As a designer, you need to make some key decisions about the types of components used in your circuit board. Follow these guidelines when selecting parts for your board components.

　 　1. Source components from reputable suppliers

　　Sourcing all components from reputable manufacturers reduces the risk of counterfeit or damaged parts.

　　 2. Choose IC packages to reduce the number of parts

　　Component packages integrate multiple parts into one housing to perform the required function. For example, a basic filter circuit consists of a resistor and a capacitor. If you choose a package that acts as a filter, you can minimize the number of components used on the circuit board. This can improve board reliability, reduce weight, and lower costs.

　 　3. Choose SMT components whenever possible

　　SMT components have shorter leads compared to through-hole components. This reduces parasitic capacitance and enhances signal integrity. Other benefits of choosing SMDs include:

　　Reduced maintenance;

　　Makes the circuit board smaller and lighter;

　　Allows for greater design flexibility by placing SMT components on both sides of the PCB;

　　Easier to achieve automated assembly compared to THT components;

　　Lower manufacturing costs;

　　Only choose THT components in special cases where the required component is unavailable and SMDs are particularly sensitive to temperature.

　　 Key points:

　　1. Always source components from reputable suppliers to avoid the risk of counterfeit parts

　　2. Implement component packaging to reduce the number and size of parts on the circuit board

　　3. Use small-lead SMT components to enhance signal integrity

　　Difference between Through-Hole Technology and Surface Mount Technology

　　SMT eliminates the limitations of through-hole mounting manufacturing processes on circuit board space.

　　The manufacturing cost of through-hole components is higher than that of SMT components.

　　Using SMT requires advanced design and production skills compared to through-hole technology.

　　SMT components can have a larger number of pins compared to through-hole components.

　　Unlike through-hole technology, SMT allows for automated assembly, making it suitable for mass production at lower costs compared to through-hole production.

　　SMT components are more compact compared to through-hole mounting, resulting in higher component density.

　　While surface mounting can reduce production costs, the mechanical capital investment is higher than that required for through-hole technology.

　　Through-hole mounting is more suitable for producing large, bulky components that are subjected to cyclical mechanical stress or even high voltage, high power components.

　　Higher circuit speeds are easier to achieve due to the reduced size and number of holes in SMT.

　　 PCB Component Placement Guide

　　Here are some recommendations for SMD placement to maintain good signal and power integrity for your circuit board.

　　Keep components as close as possible to minimize wiring distances.

　　Follow the signal path on the schematic when placing components.

　　Never place components in the return path of sensitive signals. This will cause signal integrity issues.

　　For high-speed devices, bypass capacitors should be placed close to their power pins. This will reduce parasitic inductance.

　　Group SMDs together for power circuits. This will help you provide shorter wiring and reduce inductance in the connections.

　　Try to place SMT components on one side of the board to reduce costs associated with stencils and assembly.

　　Maintain the minimum spacing between test points and SMT components as per manufacturer's specifications. This spacing may vary depending on the height of the component.

　　For ease of assembly, ensure that all component names, polarities, orientations, and locations are correctly marked in the assembly drawing. The packages in the drawing should match the actual parts. If you are considering outsourcing assembly, consult the manufacturer for their accompanying guidelines. Prepare your BOM accordingly.

　 　Before the PCB Assembly Process

　　Before the actual PCBA process begins, some preparatory steps must be taken. This helps the PCB manufacturer assess the functionality of the PCB design, primarily involving DFM checks.

　　Most companies specializing in PCB assembly require the design files of the PCB, along with other design specifications and specific requirements. This allows the PCB assembly company to check the PCB files for any issues that may affect the functionality or manufacturability of the PCB. This is called a Design for Manufacturing check, or DFM check for short.

　　The DFM check examines all design specifications of the PCB. Specifically, this check looks for any missing, redundant, or potentially problematic features. Any of these issues could severely negatively impact the functionality of the final project. For example, a common PCB design flaw is insufficient spacing between PCB components. This could lead to short circuits and other malfunctions.

　　By identifying potential problems before manufacturing begins, DFM checks can reduce manufacturing costs and eliminate unforeseen expenses. This is because these checks reduce the number of scrapped circuit boards. As part of our commitment to quality at low cost, DFM checks are standard on every Hemeixin project order. Hemeixin provides free DFM and DFA checks, but the value is priceless, as Hemeixin relies on the Valor DFM/DFA check, an automated system that helps improve speed and accuracy.

　 　After PCB Assembly

　　It's safe to say that the PCB assembly process can be messy. Solder paste leaves some flux behind, and human handling transfers oils and dirt from fingers and clothing to the PCB surface. Once everything is done, the result may look a bit dirty, which is both an aesthetic and a practical issue.

　　Flux residue, after remaining on the PCB for months, begins to smell and become sticky. It also becomes acidic and, over time, can damage the solder joints. In addition, customer satisfaction tends to suffer if new PCBs are shipped covered in residue and fingerprints. For these reasons, cleaning the product after all soldering steps are complete is very important.

　　A stainless steel high-pressure cleaning system using deionized water is the preferred tool for removing PCB residue. Cleaning PCBs with deionized water poses no threat to the equipment. This is because it is the ions in ordinary water, not the water itself, that damage circuits. Therefore, deionized water is harmless to PCBs during cleaning.

　　After cleaning, a quick drying cycle using compressed air prepares the finished PCBs for packaging and shipping.