A printed circuit board (PCB) is the body of an electronic product, and the performance, life, and reliability of the final product depend on the electrical system it constitutes. Products that have high quality circuits will have lower field failure rates and on-site return rates if properly designed. Therefore, the production cost of the product will be lower and the profit will be higher.
In order to produce high quality PCB boards on time without increasing design time and without costly rework, design and circuit integrity issues must be identified early in the design process. In order to bring products to market quickly and reliably, it is necessary to use design tools to automate the design process, but how can we ensure the design is successful? What details should you pay attention to in order to maximize design efficiency and product quality?
Design tools should obviously be intuitive and powerful enough to overcome complex design challenges, but what else is worth noting? This article lists the four steps you can take to ensure a successful PCB board design. The first step—do not stop at the basic schematic input. The schematic input is critical to the logical connection of the generated design. It must be accurate, easy to use, and integrated with the layout to ensure successful design.
Simply entering the schematic and transferring it to the layout is not enough. In order to create a high-quality design that meets expectations, you need to ensure that the best components are used and that simulation analysis can be performed to ensure that the design will not go wrong when it is delivered. The second step - don't ignore the library management library management is an important part of the design process.
In order to quickly select the best components and place them in the design, easy creation and easy management of the device is necessary. PADS allows you to maintain all your design tasks in one library and update the library in real time to make it easy to use and ensure the accuracy of your design development. You can access all component information from a single spreadsheet without worrying about data redundancy, multiple libraries, or time-consuming tooling overhead.
The third step - effective management of design constraints rules Today's key high-speed design is extremely complex, if there is no effective means to manage the constraint rules, the design, constraints and management of routing, topology and signal delay will become extremely difficult . In order to build a successful product in the first iteration, constraints must be set early in the design process in order to achieve the desired goals. Good constraint rule management prevents you from using expensive or unpurchasable components and ultimately ensures that your board meets performance and manufacturing requirements.
Step 4 - Make sure you have the layout capabilities you need In recent years, the complexity of PCB layout design has been significantly higher than before. In order to make smaller, more portable electronic devices, the density of the design has to be increased. In addition, the operating frequency is increased, which requires designers to evaluate electrical characteristics that may have been previously overlooked to ensure that the design is available. To keep up with increasingly complex steps, designers must have a broader range of capabilities to define advanced rule sets, create unique RF shapes, and implement correction structures to improve overall design performance. Smart layout tools help create efficient placement and routing strategies during the layout process. Precision placement reduces post-design violations, allowing you to complete projects faster with fewer mistakes.
While manual routing is typically used to achieve true design intent, the effective use of interactive routing with automated routing helps meet market timelines and improves design quality. Automated routing can also help with difficult tasks such as differential pair routing, network tuning, manufacturing optimization, microvia and build-up technology. If the routing strategy is planned in advance, the efficiency of using automatic routing will be greatly improved. Another challenge is that modern PCBs have to maintain thousands of networks, which can make it difficult to route critical areas in the design. The best way to avoid this problem is to divide the network lines into groups in order to create an effective routing strategy. Once you have created a planning group, you can tag and filter the network groups to highlight the critical networks that need to be routed.
1. The problem of line deformation caused by poor etching of the multilayer circuit board. When the outer layer of the multilayer circuit board is etched, if the ridge line of the copper foil is deep into the resin on the board surface, there may be residual copper in the dense line area after etching. These phenomena may not be easily noticeable after etching, but after the nickel immersion gold process, it may be found that the line or the edge of the pad grows deformed lines or metal regions. This problem is sometimes considered to be a problem of poor residue or water washing, but it is actually a problem of circuit etching or improper copper selection. It is necessary to pay attention to whether there is still a strip of light gray intermetallic metal. If it is not removed, the brushing, pickling, and micro-etching may not be completely removed. This will inhibit the initiation of the nickel immersion gold reaction. If the reaction is completely unsuccessful, the gold-plated copper leakage may occur.
2. the problem of copper-free through-hole hole wall copper Currently there is no copper through-hole method, mainly after the overall copper plating is etched away, or the cover hole process is not allowed to plate the tin, and then the copper is removed by etching. However, there is no way to remove the palladium metal from the etching solution, so the nickel gold is still adsorbed on the pore walls during the process. This is a direct problem for products where the walls of the holes are not metal.
At present, some multi-layer circuit board manufacturers have introduced a so-called chemical copper process that is plagued by nickel-free immersion gold. In fact, the simple method is to reduce the concentration of palladium metal. This way, the subsequent nickel gold cannot be quickly plated, so it can be reduced. The production of copper-free through holes is troublesome. However, such a practice may have a potential crisis of insufficient chemical copper activity and pore breakage, which will be reduced in terms of the operating range of chemical copper. Some manufacturers have adopted the practice of removing palladium to increase the treatment of palladium after stripping the tin bath. However, in the current process, the setting of the liquid tank must be increased, and the operating cost will also increase. At the same time, most of the palladium removal systems have the risk of eroding copper, and some so-called special syrups have patent and cost problems.
Another method is to passivate the palladium layer in the pores with a thiol solution before stripping the tin, so that the subsequent nickel immersion gold process cannot function. However, if the mercaptan treatment is not cleaned, the residue will be carried into the stripping bath to make the copper surface stained with sulfide. The sulfur on the copper surface is a fatal injury to the nickel reaction, so it is very difficult to prevent the problem of copper exposure. As a result, the exact solution for copper-free through holes is still under development. Figure 9.10 shows a typical example of a copper exposed pad. Basically, if the copper surface is not inactive, it may be that the negative electricity of the copper surface is not strong enough to be plated or the surface has been contaminated and cannot be reacted.