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        Tongling Yuanyi Precision Machinery Co., Ltd.
        Address: 129 west Cuihu road 5, Tongling Economic Development   Zone, Anhui Province

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        Material selection of main components in semiconductor package molds
        Release time:2019-05-24 15:46:41 | Browse times:

        The semiconductor package mold is a device for protecting the chip, the gold wire and the lead frame together with a thermosetting epoxy resin. The mold is generally an open and close mold cycle of about 250 seconds, and each cycle is different according to the type of the package product. Tens or even thousands of finished products can be packaged, and a heating device is arranged on the mold to make the mold work at a high temperature of about 180 degrees for a long time, and the pressure at the time of clamping is also different according to the type and quantity of the packaged product. Difference, the general clamping work pressure is between 150 tons and 350 tons. Due to the special working environment of semiconductor components, it is required to have good electrical properties and heat dissipation performance, as well as anti-aging, weldability and pressure resistance. Higher requirements, so lead frame, epoxy resin and other options have greater limitations, and semiconductor packaging mold is a low-temperature hot work, multi-cavity, thermosetting extrusion mold, its structure and material selection needs In the condition of satisfying the relatively narrow condition of the mold, it is necessary to ensure the stability and the certain service life, and the structure is light and convenient to operate. MGP mode and AUTO mode are currently the most widely used package mold structures on the market. This article mainly addresses the material selection and heat treatment of the mold box part.
        1 Working environment and state of semiconductor package mold
        The mold box part is the core part of the mold, where the epoxy resin is softened, flowed, formed, solidified, and the product is demolded. Since the epoxy resin contains filler such as silicon powder, the mold rubs and generates heat during the flow. The surface of the mold is slowly worn and oxidized, especially in the narrow feeding parts such as runners and gates. The wear is particularly serious. At the same time, the mold moves in the manner of clamping the upper and lower molds. To ensure the accuracy of the mold clamping, each mold box is The positioning guide mechanism is designed in four directions to prevent defects such as damage of the die surface caused by misalignment of the upper and lower molds and misalignment of the upper and lower chambers of the product, and the mold is operated under a high pressure of a high temperature of about 180 degrees for a long time. Some parts need to meet the following technical features:
        1.1 Good processing characteristics
        Semiconductor products have strict requirements on appearance. Matte surface products need uniform shape roughness, no abnormal surface protrusions, spots and other phenomena. Smooth products require flat surface and no color difference, so follow the steps of laser marking. In order to make the surface of the product clear, it is not easy to wipe the flowers. Therefore, for the packaging mold, the purity of the steel must be improved and the organization should be uniform. Generally, the smelting method of electroslag remelting steel (ESR) or vacuum arc dissolution method (VAR) is used. Achieved, powder metallurgy can also be achieved, but the cost will increase, generally used on more important inserts.
        1.2 Matrix rigidity and pressure resistance
        The mold works in a high-pressure environment for a long time, which requires a certain rigidity. If the rigidity and the compressive strength are insufficient, the parts may be deformed or even cracked. The molding of the molding part and the gate part is smaller, and the rigidity and toughness are more important. The hardness of the material is required to be above HRC60, and the hardness of the base of the other pressure-bearing parts is required to be above HRC55.
        1.3 wear resistance
        During the work of the mold, the sprue, gate and cavity are continuously in contact with the values of fillers containing silicon powder and glass fiber, which constantly rubs and generates a large amount of heat, which will cause the wear of the runners of the strip to wear, and the draft angle As the size becomes smaller, the size of the gate becomes larger, and the amount of the resin is increased, and the product is not easily demolded, which affects the quality of the product. Therefore, the insert portion must have high wear resistance and superhardness.
        1.4 dimensional stability
        The dimensional tolerance of the core components on the mold is generally within 0.005mm, and the mold does not have to work for 24 hours. When the machine is stopped, the heating device is not heated, the mold will be cooled to room temperature, and it needs to be reheated when it is needed to ensure the mold. The size can not be changed after repeated heating and cooling, and the dimensional of the part should be kept stable during the work process. The minimum required length of the 300,000 mold inner strip is less than 0.02 mm.
        1.5 Good release and corrosion resistance
        Excellent mold release can ensure product quality and production efficiency. The working temperature of the mold is around 180 °C. It is in contact with epoxy resin. The plastic molecules in the inner solution will corrode the parts. The washing and demoulding strips are also set. Strips are corrosive and are generally achieved by the selection of corrosion-resistant materials and surface treatment of the parts.
        2 Influence of chemical composition on the properties of materials
        The properties of materials are determined by the composition of chemical components. Generally, the determination and combination of various alloying elements determine the properties of steel. Although these properties may need to be achieved through heat treatment, they are essentially determined by their composition. The addition of alloying elements is very important to the physical properties, chemical properties and microstructure of the material. For example, the role of carbon is to improve the hardenability of the steel, increase the strength and wear resistance of the steel matrix, but have a certain loss to the toughness of the steel; The effect of chromium can greatly improve the hardenability of steel, increase wear resistance and corrosion resistance. The data show that steel containing more than 12% chromium has good corrosion resistance, and the presence of chromium forms alloy carbide with carbon. Maintaining the stability of the structure restricts the tendency of the steel to grow when the steel is heated at a high temperature, and reduces the superheat sensitivity of the steel, thereby improving the toughness of the steel.
        3 Material selection of parts in different parts of the mold box
        3.1 Material selection of molded strips and gate strips
        The molding strips and gate strips in the mold box are generally selected from powder metallurgy steels with good wear resistance, high hardness and good processing performance, such as ASP23, ASP30, etc. These materials require multiple deep cryogenic treatments in the heat treatment process. High temperature tempering is guaranteed, and after aging at 200 °C for 72h, the front and rear dimensional change value (RCD) is within the range of ±10*10-6. The workpiece needs to be tempered under vacuum, decarburized and oxidized, and multi-stage temperature is not used. Tempering ensures the brightness and surface cleanliness of the material. The deep cooling needs to be carried out under the protection of nitrogen gas to avoid the damage of the appearance of the workpiece due to the water vapor leakage. For the special requirements of the product, the cemented carbide material can be assembled. For example, F20, CD650, etc.
        3.2 Supporting component material selection
        For supporting base parts, such as insert seat, support column, ejector push plate, etc., cold work die steel with quenching hardness HRC57-HRC60 and material thermal expansion coefficient close to the insert is generally selected, such as Cr12Mo1V1, SLD, etc.; Such a part of the backing plate that is often disassembled and moved back and forth, considering the working environment of its rigid friction, SUS440C is generally used. This kind of material is used as a backing plate, and the surface can be used without plating to avoid the thickness change of the chrome layer caused by friction. .
        3.3 Material selection of shaft parts
        The shaft parts in the mold box are divided into two types, one is the pot and the plunger which are involved in the injection molding, the part is the main part that transmits the pressure to the resin, and the surfaces rubbed between the two parts are particularly easy to wear. Therefore, the material selection of the part is generally selected from cemented carbide, such as F10, and the surface and inner wall need to be ground to the mirror surface, or the tool steel M2 with strong toughness after quenching is selected, and the finished surface is processed by nano coating to increase the surface of the friction surface. Hardness and wear resistance, another type of shaft parts are ejector rods and reset rods. The parts are mainly used for the ejection and release of the packaged products, and the number is large. The pressure of a single part is not large, mainly When resetting, it is subject to tensile force and friction between the holes and the movement. Therefore, materials with a hardness of HRC60 after quenching are generally used, such as SKH51. The base material of this kind of material has strong toughness, especially the tail end is partially annealed to reduce shoulder hardness. Avoid pulling off when you roll back.
        3.4 Positioning and guiding parts and materials selection
        The parts that position and guide the upper and lower molds are generally referred to as fine positioning blocks. These parts are important parts that make the mold accurate and ensure that the packaged products are misaligned. They mainly withstand the frictional force of the up and down motion and the shearing force of the lateral direction, and Generally, fine positioning blocks are designed in all four directions. Therefore, such parts are generally selected from powder metallurgy steels with a hardness of HRC68 or higher, such as ASP60, or hard alloys such as CD650 and F10. The surface needs fine grinding or polishing to reduce friction. resistance.

         
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        Tel:+86 13956259526        Tel:+86 13905620906       

        E-mail:sale@yyjgjx.com     
        Address: 129 west Cuihu road 5, Tongling Economic Development Zone, Anhui Province

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