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Effective measures to reduce the production cost of printed circuits

As a measure to reduce the production cost of rigid multi-layer printed circuit boards, various aspects such as the type, size, processing technology, and materials of printed circuit boards can be considered. 1、 The impact of printed circuit board size design on cost is that the original size of the copper-clad board is too large, making it inconvenient to process. Sometimes, it cannot even be placed in the printed circuit board processing equipment for processing. Therefore, it is necessary to first cut it into several copper-clad boards of different processing sizes. As for the specific size of the processing size, it needs to be determined based on the processing equipment for producing printed circuit boards, the size of each printed circuit board, and some process parameters. These process parameters not only include the length and width required for the printed circuit graphics themselves, but also the width consumed for fixing the screw holes on the printed circuit board to the electronic product frame, the process allowance for external processing, the clamping allowance for fixtures during chemical plating, electroplating, and corrosion, the positioning pin allowance for multi-layer printed circuit boards, the alignment mark allowance between layers, the mark allowance for printed circuit board manufacturers, and the edge width of printed circuit boards. Some recommended process parameters can be obtained from copper plating manufacturers or distributors. During the production and processing of printed circuit boards, the above data can be used to determine how many copper plates to cut a large original size copper plate into, whether to cut it vertically or horizontally, and whether it is possible to perform nesting, etc. Figure 4.86 is an example of cutting an original sized copper plate. It involves cutting an original sized copper clad plate into four machined copper clad plates, each of which contains six printed circuit boards. If the longitudinal size of the printed circuit board increases by 1mm, then each copper plated board with processing size can only be cut into 4 printed circuit boards, undoubtedly increasing the cost of printed circuit boards to 150% of that of 6 printed circuit boards. It can be seen from this that it is important to design the size of printed circuit boards reasonably based on the original size of the copper-clad board. Figure 4.86 The Impact of the Number of Layers on the Cost of Printed Circuit Board (PCB): The Original Size of Copper Clad Board and the Size of Printed Circuit Board (PCB). As the number of layers increases, the production cost of PCB will sharply increase, which may result in a significant cost difference due to a momentary difference. If you encounter difficulties in designing a 6-layer printed circuit board, do not give up easily. Perhaps a significant economic benefit lies in your persistent efforts; However, it is not easy to reluctantly do so, as in most cases, designers may not hesitate to choose to design an 8-layer printed circuit. 3、 The double-sided copper coated board used in the production of double-sided printed circuit boards using CEM-3 material, in addition to the widely used double-sided epoxy resin glass cloth copper coated board, also has a low-cost CEM-3 material, as shown in Figure 4.87. Its structure is to change the thicker epoxy resin glass cloth used as the substrate in the original double-sided epoxy resin glass cloth copper coated board into very thin two sheets. At this time, due to insufficient strength, epoxy resin glass non-woven fabric is sandwiched between the two sheets of epoxy resin glass cloth, thereby reducing costs. CEM-3 material has a soft texture and can be used as a core material for multi-layer rigid printed circuit boards, in addition to being used alone. Figure 4.87 Structure of CEM-3 Material 4. The Influence of Cost on the Ratio of Line Width to Gap Width of the Conductive Pattern. If the width of the conductive pattern in a printed circuit board is represented by L and the gap width between the conductive patterns is represented by S, then LIS represents the ratio of the width of the conductive tape to the gap width. As this ratio decreases, the production yield of printed circuit boards will sharply decrease, and the cost will also increase. This phenomenon is more pronounced in situations with higher circuit density. Therefore, the value of LIS cannot be arbitrarily reduced. 5、 The impact of through-hole diameter on cost When using a drill bit to drill holes in printed circuit boards, when the diameter is below a certain value, the drilling depth of the drill bit will sharply shorten. That is to say, when drilling a hole with a smaller diameter, the drill bit needs to be removed multiple times for heat dissipation, which will reduce production efficiency and increase costs. So, do not arbitrarily reduce the aperture of the through-hole; And the number of through holes should also be minimized as much as possible. 6、 Using silver paste to fill the through holes in double-sided printed circuit boards does not require copper plating to achieve the connection of the two circuits. Instead, the method of filling silver paste into the through holes can also reduce the cost of double-sided printed circuit boards. The specific process diagram is shown in Figure 4 88. This method is generally used for ordinary phenolic resin paperboard with double-sided copper coating. This method first cleans the surface of ordinary phenolic resin paperboard coated with copper on both sides, and then prints corrosion-resistant patterns on both sides using screen printing method. After corrosion, a conductive pattern is formed. After removing the corrosion-resistant layer, through holes are drilled, and silver paste is filled into the holes. In order to ensure good contact between the silver paste and the conductive patterns on both sides, the silver paste should protrude through holes, and the diameter of the protruding silver paste pattern should be greater than the aperture of the through holes. In order to block the migration of silver ions, a covering layer is added to the surface of the protruding part of the silver paste through screen printing. Subsequently, solder mask patterns and isolation patterns are printed on both sides of the screen, and screw holes for fixing the printed circuit board are stamped or drilled to process the shape. Finally, through inspection, the double-sided printed circuit board filled with silver paste through holes has been completed. Generally speaking, due to the substrate, the double-sided printed circuit board filled with silver paste through holes in Figure 4.88 is not suitable for high reliability circuits. In addition, due to the presence of a large amount of non-conductive materials in addition to conductive substances in silver paste, the conductivity of silver paste is not as good as that of copper foil, and readers should also be reminded to pay attention.