A reflow fixture structure for large power modules

Abstract

The invention discloses a reflow fixture structure for a large power module, which is used for clamping the power module during reflow soldering. The structure mainly comprises a matching printed patch carrier, a reflow base, an insulating substrate fixing frame and a terminal cover plate. The printed patch carrier is used for solder printing and chip mounting on insulating substrates of different sizes and types; the reflow base is used for placing the power module so as to facilitate solder flux printing and solder sheet placement on the substrate of the power module; the insulating substrate fixing frame is placed on the substrate of the power module and fixedly connected to the substrate through substrate positioning columns so as to place the printed and mounted insulating substrate on the substrate in the insulating substrate fixing frame according to the design drawing; the terminal cover plate is installed on the substrate of the power module and an insulating substrate isolation pin is inserted into the terminal cover plate to prevent the insulating substrate from shifting. After placement, the power module and the corresponding fixture are put into a reflow furnace for reflow soldering.

Description

Technical Field

[0001] The invention relates to the field of power electronics, and in particular to a reflow fixture structure of a large power module. Background Art

[0002] Most traditional power modules use a two-step reflow method, with separate reflow from chip to DBC and DBC to substrate. The reflow fixture design is relatively simple, and only the soldering process of a single solder needs to be considered. It is not suitable for reflow soldering of large power modules. Using an integrated DBC fixing frame will cause abnormal conditions such as DBC corner missing when the fixture is removed after reflow. The bottom of traditional power modules is generally a flat design, which is in direct and complete contact with the bottom surface of the reflow oven. When the bottom of a large module is designed with a more complex protruding structure, it cannot be placed directly on the flat bottom surface of the reflow oven for reflow. Due to the lack of complete contact, the heat conduction is greatly affected and the soldering process cannot be completed. There are many types and quantities of DBC designs for large power modules, and they are easy to shift during reflow. If the distance between DBCs is too close or the displacement is too much, it will affect the module performance and the subsequent process steps. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a reflow fixture structure for a large power module which has a simple structure and can effectively simplify the reflow soldering process in view of the above-mentioned defects of the prior art.

[0004] The objective of the present invention is achieved through the following technical scheme: a reflow fixture structure for a large power module, which is used for clamping the power module during reflow soldering, and mainly includes a matching printed patch carrier, a reflow base, an insulating substrate fixing frame and a terminal cover plate. The printed patch carrier is used for solder printing and chip mounting on insulating substrates of different sizes and types; the reflow base is used to place the power module to facilitate flux printing and solder sheet placement on the substrate of the power module; the insulating substrate fixing frame is placed on the substrate of the power module and fixedly connected to the substrate through substrate positioning columns to place the printed and mounted insulating substrate on the substrate in the insulating substrate fixing frame according to the design drawing; the terminal cover plate is installed on the substrate of the power module and an insulating substrate isolation pin is inserted into the terminal cover plate to prevent the insulating substrate from shifting. After placement is completed, the power module and the corresponding fixture are put into a reflow furnace for reflow soldering.

[0005] Furthermore, the upper surface of the printed patch carrier is provided with a plurality of recessed grooves matching the shape and size of the insulating substrate, and a plurality of small holes are evenly penetrated in the recessed grooves. The lower surface of the printed patch carrier is provided with a vacuum cavity and a vacuum system is arranged through the vacuum cavity to adsorb the insulating substrate.

[0006] Furthermore, the terminal cover plate mainly includes an upper cover plate and a lower cover plate which are arranged in sequence, and a plurality of cover plate sleeves are arranged between the upper cover plate and the lower cover plate and are fastened and connected through substrate positioning columns and nuts; the terminal cover plate is plugged into the substrate of the power module through the substrate positioning columns, and a plurality of small circular holes for plugging in insulating substrate isolation pins and PIN pins are arranged on the terminal cover plate.

[0007] Furthermore, the shape of the reflow base matches the shape of the back of the power module; the size of the insulating substrate fixing frame is calculated according to the margin value of the thermal expansion coefficient of the substrate and is made into a left and right split type to prevent the insulating substrate from being chipped during or after reflow when the insulating substrate fixing frame is disassembled.

[0008] Furthermore, the upper surface of the printed patch carrier is anodized or colored, and a clamping groove is provided between two adjacent recessed grooves on the printed patch carrier to facilitate clamping of the insulating substrate; and a reinforcing rib structure is provided on the lower surface of the printed patch carrier.

[0009] Furthermore, the substrate positioning column is composed of a slender cylinder and a column seat integrally arranged on the slender cylinder, and the diameter of the slender cylinder is consistent with the diameter of the positioning hole on the substrate.

[0010] Furthermore, the insulating substrate isolation needle is composed of a slender cylinder and a flat cylinder above, a sharp corner is arranged below the slender cylinder and is inserted into the gap between two adjacent insulating substrates on the substrate through the sharp corner.

[0011] The beneficial technical effect of the present invention is that: the present invention is mainly composed of a matching printed patch carrier, a reflow base, an insulating substrate fixing frame and a terminal cover. The printed patch carrier suitable for various insulating substrate sizes can be designed according to actual needs, so that solder can be printed on multiple insulating substrate styles on the module on the same carrier at the same time. The welding time and welding cost are effectively shortened; the reflow base, the insulating substrate fixing frame and the terminal cover can realize the one-step reflow from chip to insulating substrate and insulating substrate to substrate. The insulating substrates are positioned by isolation pins. After reflow, the removal of the fixture is not easy to cause abnormalities such as missing corners of the insulating substrate ceramic, and it also solves the problem that various protruding designs at the bottom of the substrate cannot be directly reflowed on the plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of the structure of the power module of the present invention;

[0013] Figure 2 It is a schematic diagram of the front structure of the printed patch carrier of the present invention;

[0014] Figure 3 It is a schematic diagram of the back structure of the printed patch carrier of the present invention;

[0015] Figure 4 It is a structural schematic diagram of the reflux base of the present invention;

[0016] Figure 5 It is a structural schematic diagram of the insulating substrate fixing frame of the present invention;

[0017] Figure 6 This is a schematic diagram of the structure of the terminal cover plate of the present invention;

[0018] Figure 7 A schematic diagram of placing an insulating substrate on a printed patch carrier;

[0019] Figure 8 This is a schematic diagram of the structure of the fixture after assembly. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to more clearly understand the objectives, technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0021] In the description of the present invention, it is necessary to understand that the orientation or position relationship indicated by the terms such as "up", "down", "left", "right", "inside", "outside", "horizontal" and "vertical" is based on the orientation or position relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or original referred to must have a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0022] like Figure 1-8 As shown, a reflow fixture structure of a large power module described in the present invention is used for clamping a power module 1 during reflow soldering, and mainly includes a matching printed patch carrier 2, a reflow base 3, an insulating substrate fixing frame 4 and a terminal cover 5. The printed patch carrier 2 is used for solder printing and chip mounting on insulating substrates 7 of different sizes and types; the reflow base 3 is used to place the power module 1 so as to facilitate flux printing and solder sheet placement on the substrate 11 of the power module 1; the insulating substrate fixing frame 4 is placed on the substrate 11 of the power module 1 and is fixedly connected to the substrate 11 through a substrate positioning column 51 to place the printed and mounted insulating substrate 7 on the substrate 11 in the insulating substrate fixing frame 4 according to the design drawing; the terminal cover 5 is installed on the substrate 11 of the power module 1 and an insulating substrate isolation pin 6 is inserted into the terminal cover 5 to prevent the insulating substrate 7 from shifting. After placement is completed, the power module 1 and the corresponding fixture are put into the reflow furnace together for reflow soldering.

[0023] Reference Figure 2-3As shown, the upper surface of the printed patch carrier 2 is provided with a plurality of recessed grooves 21 matching the shape and size of the insulating substrate 7, and a plurality of small holes 22 are evenly penetrated in the recessed grooves 21. The lower surface of the printed patch carrier 2 is provided with a vacuum cavity 23 and a vacuum system is arranged through the vacuum cavity 23 to adsorb the insulating substrate 7. When in use, a variety of printed patch carriers 2 suitable for different sizes of insulating substrates 7 can be designed according to processing requirements, so that solder can be printed on a variety of insulating substrate styles on the module on one carrier at the same time.

[0024] The upper surface of the printed patch carrier 2 is anodized or colored to avoid strong reflections interfering with the sensor, thereby affecting the recognition effect, and a clamping groove 24 is provided between two adjacent recessed grooves 21 to facilitate clamping of the insulating substrate 7; the lower surface of the printed patch carrier 2 is provided with a reinforcing rib structure, so that the carrier can ensure sufficient vacuum when vacuuming, and can keep the overall flatness of the carrier and not easy to deform.

[0025] Reference Figure 4-5 As shown, the shape of the reflow base 3 matches the shape of the back of the power module 1; the size of the insulating substrate fixing frame 4 is calculated according to the margin value of the thermal expansion coefficient of the substrate 11 and is made into a left and right split type to prevent inaccurate limiting due to different thermal expansion coefficients or the insulating substrate from being missing corners when the insulating substrate fixing frame 4 is disassembled during and after reflow.

[0026] Reference Figure 6 As shown, the terminal cover plate 5 mainly includes an upper cover plate 52 and a lower cover plate 53 arranged in sequence, and a plurality of cover plate sleeves 54 are arranged between the upper cover plate 52 and the lower cover plate 53 and are fastened and connected by substrate positioning columns 51 and nuts 55; the terminal cover plate 5 is plugged into the substrate 11 of the power module 1 through the substrate positioning columns 51, and the terminal cover plate 5 is provided with a plurality of small round holes 56 for plugging the insulating substrate isolation pins 6 and the PIN pins. The terminal cover plate is designed with a plurality of openings, which correspond to the substrate positioning columns 51, the insulating substrate isolation pins 6 and the PIN pins respectively. The opening position of the substrate positioning columns 51 on the terminal cover plate 5 should be consistent with the position of the substrate positioning holes, and the opening position of the insulating substrate isolation pins 6 should be consistent with the gap position of the corresponding adjacent insulating substrates; the opening position of the PIN pin on the terminal cover plate 5 is consistent with the position of the PIN pin on the insulating substrate, which is used to insert the PIN pin before reflow.

[0027] Reference Figure 6-8As shown, the substrate positioning column 51 is composed of a slender cylinder and a column seat integrally arranged on the slender cylinder, and the diameter of the slender cylinder is consistent with the diameter of the positioning hole on the substrate, and the positioning column is just inserted therein, and a matching gap is designed. The diameter of the opening on the terminal cover plate 5 and the insulating substrate fixing frame 4 is consistent with the diameter of the substrate positioning column, and a matching gap is designed. The height of the larger diameter cylinder on the substrate positioning column 51 is determined according to the height of the PIN pin on the module. After assembly, the closer the lower terminal cover plate is to the PIN pin base, the better the limiting effect can be achieved.

[0028] The insulating substrate isolation pin 6 is composed of a slender cylinder and a flat cylinder above. A sharp corner is set below the slender cylinder and inserted into the gap between two adjacent insulating substrates on the substrate through the sharp corner. The cover sleeve 54 is a cylindrical structure. The inner diameter of the cover sleeve 54 is consistent with the diameter of the substrate positioning column. The substrate positioning column 51 is just inserted into it, and a matching gap is designed. The height of the cover sleeve 54 determines the height of the upper position of the terminal cover to limit the PIN pin, which needs to be determined according to the height of the PIN pin.

[0029] Reference Figure 7 As shown, there are six different insulating substrates 7, abcdef, on the front of the power module. The insulating substrates 7 are processed as follows on the printed patch carrier 2: Figure 7 The arrangement shown has the same quantity ratio of different types. The insulating substrates 7 are placed on the printed patch carrier according to different sizes and directions. After all are placed, the vacuum system on the back of the fixture will adsorb the insulating substrate 7 on the printed patch carrier 2 during printing, so that the fixed position will not shift, and solder printing and chip mounting are performed on the upper surface of the insulating substrate.

[0030] There are protrusions on the back of the power module, such as Figure 4 As shown in the figure, the design of the reflow base should match the protruding part on the back of the module, so that the bottom surface is flat after matching, which is conducive to heat transfer when the reflow oven heats the bottom plate. Figure 8As shown, the power module 1 is placed on the reflow base 3. After matching, the flux is printed and the solder piece is placed on the upper surface of the substrate 11, and then the insulating substrate fixing frame 4 is placed. The insulating substrate fixing frame 4 is fixedly connected to the substrate 11 through the substrate positioning column 51. The printed and patched insulating substrate 7 is placed in the insulating substrate fixing frame 4 according to the design drawing. Then the terminal cover 5 is assembled and placed on the module, and the substrate positioning column 51 is inserted into the substrate opening g. After the position is fixed, the insulating substrate isolation needle 6 is inserted into the corresponding opening on the terminal cover 5, and the lower end of the insulating substrate isolation needle 6 is inserted into the gap between the insulating substrates to isolate the adjacent insulating substrates and prevent the insulating substrates from shifting. After the placement is completed, the module and the carrier are placed in the reflow furnace for reflow soldering. The melting temperature of the solder under the chip is slightly lower than the melting temperature of the solder under the insulating substrate. Because the reflow furnace transfers heat through contact, the heat transferred to the upper layer is relatively small, so that the upper and lower layers of solder can be melted in the same reflow process, achieving the effect of one-step soldering.

[0031] After the chip, insulating substrate and substrate are reflow soldered, they are bonded as a whole. After the overall bonding is completed, PIN pin welding is carried out. When welding the PIN pin, after the solder paste is applied to the terminal welding position on the insulating substrate, the insulating substrate fixing frame needs to be pre-installed on the terminal cover through the substrate positioning column, and then the module is turned upside down and buckled on the terminal cover along the substrate positioning column, and then flipped 180°, the terminal cover is placed upwards, and after the insulating substrate isolation pin is inserted, it can be reflowed after inspection.

[0032] The present invention is mainly composed of a matching printed patch carrier, a reflow base, an insulating substrate fixing frame and a terminal cover. The printed patch carrier suitable for various insulating substrate sizes can be designed according to actual needs, so that multiple insulating substrate styles on the module can be printed with solder on the same carrier at the same time. The welding time and welding cost are effectively shortened; the reflow base, the insulating substrate fixing frame and the terminal cover can realize the one-step reflow from chip to insulating substrate and insulating substrate to substrate. The insulating substrates are positioned by isolation pins. After reflow, the removal of the fixture is not likely to cause abnormalities such as missing corners of the insulating substrate ceramic, and it also solves the problem that various protruding designs at the bottom of the substrate cannot be directly reflowed on the plane.

[0033] The specific embodiments described herein are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A reflow fixture structure for a large power module, used for clamping the power module during reflow soldering, characterized in that: The invention comprises a matching printed patch carrier, a reflow base, an insulating substrate fixing frame and a terminal cover plate. The printed patch carrier is used for solder printing and chip mounting on insulating substrates of different sizes and types; the reflow base is used for placing a power module so as to facilitate solder flux printing and solder sheet placement on the substrate of the power module; the insulating substrate fixing frame is placed on the substrate of the power module and fixedly connected to the substrate through a substrate positioning column so as to place the printed patch insulating substrate on the substrate in the insulating substrate fixing frame according to the design drawing; the terminal cover plate is installed on the substrate of the power module and an insulating substrate isolation pin is inserted into the terminal cover plate to prevent the insulating substrate from shifting. After placement, the power module is placed Put it into a reflow furnace together with the corresponding fixture for reflow soldering; the upper surface of the printed patch carrier is provided with a plurality of recessed grooves matching the shape and size of the insulating substrate, and a plurality of small holes are evenly pierced in the recessed grooves; the lower surface of the printed patch carrier is provided with a vacuum cavity and a vacuum system is arranged through the vacuum cavity to adsorb the insulating substrate; the terminal cover plate comprises an upper cover plate and a lower cover plate arranged in sequence, a plurality of cover plate sleeves are arranged between the upper cover plate and the lower cover plate, and are fastened and connected through substrate positioning columns and nuts; the terminal cover plate is plugged into the substrate of the power module through the substrate positioning columns, and a plurality of small circular holes for plugging in insulating substrate isolation pins and PIN pins are provided on the terminal cover plate.

2. The reflow fixture structure for a large power module according to claim 1, characterized in that: The shape of the reflow base matches the shape of the back of the power module; the size of the insulating substrate fixing frame is calculated according to the thermal expansion coefficient of the substrate and is made into a left and right split type to prevent the insulating substrate from being chipped when the insulating substrate fixing frame is disassembled during or after reflow.

3. The reflow fixture structure for a large power module according to claim 1 or 2, characterized in that: The upper surface of the printed patch carrier is anodized or colored, and a clamping groove for facilitating clamping of the insulating substrate is provided between two adjacent recessed grooves on the printed patch carrier; The lower surface of the printed patch carrier is provided with a reinforcing rib structure.

4. The reflow fixture structure for a large power module according to claim 3, characterized in that: The substrate positioning column is composed of a slender cylinder and a column seat integrally arranged on the slender cylinder, and the diameter of the slender cylinder is consistent with the diameter of the positioning hole on the substrate.

5. The reflow fixture structure for a large power module according to claim 4, characterized in that: The insulating substrate isolation needle consists of a slender cylinder and a flat cylinder above. A sharp corner is arranged below the slender cylinder and is inserted into the gap between two adjacent insulating substrates on the substrate through the sharp corner.

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