For the processing of low-volume PCB assembly, there are many factors to be considered in PCB wiring. In actual production, the effect can not be achieved simply by using automatic wiring tools, which is not only related to PCB production cost, electromagnetic interference between components, beautiful appearance, and many other factors, but also affects the effect of SMT chip processing.
1、 For double-sided boards or multilayer boards, the lines on both sides of the circuit board should be perpendicular to each other to prevent mutual induction and crosstalk.
2、 Wiring priority: priority of key signal lines, such as power supply, analog small signal, high speed signal, clock signal and synchronous signal.
3、 If the PCB board is equipped with high current devices, such as relays, indicator lights and horns, the ground wire should be separated to reduce the noise on the ground wire.
4、 If there is a small signal amplifier on the circuit board of SMT chip processing plant, the weak signal line before amplification should be far away from the strong signal line, and the line must be as short as possible, and it should be shielded by ground wire if possible.
5、 In order to reduce the interference of the board, SMT electronic factory should leave a large gap between the parallel signal lines. If there are two signal lines close to each other, it is better to take a grounding wire between the two lines, which can play a shielding role. The distance between high voltage signal lines needs to consider the requirements of insulation resistance and breakdown voltage under the worst conditions.
6、 When designing signal transmission line for SMT chip proofing, it is necessary to avoid too large steering angle, so as to prevent reflection due to sudden change of characteristic impedance of transmission line. Uniform arc line or obtuse angle with certain size can be considered. In addition, the copper foil is easy to be peeled or warped at the outer corner of the tip.
The above four aspects are the important basis for selecting SMT small batch SMT processing manufacturers. In addition, product quality, technical support, value creation, etc. can become the criteria for judging whether SMT processing manufacturers are worthy of cooperation. Here, also reminds the enterprise to choose must be careful.
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Many people have heard about the production and processing of low volume PCB assembly , But I didn’t know the whole detailed process. SMT proofing refers to the process of experimental production before batch manufacturing and small batch trial production in the factory.
The following is an aspcb . COM: the whole process of low volume PCB assembly.
Cost advantage – although the traditional scale economy has known large production, it has a significant cost advantage in the changing technology scheme low capacity PCB production. First, you won’t get more production boards than you need. In addition, the board will not become redundant as technology changes.
In the prototype phase, you often improvise your product in terms of design and functionality. Low volume PCB assembly means you will not encounter defective products. In addition, because you can outsource small batch PCB assembly, this means lower management costs for your own business. You can also save valuable time available in other production areas. For lower batches, you can also save storage costs, in case you encounter a large inventory load, and if the prototype fails, it can also lead to excess inventory. Therefore, low volume PCB assembly can provide low-cost testing methods Turnover time – low yield also has a rapid turnaround time. Therefore, you can quickly assess whether there are any design changes. This in turn shortens the time to market and can be a source of significant competitive advantage in the world today.
Agility – the agility of an enterprise to respond to changes if there is an attribute between business success and failure. Low volume PCB assembly itself provides the enterprise with this advantage because the enterprise will not encounter a large number of products and has the advantage of rapid turnover time. By better understanding whether there are any defects in the product, no matter whether the design needs to make any changes, the enterprise can combine the product with the customer requirements very quickly. There is no doubt that the chances of success are increasing.
The quality end product – PCB’s ability to turn around time fast prototyping and early detection of defects, your advantage is to improve the product and enter the market with high-quality products. This has a long way to go in terms of improving credibility because the product has been successful in the market and has brought a reputation to the manufacturer.
It’s also possible for startups and amateurs – businesses are no longer just big business companies. Through the low volume PCB assembly and low cost related to the test idea, the business has become a fair competition environment. For small businesses and amateurs, it’s easy to test their ideas without having to invest a lot of money. For startups that want investors, it is easy to get proof of concept in addition to the paper business plan.
In a word, low volume PCB assembly has many advantages, which saves management costs from outsourcing. Small order size can automatically shorten the turnover time. In addition, it is a simple and low-cost method to test product design concepts without a lot of costs.
Thank you very much for coming to our Shenzhen IDEASPCBb technology. We are a professional PCB manufacturer, which specializes in fast proofing, large, low volume PCB assembly. The whole production process is controlled by computer and barcode tracking. Only a few factories in China have this production technology. At the same time, we also provide SMT patch, plug-in machine, PCBA finished product assembly one-stop service. Quality assurance, punctuality of delivery, affordable price, welcome to consult quotation!
Printed circuit board mound, also known as "fill" or "fill bare printed circuit board," is a process that involves many different stages.
For low volume PCB assembly, to maximize production and minimize cost, What should consider some restrictions. Also, What should consider human factors before designing. Here are some of the factors that IDEANSPCB summarizes:
1) If the wire spacing is less than 0.1 mm, the etching process can not be carried out because if the etching solution can not effectively diffuse in the narrow space, part of the metal will not be etched out.
2) If the wire width is less than 0.1 mm, it will break and damage during the etching process.
3) The pad size should be at least 0.6 mm larger than the hole size.
The following constraints determine the design method of the panel:
1) The size performance of the reproduction camera used for the original film of the product;
2) Tabulated dimensions of original drawings;
3) The smallest or largest operating size of the circuit board;
4) Drilling accuracy;
5) Excellent linear etching equipment.
In the design, from the perspective of low volume PCB assembly, the following parameters should be considered:
1) The diameter of the hole depends on the maximum material condition (MMC) and minimum material condition (LMC). Who should select the diameter of the hole of an unsupported component in such a way that the MMC of the pin is subtracted from the MMC of the hole, and the difference is between 0.15-0.5mm. Moreover, for the band pin, the difference between the pin’s nominal diagonal and the inner diameter of the unsupported hole will not exceed 0.5mm, and not less than 0.15mm.
2) Place smaller components reasonably so that larger components will not cover them.
3) The thickness of solder resist shall not be greater than 0.05mm.
4) The screen-printed logo cannot intersect with any pad.
5) The top half of the circuit board should be the same as the bottom half to achieve structural symmetry because asymmetric circuit boards can bend.
From the perspective of quality control of low volume PCB assembly, an important factor to be considered is that IT should pay special attention to the possible short circuit problem caused by the inclination between the inserted components and their theoretical positions before welding. According to experience, What should keep the maximum allowable inclination of component pins at 15 degrees from the theoretical position. Within the corner. When the diameter difference between the hole and pin is large, the inclination can be up to 20 degrees. For vertically mounted components, the inclination can reach 25. Or 30 degrees, but this will lead to a reduction in package density. Figure 3-13 shows the package of the TO-18 transistor with different pin inclination. In the figure, the installation position of the to-i8 transistor is 2mm away from the printed circuit board. If the aperture is IMM, the inclination can reach 20 degrees. Of course, the pin itself does not have any inclination.
The assembly mode of multiple circuit boards usually makes the field maintenance as easy as pulling out the circuit board for the replacement. Of course, the precondition is that each independent circuit board can exercise its unique function. There will not be much disassembly for replacing circuit boards, and the minimum number of soldering / desoldering is ensured. Therefore, the design of PCB must consider its maintainability.
In the production of low volume PCB assembly, the required welding technology and equipment also add many limitations to the circuit board’s design and layout. For example, in wave soldering, the groove’s maximum size, the distance between the edges, and the operating space are all important factors. Simultaneously, designers must be aware of what the final product should look like as much as possible and try their best to protect its most sensitive parts.
There are four main steps in the assembly process of low volume PCB assembly.