Chip welding method

Abstract

The invention provides a chip welding method, a gold-gallium alloy is used as a welding material, the weight ratio of gallium metal in the gold-gallium alloy is 3%, the method comprises the steps that a chip and a ceramic lead chip carrier are preprocessed, and the ceramic lead chip carrier comprises a bonding pad of the chip; calculating according to the area of the bonding pad and a preset dosage formula to obtain the welding dosage of the gold-gallium alloy; respectively presetting gold-gallium alloy corresponding to the welding amount on the pins of the chip and the bonding pad of the ceramic lead chip carrier; an inert gas welding environment is set according to the preset first nitrogen dosage, and the gold-gallium alloy is heated to a preset temperature interval through laser or electron beams; adjusting the first nitrogen consumption according to the area of the chip and a preset adjustment function to obtain a second nitrogen consumption; and setting a cooling environment based on the second nitrogen dosage, and rapidly cooling the chip and the ceramic lead chip carrier.

Description

Technical Field

[0001] This application relates to the field of semiconductor welding technology, and particularly to a chip welding method. Background Art

[0002] Currently, in the semiconductor packaging industry, eutectic welding, as a highly reliable connection technology, is widely used in the connection between chips and substrates. However, in this process, the control of the cooling stage is crucial. Improper cooling strategies, especially the selection of cooling rate and cooling medium, often lead to a significant decline in welding quality. When the chip is rapidly cooled from a high-temperature state, if the cooling process is not properly set, it is extremely easy to generate uneven thermal stress, which not only affects the microstructure of the solder joints, but may also cause an increase in solder joint cracks and voids, and even lead to warping and deformation of the chip or substrate. Especially in the chip packaging for high-power and high-frequency applications, this stress problem caused by improper cooling is more prominent, seriously affecting the performance stability and service life of the product. Summary of the Invention

[0003] This application provides a chip welding method for improving the welding quality of chips.

[0004] In a first aspect, an embodiment of this application provides a chip welding method, using a gold-gallium alloy as the welding material, and the weight percentage of gallium metal in the gold-gallium alloy is 3%. The method includes: Preprocessing the chip and the ceramic lead chip carrier, where the ceramic lead chip carrier includes the pads of the chip; Calculating according to the area of the pad and a preset dosage formula to obtain the welding dosage of the gold-gallium alloy; Pre-setting the gold-gallium alloy corresponding to the welding dosage on the pins of the chip and the pads of the ceramic lead chip carrier respectively; Setting an inert gas welding environment according to a preset first nitrogen dosage, and heating the gold-gallium alloy to a preset temperature range using a laser or an electron beam; Adjusting the first nitrogen dosage according to the area of the chip and a preset adjustment function to obtain a second nitrogen dosage; Based on the second nitrogen dosage, setting a cooling environment and rapidly cooling the chip and the ceramic lead chip carrier.

[0005] In some embodiments, the lower limit value of the preset temperature range is greater than the melting point temperature of the gold-gallium alloy, and the upper limit value of the preset temperature range is less than the thermal damage temperature of the chip and the thermal damage temperature of the ceramic lead chip carrier.

[0006] In some embodiments, the pretreatment of the chip and the ceramic lead chip carrier includes: forming an adhesion promoting layer of gold or nickel on the pins of the chip and the pads of the ceramic lead chip carrier through physical vapor deposition process or chemical vapor deposition process.

[0007] In some embodiments, the step of heating the gold-gallium alloy to a preset temperature range using a laser or an electron beam further includes: obtaining temperature data of the area near the pads of the ceramic lead chip carrier using an infrared thermal imager, and reducing or increasing the heating power of the laser or the electron beam according to the temperature data.

[0008] In some embodiments, the material of the ceramic lead chip carrier includes: and .

[0009] In some embodiments, the specific formula of the preset adjustment function is: ; where is the amount of the second nitrogen, is the amount of the first nitrogen, k(t) is an adjustment coefficient related to time, k(t) is determined according to the stress change curve of the gold-gallium alloy, and A is the area of the chip.

[0010] An embodiment of the present application provides a chip welding method, using a gold-gallium alloy as a welding material, where the weight ratio of gallium metal in the gold-gallium alloy is 3%. The method includes: pretreating a chip and a ceramic lead chip carrier, where the ceramic lead chip carrier includes pads of the chip; calculating the welding amount of the gold-gallium alloy according to the area of the pads and a preset dosage formula; respectively pre-setting the gold-gallium alloy corresponding to the welding amount on the pins of the chip and the pads of the ceramic lead chip carrier; setting an inert gas welding environment according to a preset amount of the first nitrogen, and heating the gold-gallium alloy to a preset temperature range using a laser or an electron beam; adjusting the amount of the first nitrogen according to the area of the chip and a preset adjustment function to obtain the amount of the second nitrogen; and setting a cooling environment based on the amount of the second nitrogen, and quickly cooling the chip and the ceramic lead chip carrier. Through the above method, when welding a chip to a ceramic lead chip carrier, a gold-gallium alloy with a weight ratio of gallium metal of 3% is used as a welding material, and an inert gas welding environment is set by nitrogen to improve the welding quality. After welding, by increasing the amount of nitrogen, the high cooling capacity of nitrogen is utilized to quickly reduce the temperature of the solder joint, so as to increase the strength of the solder joint, thereby reducing the stress of the solder joint and improving the welding quality of the chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0012] Figure 1 The schematic flowchart of a chip soldering method provided by an embodiment of the present application. Detailed implementation manners

[0013] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0014] The flowchart shown in the drawings is only an example illustration, and does not necessarily include all contents and operations / steps, nor does it necessarily execute in the described order. For example, some operations / steps can be decomposed, combined, or partially merged, so the actual execution order may change according to the actual situation.

[0015] It should also be understood that the terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification of the present application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0016] It should be further understood that the term " / and / " used in the specification of the present application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0017] To more clearly introduce the technical solutions of the present application, the following will also introduce the technical solutions of the present application through specific embodiments. It should be noted that this specific embodiment is used to expand the description of the technical solutions of the present application, rather than limiting the present application.

[0018] In the embodiment of the present application, it is necessary to solder a chip on a ceramic lead chip carrier, and the material of the ceramic lead chip carrier includes: and .

[0019] Please refer to Figure 1 , Figure 1 which is also a schematic flowchart of a chip soldering method provided by an embodiment of the present application. AsFigure 1 As shown, the specific steps of the chip soldering method include: S101 - S106.

[0020] S101. Pre - process the chip and the ceramic lead chip carrier. The ceramic lead chip carrier includes the pads of the chip.

[0021] Exemplarily, the pre - processing includes: cleaning. Solvents such as ultrapure water, isopropyl alcohol or acetone are used to remove oil stains, dust and particles on the chip and the ceramic lead chip carrier to ensure a clean surface without residue. The pre - processing also includes: adding a soldering promotion layer to improve the soldering quality.

[0022] In some embodiments, the pre - processing of the chip and the ceramic lead chip carrier includes: forming a soldering promotion layer of gold or nickel on the pins of the chip and the pads of the ceramic lead chip carrier through physical vapor deposition process or chemical vapor deposition process.

[0023] Through the above pre - processing steps, the initial quality of the soldering between the chip and the ceramic lead chip carrier and the reliability of subsequent packaging can be significantly improved, and the soldering defects caused by surface contamination or oxidation can be reduced.

[0024] S102. Calculate according to the area of the pad and the preset dosage formula to obtain the soldering dosage of the gold - gallium alloy.

[0025] Exemplarily, the areas of the pads are different, and the soldering dosages of the gold - gallium alloy required are different. The larger the area of the pad, the more soldering dosage of the gold - gallium alloy is required. When calculating the soldering dosage of the gold - gallium alloy, according to the area of the pad and the preset dosage formula, this process needs to consider factors such as alloy melting point, pad material, solder joint shape, etc. to ensure the reliability and consistency of the solder joints. For pads with irregular shapes, the total area can be approximately calculated by dividing them into multiple geometric figures. The preset dosage formula is: ; where m is the soldering dosage of the gold - gallium alloy (unit: milligram or gram). A is the area of the pad (unit: square millimeter or square centimeter). c is the preset soldering dosage coefficient per unit area, and this coefficient may need to be determined through experiments or refer to industry standards and recommended values.

[0026] Through the above steps, based on the pad area and the preset dosage formula, the soldering dosage of the gold - gallium alloy can be accurately calculated and controlled, so as to achieve a high - quality soldering effect.

[0027] S103. Pre - place the gold - gallium alloy corresponding to the soldering dosage on the pins of the chip and the pads of the ceramic lead chip carrier respectively.

[0028] Exemplarily, the gold-gallium alloy is usually provided in the form of solder balls, solder chips or solder paste, and the appropriate state is selected according to the specific process, and the common state is solder paste. Using a precision dispensing machine or a solder paste printer, place the gold-gallium alloy solder paste accurately on each pin according to the calculated dosage. Similarly, use a dispensing machine or a printer to place the gold-gallium alloy solder paste on each pad. The shape and size of the solder paste need to match the pads to ensure good contact and wettability during soldering.

[0029] Through the above steps, the presetting of the gold-gallium alloy can be ensured to be accurate without error, providing a solid foundation for eutectic soldering, thereby improving the packaging quality and production efficiency.

[0030] S104. Set an inert gas welding environment according to the preset first nitrogen dosage, and use a laser or an electron beam to heat the gold-gallium alloy to a preset temperature range.

[0031] Exemplarily, before soldering, it is necessary to ensure that each pin of the chip is accurately aligned with the pads of the corresponding ceramic lead chip carrier. This usually requires the use of high-precision alignment equipment, such as an optical alignment system, to ensure that the alignment error between the chip pins and the pads is within the allowable range. Then, according to the preset first nitrogen dosage, adjust the nitrogen flow rate to ensure that the welding area is filled with nitrogen to form an inert gas protection layer. This helps to isolate the air, prevent oxidation during the soldering process, and maintain the purity of the welding area.

[0032] During the soldering process, temperature control and heating rate control are required. Temperature control: Use a temperature sensor to monitor the heating process to ensure that the temperature of the gold-gallium alloy rises evenly to the preset eutectic temperature range. The eutectic temperature of the gold-gallium alloy is about 282°C, and during heating, it is necessary to ensure that the temperature is controlled between 280°C and 285°C to achieve the best eutectic reaction effect. Heating rate: Control the heating rate to avoid thermal stress caused by overheating too quickly, and at the same time prevent the production efficiency from being affected by too slow heating. An appropriate heating rate also helps to reduce the generation of pores and cracks.

[0033] In some embodiments, the lower limit value of the preset temperature range is greater than the melting point temperature of the gold-gallium alloy, and the upper limit value of the preset temperature range is less than the thermal damage temperature of the chip and the thermal damage temperature of the ceramic lead chip carrier.

[0034] In some embodiments, the step of using a laser or an electron beam to heat the gold-gallium alloy to a preset temperature range further includes: using an infrared thermal imager to obtain temperature data of the area near the pads of the ceramic lead chip carrier, and reducing or increasing the heating power of the laser or the electron beam according to the temperature data.

[0035] Exemplarily, the temperature distribution information of the area near the pad is collected in real time by a thermal imager to generate a temperature image and data. The above temperature data is analyzed by data analysis software to identify the uniformity of the temperature distribution and the hot spot area. If the temperature is lower than the lower limit of the preset heating range, it indicates that the heating power is insufficient and the power needs to be increased; if the temperature exceeds the upper limit, it means that the heating is too strong and the power should be reduced. According to the feedback of the temperature data, the heating power of the laser or electron beam is manually or automatically adjusted through the interface of the control system. For example, increasing the power can shorten the heating time, while reducing the power extends the heating time to achieve an ideal temperature balance. For complex pad layouts, it may be necessary to adjust the heating power for different regions separately to ensure the temperature uniformity of the entire welding area.

[0036] By obtaining the temperature data of the area near the pad in real time through a thermal imager and dynamically adjusting the heating power of the laser or electron beam according to these data, precise temperature control can be achieved, ensuring the stability of the welding process and the consistency of the welding quality.

[0037] S105. According to the area of the chip and the preset adjustment function, adjust the first nitrogen consumption to obtain the second nitrogen consumption.

[0038] In some embodiments, the specific formula of the preset adjustment function is: ; Wherein, is the second nitrogen consumption, is the first nitrogen consumption, k(t) is an adjustment coefficient related to time, k(t) is determined according to the stress change curve of the gold-gallium alloy, and A is the area of the chip.

[0039] Exemplarily, at the initial stage of cooling, a higher nitrogen flow rate can be adopted to quickly remove a large amount of heat, and then the nitrogen flow rate is gradually reduced according to the stress change curve of the gold-gallium alloy until the stable room temperature or the target temperature is reached, ensuring a smooth and efficient cooling process. During the cooling process, a high nitrogen consumption cannot be maintained all the time, which is likely to cause stress imbalance at the solder joints. With the assistance of the stress change curve of the gold-gallium alloy, the temperature decrease value corresponding to the stress value that can be tolerated is used as the cooling value, and then the nitrogen reduction value is calculated according to the cooling value to track and calculate the second nitrogen consumption.

[0040] Through the above mechanism, under the requirement of achieving rapid cooling, solder joints with higher strength can be formed, and stress imbalance caused by improper cooling can also be prevented.

[0041] S106. Based on the second nitrogen consumption, set the cooling environment to quickly cool the chip and the ceramic lead chip carrier.

[0042] Exemplarily, a precise nitrogen flow controller is used to adjust the nitrogen flow rate according to the second nitrogen consumption, thereby controlling the cooling rate.

[0043] An embodiment of the present application provides a chip soldering method, which uses a gold-gallium alloy as a soldering material. The weight ratio of gallium metal in the gold-gallium alloy is 3%. The method includes: preprocessing a chip and a ceramic lead chip carrier, where the ceramic lead chip carrier includes the solder pads of the chip; calculating according to the area of the solder pads and a preset dosage formula to obtain the soldering dosage of the gold-gallium alloy; respectively pre-setting the gold-gallium alloy corresponding to the soldering dosage on the pins of the chip and the solder pads of the ceramic lead chip carrier; setting an inert gas soldering environment according to a preset first nitrogen dosage, and heating the gold-gallium alloy to a preset temperature range using a laser or an electron beam; adjusting the first nitrogen dosage according to the area of the chip and a preset adjustment function to obtain a second nitrogen dosage; setting a cooling environment based on the second nitrogen dosage, and rapidly cooling the chip and the ceramic lead chip carrier. Through the above method, when soldering the chip to the ceramic lead chip carrier, a gold-gallium alloy with a weight ratio of gallium metal of 3% is used as the soldering material, and an inert gas soldering environment is set by nitrogen to improve the soldering quality. After soldering, by increasing the nitrogen dosage and utilizing the high-efficiency cooling ability of nitrogen, the temperature of the solder joints is rapidly reduced to increase the strength of the solder joints, thereby reducing the stress of the solder joints and improving the soldering quality of the chip.

[0044] As described above, the above is only the specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present application can easily think of various equivalent modifications or replacements, and these modifications or replacements should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A chip welding method, characterized in that: A gold-gallium alloy is used as a welding material, wherein the weight proportion of gallium metal in the gold-gallium alloy is 3%. The method comprises: Preprocessing the chip and a ceramic lead chip carrier, the ceramic lead chip carrier including a pad of the chip; Calculating the welding amount of the gold-gallium alloy according to the area of ​​the welding pad and a preset dosage formula; Pre-placing the gold-gallium alloy corresponding to the welding amount on the pins of the chip and the pads of the ceramic lead chip carrier respectively; Setting an inert gas welding environment according to a preset first nitrogen dosage, and heating the gold-gallium alloy to a preset temperature range using a laser or an electron beam; According to the area of ​​the chip and a preset adjustment function, adjusting the first nitrogen gas dosage to obtain a second nitrogen gas dosage; A cooling environment is set based on the second nitrogen gas usage to quickly cool the chip and the ceramic lead chip carrier.

2. The chip bonding method according to claim 1, characterized in that: The lower limit of the preset temperature range is greater than the melting point of the gold-gallium alloy, and the upper limit of the preset temperature range is less than the thermal damage temperature of the chip and the thermal damage temperature of the ceramic lead chip carrier.

3. The chip bonding method according to claim 1, characterized in that: The pre-processing of the chip and the ceramic lead chip carrier comprises: A gold or nickel soldering promotion layer is formed on the pins of the chip and the soldering pads of the ceramic lead chip carrier by a physical vapor deposition process or a chemical vapor deposition process.

4. The chip bonding method according to claim 1, characterized in that: The step of heating the gold-gallium alloy to a preset temperature range using a laser or an electron beam further comprises: A thermal imager is used to obtain temperature data of an area near the solder pad of the ceramic lead chip carrier, and the heating power of the laser or electron beam is reduced or increased according to the temperature data.

5. The chip bonding method according to claim 1, characterized in that: The materials of the ceramic lead chip carrier include: and .

6. The chip bonding method according to claim 1, characterized in that: The specific formula of the preset adjustment function is: ； in, is the second nitrogen dosage, is the first nitrogen gas dosage, k(t) is an adjustment coefficient related to time, k(t) is determined according to the stress change curve of the gold-gallium alloy, and A is the area of ​​the chip.

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