Avoid the trap of PCB design--to give you a few tricks


? ? ? ? For a Electronic Engineer, PCB design is a basic skill. But even if the ORCAD is perfect, if in the process into a PCB circuit board, does not understand the common problems and challenges, and to take precautions, can still cause a reduction in overall system performance, serious and would not work. In order to avoid design changes, increase efficiency, reduce costs, and so today I will describe most prone to problems one by one.

1, component selection and layout

? ? ? ? Each component specifications are different, even though the same product but different manufacturers may not have the same characteristics, so the choices for components and the design time, need o contact the vendor to understand the characteristics of component, and know that effects of these properties on the design.

? ? ? ? Today, selecting the right memory for electronic product design and it’s a very important thing, as DRAM and Flash memory constantly updated, PCB designers to new memory ont amenable to changing the design’s impact on the market is a very big challenge. DDR3 occupation of 85% per cent of the current DRAM market now, but in 2014, DDR4 are expected to rise from 12% per cent to 56%. Therefore designers must aim tight memory market, maintain close contact with the manufacturer.

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Components overheating burn

? ? ? ? For some large heat capacity components must make the necessary calculations, their layout also requires special consideration, a large number of components together can generate more heat, causing deformation of solder mask layer separation, even igniting the entire board. Design and layout engineer must work together to ensure components suitable layout.

? ? ? ? Layout is the first thing to consider when PCB size. PCB size is too large, the printing of lines long, resistance increases, noise resistance ability drop, cost also increases; too small,?Bad heat and adjacent lines are subject to interference. In determining the PCB size, and then determine the location of specific components. Finally, according to the circuit’s functional units, laying out all the components on the circuit.

2,cooling system

? ? ? ? Thermal system design including cooling and thermal components selected, as well as on cold expansion coefficient taking into account. Current PCB thermal main through PCB board itself, the heat sink, extra heat sink and thermal panels.

? ? ? ? In the traditional PCB design, due to plate with copper-clad glass cloth/epoxy or phenolic glass cloth substrate, and a few paper base copper-clad plates, these materials are good electrical properties and processability, but poor heat conduction performance. Due to the current design of QFP,BGA surface-mount components such as heavy use, solving the heat the best way is to make direct contact with the heating element in PCB’s own cooling capacity, distributed through the PCB board transfer out or going out.

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? ? ? ? When you heat a few devices relatively large PCB can be on the heating device and the heat sink or heat pipe, when the temperature doesn’t drop down, can be used with a fan heatsink. When greater heating devices, and can be a large heat sink and heat sink overall buckles on the component surface, contact with each component and heat dissipation. Specialized computer for video and animation production, even in eater cooling approaches to cooling…

3,Humidity level MSL

? ? ? ? MSL: ?Moisure Sensitive Levels, in moisture-proof packaging label on the outside of the bag comes with instructions, are: 1,2,2A,3,4,5,5A,6. Have specific requirements for moisture or humidity sensor mark on the packaging components must be effectively managed to provide a material storage and manufacturing environments of temperature and humidity control, temperature and humidity sensitive components so as to ensure reliability of performance. When baking, BGA, QFP, MEM, BIOS requirements, such as vacuum packaging improvement, heat-resistant and non-heat-resistant baking components at different temperatures, pay attention to baking time. PCB bake first reference PCB packaging requirements or customer requirements. Roasted PCB at room temperature and humidity sensors should not exceed 12H, finish is not used or is not used at room temperature does not exceed the 12H humidity sensor vacuum packaging or PCB must be kept in the sealed or in a drying oven.

4,Measurability design

PCB will test key technologies including: testability, testability, mechanism design and optimization of measurement and test information processing and fault diagnosis. Testability design of PCB is actually some sort of easy to introduce Testability into the PCB tests, providing access to information inside the object under test testing information channel. Therefore, rational and effective design for testability, Testability mechanisms were successfully raised PCB levels of protection. High product quality and reliability, reduce product life-cycle costs, calls for Testability design techniques to quickly and easily get feedback information for testing, can easily make fault diagnosis based on feedback.PCB design, to ensure that the DFT probe and enter the path to the location of the sensor is not affected, with the miniaturization of electronic products, pitch components getting smaller and smaller, mounting density will grow. To test circuits and fewer nodes, and online testing of printed circuit board assemblies is also growing more difficult, so the design for test of PCB should be fully considered when electrical and physical and mechanical conditions, and use of appropriate machinery and electronic equipment for testing. 




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