PCB部落格 - PCB板散熱設計技巧

1 的重要性 PCB電路板 熱設計
The electrical energy consumed by electronic equipment during operation, 例如射頻功率放大器, FPGA晶片, 和電力產品, 除了有用的工作, 大部分轉化為熱量進行耗散. 電子設備產生的熱量導致內部溫度快速上升. 如果沒有及時散熱, 設備將繼續加熱, 設備將因過熱而發生故障, 電子設備的可靠性會降低. 表面貼裝科技提高了電子設備的安裝密度, 减少有效散熱面積, 而設備的溫昇嚴重影響了可靠性. 因此, 熱設計的研究非常重要. 散熱器的散熱 PCB板 是一個非常重要的環節, 那麼，太陽能電池的散熱科技是什麼 PCB板 電路板, 讓我們一起討論吧. 用於電子設備, 運行期間會產生一定量的熱量, 使設備內部溫度快速上升. 如果沒有及時散熱, 設備將繼續加熱, 設備將因過熱而失效. 電子設備效能的可靠性將降低. 因此, 對電路板進行良好的散熱處理非常重要.

2. 分析 PCB板 temperature rise factors
The direct cause of the temperature rise of the printed board is due to the existence of circuit power consumption devices. 電子設備都有不同程度的功耗, 加熱强度隨耗電量的大小而變化.
Two phenomena of temperature rise in printed boards:
(1) Local temperature rise or large area temperature rise;
(2) Short-term temperature rise or long-term temperature rise. 在分析 PCB板, 一般從以下幾個方面進行分析.
2.1 Electrical power consumption
(1) Analyze the power consumption per unit area;
(2) Analyze the distribution of power consumption on the PCB.
2.2 The structure of the printed board
(1) The size of the printed board;
(2) The 材料 of the printed board.
2.3 How to install the printed board
(1) Installation method (such as vertical installation, horizontal installation);
(2) The sealing condition and the distance from the casing.
2.4 Thermal radiation
(1) The emissivity of the printed board surface;
(2) The temperature difference between the printed board and the adjacent surface and their temperature
2.5 Heat conduction
(1) Install the radiator;
(2) Conduction of other installation structures.
2.6 Thermal convection
(1) Natural convection;
(2) Forced cooling convection.
對上述因素的分析從 PCB板 是解决印製板溫昇的有效途徑. 在產品和系統中，這些因素往往相互關聯和依賴. 大多數因素應根據實際情況進行分析. 可以更準確地計算或估計具體的實際情況參數，如溫昇和功耗.

3. 一些方法 PCB板 thermal design
1. 通過 PCB板 itself
At present, 廣泛使用的 PCB板s為包銅/環氧玻璃布基材或酚醛樹脂玻璃布基材, 使用少量紙基覆銅板. 儘管這些基板具有優异的電力效能和加工效能, 散熱性差. 作為高熱量部件的散熱方法, 幾乎不可能指望PCB樹脂本身的熱量傳導熱量, 而是將部件表面的熱量散發到周圍的空氣中. 然而, 隨著電子產品進入元器件小型化時代, 高密度安裝, 和高熱組件, 僅依靠表面積非常小的部件表面散熱是不够的. 同時, 由於大量使用表面貼裝元件，如QFP和BGA, 部件產生的熱量被傳遞到 PCB板 大量地. 因此, 散熱的解決方案是提高 PCB板 與加熱元件直接接觸, 並通過 PCB板. 出去或送出.
2. High heat-generating components plus radiator and heat conduction plate
When a small number of components in the PCB板 generate a large amount of heat (less than 3), 可以將散熱器或熱管添加到加熱部件中. 當溫度無法降低時, 帶風扇的散熱器可用於增强熱輻射. When the number of heating devices is large (more than 3), a large heat dissipation cover (board) can be used, 這是一種根據加熱裝置在PCB上的位置和高度定制的特殊散熱器，或者是一個大的平面散熱器，切割出不同的組件高度位置. 散熱蓋整體扣在元件表面, 它與每個元件接觸以散熱. 然而, 構件組裝焊接時高度一致性差，散熱效果不好. 通常, 在元件表面添加軟熱相變熱墊，以改善散熱效果.
3. 對於採用自由對流空氣冷卻的設備, the integrated circuits (or other devices) are arranged vertically or horizontally.
4. Use reasonable wiring design to achieve heat dissipation
Because the resin in the plate has poor thermal conductivity, 銅箔線和孔是良好的導熱體, 新增銅箔的剩餘率和新增導熱孔是散熱的主要手段. 評估 PCB板, 有必要計算由具有不同熱導率的各種資料組成的複合材料的等效熱導率 PCB板.
5. 同一印製板上的設備應盡可能根據其熱值和散熱程度進行佈置. Devices with low calorific value or poor heat resistance (such as small signal transistors, 小型集成電路, 電解電容, 等.) should be placed On the upstream (inlet) of the cooling airflow, devices with large heat or heat resistance (such as power transistors, 大規模集成電路, 等.) are placed downstream of the cooling airflow.
6. 在水平方向上, 大功率器件放置在盡可能靠近印製板邊緣的位置，以縮短傳熱路徑； 在垂直方向上, 高功率設備放置在盡可能靠近印製板頂部的位置，以降低其他設備工作時的溫度. 影響.
7. 設備中印制板的散熱主要依靠氣流, 囙此，在設計過程中應研究氣流路徑, 設備或印刷電路板應合理配置. 當空氣流動時, 它總是傾向於在低阻力的地方流動, 囙此，在印刷電路板上配寘設備時, 避免在某個區域內留下較大的空域. 整臺機器中多塊印刷電路板的配寘也應注意同一問題.
8. The temperature-sensitive device is placed in a temperature area (such as the bottom of the device). 切勿將其直接放在加熱裝置上方. 多個裝置佈置在交錯的水平面上.
9. 在散熱位置附近佈置功耗和發熱部件. 不要在印製板的角落和週邊邊緣放置高溫設備, 除非附近有散熱器. 設計功率電阻器時, 盡可能選擇更大的設備, 並在調整印製板佈局時，使其有足够的散熱空間.
10. 射頻功率放大器或LED PCB板 採用金屬基底.
11. 避免熱點集中在 PCB板, 將功率均勻分佈在 PCB板 盡可能多地, 並保持其表面溫度效能 PCB板 統一且一致. 在設計過程中，通常很難實現嚴格的均勻分佈, 但必須避免功率密度過高的區域，以防止熱點影響整個電路的正常運行. 如果可能的話, 有必要分析印刷電路的熱效能. 例如, 新增了熱性能指標分析軟體模塊 PCB板 設計軟體可以幫助設計者優化電路設計.

4. Summary
4.1 Material selection
(1) The temperature rise of the wires of the PCB板 due to the passing current plus the specified ambient temperature should not exceed 125 degree Celsius (commonly used typical value. It may be different depending on the selected board). 因為安裝在印製板上的元件也會散發一些熱量, 這會影響工作溫度, 在選擇資料和印製板設計時，應考慮這些因素, 熱點溫度不應超過125攝氏度. 盡可能選擇較厚的覆銅板.
(2) In special cases, 鋁基, 陶瓷基脆性的, 也可以選擇其他熱阻低的板材.
(3) Adopting multilayer board structure is helpful for PCB板 thermal design.
4.2 Ensure that the heat dissipation channel is unblocked
(1) Make full use of the components arrangement, 銅皮, 窗戶開孔和散熱孔建立合理有效的低熱阻通道，確保熱量順利從窗戶出口 PCB板.
(2) The setting of heat dissipation through holes Design some heat dissipation through holes and blind holes, 有效新增散熱面積，降低熱阻, 並提高電路板的功率密度. 例如, 在LCCC設備的焊盤上設定通孔. 焊料填充在電路生產過程中，以提高導熱性. 電路運行過程中產生的熱量可以通過要耗散的通孔或盲孔快速轉移到金屬散熱層或背面的銅墊上. 在某些特定情况下, 具有散熱層的電路板是專業設計和使用的. 散熱資料通常為銅/鉬和其他資料, 例如某些模組電源上使用的印製板.
(3) The use of thermally conductive 材料 In order to reduce the thermal resistance in the thermal conduction process, 在高功耗器件和基板之間的接觸面上使用導熱資料，以提高導熱效率.
(4) The process method is likely to cause local 高的 temperature in some areas where the device is mounted on both sides. 為了改善散熱條件, 錫膏中可以混合少量的銅, 流動焊接後，設備下方會有一定數量的焊點. high. 裝置和印製板之間的間隙增大, 對流散熱新增.
4.3 Arrangement requirements of components
(1) Perform software thermal analysis on the PCB板, and design and control the internal temperature rise;
(2) It can be considered to specially design and install components with high heat generation and large radiation on a printed circuit board;
(3) The heat capacity of the board is evenly distributed. 小心不要集中放置大功率部件. 如果不可避免, place short components upstream of the airflow and ensure that sufficient cooling air flows through the heat-consumption concentrated area;
(4) Make the heat transfer path as short as possible;
(5) Make the heat transfer cross section as large as possible;
(6) The layout of components should take into account the influence of heat radiation on surrounding parts. Heat sensitive parts and components (including semiconductor devices) should be kept away from heat sources or isolated;
(7) (Liquid medium) Keep the capacitor away from the heat source;
(8) Pay attention to the direction of forced ventilation and natural ventilation;
(9) The additional sub-boards and device air ducts are in the same direction as the ventilation;
(10) As far as possible, make the intake and exhaust have a sufficient distance;
(11) The heating device should be placed above the product as much as possible, and should be placed in the air flow channel when conditions permit;
(12) Components with high heat or high current should not be placed on the corners and peripheral edges of the printed board. 它們應盡可能長地安裝在散熱器上, 並遠離其他部件, and ensure that the heat dissipation channel is unobstructed;
(13) (Small signal amplifier peripheral devices) Try to use devices with small temperature drift;
(14) Use metal chassis or chassis to dissipate heat as much as possible.4.4 Requirements for wiring
(1) Board selection (reasonable design of printed board structure);
(2) Wiring rules;
(3) Plan the channel width according to the current density of the device; pay special attention to the channel wiring at the junction;
(4) The high-current lines should be as surface as possible; if the requirements cannot be met, the use of bus bars can be considered;
(5) To minimize the thermal resistance of the contact surface. 因此, 應擴大導熱面積； 接觸面應平整光滑, and thermally conductive silicone grease can be coated if necessary;
(6) Consider stress balance measures for thermal stress points and thicken the lines;
(7) The heat-dissipating copper skin needs to adopt the window method of heat dissipation stress, and use the heat-dissipating solder mask to open the window properly;
(8) If possible, use large-area copper foil on the surface;
(9) Use larger pads for the ground mounting holes on the printed board to make full use of the mounting bolts and the copper foil on the surface of the printed board for heat dissipation;
(10) Place as many metalized vias as possible, 孔徑和磁片表面應盡可能大, relying on vias to help heat dissipation;
(11) Supplementary means for device heat dissipation;
(12) In the case that the large-area copper foil on the surface can be guaranteed, the method of adding a heat sink may not be used for economic considerations;
(13) Calculate the appropriate heat dissipation copper area of the PCB板 根據設備功耗確定表面, the ambient temperature and the allowable junction temperature (guarantee principle tjâ ¤(0.50.8)tjmax).