A semiconductor power chip mounting process method

Abstract

The present invention discloses a semiconductor power chip mounting process method, which includes processes such as metal lead frame input, conductive metal tin film tape mounting, semiconductor power chip mounting, and metal lead frame output. A thin film strip-shaped conductive metal tin film tape is used to replace traditional conductive epoxy resin, conductive metal tin wire or conductive metal tin paste adhesive, etc., to bond the base island in the metal lead frame to the semiconductor power chip to achieve the purpose of metal bonding.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor chips, and in particular to a semiconductor power chip mounting process method. Background Art

[0002] Traditional semiconductor power chips are mounted on metal lead frames ( Figure 1 The bonding materials used on the base island (schematic diagram of the existing metal lead frame) are mostly conductive epoxy resin, conductive metal tin wire and conductive metal solder paste bonding materials.

[0003] The process technology, process steps, process equipment and production environment required will vary depending on the different bonding materials used, as detailed below.

[0004] (1) Conductive epoxy resin:

[0005] Process steps: metal lead frame input → dotting / writing → chip installation → high temperature baking and curing

[0006] Process equipment: semiconductor chip mounter, high-temperature oxygen-free oven;

[0007] Process environment: no chemical cleaning required, no environmental risks;

[0008] (2) Conductive metal tin wire:

[0009] Process steps: metal lead frame input → high temperature spot coating / writing → chip installation → metal lead frame with chip output;

[0010] Process equipment: high-temperature bonding machine for dispensing / writing and chip mounting;

[0011] Process environment: no chemical cleaning required, no environmental risks;

[0012] (3) Conductive metal solder paste adhesive material:

[0013] Process steps: metal lead frame input → metal solder paste adhesive dispensing / surface printing → chip installation → high temperature reflow soldering sintering → flux cleaning → high temperature drying;

[0014] Process equipment: metal solder paste adhesive printing machine / chip mounting machine / high temperature reflow soldering machine / chemical cleaning machine / drying oven;

[0015] Process environment: During the production process, the metal solder paste adhesive contains flux chemicals. Therefore, after high-temperature reflow soldering and sintering, the flux will float on the metal tin layer and needs to be cleaned and purified with chemicals to reduce the corrosiveness. Therefore, the emission of chemicals after cleaning needs to be considered in the production process environment.

[0016] However, the traditional processes or technologies have the following defects:

[0017] 1. The thermal conductivity of traditional conductive epoxy resin is about 3 watts, which is suitable for chips with power below 3 watts, but is insufficient for higher power semiconductor power chips.

[0018] 2. Traditional conductive epoxy resins are mainly used as adhesives, and the characteristic defect of epoxy resins is that the higher the temperature and the longer the time, the worse the reliability of the product structure, especially for semiconductor power chips above 3 watts.

[0019] 3. Traditional metal tin wire adopts dot painting / writing method ( Figure 2 Schematic diagram of applying tin adhesive material on the base island 101 of the metal lead frame, Figure 3 Schematic diagram of the semiconductor power chip 3 being coated with tin material and pressed thin during chip mounting. Figure 7 Draw a schematic diagram of the tin bonding material pattern for Jidao 101; Figure 8 As shown in the diagram showing the thinning of the tin adhesive during chip mounting, the production process requires high temperatures of approximately 350 degrees Celsius, and the chip installation process reaches as high as 380 degrees Celsius. In addition to the relatively long production time and high electricity costs, this also requires more energy.

[0020] 4. Traditional metal tin wire adopts dot coating / writing method, and often has the phenomenon of wire breakage and separation during the production process (such as Figure 9 (a schematic diagram of the broken lines of the tin material adhesive material written and drawn on the base island 101) will cause the semiconductor power chip 3 to be installed with insufficient metal tin or internal voids (such as Figure 10 (Schematic diagram of internal voids formed by broken wires in the tin bonding material after mounting) This is an uncertain hidden danger in quality control and reliability safety.

[0021] 5. The traditional metal tin wire adopts the method of dotting or writing. The time and temperature of dotting or writing will directly affect the matching of the conductive metal tin bonding material and the size of the semiconductor power chip 3 in the conductive metal tin amount. Excessive tin amount will cause contamination or insufficient tin amount will cause insufficient coverage of the semiconductor power chip 3 ( Figure 4 Schematic diagram of the tin adhesive material overflowing from the base island during the process of the spot-coated tin adhesive material being pressed thin; Figure 5 Schematic diagram of the corner of the semiconductor power chip 3 after the spot-applied tin adhesive material is pressed thin and there is no tin adhesive material; Figure 6 As shown, there is tin bonding material underneath the semiconductor power chip 3, which increases the difficulty of heat conduction and the hidden dangers of reliability and safety.

[0022] 6. The process of writing and drawing on the base island 101 in the metal lead frame using traditional metal tin wire is quite time-consuming. The more times of writing and drawing are accumulated and the larger the semiconductor power chip 3 is, the more time is consumed for writing and drawing, which invisibly increases a lot of production time costs.

[0023] 7. Traditional metal solder paste adhesives contain lightly corrosive flux for cleaning purposes. Its purpose is to use its lightly corrosive properties to remove the oxide layer on the surface of the object to be welded during the production process. After the metal solder paste adhesive is printed and subjected to high-temperature reflow soldering and sintering, the metal solder paste adhesive forms a solidified state of metal bonding. When the conductive metal solder paste adhesive is subjected to high-temperature reflow soldering and sintering, the flux contained in the metal solder paste adhesive will emerge on the surface of the solidified tin material. Because the flux contains lightly corrosive properties, there is a risk of corrosion of the welding points, so chemical cleaning is required. After cleaning, this chemical agent will have an environmental risk of wastewater discharge.

[0024] 8. Traditional metal solder paste adhesives contain slightly corrosive flux. After the semiconductor power chip is installed, it enters high-temperature reflow soldering. Because traditional metal solder paste adhesives contain slightly corrosive flux (especially water-based flux), when performing high-temperature reflow soldering, the metal solder paste adhesive is prone to tin explosion, resulting in tin beads splashing. Because the splashing of tin beads can easily cause contamination or short circuit to places where tin should not stay, it affects the safety of production quality, reduces production efficiency, increases the probability of rework, and increases the hidden dangers of product reliability.

[0025] 9. When the metal tin is unevenly applied, the semiconductor power chip 3 cannot be mounted so that the tin is completely flat, which will cause the semiconductor power chip 3 to tilt ( Figure 11 , as shown in the schematic diagram of the semiconductor power chip 3 being installed tilted, which affects bonding, thermal conductivity, etc. Summary of the Invention

[0026] The purpose of the present invention is to provide a semiconductor power chip mounting process method, which uses a thin film strip-shaped conductive metal tin film tape to replace the traditional conductive conductive epoxy resin, conductive metal tin wire or conductive metal tin paste adhesive material, so as to bond the base island in the metal lead frame and the semiconductor power chip to achieve the purpose of metal bonding.

[0027] In order to solve the above technical problems, the present invention provides the following technical solutions: A semiconductor power chip mounting process method, comprising the following steps: Step S1, metal lead frame input: introducing the metal lead frame including the base island into the tin wire mounting machine; Step S2, conductive metal tin film tape feeding: conductive metal tin film tape feeding: curling the thin film strip-shaped conductive metal tin film tape into a loop and mounting it on the conductive metal tin film tape mounting machine, and transporting a section of the conductive metal tin film tape extending to the corresponding position of the base island to be mounted; Step S3, conductive metal tin film tape mounting: placing the conductive metal tin film tape on the conductive metal tin film tape; The portion corresponding to the base island to be mounted is pressed onto the base island to be mounted, and the portion of the conductive metal tin film tape corresponding to the base island to be mounted is simultaneously fully cut or half-cut; step S4, semiconductor power chip mounting: the semiconductor power chip is mounted on the conductive metal tin film tape on the surface of the metal lead frame, and the mounted semiconductor power chip and the conductive metal tin film tape are fused and cooled and condensed; step S5, metal lead frame output: the metal lead frame with the semiconductor power chip mounted is transported to the metal lead frame storage and transport box for storage through the conductive metal tin film tape mounting machine.

[0028] Furthermore, steps S1 to S5 are repeated to transport the plurality of metal lead frames on which semiconductor power chips have been mounted to a metal lead frame storage and transport box for storage.

[0029] Furthermore, it also includes step S6, a traditional subsequent process: that is, the metal lead frames of each semiconductor power chip that has been mounted in the storage and transportation box are subjected to thermosetting plastic packaging, laser printing, tin layer electroplating, singulation, electrical testing, packaging or warehousing.

[0030] Furthermore, the conductive metal tin film tape loading machine in step S1 includes a tin film tape conveying mechanism and a tin tape pressing and cutting mechanism; the tin film tape conveying mechanism is used to convey the protruding end of the conductive metal tin film tape; the tin tape pressing and cutting mechanism includes a cutter and a pressing block, and the pressing block is used to press the portion of the conductive metal tin film tape corresponding to the base island to be mounted on the base island to be mounted; the cutter is used to fully or half-cut the portion of the conductive metal tin film tape corresponding to the base island to be mounted.

[0031] Furthermore, in step S3, after the portion of the conductive metal tin film tape corresponding to the base island to be mounted is fully cut or half cut, the tin tape pressing and cutting mechanism is pulled up as a whole and separated from the base island position of the metal lead frame.

[0032] Furthermore, in step S4, the semiconductor power chip is completely mounted on the conductive metal tin film tape with the source / gate on the front side of the semiconductor power chip facing upward and the drain on the back side of the power chip facing downward.

[0033] Furthermore, in step S4, the working conditions for fusing the mounted semiconductor power chip with the conductive metal tin film tape and cooling and condensing the chip are to cool down at a high temperature of 330-380 degrees Celsius in a hydrogen-nitrogen mixed gas.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The thermal conductivity of the thin film conductive metal tin film can reach about 50 watts, which is more suitable for the thermal conductivity requirements of semiconductor high-power chips. The smooth thermal conductivity can have a better performance in terms of the service life, power saving and reliability and safety of semiconductor power chips.

[0036] 2. During the installation process of the semiconductor power chip, it is only necessary to attach the metal tin mold tape to the surface of the base island in the metal lead frame, and in the synchronous shearing, mounting and pressing process, the metal tin film with an area that matches the size of the chip is cut off simultaneously. The entire production efficiency is high, which reduces the production cost wasted in many steps and also improves the efficiency and capacity of the production process.

[0037] 3. After the semiconductor power chip is installed, the levelness and height are very stable, which is very beneficial to the safety, quality and production efficiency of the metal wire or metal aluminum ribbon bonding process after the semiconductor power chip is installed; and the thinner the metal tin layer between the base island in the metal lead frame and the semiconductor power chip, the better the levelness and installation position accuracy of the semiconductor power chip after installation.

[0038] 4. The conductive metal tin film tape material is not mixed with any lightly corrosive flux. The semiconductor power chip is installed at a high temperature of 330-380 degrees Celsius in a hydrogen and nitrogen mixed gas, and the metal bonding can be completed by gradually cooling down. There is no need for chemical cleaning and drying processes afterwards. Therefore, the conductive metal tin film tape used in the bonding technology has no environmental risks.

[0039] 5. The conductive metal tin film tape is not mixed with any lightly corrosive flux, and completely avoids the tin explosion phenomenon caused by lightly corrosive flux when entering the high temperature zone of 330-380 degrees Celsius. It also completely avoids the splashing of metal tin beads caused by tin explosion, thereby ensuring that there will be no safety hazards such as pollution, short circuit, rework and reliability caused by the splashing of metal tin beads in the production process. At the same time, it also solves or alleviates and solves the quality and reliability problems of tin bead splashing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0041] Figure 1 is a schematic diagram of an existing metal lead frame;

[0042] Figure 2 This is a schematic diagram of applying tin bonding material on the base island of the metal lead frame;

[0043] Figure 3 This is a schematic diagram of the semiconductor power chip after the tin adhesive material is applied and pressed thinly during chip mounting;

[0044] Figure 4 Schematic diagram of the tin adhesive material overflowing from the base island during the process of the spot-coated tin adhesive material being pressed thin;

[0045] Figure 5 This is a schematic diagram showing that the spot-applied tin adhesive is thinned and there is no tin adhesive at the corner of the semiconductor power chip;

[0046] Figure 6 A schematic diagram showing the entire area below the semiconductor power chip where there is tin bonding material and the size relationship between the base island and the semiconductor power chip;

[0047] Figure 7 Draw a schematic diagram of the tin bonding material pattern for the base island;

[0048] Figure 8 Draw a diagram of the thinning of the tin bonding material during mounting;

[0049] Figure 9 Draw a schematic diagram of the broken lines of the tin bonding material on the base island;

[0050] Figure 10 This is a schematic diagram of the internal voids formed by the broken wires and tin bonding material after mounting;

[0051] Figure 11 A schematic diagram of the tilt installation of semiconductor power chips;

[0052] Figure 12 It is a process flow chart of the present invention;

[0053] Figure 13 This is a schematic diagram of the conductive metal tin film tape mounting of the present invention;

[0054] Figure 14 This is a schematic diagram of a standard installation of a semiconductor power chip without tilting according to the present invention;

[0055] In the figure: 1. Metal lead frame; 101. Base island; 2. Conductive metal tin film tape; 3. Semiconductor power chip; 4. Cutter; 5. Pressing block. DETAILED DESCRIPTION

[0056] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0057] See also Figures 1-14 The present invention provides a technical solution: a semiconductor power chip installation process method, step S1, metal lead frame 1 input, that is, the metal lead frame 1 including the base island 101 is introduced into the tin wire mounting machine, the tin wire mounting machine has its own conveying track, which can be a conveyor belt or a conveyor roller, and the conveying track is used to convey the metal lead frame 1. After the metal lead frame 1 is introduced, the conveying track conveys the metal lead frame 1 to the work station for mounting the conductive metal tin film tape 2.

[0058] like Figure 13 , step S2, the conductive metal tin film tape 2 is fed, that is, the thin film strip-shaped conductive metal tin film tape 2 is rolled into a loop and mounted on a conductive metal tin film tape loading machine, and a section of the conductive metal tin film tape 2 extending out (that is, the portion of the metal tin film extending out from the loop) is transported to a position corresponding to the base island 101 to be mounted (the position to be mounted is used to mount the conductive metal tin film tape 2); in this step, specifically, one end of the conductive metal tin film tape 2 that is separated from the looped portion of the conductive metal tin film tape corresponds to the edgemost side of the position to be mounted on the base island 101 away from the conductive metal tin film tape 2.

[0059] Step S3, the conductive metal tin film tape 2 is mounted, that is, the conductive metal tin film tape 2 corresponding to the portion to be mounted on the base island 101 is pressed onto the portion to be mounted on the base island 101 by the conductive metal tin film tape loading machine, and the portion of the conductive metal tin film tape 2 corresponding to the portion to be mounted on the base island 101 is fully cut or half cut simultaneously; the conductive metal tin film tape loading machine includes a tin film tape conveying mechanism and a tin film pressing and cutting knife 4 mechanism; the tin film tape conveying mechanism is used to convey the portion of the conductive metal tin film tape 2 that extends out of its curled coil, and a conveyor belt or the like can be used; the tin film tape pressing and cutting knife 4 The mechanism includes a cutter 4 and a pressing block 5, and the cutter 4 and the pressing block 5 work synchronously, that is, the cutter 4 and the pressing block 5 descend synchronously during operation; the cutter 4 descends to fully or half-cut the conductive metal tin film strip 2, and the area of ​​the cut part just corresponds to the part to be mounted on the base island 101; the pressing block 5 descends to press the part of the conductive metal tin film strip 2 corresponding to the part to be mounted on the base island 101 (that is, the part cut by the cutter 4) onto the part to be mounted on the base island 101, and the conductive metal tin film strip 2 of the cut part is subjected to gravity through the pressing block 5 and pressed on the base island 101.

[0060] Since the thin film-shaped conductive metal tin film tape 2 has a thermal conductivity of up to approximately 50 watts, it is more suitable for the thermal conductivity requirements of high-power semiconductor chips. Smooth thermal conductivity can have a better performance in terms of the service life, power saving, reliability and safety of the semiconductor power chip 3. Moreover, during the installation process of the semiconductor power chip 3, the conductive metal tin film tape 2 only needs to be attached to the surface of the base island 101 in the metal lead frame 1. During the simultaneous cutting, mounting and pressing process, the conductive metal tin film tape 2 is simultaneously cut off in an area of ​​the size that matches the semiconductor power chip 3. Therefore, the entire production efficiency is very high, which invisibly reduces the production costs wasted in many steps and also improves the efficiency and capacity of the production process.

[0061] Step S4, mounting the semiconductor power chip 3, mounting the semiconductor power chip 3 on the conductive metal tin film tape 2 on the surface of the metal lead frame 1, and allowing the mounted semiconductor power chip 3 to fuse with the conductive metal tin film tape 2 and cool and condense. Specifically, with the source / gate on the front of the semiconductor power chip 3 facing upward and the drain on the back of the power chip facing downward, the semiconductor power chip 3 is completely mounted on top of the conductive metal tin film tape 2. The working conditions for fusing the semiconductor power chip 3 with the conductive metal tin film tape 2 and cooling and condensing are 330-380 degrees Celsius containing a hydrogen-nitrogen mixed gas (hydrogen content is approximately 5%, nitrogen and hydrogen content are both 95%), and the temperature is gradually lowered in multiple sections to achieve the tin film material from melting and synthesis to cooling and solidification. All these stages need to be completed in a tunnel sealed and protected by nitrogen and hydrogen gas.

[0062] The conductive metal tin film strip 2 is in a flat film state, so when the semiconductor power chip 3 is installed, the levelness and height are very stable (ie Figure 14 As shown), it is very beneficial to the safety, quality and production efficiency of the metal wire or metal aluminum tape bonding process after the semiconductor power chip 3 is installed; and the thinner the metal tin layer between the base island 101 in the metal lead frame 1 and the semiconductor power chip 3, the better the levelness of the semiconductor power chip 3 after installation and the better the installation position accuracy.

[0063] The conductive metal tin film strip 2 is free of any lightly corrosive soldering flux, so metal bonding can be completed with the semiconductor power chip 3 by gradually cooling it down at a high temperature of 330-380 degrees Celsius in a hydrogen-nitrogen mixed gas. No chemical cleaning or drying processes are required. Therefore, the use of this thin film-shaped conductive metal tin film strip 2 in bonding technology poses no environmental risks. Furthermore, the conductive metal tin film strip 2 is free of any lightly corrosive soldering flux, completely avoiding the tin explosion phenomenon caused by lightly corrosive soldering flux when it enters the high temperature zone of 330-380 degrees Celsius. This also completely avoids the splashing of metal tin beads caused by tin explosion, thereby ensuring that there are no safety hazards such as pollution, short circuits, rework, and reliability issues caused by metal tin beads splashing during the production process.

[0064] In step S5, the metal lead frame 1 is output, and the metal lead frame 1 on which the semiconductor power chip 3 has been mounted is transported to a metal lead frame storage and transport box for storage through a tin film tape conveying mechanism. Specifically, a special material box can be used in the metal lead frame storage and transport box; and steps S1-S5 are repeated to transport multiple metal lead frames 1 on which the semiconductor power chip 3 has been mounted to a metal lead frame storage and transport box for storage; in this step, since the tin film tape conveying mechanism conveys the metal lead frame 1 on which the semiconductor power chip 3 has been mounted, the half-cut conductive metal tin film tape 2 can be completely separated from the conductive metal tin film tape roll under the output pulling action.

[0065] Step S6, subsequent traditional processes, namely, performing thermosetting plastic encapsulation, laser printing, tin layer electroplating, singulation, electrical testing, packaging or storage on each metal lead frame 1 with the semiconductor power chip 3 mounted in the storage and transportation box.

[0066] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0067] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A semiconductor power chip mounting process method, characterized by: The following steps are involved: Step S1, metal lead frame input: introducing the metal lead frame including the base island into a tin wire bonding machine; Step S2, feeding the conductive metal tin film tape: rolling the thin film-shaped conductive metal tin film tape into a coil and loading it on a conductive metal tin film tape loading machine, and feeding the extended portion of the conductive metal tin film tape to the position corresponding to the base island to be mounted; Step S3, conductive metal tin film tape placement: Pressing the portion of the conductive metal tin film tape corresponding to the portion of the base island to be mounted onto the portion of the base island to be mounted, and simultaneously fully or half-cutting the portion of the conductive metal tin film tape corresponding to the portion of the base island to be mounted; Step S4, semiconductor power chip mounting: Mounting the semiconductor power chip on the conductive metal tin film tape on the surface of the metal lead frame, and allowing the mounted semiconductor power chip and the conductive metal tin film tape to fuse and cool and condense; Step S5, metal lead frame output: The metal lead frame on which the semiconductor power chip has been mounted is transported to a metal lead frame storage and transport box for storage by a conductive metal tin film tape mounting machine; The conductive metal tin film tape is not mixed with any lightly corrosive soldering flux; In step S4, the semiconductor power chip is mounted on the conductive metal tin film tape for fusion and cooling and condensation under the working conditions of cooling at a high temperature of 330-380 degrees Celsius in a hydrogen-nitrogen mixed gas.

2. The semiconductor power chip mounting process according to claim 1, wherein: Repeat steps S1-S5 to transport the plurality of metal lead frames on which semiconductor power chips have been mounted to the metal lead frame storage and transportation box for storage.

3. The semiconductor power chip mounting process according to claim 1, wherein: It also includes step S6, a traditional subsequent process: That is, the process of thermosetting plastic packaging, laser printing, tin layer electroplating, singulation, electrical testing, packaging or warehousing of the metal lead frames with completed semiconductor power chips stored in the storage and transportation boxes.

4. The semiconductor power chip mounting process according to claim 1, wherein: The conductive metal tin film tape loading machine in step S1 includes a tin film tape conveying mechanism and a tin tape pressing and cutting mechanism; The tin film strip conveying mechanism is used to convey the protruding end of the conductive metal tin film strip; The tin ribbon pressing and cutting mechanism includes a cutter and a pressing block. The pressing block is used to press the portion of the conductive metal tin film tape corresponding to the portion of the base island to be mounted onto the portion of the base island to be mounted; The cutter is used to fully or half-cut the portion of the conductive metal tin film tape corresponding to the base island to be mounted.

5. The semiconductor power chip mounting process according to claim 4, characterized in that: In step S3, after the portion of the conductive metal tin film tape corresponding to the base island to be mounted is fully cut or half cut, the tin tape pressing and cutting mechanism is pulled up as a whole and separated from the base island position of the metal lead frame.

6. The semiconductor power chip mounting process according to claim 1, wherein: In step S4, the semiconductor power chip is completely mounted on the conductive metal tin film tape with the source / gate on the front side of the semiconductor power chip facing upward and the drain on the back side of the power chip facing downward.

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