Semiconductor reflow soldering tray

Abstract

The embodiment of the utility model relates to the technical field of semiconductor processing, and discloses a semiconductor reflow soldering tray. The semiconductor reflow soldering tray comprises a supporting part and a mesh enclosure structure. The supporting part comprises a body, a plurality of hollow parts formed by hollowing on the body, a plurality of structural points consistent with the height of the upper surface of the body, and a connecting bridge for connecting the body and the structural points, and the periphery of each hollow part is used for placing a single lead frame for a reflow soldering process; the mesh enclosure structure covers the front surface of the supporting part and prevents part of hot air in the reflow oven from directly blowing to the front surface of the lead frame. According to the semiconductor reflow soldering tray provided by the embodiment of the invention, the condition that the lead frame cracks after reflow due to overlarge temperature difference and non-uniform heating can be improved, and the quality and reliability of a semiconductor reflow soldering product are improved.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of semiconductor processing technologies, and particularly to a semiconductor reflow soldering tray. Background Art

[0002] Semiconductor reflow soldering is a soldering technology that uses high-temperature molten solder to connect the lead frame and the circuit board solder joints. Its main principle is to control the soldering temperature and time, and under the correct process conditions, melt the solder and form a reliable soldering connection with the metal solder joints on the frame and the circuit board. The specific soldering process includes steps such as substrate pretreatment, solder coating, assembly positioning, reflow soldering furnace heating, and cooling. The reflow soldering tray is a structure used to place the lead frame in the reflow soldering furnace, and the structure of the tray has an important impact on the quality of the reflow soldering products.

[0003] In the chip packaging process, the lead frame using solder paste as an adhesive is sensitive to the temperature in the reflow soldering furnace. Especially for the packaging products using copper sheets for connection, the temperature on the front and back of the product needs to be the same. The existing lead frame reflow tray products are prone to temperature differences between the back and front of the frame during the reflow process. The highest temperature on the front of the frame can reach 360°C, and the back is generally about 10°C lower than the front, resulting in uneven thermal stress of the frame, which is likely to cause cracking of the surface plating layer and even overall cracking of the ultra-thin chip (50um - 100um), affecting the subsequent reliability of the product. And the traditional solid metal support structure is also more likely to cause the accumulation of flux, which cannot be normally improved by the purification system of the reflow furnace; therefore, improving the structure of the semiconductor reflow tray is beneficial to improving the cracking situation after the lead frame reflows and enhancing the quality and reliability of the semiconductor reflow soldering products. Summary of the Utility Model

[0004] The purpose of the embodiments of the present application is to provide a semiconductor reflow soldering tray to improve the cracking situation after reflow of the lead frame caused by excessive temperature difference and uneven heating, and enhance the quality and reliability of the semiconductor reflow soldering products.

[0005] To solve the above technical problems, the embodiments of the present application provide a semiconductor reflow soldering tray, which includes a support part and a mesh structure. The support part includes a body, a plurality of hollow parts formed by hollowing out the body, a plurality of structure points having the same height as the upper surface of the body, and connection bridges connecting the body and the structure points. The periphery of a single hollow part is used to place a single lead frame during the reflow soldering process; the mesh structure covers the front of the support part to block some hot air in the reflow furnace from directly blowing to the front of the lead frame.

[0006] The semiconductor reflow soldering tray provided by the embodiments of the present application forms a plurality of hollow parts by hollowing out the tray body and is provided with a mesh structure above the supporting part. A single lead frame is placed above a single hollow part. In this way, the front of the frame is affected by the mesh structure, avoiding the uneven heating of the products on the tray surface caused by direct hot air blowing. Due to the existence of the hollow part, the temperature on the back of the frame will rise compared with the temperature on the back of the existing solid tray frame, making the temperature on the back and front of the lead frame consistent. Thus, the situation of cracking after reflow caused by excessive temperature difference and uneven heating of the lead frame is improved, and the quality and reliability of semiconductor reflow soldering products are enhanced.

[0007] In some embodiments, the structure point is provided with a hollow hole.

[0008] In some embodiments, the shape of the structure point is circular, and the hollow hole is a circular hole.

[0009] In some embodiments, the mesh structure includes a grid at the top and an outer frame located around the grid.

[0010] In some embodiments, the hollow part is irregular in shape.

[0011] In some embodiments, the proportion of the area of the hollow part occupying the area of the supporting part is between 10% and 90%.

[0012] In some embodiments, the material of the body is aluminum or stainless steel. Description of the Drawings

[0013] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, unless otherwise stated, and the drawings in the figures do not constitute a proportional limitation.

[0014] Figure 1 It is a top view of the supporting part of the semiconductor reflow soldering tray provided by some embodiments of the present application;

[0015] Figure 2 It is a side view of the semiconductor reflow soldering tray provided by some embodiments of the present application;

[0016] Figure 3 It is a three-dimensional schematic diagram of the mesh structure of the semiconductor reflow soldering tray provided by some embodiments of the present application;

[0017] Figure 4 It is a top view of the supporting part of the semiconductor reflow soldering tray provided by some embodiments of the present application when the structure point does not include a hollow hole.

[0018] Explanation of the reference numerals: 11 - supporting part; 111 - main body; 112 - hollow part; 113 - structural point; 114 - connecting bridge; 115 - hollow hole; 12 - mesh cover structure; 121 - grid; 122 - outer frame. DETAILED DESCRIPTION

[0019] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, each embodiment of the present application will be described in detail below in conjunction with the accompanying drawings. However, it will be appreciated by those skilled in the art that in each embodiment of the present application, many technical details are proposed in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical scheme claimed in the present application can also be implemented. The division of the following embodiments is for the convenience of description, and the specific implementation of the present application should not constitute any limitation, and the various embodiments can be combined with each other and referenced to each other without contradiction.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0021] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0022] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0023] Semiconductor reflow soldering is a soldering technology that uses high-temperature molten solder to connect the lead frame and the circuit board solder joints. Its main principle is to control the soldering temperature and time, and under the correct process conditions, melt the solder and form a reliable soldering connection with the metal solder joints on the frame and the circuit board. The specific soldering process includes steps such as substrate pretreatment, solder coating, assembly positioning, heating in the reflow oven, and cooling. The reflow tray is a structure used to place the lead frame in the reflow oven, and the structure of the tray has an important impact on the quality of the reflow soldering products.

[0024] In the chip packaging process, the lead frame using solder paste as an adhesive is sensitive to the temperature in the reflow oven. Especially for packaging products using copper sheets for connection, the temperature on the front and back of the product needs to be the same. The existing lead frame reflow tray products are prone to temperature differences between the back and front of the frame during the reflow process. The highest temperature on the front of the frame can reach 360 °C, and the back is generally about 10 °C lower than the front, resulting in uneven thermal stress of the frame, which is likely to cause cracking of the surface plating layer, and even cause the overall cracking of ultra-thin chips (50um - 100um), affecting the subsequent reliability of the product. And the traditional solid metal support structure is also more likely to cause the accumulation of flux, which cannot be improved by the purification system of the reflow oven normally; therefore, improving the structure of the semiconductor reflow tray is beneficial to improving the cracking situation after the lead frame is reflowed, and enhancing the quality and reliability of semiconductor reflow soldering products.

[0025] To solve the problem of cracking after reflow caused by excessive temperature difference of the existing lead frame, and to improve the quality and reliability of semiconductor reflow soldering products. Some embodiments of this application provide a semiconductor reflow tray. By hollowing out the tray body to form a plurality of hollow parts and setting a mesh structure above the support part, a single lead frame is placed on a single hollow part. In this way, the temperature on the front of the frame is affected by the mesh structure and will decrease, and the temperature on the back of the frame will increase compared with the back of the existing solid tray frame due to the existence of the hollow part, and will be consistent with the front. Thus, it improves the cracking situation after reflow caused by excessive temperature difference and uneven heat absorption of the lead frame, and enhances the quality and reliability of semiconductor reflow soldering products.

[0026] The following combines Figure 1 , Figure 2 , Figure 3 and Figure 4 to illustrate the semiconductor reflow tray provided by some embodiments of this application.

[0027] As Figure 1 , Figure 2As shown in the figure, the semiconductor reflow soldering tray provided by some embodiments of the present application includes a support portion 11 and a mesh structure 12. The support portion 11 includes a main body 111, a plurality of hollow portions 112 formed by hollowing out the main body 111, a plurality of structural points 113 having the same height as the upper surface of the main body 111, and a connection bridge 114 connecting the main body 111 and the structural points 113. The periphery of a single hollow portion 112 is used to place a single lead frame during the reflow soldering process; the mesh structure 12 covers the front of the support portion 11 to block some hot air in the reflow furnace from directly blowing onto the front of the lead frame.

[0028] It should be noted that the main body 111, the structural points 113, and the connection bridge 114 of the support portion 11 are an integral structure with the same upper surface height. They can be made of materials such as metal or high-temperature resistant ceramics by using a mold or 3D printing integrally, or different components can be welded and assembled into a whole. The three together play a role in supporting the lead frame. The structural points 113 are located in the middle position between two hollow portions 112 and can support the middle position of the side of the lead frame, ensuring that a longer frame will not deform under the action of weight due to the existence of the hollow portions 112. The structural points 113 have a certain size, and the left and right sides are respectively used to support adjacent different lead frames. The lead frame is located above the hollow portion 112 and within the mesh structure 12. After placing several lead frames, a mesh structure 12 of an appropriate size is directly clamped in place. After the reflow soldering process is completed, the mesh structure 12 is removed. The mesh structure 12 can be made of materials such as metal or high-temperature resistant ceramics. The periphery of the mesh structure 12 is sealed, and the top has mesh holes in shapes such as circular, rectangular, or square. On the one hand, it blocks some hot air from directly blowing onto the front of the frame to ensure that the frame will not drift in the reflow furnace and ensure the accuracy of the chip position on the frame; on the other hand, it can make the front of the product receive heat more evenly, avoiding the phenomenon of uneven heat caused by direct blowing of the wind as before, and also reducing the heat on part of the front to keep its temperature consistent with the back.

[0029] In addition, the traditional solid metal support structure is also prone to the accumulation of flux, which cannot be improved by the purification system of the reflow furnace. The semiconductor reflow soldering tray provided by some embodiments of the present application has a hollow structure, which is beneficial to the volatilization of the flux into the clean management system of the reflow furnace, thereby ensuring the crack-free of the ultra-thin chip and the stability of the chip surface coating, and enabling the product to perform all its functions for a longer time. When the lead frame is heated by encapsulation hot air reflow (or infrared reflow), the highest temperature on the front of the chip can reach 360°C. The temperature on the front of the chip is consistent with the temperature on the back, and the thermal stress on the front and back of the chip can be kept the same. The warping phenomenon of the whole chip during the reflow process is effectively reduced.

[0030] Some embodiments of the present application provide a semiconductor reflow soldering tray. By hollowing out the tray body 111 to form a plurality of hollow portions 112 and providing a mesh structure 12 above the support portion 11, a single lead frame is placed above a single hollow portion 112. In this way, the temperature on the front of the frame is affected by the mesh structure 12 and will decrease. Due to the existence of the hollow portion 112, the temperature on the back of the frame will increase compared to the temperature on the back of the existing solid tray frame, making the temperature on the back and front of the lead frame consistent. Thereby, it improves the situation of cracking after reflow caused by excessive temperature difference and uneven heating of the lead frame, and enhances the quality and reliability of semiconductor reflow soldering products.

[0031] In some embodiments of the present application, a hollow hole 115 is provided in the structural point 113.

[0032] It should be noted that the structural point 113 has a certain size. Therefore, in order to ensure the consistency of the temperature on the back and front of the lead frame, a hollow hole 115 needs to be provided in the structural point 113 to minimize the influence of the structural point 113 on the temperature difference of the lead frame. Due to the existence of the hollow portion 112 and the hollow hole 115, heat can be better conducted to the back of the lead frame, thus making the temperature on the back of the lead frame consistent with the temperature on the front.

[0033] In some embodiments of the present application, the structural point 113 is circular in shape, and the hollow hole 115 is a circular hole.

[0034] It should be noted that the shape of the structural point 113 can be circular, square, or irregular. The circular shape is the preferred shape, which is convenient to manufacture, has better thermal stability, and has the least impact on the back of the frame. Figure 1 A schematic structural diagram of the support portion 11 is provided in which the structural point 113 has a hollow hole 115 and is a circular hole; Figure 4 A schematic structural diagram of the support portion 11 is provided in which the structural point 113 is circular but solid and has no hollow hole 115.

[0035] In some embodiments of the present application, the mesh structure 12 includes a grid 121 at the top and a frame 122 located around the grid 121.

[0036] Such as Figure 3As shown, the top of the mesh cover structure 12 has a grid 121 structure composed of mesh holes in the shape of a circle, rectangle, square, etc. The middle part of the top of the mesh cover structure 12 is a fine metal mesh, and the periphery is composed of hard metal for shaping. On the one hand, the mesh cover structure 12 can block part of the hot air from directly blowing towards the front of the frame, ensuring that the frame will not be blown and drifted in the reflow oven and ensuring the accuracy of the chip's position on the frame; on the other hand, it can make the front of the product receive heat more evenly, without the phenomenon of uneven heat caused by direct blowing of the wind as before. The outer frame 122 around the grid 121 can be sealed or in a hollow mesh shape, playing a role in supporting and installing. The mesh cover structure 12 is detachably installed above the hollow part 112, and the outer frame 122 is supported on the body 111. The connection method between the mesh cover structure 12 and the support part 11 can be various. For example, the edge of the mesh cover structure 12 can be stuck on the support part 11, or a hinge connection can be used. When the support part 11 places the frame, the hinge can be opened.

[0037] In some embodiments of the present application, the hollow part 112 is in an irregular shape.

[0038] It should be noted that the shape of the hollow part 112 is related to the shape of the lead frame to be welded, and it can be circular, rectangular or irregular. The irregular shape is the preferred shape of the hollow part 112 because the irregular shape can better place the lead frame.

[0039] In some embodiments of the present application, the proportion of the area of the hollow part 112 in the area of the support part 11 is between 10% and 90%.

[0040] It should be noted that the proportion of the area of the hollow part 112 in the area of the support part 11 depends on factors such as the shape, size, welding position of the lead frame, and the hardness of the material, and it is necessary to ensure that the heat can be fully conducted on the back of the lead frame.

[0041] In some embodiments of the present application, the material of the body 111 is aluminum or stainless steel.

[0042] Generally, the body 111, the structural point 113, and the connection bridge 114 are an integrally formed structure made of the same material, and can be cast via a mold at a temperature higher than the melting point of the metal material. The performance of the metal is stable, and it can conduct heat well during the welding process, ensuring the smooth progress of reflow soldering. The most commonly used materials in the industry are aluminum and stainless steel, mainly considering the appropriate specific heat capacity and thermal expansion coefficient. The thermal expansion coefficient of stainless steel is about 16×10^-6 / ℃, while the thermal expansion coefficient of aluminum is about 23×10^-6 / ℃. The specific heat capacity of stainless steel is about 0.5J / g℃, while the specific heat capacity of aluminum is about 0.9J / g℃, meeting the requirements for the material of the body 111.

[0043] In some embodiments of the present application, the mesh cover structure 12 can cover three hollow portions 112.

[0044] It should be noted that after placing a certain number of lead frames above the hollow portion 112, the mesh cover structure 12 is then placed above the hollow portion 112 and covers the lead frames. The mesh cover structure 12 can cover at least three hollow portions 112 at one time. If the mesh cover structure 12 is too small, during use, if a mesh cover structure 12 needs to be placed for each hollow portion 112, it will cause troublesome operations.

[0045] Those of ordinary skill in the art can understand that the above-described embodiments are specific embodiments for implementing the present application, and in actual applications, various changes can be made in form and details without departing from the spirit and scope of the present application.

Claims

1. A semiconductor reflow tray, characterized in that: include: The support part includes a main body, a plurality of hollow parts formed by hollowing out the main body, a plurality of structural points that are highly consistent with the upper surface of the main body, and a connecting bridge connecting the main body and the structural points; The mesh cover structure covers the front of the support portion to reduce the amount of hot air in the reflow oven blowing directly toward the front of the lead frame.

2. The semiconductor reflow tray according to claim 1, characterized in that: The structural points are provided with hollow holes.

3. The semiconductor reflow tray according to claim 2, characterized in that: The structural point is circular in shape, and the hollow hole is a circular hole.

4. The semiconductor reflow tray according to claim 1, characterized in that: The mesh cover structure comprises a grid at the top and an outer frame located around the grid.

5. The semiconductor reflow tray according to claim 1, characterized in that: The hollow portion is irregular in shape.

6. The semiconductor reflow tray according to claim 1, characterized in that: The ratio of the area of ​​the hollow portion to the area of ​​the support portion is between 10% and 90%.

7. The semiconductor reflow tray according to claim 1, characterized in that: The body material is metal aluminum or stainless steel.

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