Homepage  >  中文版
Contacts
Tel:86-755-83416111
Fax:86-755-83416961
E-mail:sales@szektech.com
Add: Building 3,No.3,West Area,Shangxue Technology City,Bantian,Longgang District,Shenzhen,China
  • Support
  • PCB heat dissipation techniques
     
    Date :2017-7-14

     

    Electronic equipment work generated heat, so that the internal temperature of the device increased rapidly, if not the timely distribution of the heat, the device will continue to heat up, the device will be due to overheating failure, the reliability of electronic equipment will decline. Therefore, it is very important to heat the circuit board.

     

    First, the circuit board temperature factor analysis

    The direct cause of the temperature rise of the printed circuit board is due to the existence of circuit power devices, electronic devices are varying degrees of power consumption, heat intensity changes with the size of power consumption.
    Print plate in the temperature rise of the two kinds of phenomena:
    (1) local temperature rise or large area temperature rise;
    (2) short temperature or long temperature rise.

    In the analysis of PCB thermal power, the general from the following aspects to analyze.
    Electrical power
    (1) to analyze the power consumption per unit area;
    (2) Analyze the distribution of power consumption on the PCB board.
    2. The structure of the printed circuit board
    (1) the size of the printed circuit board;
    (2) the material of the printed board.
    3. How to install the printed circuit board
    (1) installation (such as vertical installation, horizontal installation);
    (2) the sealing situation and the distance from the shell.
    Heat radiation
    (1) the radiation coefficient of the printed board surface;
    (2) the temperature difference between the printed board and the adjacent surface and their absolute temperature;
    5. Heat conduction
    (1) install the radiator;
    (2) conduction of other mounting structures.
    6. Thermal convection
    (1) natural convection;
    (2) forced cooling convection.

    The analysis of the above factors from the PCB is an effective way to solve the temperature rise of the printed circuit board, often in a product and system of these factors are interrelated and dependent, most factors should be based on the actual situation to analyze, only for a specific The actual situation can be more accurately calculate or estimate the temperature rise and power consumption and other parameters.

     

    Second, the circuit board cooling method
    1, high fever devices plus radiator, thermal plate
    When a small number of devices in the PCB when the heat is relatively large (less than 3), the heat sink can be added to the radiator or heat pipe, when the temperature can not be down, you can use a fan with a fan to enhance the heat effect. When the amount of heat generating device is more (more than 3), a large heat sink (plate) can be used. It is a special radiator customized by the position and height of the heating device on the PCB board or in a large plate radiator On the different elements out of the high and low position. The overall cooling element on the element surface, with each component in contact with the heat. But because of the high and low consistency of components installed welding, cooling effect is not good. Usually in the component surface plus soft thermal phase change thermal pad to improve the cooling effect.
    2, through the PCB board itself heat
    Currently widely used PCB sheet is copper / epoxy glass cloth substrate or phenolic resin glass cloth substrate, there are a small amount of paper-based CCL. Although these substrates have excellent electrical properties and processability, they are poor in heat dissipation and can hardly be expected to heat heat from the PCB itself, but from the surface of the component to the surrounding air. But with the electronic products have entered the miniaturization of components, high-density installation, high fever assembly era, if only the surface area is very small components to heat is not enough. At the same time due to QFP, BGA and other surface-mounted components of the large-scale use of components generated by the heat generated by a large number of PCB board, so the best way to solve heat dissipation is to improve the thermal contact with the heating element PCB itself, Pass out or emit out.
    3, the use of reasonable alignment design to achieve heat
    As the resin in the plate is poor in thermal conductivity, and copper foil lines and holes are hot good conductor, so to improve the copper foil residual rate and increase the thermal hole is the main means of heat dissipation.
    Evaluating the heat dissipation capacity of the PCB requires calculation of the equivalent thermal conductivity (Nine eq) of the composite substrate consisting of a composite material consisting of a variety of materials with different thermal conductivity.
    4, for the use of free convection air cooling equipment, it is best to integrated circuits (or other devices) arranged in a vertical way, or arranged in a horizontal manner.
    5, the same piece of printed circuit board devices should be as far as possible the size of its heat and heat degree of partition arrangement, heat or heat resistance of poor devices (such as small signal transistors, small scale integrated circuits, electrolytic capacitors, etc.) on The most upstream (inlet) of the cooling airflow, heat-generating or heat-resistant devices (such as power transistors, large scale integrated circuits, etc.) are placed downstream of the cooling airflow.
    6, in the horizontal direction, high-power devices as close as possible to the edge of the printed circuit board layout in order to shorten the heat transfer path; in the vertical direction, high-power devices as close as possible to the top of the printed circuit board in order to reduce these devices work on other device temperature Impact.
    7, the temperature sensitive devices are best placed in the lowest temperature areas (such as the bottom of the device), do not put it in the heating device directly above the multiple devices is best in the horizontal plane staggered layout.
    8, the equipment within the printed circuit board cooling mainly rely on air flow, so in the design to study the air flow path, a reasonable configuration device or printed circuit board. Air flow always tends to flow where the resistance is small, so when configuring the device on a printed circuit board, avoid having a larger airspace in a certain area. Machine in the multi-block printed circuit board configuration should also pay attention to the same problem.
    9, to avoid the concentration of hot spots on the PCB, as far as possible the power evenly distributed in the PCB board to maintain the PCB surface temperature performance uniformity and consistency. Often the design process to achieve a strict uniform distribution is more difficult, but must avoid the power density is too high in the area, so as to avoid overheating the normal operation of the entire circuit. If conditions permit, the thermal performance analysis of the printed circuit is necessary, such as some of the professional PCB design software to increase the thermal performance index analysis software module, you can help designers optimize the circuit design.
    10, the highest power consumption and heat the largest device arranged in the vicinity of the best heat dissipation. Do not place higher heaters on the corners of the printed circuit board and the surrounding edges unless a heat sink is arranged near it. In the design of power resistors as much as possible to choose a large number of devices, and adjust the layout of the printed circuit board to have enough room for cooling.
    11, high heat dissipation devices should be connected with the substrate should be able to reduce the thermal resistance between them. In order to better meet the thermal characteristics of the requirements, in the bottom of the chip can use some thermal conductivity materials (such as applying a layer of thermal silica gel), and maintain a certain contact area for the device heat.
    12, the device and the substrate connection:
    (1) to minimize the device lead length;
    (2) When selecting high power devices, consider the thermal conductivity of the lead material, if possible, try to choose the maximum cross-section of the lead;
    (3) select the pin count more devices.
    13, the device package selection:
    (1) in considering the thermal design should pay attention to the device package instructions and its thermal conductivity;
    (2) Consideration should be given to providing a good heat transfer path between the substrate and the device package;
    (3) in the heat conduction path should be avoided with air partition, if this situation can be used to fill the thermal material.

     

  • Tel:86-755-83416111   Fax:86-755-83416961   E-mail:sales@szektech.com   sitemap
  • Copyright 2014 © E-Tech (Shenzhen) Technology Ltd. All Rights Reserved