PCB Blog - The impact of fully printed electronic technology on PCB boards

The application of inkjet printing technology of fully printed electronics in PCB board is mainly manifested in three aspects: application in pattern transfer; application in embedded passive components; fully printed electronics that directly form lines and connections (including packaging) applications. These applications bring changes and progress to the PCB board industry. From the perspective of current and future application and development prospects, the application of fully printed electronic inkjet printing technology in PCB boards is mainly manifested in the following three aspects: application in pattern transfer; application in embedded passive components Applications; applications in fully printed electronics (including packaging) for direct formation of lines and connections. These applications will bring revolutionary changes and progress to the PCB industry.

Application in PCB board graphics transfer: mainly reflected in 4 aspects. The application of inkjet printing technology in PCB pattern transfer is mainly in four aspects: corrosion resistance, plating resistance, solder resistance and characters. Since the process of forming a resist pattern and a plating resist pattern by inkjet printing is basically the same, and the solder resist pattern formed by inkjet printing is very close to the character pattern, it is divided into forming a resist (plating) pattern and forming a solder resist pattern below. /Character graphics are briefly reviewed in two parts.

1. Application in forming resist/plating pattern
Using a digital inkjet printer to directly print the resist (etching-resistant ink) on the inner layer (or outer layer) on the board, an acid or alkaline resist pattern can be obtained, which is cured by UV (ultraviolet) light. After that, etching and film removal can be performed to obtain the required circuit patterns such as the inner layer. In the same way, the process of anti-plating pattern is basically the same. The use of digital inkjet printing technology and technology to obtain resist/plating patterns not only reduces the production process of photographic negatives, but also avoids the process of exposure and development. Material consumption (especially negatives and equipment, etc.) is shortened, product production cycle is shortened, environmental pollution is reduced, and costs are reduced. At the same time, it is more important to significantly improve the position of the pattern and the alignment between layers (especially to eliminate the dimensional deviation of the negative film and exposure alignment, etc.), improve the quality and improve the quality of multi-layer PCB boards. Product qualification rate is extremely favorable. It will be the same as laser direct imaging (LDI), which can shorten the production cycle of PCB boards and improve product quality, which is an important reform and progress of PCB board industry technology. The graphic transfer technology using digital inkjet printing has fewer processing steps (less than 40% of the traditional technology), less equipment and materials, and shorter production cycle. Therefore, the effect of energy saving and emission reduction is significant, and the environmental pollution and cost are also reduced.

2. Application in forming solder mask/character graphics
In the same way, the solder resist (solder resist ink) or character ink is directly sprayed on the PCB board by a digital inkjet printer, and after UV light curing, the final required solder resist graphics and character graphics are obtained. . The use of digital inkjet printing technology and process to obtain solder mask and character graphics significantly improves the position of solder mask and character graphics of PCB board products, which is also extremely beneficial for improving PCB board quality and product qualification rate. Application in embedded passive components: production of inferior products. At present, most of the methods of embedding passive components are realized by copper clad laminates (CCL) containing resistance/capacitance or inks related to screen printing. However, these methods not only have many and complex processes, but also have a long cycle , the equipment is many and occupies a lot of space, and the product performance deviation is large, it is difficult to produce sub-products. More importantly, it consumes a lot of energy during processing and produces a lot of pollution, which is not conducive to environmental protection. The use of inkjet printing technology to realize the method of embedding passive components will greatly improve these situations. The application of inkjet printing in embedded passive components means that the inkjet printer directly prints the conductive ink and other related inks used as passive components to the position set inside the PCB board, and then undergoes UV light treatment or drying/drying. A sintering process is performed to form a PCB board product with embedded passive components. Passive components mentioned here refer to resistors, capacitors and inductors (which have now been developed to embedded active components, such as system packaging). Due to the development of high-density and high-frequency electronic products, more and more passive components are required to minimize distortion and noise caused by crosstalk (inductive and capacitive reactance). At the same time, due to the increasing number of passive components, not only do they occupy a larger and larger proportion of the area, but also more and more solder joints, which have become a factor in the failure rate of industrial electronic products. In addition, the secondary interference caused by the loop formed by the surface-mounted passive components, etc., these factors are more and more serious threats to the reliability of electronic products. Therefore, embedding passive components in PCB boards to improve the electrical performance of electronic products and reduce the failure rate has begun to become one of the mainstream products in PCB board production. About the principle and method of embedding passive components in the PCB board. Generally speaking, the passive components of embedded resistors, capacitors and inductors are mostly placed on the second and penultimate layers (n-1 )superior. The resistive conductive glue (ink) used as a resistor is sprayed onto the set position of the inner layer (etched) of the PCB board by inkjet printing equipment, and the two ends of the bottom are connected with etched wires (open circuit). , after baking, testing, and then pressing into the PCB board, that's it. In the same way, the capacitive conductive adhesive (ink) used as a capacitor is sprayed on the copper foil at the preset position by an inkjet printer, dried and/or sintered, and then sprayed with a layer of conductive ink containing silver and other conductive inks, and then dried. and/or sintering, then lamination (upside down), etched to form both capacitors and interlayer wiring. In electronic products and electronic equipment, the number of inductors used is much smaller than that of resistors and capacitors. In the same way, the conductive ink (forming the central electrode) and the inductive material ink are formed into a high-inductance medium layer by an inkjet printer, and then the conductive ink is printed on the high-inductance medium layer to form a coil.

Application in the direct formation of circuit graphics: two major problems must be solved. The line formed directly by inkjet printing refers to the conductive lines and patterns formed on the substrate (without copper foil) by the inkjet printer directly using conductive ink. All-printed electronics technology means that the entire printed circuit board formation process is completed by inkjet printing technology. Currently, all-printed electronics technology is under engineering development and research, but will soon be promoted and applied. At present, the main problems of all-printed electronic technology are: 1) Development of advanced inkjet printers for industrialization (large-scale production), especially super inkjet printing equipment; 2) Development of advanced inkjet printing inks for industrialization, Especially a variety of metal nanoscale inks, such as silver, copper and gold nanoscale inks. Currently, the use of inkjet printing technology is being developed to produce multilayer printed circuit boards, system-in-package (SIP), and the like. Such as the use of super inkjet equipment and silver nano-ink technology developed by the Japan Institute of Industrial Technology to directly form multi-layer circuit boards. The process is to use a super inkjet printer to print silver nano-ink on a copper-free substrate to form a planar circuit layer, and then print connection bumps on this layer plane for interlayer connection, and then form the interlayer. The insulating layer is then formed on the insulating layer to form the second layer of circuits, and so on, to form a multi-layer circuit board with the required number of layers, that is, a fully printed electronic PCB board.