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Choose the PCB components six skills
 

The best PCB design methods: based on the component packaging options six things to consider when PCB components. All the examples in this article is to use Multisim design environment development, but even with different EDA tools, the same concept applies.

 

1. Consider the choice of protel

In the schematic drawing stage, you should consider to in the map phase components encapsulation and solder design decisions. Here are the need to consider when choose according to protel components of some Suggestions.

Remember, encapsulation includes components of welding plate connection and mechanical dimensions (X, Y, and Z), the appearance of the component ontology and the pin connection PCB. When choosing element, the top and the bottom of the need to consider the final PCB possible any restriction on the installation or packaging. Some components (such as polar capacitor) may have high clearance limit, need in component selection process into consideration. At the beginning of the original design, we can draw a basic circuit board frame shape, then put on some of the large or plan to use the location key components (such as connector). So, can directly see quickly (no) of wiring circuit board virtual perspective, and gives relative precise relative positioning of PCB and components and component level. This will help to ensure the PCB after assembly components can be appropriately in the outer packing (plastic products, chassis, machine box, etc.). Calling the 3 d preview mode from the tools menu to browse the whole piece of circuit board.

Low welding plate design shows the PCB welding device of actual welding plate or hole shape. The copper on the PCB design also includes some basic shape information. Need to correct the size of welding plate pattern can ensure that the correct welding, even components and ensure that the correct mechanical and thermal integrity. In the design of PCB layout, how will need to consider the circuit board manufacturing, or is the manual welding, welding plate to weld. Reflow soldering (flux in a controlled high temperature furnace melting) can handle a wide variety of devices (SMD) table. Wave soldering are commonly used to weld the reverse of the circuit board, at a fixed hole device, but can also handle some placed on the PCB on the back of the table element. Usually when using this technique, the underlying table paste device must be arranged according to a certain direction, and in order to adapt to this kind of welding method, may need to modify the welding plate.

Low throughout the design process can change the element of choice. Early in the design process is to determine which devices should use the plating through hole (PTH), which should be with table technology (SMT) will help the overall planning of PCB. Factors to consider are cost, availability, components area density, power consumption and so on. From the manufacturing point of view, table device is usually cheaper than hole device, and general availability is higher. For the prototype of the small and medium-sized projects, had better choose a larger table device or hole device, not only convenient for manual welding, but also to check the wrong in the process of debugging and welding plate and the signal better connection.

If there is no ready-made encapsulate database, usually in the tool to create custom packaging.

2. Use good grounding method

To ensure that the design has enough bypass capacitors and the ground plane. In the use of integrated circuit, make sure to the ground near the power end (preferably ground plane) the location of the appropriate use of decoupling capacitor. Capacitance of appropriate capacity depends on the specific application, technology and operating frequency. When the bypass capacitor is placed between the power and ground pins, and close to the correct IC pins, when putting the electromagnetic compatibility of the circuit can be optimized and susceptibility.

Print a copy of the bill of materials (BOM) used to check the virtual components. Virtual components without access to relevant encapsulation, not transmitted to the map phase. Create a list of materials, and then look at the design of all virtual components. The only entry should be the power and ground signals, because they are considered to be virtual element, only in the schematic diagram environment for special processing, not transmitted to the landscape design. Unless for the purpose of the simulation, in the virtual part of a display element should be used with encapsulation component replacement.

4. Make sure you have the complete material list data

Check whether there is enough material listing report complete data. After creating material listing report, must carry on careful inspection, for all components are incomplete entry device information complete, suppliers or manufacturers.

5. According to component label sorting

Material lists in order to help to sorting and check, ensure the component label are numbered consecutively.

6. Check the redundant gate

In general, all extra gate input should be have signal connection, avoid the input dangling. Make sure you check all the gate extra or missing, and all without attachment of input are fully connected. In some cases, if the input in a suspended state, the whole system can work properly. Take the frequently used in the design of double op-amp. If two op-amp IC components in only one of the op-amp, suggest put another shipment or use, or will not the op-amp input end of the ground, and cloth a suitable unity gain (or other) gain feedback network, to ensure that the device can work normally.

In some cases, the existing suspension pins of the IC may not be able to work within the scope of the indicators. Usually only when IC devices or other door is not working in the same device in a saturated state, input or output near or in the element power rail, the IC is working to meet the requirements of indicators. Simulation can't capture this kind of situation, usually because of simulation model in general will not IC parts together is used for modeling of suspended connection effect.

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