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Advantages of vacuum reflow soldering process

  • Time of issue:2022-06-14 10:28
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Advantages of vacuum reflow soldering process

(Summary description)With the continuous enhancement of the functions of electronic products, the integration of printed circuit boards is getting higher and higher, and the unit power of devices is also increasing, especially in the fields of communications, automobiles, rail transit, photovoltaics, military, aerospace and other fields. There are more and more applications of high-power transistors, RF power supplies, LEDs, IGBTs, MOSFETs and other devices. These components are usually packaged in BGA, QFN, LGA, CSP, TO packages, etc. The common feature is that the device consumes a lot of power. , the heat dissipation performance is high, and the void rate of the heat dissipation pad will directly affect the reliability of the product. Due to the influence of voids, the mechanical strength of the solder joint will decrease, and the thermal resistance will increase and the current path will decrease, which will affect the thermal conductivity and electrical conductivity of the solder joint, thereby reducing the electrical reliability of the device.

  • Time of issue:2022-06-14 10:28
  • Views:
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With the continuous enhancement of the functions of electronic products, the integration of printed circuit boards is getting higher and higher, and the unit power of devices is also increasing, especially in the fields of communications, automobiles, rail transit, photovoltaics, military, aerospace and other fields. There are more and more applications of high-power transistors, RF power supplies, LEDs, IGBTs, MOSFETs and other devices. These components are usually packaged in BGA, QFN, LGA, CSP, TO packages, etc. The common feature is that the device consumes a lot of power. , the heat dissipation performance is high, and the void rate of the heat dissipation pad will directly affect the reliability of the product. Due to the influence of voids, the mechanical strength of the solder joint will decrease, and the thermal resistance will increase and the current path will decrease, which will affect the thermal conductivity and electrical conductivity of the solder joint, thereby reducing the electrical reliability of the device.

In IPC-A-610, IPC7095, IPC7093 and other specifications, the solder joint voids of BGA and BTC packaged devices are described in detail. In other cases, there is no clear standard, which needs to be determined through consultation between the manufacturer and the customer; for the ground pads of high-power devices, users of some high-reliability products often have higher void ratio requirements than the industry standard, which is further reduced to 10%, or even lower.

Therefore, how to reduce voids in the solder joints of such SMT devices is one of the key issues to improve product quality and reliability. There are many solutions in the industry, such as using low voiding solder paste, optimizing PCB pad design, using lattice stencil openings, soldering in nitrogen environment, using solder preforms, and more. But the final effect is not very ideal. For large-area ground pads, it is difficult to stably control the void rate below 10%. After reflow soldering of SMD devices, there are usually some voids left in the solder joints. The larger the area of ​​the solder joints, the larger the area of ​​the voids; the reason is that when the molten solder cools and solidifies, the gas generated in the solder does not Escaped, but was "frozen" down to form a void. There are many factors that affect the generation of voids, which are related to the selection of solder paste, device packaging form, pad design, PCB pad surface treatment method, stencil opening method, and reflow profile settings.

The vacuum reflow soldering process can stably achieve a void ratio below 5%, which is a very effective means to solve the void ratio problem. The vacuum reflow soldering process has a very significant effect on removing solder joint voids. Under vacuum conditions, by setting the process parameters reasonably, mass production with a void ratio below 5% can be stably achieved.

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