The printed circuit board is the provider of electrical connections for electronic components. Its development has a history of more than 100 years; its design is mainly layout design; the main advantage of using circuit boards is that it greatly reduces wiring and assembly errors, and improves automation and production labor rates.
With the continuous advancement of PCB technology, the printed circuit board (PCB) industry has developed rapidly, and at the same time the competition for products has become increasingly fierce, and the PCB industry has entered the era of meager profits. Manufacturability and cost control of products are particularly important for enterprises to survive and develop in the competition, but it has become very difficult for enterprises to gain competitive advantages in technology and technology.
However, engineering design is the front end of the product manufacturing process. Under the premise of meeting customer requirements during product design, it is very important to fully consider the material cost of the product, the difficulty of the manufacturing process, avoid the limit capacity of the product, and ensure the smooth production process of the product. effect. Below we introduce how to reduce the cost in the PCB manufacturing process.
Printed circuit board size optimization Generally speaking, the smaller the size of the printed circuit board, the lower the cost, but it is not an absolute linear relationship. This has something to do with the cutting process of printed circuit board manufacturing, so when selecting the estimated printed circuit board size before design, it is necessary to confirm the price of each size with the purchasing department first, and then pre-select the most economical one that meets the needs. size.
According to the type of order and processing capacity, operating skills, determine the best imposition size of the processing board. Imposition processing is beneficial to improve material utilization, improve efficiency, and save water and electricity consumption. However, imposition size processing will bring handling, scratches, and operation problems, and even increase the scrap rate in the short term, making quality control more difficult. The engineering review should proceed from reality to determine the optimal processing plate size.
When starting the printed circuit board layout design, in addition to the architectural design according to the functional design requirements, in order to save costs, the following aspects need to be considered: Considering that the same circuit diagram design corresponds to many similar products at the same time. Similar products require different or similar designs due to differences in product size, sales regions, functions, and product grade positioning.
If two printed circuit board layout designs are carried out due to a small amount of differences, first of all, it is necessary to apply for the design of two or more printed circuit boards, which will generate an additional design fee; secondly, the printed circuit board design After completion, in order to ensure the quality of the product, each printed circuit board needs to be tested for reliability and electrical performance. Additional costs will be incurred for the prototype and the experiment itself.
In addition, the original size of the copper clad board is too large, which is inconvenient to process, and sometimes it cannot even be processed in the printed circuit board processing equipment, so it needs to be cut into several copper clad boards of the processing size first. As for the specific size of the processing size, it needs to be determined according to the processing equipment for making printed circuit boards, the size of each printed circuit board and some process parameters.
In addition to the length and width required by the printed circuit pattern itself, these process parameters also include the width consumed by the screw holes for fixing the printed circuit board on the electronic product frame, the process allowance for shape processing, chemical plating, electroplating and corrosion Fixture clamping allowance, positioning pin allowance for multi-layer printed circuit boards, alignment mark allowance between layers, printed circuit board manufacturer's logo allowance, printed circuit board side width, etc., among which Some recommended values of process parameters can be obtained from copper-clad laminate manufacturers or distributors.
During the production and processing of printed circuits, the above data can be used to determine how many copper-clad boards of a large original size are cut into processed-size copper-clad boards, whether to cut vertically or horizontally, whether nesting can be performed, etc.
Improving engineering review ability can also achieve cost control, which is mainly reflected in the following aspects: use computer imposition software, optimize graphic processing imposition method, optimize imposition spacing, optimize process edge settings, and optimize substrate according to customer design (or assembly) size The utilization rate, optimize the feed specification, reduce the waste of edge material; optimize the slot hole of the printed board, the machining method of the outer dimension (drilling, punching, cutting, milling), different machining methods and procedures, will mean different Machining costs; understand the customer's design, assembly, and use requirements, and use CAD software to optimize line width spacing, welding rings, reduce processing difficulty, improve the pass rate of finished products, and reasonably control material grades on the premise of meeting customer requirements.
As the number of layers of printed circuit boards increases, the production cost will increase sharply, so there may be a large difference in cost due to a difference in thinking. If you encounter difficulties in designing a 6-layer printed circuit board, you must not give up lightly, maybe a large amount of economic benefits are in your persistent efforts; however, it is not easy to do what you want, because when When encountering this kind of thing, in most cases, the designer may choose to design an 8-layer printed circuit without hesitation.
As the number of layers of printed circuit boards increases, the production cost will increase sharply, so there may be a large difference in cost due to a difference in thinking. If you encounter difficulties in designing a 6-layer printed circuit board, you must not give up lightly, maybe a large amount of economic benefits are in your persistent efforts; however, it is not easy to do what you want, because when When encountering this kind of thing, in most cases, the designer may choose to design an 8-layer printed circuit without hesitation.
If the width of the conductive pattern in the 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 strip to the gap width. As this ratio decreases, the production yield of printed circuit boards will decrease sharply, and the cost will also increase. This phenomenon is more obvious when the circuit density is relatively high. Therefore, the value of LIS must not be reduced arbitrarily.
In the case of using a drill bit to drill a hole in a printed circuit board, when the hole diameter is lower than a certain value, the drilling depth of the drill bit will be shortened sharply. That is to say, the same hole is drilled. When drilling a hole with a small diameter, the drill bit needs to be withdrawn for heat dissipation many times, which will reduce production efficiency and increase cost. Therefore, do not arbitrarily reduce the aperture of the through hole; but also reduce the number of through holes as much as possible.
For the through-holes of double-sided printed circuit boards, the method of filling silver paste into the through-holes instead of copper plating to realize the connection of the circuits on both sides can also reduce the cost of double-sided printed circuit boards. This method is generally used for ordinary phenolic resin cardboard with copper clad on both sides. The method first cleans the surface of the common phenolic resin cardboard coated with copper on both sides, and then prints the anti-corrosion pattern on both sides by screen printing method, forms a conductor pattern after corrosion, and drills through holes after removing the anti-corrosion layer. Fill the hole with silver paste.
In order for the silver paste to be in good contact with the conductor patterns on both sides, the silver paste should bulge out of the through hole, and the diameter of the silver paste pattern in the bulged part is larger than the aperture of the through hole. In order to block the migration of silver ions, the surface of the bulging part of the silver paste is covered with a cover layer by screen printing. Then, screen print solder resist patterns and isolation patterns on both sides, punch or drill screw holes to fix the printed circuit board, and process the shape. Finally, after passing the inspection, the double-sided printed circuit board with silver paste filling the through hole is completed.
Generally speaking, such double-sided printed wiring boards with silver paste filled through-holes are not suitable for high-reliability circuits due to the base material. In addition, since there are a lot of non-conductive materials in silver paste besides conductive substances, the conductivity of silver paste is not as good as that of copper foil, so readers should also be reminded.
Strictly controlling the amount of material fed can achieve energy saving and emission reduction in the manufacturing process, which meets the requirements of green production and reduces cost input at the same time. It is mainly reflected in the following points: printed board is a non-universal (or characteristic) commodity. If there is too much production, the customer refuses to waste it, and if the production is less, it needs to be fed again, resulting in waste of materials, labor, water and electricity, and time.
How to reasonably control the quantity of feeding? One is that it depends on the control range of the customer's real demand, and the salesman needs to ask the customer clearly. The second is to evaluate and calculate based on the control ability of the production and processing process, optimize the quantity of feeding materials, and strengthen the control of the remaining number of finished boards. Inventory accounting is carried out according to customers, product models, and remaining quantities, and the remaining information is communicated to customers, engineering, production, and planning personnel. Make full use of the remaining printed boards in stock, digest or reduce the inventory of finished boards, and reduce the amount of finished boards; control rework/replenishment. Be sure to investigate the reasons and responsibilities for rework/scrapping, and implement economic penalties so that violations of operations or failure to perform duties can be corrected.
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