Solder flux cleaning method for chip package and chip package

Abstract

The embodiments of the present disclosure provide a flux cleaning method for a chip package and the chip package, the method comprising: sequentially performing multiple times of heating and pressurizing on a welding surface of the chip package to make the flux volatilize multiple times, and after each volatilization, performing vacuum oscillation on the welding surface at a preset high temperature to discharge flux volatilates; and performing water washing on the welding surface to remove remaining flux solid residues on the welding surface. The cleaning method of the embodiments of the present disclosure does not need to reduce the cleaning speed to clean multiple times, improves the production capacity of the chip package, saves the packaging cost, improves the flux cleaning effect and the quality of the chip package, and can be applied to the cleaning of fluxes in different types of chip packages, and can well solve the bottleneck problem encountered by the traditional flux cleaning process in the current 2.5D large-size multi-chip flip-chip welding process, and effectively improve the flux cleaning effect of the 2.5D large-size multi-chip product.

Description

Technical Field

[0001] This disclosure pertains to the field of semiconductor packaging technology, specifically relating to a flux cleaning method for a chip package and a chip package. Background Technology

[0002] Chips, especially high-end chips and 2.5D large-size multi-chip products, are becoming increasingly integrated and larger in size. The number of I / O bumps on the chips is increasing, the bump spacing is decreasing, and the gap between the chip and the substrate is shrinking. As a result, the flux used in the flip chip soldering process is difficult to clean completely. Flux that is difficult to clean will remain inside the product, causing defects during the packaging process and affecting the reliability of the product.

[0003] To address the above issues, the industry currently uses a saponifying agent and pure water to clean the flux after flip-chip bump soldering. For products that are difficult to clean, the cleaning speed is reduced and multiple cleaning cycles are performed. The current problems with this traditional method are: 1) Traditional cleaning with saponifying agents and pure water requires multiple cleaning cycles and a reduced cleaning speed to meet quality requirements, which limits the overall packaging capacity. 2) Increasing the amount of saponifying agent used will correspondingly increase the packaging cost; 3) Prolonged exposure to high humidity will accelerate surface oxidation of the product and cause other defects; 4) Moreover, traditional flux cleaning processes are not very effective, and flux residue can still cause poor encapsulation.

[0004] To address the aforementioned issues, it is necessary to propose a reasonable and effective flux cleaning method for chip packages, as well as a chip package itself, that solves these problems. Summary of the Invention

[0005] The present disclosure aims to at least solve one of the technical problems existing in the prior art, and provides a flux cleaning method for chip packages and a chip package.

[0006] One aspect of this disclosure provides a flux cleaning method for a chip package, the method comprising: Step S1: The soldering surface of the chip package is heated and pressurized multiple times to allow the flux to evaporate multiple times. After each evaporation, the soldering surface is vacuum-vibrated at a preset high temperature to remove the flux volatiles. Step S2: Wash the welding surface with water to remove any remaining solid flux residue.

[0007] Optionally, step S2 specifically includes: The welding surface is heated to a first preset high temperature and simultaneously pressurized to a first preset high pressure to allow the flux to volatilize for the first time. The welding surface is further heated to a second preset high temperature, and a vacuum is first applied to the welding surface during the heating process, wherein the second preset high temperature is greater than the first preset high temperature; The welding surface is maintained at the second preset high temperature, while being pressurized to the second preset high pressure to allow the flux to volatilize for the second time, wherein the second preset high pressure is greater than the first preset high pressure; The welding surface is heated to a third preset high temperature, and a second vacuum is applied to the welding surface during the heating process; The welding surface is maintained at the third preset high temperature, while being pressurized to the second preset high temperature, so that the flux will volatilize for the third time; The welding surface is kept at the third preset high temperature, and a third vacuum is applied to the welding surface to remove the flux volatiles.

[0008] Optionally, after performing a third vacuum on the weld surface to remove the flux volatiles, the method further includes: The welding surface is maintained at the third preset high temperature, and the welding surface is pressurized to the second preset high temperature; After maintaining the third preset high temperature and the second preset high pressure for a preset time, the temperature and pressure are reduced.

[0009] Optionally, the range of the first preset high temperature is 90℃~110℃, and the range of the first preset high pressure is 0.1Mpa~0.3Mpa. Optionally, the second preset high temperature range is 130℃~150℃, and the second preset high pressure range is 0.7Mpa~0.9Mpa.

[0010] Optionally, the range of the third preset high temperature is 180℃~200℃.

[0011] Optionally, step S2 specifically includes: According to the preset cleaning parameters, the welding surface is washed with water once using a saponifying agent at different cleaning angles to remove the remaining flux solid residues on the welding surface.

[0012] Optionally, the preset cleaning parameters include: The concentration of the saponifying agent is in the range of 2% to 4%, the cleaning water temperature is in the range of 70° to 80°, the cleaning speed is 18 inches / minute to 22 inches / minute, the cleaning angle is 40° to 50°, and the cleaning water pressure is 0.8 MPa to 1.0 MPa.

[0013] Optionally, prior to step S1, the method further includes: The welding surface is evacuated and filled with protective gas.

[0014] Another aspect of this disclosure provides a chip package in which the soldering surfaces of the chip package are cleaned with flux using the method described above.

[0015] The present disclosure discloses a flux cleaning method for chip packages and a chip package. The cleaning method, based on the volatility characteristics of the flux material, sequentially heats and pressurizes the soldering surface of the chip package multiple times to allow the flux to volatilize multiple times. After each volatilization, the soldering surface is subjected to vacuum vibration at a preset high temperature, which can effectively extract the flux volatiles from the soldering surface. The remaining solid flux residues after volatilization are washed with water to achieve the purpose of cleaning.

[0016] Compared with existing cleaning methods, the cleaning method of this disclosure does not require reducing the cleaning speed for multiple cleaning passes, thus increasing the production capacity of chip packages; saving packaging costs; improving the flux cleaning effect and enhancing the quality of chip packages; and it can be applied to the cleaning of flux in different types of chip packages. It can effectively solve the bottleneck problems encountered by traditional flux cleaning processes in current 2.5D and other large-size multi-chip flip-chip bonding processes, and effectively improve the flux cleaning effect of 2.5D large-size multi-chip products. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the flux volatilization curve of flux materials in the prior art; Figure 2 This is a schematic flowchart of a flux cleaning method for a chip package according to one embodiment of the present disclosure; Figure 3 This is a schematic flowchart illustrating the specific process of step S1 in one embodiment of the present disclosure. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the embodiments of this disclosure, the embodiments of this disclosure will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0019] like Figure 1The diagram shows the flux volatilization curves. Curve 1 is the temperature curve, curve 2 is the volatilization curve of flux type A at different temperatures and times, and curve 3 is the volatilization curve of flux type B at different temperatures and times. The volatilization curves show that some flux will volatilize within a certain temperature and time. After a certain amount, the volatilization zone stabilizes, and the remaining flux after volatilization is a solid residue.

[0020] Based on the volatility characteristics of the flux, such as Figure 2 As shown, one aspect of this disclosure provides a flux cleaning method S10 for a chip package, the cleaning method S10 including: Step S1: The soldering surface of the chip package is heated and pressurized multiple times to allow the flux to evaporate multiple times. After each evaporation, the soldering surface is vacuum-vibrated at a preset high temperature to remove the flux volatiles.

[0021] In this embodiment, before performing step S1, the cleaning method S10 further includes: The chip package is placed in a sealed chamber, and the chamber is evacuated to remove the solder surfaces of the chip package. A protective gas is then introduced into the chamber to reduce the oxygen content and provide a clean environment for the chip package. Simultaneously, the sealed chamber is preheated in preparation for the subsequent cleaning process.

[0022] It should be noted that the protective gas can be nitrogen or other protective gases. This embodiment does not impose specific limitations and can be selected according to actual needs.

[0023] In this embodiment, as Figure 3 As shown, step S1 may specifically include: Step S11: Heat the welding surface to a first preset high temperature and pressurize it to a first preset high pressure to allow the flux to volatilize for the first time.

[0024] Specifically, the preheated sealed chamber is heated to raise the welding surface to a first preset high temperature, while simultaneously pressurizing it to a first preset high pressure. The first preset high temperature and the first preset high pressure are maintained for a period of time to allow the flux to volatilize for the first time, generating some flux volatiles.

[0025] In this embodiment, the first preset high temperature ranges from 90°C to 110°C, and the first preset high pressure ranges from 0.1 MPa to 0.3 MPa. Preferably, in this embodiment, the first preset high temperature is 100°C, the first preset high pressure is 0.2 MPa, and the first preset high temperature and the first preset high pressure are maintained for approximately 20 minutes.

[0026] In this embodiment, under the action of the first preset high temperature, the flux can better volatilize for the first time to generate some flux volatiles on the welding surface; under the action of the first preset high pressure, some flux volatiles generated by the first volatilization of the flux on the welding surface can be squeezed out.

[0027] Step S12: Continue to heat the welding surface to a second preset high temperature, and perform a first vacuuming of the welding surface during the heating process, wherein the second preset high temperature is greater than the first preset high temperature.

[0028] Specifically, after the flux has completed its first evaporation and produced some flux volatiles, the welding surface is heated to a second preset high temperature, and a vacuum is applied to the welding surface for the first time during the heating process.

[0029] In this embodiment, by performing a first vacuum on the welding surface, some of the flux volatiles generated during the first evaporation of the flux can be extracted and discharged to the outside of the sealed chamber through the exhaust system, thus completing the first cleaning of the flux.

[0030] In this embodiment, the second preset high temperature ranges from 130°C to 150°C, and preferably, the second preset high temperature is 140°C. That is, in step S12, the sealed chamber is further heated from 100°C to 140°C, and a vacuum is drawn during this heating process.

[0031] Step S13: Continue to maintain the welding surface at the second preset high temperature, and at the same time pressurize it to the second preset high pressure, so that the flux will volatilize for the second time, wherein the second preset high pressure is greater than the first preset high pressure.

[0032] Specifically, after the first vacuuming of the welding surface to remove some flux volatiles, the welding surface is maintained at a second preset high temperature while being pressurized to a second preset high pressure. This second preset high temperature and pressure are maintained for a period of time, allowing the flux to volatilize a second time, generating more flux volatiles. The second preset high pressure is greater than the first preset high pressure.

[0033] In this embodiment, the second preset high pressure ranges from 0.7 MPa to 0.9 MPa. Preferably, the second preset high pressure is 0.8 MPa. Specifically, in this embodiment, the second preset high temperature of 140°C and the second preset high pressure of 0.8 MPa are maintained simultaneously for approximately 20 minutes.

[0034] In this embodiment, under the action of the second preset high temperature, the flux can better volatilize for the second time to generate some flux volatiles on the welding surface; under the action of the second preset high pressure, some flux volatiles generated by the second volatilization of the flux on the welding surface can be squeezed out.

[0035] Step S14: Heat the welding surface to a third preset high temperature, and perform a second vacuuming of the welding surface during the heating process.

[0036] Specifically, after the flux completes its second evaporation and produces some flux volatiles, the sealed chamber is heated further to raise the temperature of the welding surface to a third preset high temperature, and the welding surface is evacuated for the second time during the heating process.

[0037] In this embodiment, by performing a second vacuum on the welding surface, some of the flux volatiles generated during the second evaporation of flux can be extracted and discharged to the outside of the sealed chamber through the exhaust system, thus completing the second cleaning of the flux.

[0038] In this embodiment, the third preset high temperature ranges from 180°C to 200°C. Preferably, the third preset high temperature is 190°C. That is, in step S14, the temperature of the welding surface needs to be raised from 140°C to 190°C, and a second vacuum is applied to the welding surface during this heating process.

[0039] Step S15: Continue to maintain the welding surface at the third preset high temperature, while pressurizing it to the second preset high pressure, so that the flux will evaporate for the third time.

[0040] Specifically, after the second vacuuming of the welding surface to remove some flux volatiles, the welding surface is maintained at 190°C and pressurized to 0.8 MPa. At the same time, the third preset high temperature of 190°C and the second preset high pressure of 0.8 MPa are maintained for about 20 minutes to allow the flux to volatilize for the third time and generate some flux volatiles.

[0041] In this embodiment, under the third preset high temperature, the flux can better volatilize for the third time to generate some flux volatiles on the welding surface; under the second preset high pressure, some of the flux volatiles generated by the third volatilization of the flux on the welding surface can be squeezed out.

[0042] Step S16: Continue to maintain the welding surface at the third preset high temperature, and at the same time, perform a third vacuuming on the welding surface to remove the flux volatiles.

[0043] Specifically, after the flux has completed its third evaporation and produced some flux volatiles, the welding surface is kept at 190°C, and a third vacuum is applied to the welding surface to remove the flux volatiles.

[0044] In this embodiment, by performing a third vacuum on the welding surface, some of the flux volatiles generated during the third evaporation of the flux can be extracted and discharged to the outside of the sealed chamber through the exhaust system, thus completing the third cleaning of the flux and removing all flux volatiles, thereby completing the cleaning work of flux volatiles.

[0045] After performing a third vacuum on the welding surface to remove the flux volatiles, the cleaning method S10 further includes: First, the welding surface is kept at the third preset high temperature, and the welding surface is pressurized to the second preset high pressure.

[0046] Specifically, after the third vacuuming of the soldering surface to remove all flux volatiles, the soldering surface is maintained at 190°C while being pressurized to 0.8 MPa. Since the soldering surface is still at the third preset high temperature state, pressurizing it to the second preset high pressure can prevent the formation of voids on the soldering surface and improve the reliability of the chip package.

[0047] Then, after maintaining the third preset high temperature and the second preset high pressure for a preset time, the temperature and pressure are reduced.

[0048] Specifically, after maintaining the third preset high temperature and the second preset high pressure for about 20 minutes, the sealed chamber is cooled and depressurized to complete the flux volatiles cleaning process. The chip package is then removed from the sealed chamber for the next cleaning process.

[0049] Step S2: Wash the welding surface with water to remove any remaining solid flux residue.

[0050] Specifically, after the three cleaning processes of flux volatiles mentioned above, the flux remaining after evaporation at a certain temperature and time is a solid residue. The welding surface needs to be washed with water to remove the remaining solid flux residue, thus completing the entire flux cleaning process.

[0051] Specifically, step S2 may include: According to the preset cleaning parameters, the welding surface is washed once with water using a saponifying agent at different cleaning angles to remove the remaining solid flux residues on the welding surface.

[0052] Specifically, the preset cleaning parameters include: the concentration range of the saponifying agent is 2% to 4%; the cleaning water temperature range is 70° to 80°; the cleaning speed is 18 inches / minute to 22 inches / minute; the cleaning angle is 40° to 50°, preferably 45°; and the cleaning water pressure is 0.8 MPa to 1.0 MPa.

[0053] It should be noted that the preset cleaning parameters can be adjusted according to different chip packages. This embodiment does not impose specific limitations and can be selected according to actual needs.

[0054] In this embodiment, according to preset cleaning parameters, a saponifying agent is used to perform a single water wash on the remaining solid residues on the soldering surface, which can completely remove the remaining flux solid residues on the soldering surface and effectively improve the cleaning effect of flux in the chip package. This solves the problem of the extremely difficult-to-clean flux products in the current 2.5D large-size multi-chip flip-chip soldering process due to the large chip size, multiple chip numbers, multiple solder joints, and small bump spacing.

[0055] This disclosure discloses a flux cleaning method for chip packages. Based on the volatility characteristics of the flux material, the soldering surface of the chip package is subjected to multiple heating and pressurization cycles to allow the flux to evaporate multiple times. After each evaporation, the soldering surface is subjected to vacuum vibration at a preset high temperature, effectively extracting the volatile flux from the soldering surface. The remaining solid flux residue is then washed with water to achieve thorough cleaning. Compared with existing cleaning methods, this method eliminates the need for reduced cleaning speed and multiple cleaning cycles, increasing chip package production capacity; saving packaging costs; improving flux cleaning effectiveness and chip package quality; and is applicable to cleaning flux in different types of chip packages. It effectively solves the bottleneck problems encountered in traditional flux cleaning processes in large-size multi-chip flip-chip soldering processes such as 2.5D, significantly improving the flux cleaning effect for 2.5D large-size multi-chip products.

[0056] Another aspect of this disclosure provides a chip package in which the soldering surfaces of the chip package are cleaned with flux using the flux cleaning method S10 for chip packages described above. The specific process of the flux cleaning method S10 for chip packages has been described in detail above and will not be repeated here.

[0057] It should be noted that the chip package can be a 2.5D large-size multi-chip flip-chip product, or other package products with a large number of chips, a large number of solder joints, and a small bump pitch. This embodiment does not make specific limitations. As long as the flip-chip has undergone a soldering process, the flux cleaning method S10 described above for chip packages can be used to clean the flux.

[0058] The chip package of this disclosure uses the flux cleaning method described above to clean the flux, resulting in good cleaning effect and improving the quality and reliability of the chip package.

[0059] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the embodiments of this disclosure, and the embodiments of this disclosure are not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the embodiments of this disclosure, and these modifications and improvements are also considered to be within the protection scope of the embodiments of this disclosure.

Claims

1. A method for cleaning flux in a chip package, characterized in that, The method includes: Step S1: The soldering surface of the chip package is subjected to multiple heating and pressurization processes to allow the flux to evaporate multiple times. After each evaporation, the soldering surface is subjected to vacuum vibration at a preset high temperature to remove flux volatiles. Specifically, this includes: The welding surface is heated to a first preset high temperature and simultaneously pressurized to a first preset high pressure to allow the flux to volatilize for the first time. The welding surface is further heated to a second preset high temperature, and a vacuum is first applied to the welding surface during the heating process to extract some of the flux volatiles generated during the first evaporation, thus completing the first cleaning of the flux. The second preset high temperature is greater than the first preset high temperature. The welding surface is maintained at the second preset high temperature, while being pressurized to the second preset high pressure to allow the flux to volatilize for the second time, wherein the second preset high pressure is greater than the first preset high pressure; The welding surface is heated to a third preset high temperature, and a second vacuum is performed on the welding surface during the heating process to extract some of the flux volatiles generated in the second volatilization, thus completing the second cleaning of the flux. The welding surface is maintained at the third preset high temperature, while being pressurized to the second preset high temperature, so that the flux will volatilize for the third time; The welding surface is kept at the third preset high temperature, and the welding surface is vacuumed for the third time to extract some of the flux volatiles generated in the third volatilization, thus completing the third cleaning of the flux and discharging the flux volatiles. Subsequently, the method further includes: The welding surface is maintained at the third preset high temperature, and the welding surface is pressurized to the second preset high pressure to prevent the formation of voids on the welding surface; After maintaining the third preset high temperature and the second preset high pressure for a preset time, the temperature and pressure are reduced. Step S2: Wash the welding surface with water to remove any remaining solid flux residue.

2. The method according to claim 1, characterized in that, The first preset high temperature range is 90℃~110℃, and the first preset high pressure range is 0.1Mpa~0.3Mpa.

3. The method according to claim 1, characterized in that, The second preset high temperature range is 130℃~150℃, and the second preset high pressure range is 0.7Mpa~0.9Mpa.

4. The method according to claim 1, characterized in that, The range of the third preset high temperature is 180℃~200℃.

5. The method according to any one of claims 1 to 4, characterized in that, Step S2 specifically includes: According to the preset cleaning parameters, the welding surface is washed with water once using a saponifying agent at different cleaning angles to remove the remaining flux solid residues on the welding surface.

6. The method according to claim 5, characterized in that, The preset cleaning parameters include: The concentration of the saponifying agent is in the range of 2% to 4%, the cleaning water temperature is in the range of 70° to 80°, the cleaning speed is 18 inches / minute to 22 inches / minute, the cleaning angle is 40° to 50°, and the cleaning water pressure is 0.8 MPa to 1.0 MPa.

7. The method according to any one of claims 1 to 4, characterized in that, Before step S1, the method further includes: The welding surface is evacuated and filled with protective gas.

8. A chip package, characterized in that, The soldering surface of the chip package is cleaned with flux using the method described in any one of claims 1 to 7.

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