Hard to Read Print? The Reason is Speed and Ecology
“Fifteen years ago, printing was done by classic screen printing. A sieve had to be prepared first, then a photosensitive mask was applied to it. Each plate separately, usually from both sides, is dried then individually, and only then, it is illuminated, developed and finally cured, which led to a specific print on the plate. The whole process was a series of time-consuming steps. This was not sustainable in the long run, and with the requirement for constant acceleration of the entire prototype production, the production of the sieve ceased to pay off. That's why we gave up on this technology over time and started making it through photosensitive paint. By applying white colour to the entire board and using film and lighting, we illuminated the print and developed it. A huge advantage of such a print was the time saved in the preparation of the screen, but even so, each plate had to be lit separately”, Zdeněk Cápal thinks back on the predecessor of digital printing.
“Of course, in terms of appearance, resolution and lighting with a classic film, the result was nice to read. We use a laser photoplotter, so we achieved a resolution of five microns and, if necessary, even higher resolution. Even a very small font was always perfectly legible even on the service print. Customers have become accustomed to this, to some extent it has become a standard throughout the market, and today it is difficult to explain the benefits of digital printing to some people,” he adds.
Express Speed With No Delay
“However, things progressed. With the transition to digitization, manufacturers of printing machines began to produce digitized printers, having a huge advantage of being able to save a lot of time in production and a number of production steps. With the transition to digitization, everything runs automatically. We give the machine information that guides everything digitally to the cameras, or adjusts it so that the motive fits exactly with the printed circuit board. It prints everything and dries it immediately with a UV lamp at the same time, and the other side can be printed immediately. This can be a saving of several minutes or hours. The speed and steps saved go without saying, but there is a difference in the resolution,” Zdeněk Cápal explains.
The digital printing can work with a resolution of around 35 microns, which is a step back compared to the film. But even here, technologies are evolving. The machines have two printing heads capable of printing around two thousand printing dots - and they are expected to improve further in the future. The result meets the IPC standard because it is not completely strict in the case of printing. But the result for the customer is that it does not look completely ideal.
PCB with digital print
Ecology and QR codes
“We respect customers who insist on the original print quality. We assume that the printed circuit board is set up in the vast majority of cases and not visible then. But still, there are cases when they are visible - and the customer wants a perfect result. We still offer them the opportunity of printing using a film, which is reflected in a small price increase - because the screen printing requires more of our time and manpower. On the other hand, digitization is a trend and brings a number of other effects. Particularly in the field of environmental sustainability, which is fundamentally being addressed, especially in Europe and throughout the Western world. The digital printing is making a major difference in this regard, as water consumption is minimal. 80% of paint is saved, the necessary subsequent processes associated with development and washing are eliminated,” points out Zdeněk Cápal.
And as he adds: “It's all about communication and education. For an installation company, the printing generally makes no sense, as the installation is always based on an installation drawing, and therefore, they do not follow the print. On the other hand, print can still perform functions such as displaying a reference of a specific component, its possible polarity, or displaying the company logo. With the miniaturization of components, space is no longer available for printing, it is constantly shrinking and the demands are incompatible with digitization. It is now possible to have the installation plan in an electronic format, and to use QR codes, as is common with many other products where manuals have disappeared. But pay attention to the size and resolution of the QR code. We recommend 10 x 10 mm. To save paper, you open everything directly in the phone. Times are changing. QR codes can be in a mask, copper and print. There can then be a 3D visualization of the printed circuit board on the Internet. Anyway, nobody can read anything from the description itself today. Bar codes are a matter of course. From the customer's point of view, the possibility of digital printing with a serial number is a huge advantage. You can mark each printed circuit board differently, everything is entered automatically in data. And as long as you print the job, it works with you. If you want to proceed in a classic way, you need a different film for each panel,” the chairman of the board of the successful European PCB manufacturer explains.
Today however, digitization concerns an increasing part of production. “When it comes to resists, everything is lit digitally - it is undoubtedly beneficial for us and the customer. The installation has higher accuracy, option of positioning, and a very fair resolution. It is a resist using the illumination by a single light only. We are able to reach 3.5 microns as a standard there. For the time being, we are resisting the digitization of the mask printing. We would run into even more difficulties there. The result would be equally functional, but would not las good. We’ll see, maybe in the coming years,” Zdeněk Cápal concludes.
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