Double-sided heat dissipation Clip chip and grinding process for grinding surface of Clip chip

Abstract

The invention relates to a double-sided heat dissipation Clip chip and a grinding process for grinding the surface of the Clip chip, the chip is arranged in the middle of a lead frame, a copper sheet body is fixed at the upper parts of the lead frame and the chip through a plastic package colloid, the copper sheet body comprises a body layer and a mounting layer at the lower part of the body layer, and the mounting layer is provided with steps along the periphery of the body layer. The mounting step is added on the product design, so that the grinding machine can be more suitable for grinding, and grinding standards and limiting are provided. In the grinding process, the workbench rotates at a certain speed, the grinding wheel on the upper side rotates at a certain speed and grinds from top to bottom, meanwhile, a two-fluid process is adopted for washing, copper cuttings generated in the grinding process can be discharged in time, and a product cannot be affected. And compared with laser grinding, the precision of the grinding mode is higher.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a double-sided heat dissipation Clip chip and its surface grinding process. Background Technology

[0002] MOSFETs are characterized by low control power and fast switching speed, and are widely used in low, medium and high voltage circuits. They are fundamental power semiconductor devices, and silicon-based MOSFETs are indispensable in today's emerging new energy electric vehicles. MOSFETs are also core components in automotive electronics, used in chips for transmission controllers in automotive engines and drive systems.

[0003] Due to their inherent properties and operating environment, power devices are subject to a combination of electric fields, stress, and heat within their packaged components. Heat dissipation is a crucial characteristic that must be considered when using power devices. From a heat dissipation perspective, package design should adhere to the principles of low thermal resistance in heat dissipation paths, maximizing heat dissipation paths, and maximizing contact area.

[0004] Grinding is a common heat dissipation solution in existing technologies. The most common grinding methods are lapping and laser ablation. However, grinding requires contact with both the molding compound and the copper sheet. Due to the high ductility of copper, traditional grinding processes cannot effectively remove the copper chips, resulting in abnormal copper chip quality. Figure 1 The edge shown has a lot of excessive wear.

[0005] Therefore, the existing technology mainly uses laser ablation for grinding. The high temperature of the laser (locally reaching over 800°C) causes the organic resin in the EMC to pyrolyze and carbonize, forming microcracks that lead to moisture penetration paths and reduce product life (such as a decrease in MSL grade).

[0006] Delamination risk: The thermal expansion coefficient (CTE) of EMC and copper frame differs greatly (EMC: 8-20ppm / C, Cu: 17ppm / C), and local heating exacerbates interface delamination.

[0007] Bottlenecks in machining accuracy and efficiency 1. Material inhomogeneity leads to fluctuations in accuracy. EMC contains 30%–80% irregular silica filler (particle size 1–50 μm). When the laser encounters high-hardness SiO2, non-uniform reflection / scattering occurs, resulting in burrs (Ra>5 μm) at the cutting edge, which are far greater than those caused by mechanical grinding (Ra<1 μm).

[0008] Differences in the orientation of copper framework grains make laser absorption rate unstable (fluctuating between 10% and 40%), and the consistency of cutting depth is difficult to control (±25um error). Summary of the Invention

[0009] To address the aforementioned problems, the purpose of this invention is to provide a grinding process for grinding the surface of power heat dissipation devices, which can effectively grind and groove the product surface, promptly remove copper chips, and achieve higher processing precision.

[0010] To solve the above-mentioned technical problems, the first technical solution adopted by the present invention is as follows: A double-sided heat dissipation Clip chip, comprising a lead frame, a chip, and a copper sheet body, wherein the chip is mounted in the middle of the lead frame, and the copper sheet body is fixed to the upper part of the lead frame and the chip by a plastic encapsulant. The copper sheet body includes a body layer and a mounting layer below it. The mounting layer has a first thickened portion and a second thickened portion at both ends, respectively. The first thickened portion is connected to the lead frame. The first pin at one end of the frame is connected to the chip, the second thickened part is connected to the chip, the second pin at the other end of the lead frame is integrated with the chip, the second thickened part of the copper sheet body has an extension section, and the mounting layer has a step along the outer periphery of the body layer.

[0011] In the above technical solution, the height of the installation step is 0.2mm.

[0012] In the above technical solution, the thickness of the first thickened portion of the copper sheet body is 0.36 mm, and the thickness of the second thickened portion of the copper sheet body is 0.46 mm.

[0013] To solve the above-mentioned technical problems, the second technical solution adopted by the present invention is as follows: a grinding process for surface grinding of power heat dissipation device products, used to process the above-mentioned double-sided heat dissipation Clip chip, the specific steps of which are as follows: S1 attaches the UV film onto the substrate; S2 vacuum-adheres the substrate onto the table surface of the grinding device; The S3 equipment starts up, the worktable rotates, and it grinds the molding compound and clips on the product surface. While grinding, use clean water to rinse the product surface to wash away the debris and copper shavings that fall off during the grinding process; The S4 grinding process consists of two steps: coarse grinding of the product. S5 involves multiple fine grinding processes on the product; S6 is idling away from the product until grinding is complete; In the above technical solution, after the product is ground, it needs to be electroplated and cut. This product provides heat dissipation channels on the front and back sides. When the product has a thermal reaction in the circuit, it can effectively dissipate the heat in time and prevent the product from burning out due to thermal stress, which could cause the circuit board to fail.

[0014] In the above technical solution, the processing steps for the power heat dissipation device product are as follows: S'1 zone; S'2 welding and mounting of the wafers followed by AOI; S'3S area solder paste application clip installation; S'4 vacuum furnace welding; S'5 solvent cleaning and Plasma cleaning; S'6G area wire bonding and AOI; S'7Plasma cleaning; S'8 molding and curing; S'9 surface treatment (grinding); S'10 electroplating and molding.

[0015] In the above technical solution, the grinding device is a wafer thinning machine.

[0016] In the above technical solution, the grinding process is as follows: The grinding wheel moves at high speed before contacting the substrate. F0: Rotate at a constant speed of 120um / min at a height of 30um from the substrate; F1: Initial coarse grinding, grinding thickness set to 940um, i.e. grinding depth 110um, speed 30um / min slow grinding; F2: Secondary fine grinding reduces the size by 5µm, slow grinding at a speed of 21µm / min; F3: Three fine grinding cycles followed by a 5µm reduction in speed, slow grinding at 9µm / min; After grinding is complete, the grinding wheel should not be removed from the product surface immediately to avoid bringing copper shavings into the product. F4: S-out: Idle time 50s.

[0017] In summary, the advantages of using the technical solution of this invention compared to traditional technical means are as follows: The present invention incorporates an installation step in the product design, which makes it more adaptable to grinding and provides grinding standards and limits.

[0018] In the grinding process of this invention, the worktable rotates at a certain speed, and the upper grinding wheel rotates at a certain speed, grinding from top to bottom. Simultaneously, a two-fluid process is used for flushing, which promptly removes the copper shavings generated during grinding, without affecting the product itself. Moreover, compared to laser grinding, this grinding method offers higher precision. Attached Figure Description

[0019] The foregoing and other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0020] Figure 1This is a metallographic structure diagram of chip edge wear in the prior art; Figure 2 This is a three-dimensional structural diagram of the Clip chip in this invention; Figure 3 for Figure 2 A top-down view; Figure 4 for Figure 2 A diagram showing the view from below; Figure 5 A three-dimensional structural diagram of the present invention with the plastic sealant removed; Figure 6 for Figure 5 A top-down view; Figure 7 This is a three-dimensional structural diagram of the copper sheet body in this invention; Figure 8 This is a flow chart of the grinding process in this invention; Figure 9 For the grinding process table; Figure 10 This is a schematic diagram of the middle position of the frame in the existing technology; Figure 11 This is a schematic diagram of the middle position of the frame after leveling in this invention; Figure 12 A schematic diagram showing the Clip chip placed in a flattening frame; The following labels are used: 100, lead frame; 110, first pin; 120, second pin; 200, chip; 300, copper sheet body; 310, body layer; 320, mounting layer; 321, first thickened portion; 322, second thickened portion; 323, mounting step; 322, second thickened portion; 330, extension section; 400, encapsulant. Detailed Implementation

[0021] The following description is based on preferred embodiments of the present invention. Those skilled in the art can make various changes and modifications without departing from the inventive concept. The scope of this invention is not limited to the contents of the specification but must be determined according to the claims.

[0022] The invention will be further described with reference to the following figures: Example 1: like Figures 2-6As shown, a double-sided heat dissipation Clip chip has a lead frame 100, a chip 200, and a copper sheet body 300. The chip 200 is mounted in the middle of the lead frame 100. The copper sheet body 300 is fixed to the lead frame 100 and the upper part of the chip 200 by a plastic encapsulant 400. The copper sheet body 300 includes a body layer 310 and a mounting layer 320 below it. The mounting layer 320 has a first thickened part 321 and a second thickened part 322 at both ends. The first thickened part 321 is connected to a first pin 110 at one end of the lead frame 100, and the second thickened part 322 is connected to the chip 200. The second pin 120 at the other end of the lead frame 100 is integrated with the chip 200.

[0023] The copper sheet body 300 has an extension section 330 at the end of the second thickened portion 322, and the mounting layer 320 has an mounting step 323 along the outer periphery of the body layer 310.

[0024] It should be noted that the height of the mounting step 323 is set to 0.2mm, the X-direction dimension is 0.45mm, and the Y-direction dimension is 0.3mm. The height difference in the Z-direction is set to fully take into account the internal solder thickness (generally controllable within 25-75um), the CLIP thickness deviation (generally controllable within 10um), and the grinding process deviation (generally controllable within 20um), thereby ensuring that the step surface of the mounting step 323 is not ground during grinding.

[0025] The thickness of the first thickened portion of the copper sheet body 300 is 0.36 mm, and the thickness of the second thickened portion 322 of the copper sheet body 300 is 0.46 mm. The height difference between the two ends can be matched to the height difference of a 100 μm thick chip after mounting, preventing poor contact or no contact due to height difference during clip installation.

[0026] The clip surface has height and horizontal dimensional differences. During encapsulation, the copper sheet body 300 is completely encapsulated in the encapsulating compound 400, ensuring the bond between the copper sheet body 300 and the encapsulating compound 400. This prevents moisture from penetrating the product during subsequent grinding or due to environmental changes, which could cause delamination between the copper sheet body 300 and the encapsulating compound 400.

[0027] The Clip is designed as a "pistol-shaped" structure that matches the chip pattern, ensuring the contact area between the Clip and the chip, reducing the RDSON (drain-source on-state resistance) of the MOS, and improving the reliability of the product.

[0028] Example 2: like Figure 8As shown, a grinding process for surface grinding of power heat dissipation device products is used to process the Clip chip with double-sided heat dissipation as described in Embodiment 1. The specific steps are as follows: S1 attaches the UV film onto the substrate; S2 vacuum-adheres the substrate onto the table surface of the grinding device; The S3 equipment starts up, and the worktable rotates at a high speed, grinding the molding compound and clips on the product surface. While grinding, rinse the product surface with clean water to wash away the debris and copper shavings that fall off during the grinding process, so as to avoid contaminating the product. The S4 grinding process consists of two steps: coarse grinding of the product. S5 performs multiple fine grinding processes on the product; S6 is idling away from the product until grinding is complete.

[0029] Note: The grinding speed of the grinding wheel decreases in a stepwise manner throughout the grinding process, which is relatively slow. This is mainly to avoid the impact of excessive speed on the encapsulated body itself.

[0030] After grinding, the product needs to be electroplated and cut. This product provides heat dissipation channels on both sides. When the product has a thermal reaction in the circuit, it can effectively dissipate the heat in time, preventing the product from burning out due to thermal stress and causing the circuit board to fail.

[0031] The manufacturing process for power heat dissipation devices includes the following steps: S'1 zone; S'2 welding and mounting of the wafers followed by AOI; S'3S area solder paste application clip installation; S'4 vacuum furnace welding; S'5 solvent cleaning and Plasma cleaning; S'6G area wire bonding and AOI; S'7Plasma cleaning; S'8 molding and curing; S'9 surface treatment (grinding); S'10 electroplating and molding.

[0032] The grinding device is a wafer thinning machine, and it uses vacuum adsorption to fix the product, ensuring firmness during grinding and avoiding floating caused by grinding vibration, which would affect the grinding quality.

[0033] The grinding process is as follows: The grinding wheel moves at high speed before contacting the substrate. F0: Rotates at a constant speed of 120um / min at a height of 30um from the substrate; F1: Initial coarse grinding, grinding thickness set to 940um (i.e., grinding depth 110um), speed 30um / min slow grinding; F2: Secondary fine grinding reduces the size by 5µm, slow grinding at a speed of 21µm / min; F3: Three fine grinding cycles followed by a 5µm reduction in speed, slow grinding at 9µm / min; After grinding is complete, the grinding wheel should not be removed from the product surface immediately, otherwise copper shavings will be carried into the product. Therefore, dry grinding is required.

[0034] F4: S-out: Idle time 50s Note: The grinding speed of the entire grinding wheel decreases slowly in a stepped manner, mainly to avoid the impact of excessive speed on the encapsulated body itself.

[0035] like Figure 8 As shown, during the grinding process of this technology, the worktable rotates at a certain speed, the upper grinding wheel rotates at a certain speed, and grinds from top to bottom. At the same time, a two-fluid process is used for flushing, which can remove the copper chips generated during the grinding process in a timely manner without affecting the product itself.

[0036] like Figure 10 , 11 As shown, the chip in this invention is very small, so it is placed in a chip frame for unified processing. However, it is difficult to ensure that the chip is completely horizontal when placed, and there will be a certain degree of tilt. Therefore, the precision of the grinding process in the prior art is poor, and there is a serious delamination phenomenon. That is, there is stress between the molding body and the frame during the grinding process, which results in the edge steps of the thin product being ground out, while the surface of the thick product has not been fully ground out.

[0037] This invention increases the depth of the chip placement slot in the chip frame. At the same time, the product needs to be placed on a swivel tray for leveling before processing. This effectively solves the problem of layering, reduces the stress between the molding compound and the lead frame, and greatly improves the reliability of the chip.

[0038] Depend on Figure 10 , 11 It is evident that there are many layered chips in the existing technology, while only one chip in this invention exhibits layering.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A double-sided heat dissipating Clip chip, characterized by: The application relates to a lead frame, a chip and a copper sheet body, wherein the chip is arranged in the middle of the lead frame, the copper sheet body is fixed to the upper part of the lead frame and the chip through a plastic sealing glue body, the copper sheet body comprises a body layer and a mounting layer at the lower part of the body layer, two ends of the mounting layer are respectively provided with a first thickened part and a second thickened part, the first thickened part is connected with a first pin at one end of the lead frame, the second thickened part is connected with the chip, a second pin at the other end of the lead frame is integrated with the chip, An extension section is arranged at the end of the second thickened part of the copper sheet body, and a mounting step is arranged at the outer periphery of the body layer.

2. The dual-sided heat dissipating Clip chip of claim 1, wherein: The height of the mounting step is 0.2 mm.

3. The dual-sided heat dissipating Clip chip of claim 1, wherein: The thickness of the end of the first thickened part of the copper sheet body is 0.36 mm, and the thickness of the end of the second thickened part of the copper sheet body is 0.46 mm.

4. A lapping process for surface grinding of power dissipating device products for processing double-sided heat dissipating Clip chips as claimed in any one of claims 1 to 3, characterized in that: The specific steps are as follows: S1, pasting a UV film on a substrate; S2, vacuum adsorbing the substrate on the table surface of a grinding device; S3, starting the equipment, rotating the workbench, and grinding the plastic sealing material and the clip on the product surface Grinding is simultaneously performed by flushing the product surface with clean water to flush away the chippings and copper scraps in the grinding process; S4, the grinding process is sequentially performed on the product for rough grinding; S5, the product is ground for multiple times for fine grinding; S6, the grinding is completed by making the grinding wheel away from the product for idling.

5. The abrasive process for surface grinding of power dissipation device products according to claim 1, characterized in that: The product needs to be electroplated and cut after grinding, and the product provides heat dissipation channels on the front and back surfaces, so that heat can be effectively dissipated in time when the product generates heat in the circuit, and the product is prevented from being burnt due to thermal stress and causing the circuit board to fail.

6. The abrasive process for surface grinding of power dissipation device products of claim 1 wherein: The processing technology of the power heat dissipation device product is as follows: S'1, scribing; S'2, soldering and mounting the chip and performing AOI; S'3, tin paste mounting of the clip in the S area; S'4, vacuum furnace welding; S'5, solvent cleaning and plasma cleaning; S'6, wire bonding in the G area and performing AOI; S'7, plasma cleaning; S'8, mold pressing and curing; S'9, surface treatment (grinding); S'10, electroplating and forming.

7. The process for power dissipating device products according to claim 1, wherein: The grinding device is a wafer thinning machine.

8. The process for power dissipating device products of claim 1 wherein: The grinding process is as follows: The grinding wheel moves at a high speed before contacting the substrate F0: when the distance from the substrate is 30 um, the grinding wheel rotates at a speed of 120 um / min; F1: first rough grinding, the grinding thickness is set to 940 um, that is, the grinding depth is 110 um, and the speed is 30 um / min for slow grinding; F2: second fine grinding, the grinding depth is reduced by 5 um, and the speed is 21 um / min for slow grinding; F3: third fine grinding, the grinding depth is reduced by 5 um again, and the speed is 9 um / min for slow grinding; After the grinding is completed, the grinding wheel cannot leave the product surface at the first time to avoid bringing copper scraps into the product; F4: S-out: idling time is 50 s.

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