrates and circuits due to mechanical stress
- Damages to PCB due to accumulated debris
- Constant need for new bits, custom dies, and blades
- Lack of versatility – each new application requires ordering of custom tools, blades, and dies
- Not good for high precision, multi-dimensional or complicated cuts
- Not useful PCB De-paneling smaller boards
Lasers, on the other hand, are gaining control of the PCB De-paneling market due to higher precision, lower stress on the parts, and higher throughput. Laser De-paneling can be applied to a variety of applications with a simple change in settings. There is no bit or blade sharpening, lead time reordering dies and parts, or cracked/broken edges due to torque on the substrate. Application of lasers in PCB De-paneling is dynamic and a non-contact process.
Advantages of laser PCB de-paneling
- No mechanical stress on substrates or circuits
- No tooling cost or consumables.
- Versatility – ability to change applications by simply changing settings
- Fiducially Recognition – more precise and clean cut
- Optical Recognition before PCB De-paneling process begins. CMS Laser is one of the few companies to provide this feature.
- Ability to de-panel virtually any substrate. (Rogers, FR4, ChemA, Teflon, ceramics, aluminum, brass, copper, etc)
- Extraordinary cut quality holding tolerances as small as < 50 microns.
- No design limitation – ability to cut virtually and size PCB board including complex contours and multidimensional boards
UV laser cutting
UV laser cutting is a newer De-paneling method that eliminates bending stresses altogether. The laser makes extremely narrow, very precise cuts in any shape. It allows components to be placed much closer to the edge of the board, helping you maximize the use of board space in very small PCB assemblies. UV laser De-paneling machines that use a 20-micron laser beam are saving the day for many PCB manufacturers. Why UV laser De-paneling? You know that all PCBs are not perfectly square. They’re getting smaller and more creatively shaped to adapt to today’s technologies for mobile devices, medical devices, and other applications that demand more sensitive components. Smaller boards mean less room, so capacitors and components are pushed to the edge where they are more susceptible to damage during De-paneling. UV laser De-paneling eliminates the threat of too much waste and not enough production yields. In addition, laser cutting lets a manufacturer hold very tight tolerances on the finished assembly size; much tighter than is possible with pre-routed panels. This is a big advantage when the exact board size is critical to the finished product, which we are seeing more often as boards go into smaller and smaller products. Laser cutting may not be suitable for thick boards, due to the time and number of passes that need to be made.
For sophisticated precision micromachining applications, ultraviolet (UV) wavelength lasers have proven their value in a number of industries. The key factor for using UV laser technology as a solution is its capability of precisely ablating a wide range of materials at a high speed cost effectively. Also shorter wavelengths enable stricter focusing, which is advantageous for processing high precision, small features in a non-contact manner. Lasers are used in a range of PCB manufacturing processes such as de-paneling, drilling, profiling (cutting), laser direct imaging (LDI), marking and repair, trimming. Laser technology is a non-contact process hence eliminates mechanical stress on the material completely. Micro-cracking and burr formation in the material is also avoided. The fine focus attainable with UV lasers can remove small material volumes, minimizing ejected material deposits on the circuits. Precision micromachining possible with UV lasers enables more circuits to be arranged on one panel, improving the net usable area. UV wavelengths are also absorbed by a range of materials in PCBs from polyimide to copper films offering an all-in-one flexibility kind of solution.
Cutting and Drilling in Flex PCB Manufacturing
Flexible PCB technology is moving towards miniaturization: thinner substrate materials and smaller hole sizes for both blind via holes and through vias, with concurrent increases in feature density. It is not possible to achieve these small dimensions with longer wavelength lasers or mechanical methods. UV wavelengths help focus the beam to a considerably small spot size for drilling the needed hole dimensions in the order of Ø100µm down to a few tens of microns in diameter. Key manufacturing process can be addressed with UV lasers is cutting rigid, thick PCB panels having fiberglass-based polymer composites such as FR4. Cutting may be required for de-paneling of completed devices from the larger PCB panel or for making contoured profile cuts.
Conclusion
PCB designed for applications like wearable’s or automobiles the last thing to be considered in PCB designing is getting the final boards cut perfectly. Here comes the requirement of precise and laser de-paneling machines.
