Low temperature silver-free solder for amb ceramic substrate soldering and soldering method thereof

Abstract

The application discloses a low-temperature silver-free solder for AMB ceramic substrate welding and a welding method thereof, and the mass percentage of each component in the low-temperature silver-free solder is as follows: nickel Ni: 5%-28%, titanium Ti: 1%-7%, silicon Si: 0.05%-1%, and the balance is aluminum Al; the method comprises the following steps: adding each element in the low-temperature silver-free solder into a crucible according to the percentage and heating, after each element is melted into an alloy, the alloy is atomized into spherical powder alloy by using a vacuum air atomization device and a screen, and the powder with a particle size of less than 48 microns is screened out, or the alloy is rolled into a foil-shaped alloy by using a high-precision rolling mill; the application has the characteristics that the requirements of reliable connection of the AMB ceramic substrate can be met, the welding temperature and the amount of silver are reduced, and the material cost of the solder and the brazing electricity cost are greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of brazing materials technology, and in particular to a low-temperature silver-free solder for welding AMB ceramic substrates and a welding method thereof. Background Technology

[0002] Current AMB solders are mainly silver-copper-titanium solders. However, due to the high melting temperature of silver-copper-titanium solders, copper foil grains in AMB ceramic substrates are prone to grow, affecting the thermal and electrical properties of AMB ceramic substrates. At the same time, the solders contain silver, which increases the cost. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing silver-copper-titanium solders, such as high melting temperature affecting the thermal and electrical properties of AMB ceramic substrates and high solder cost, and to provide a low-temperature silver-free solder for welding AMB ceramic substrates and its welding method.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A low-temperature silver-free solder for soldering AMB ceramic substrates, wherein the mass percentages of each component in the low-temperature silver-free solder are: nickel (Ni): 5%-28%, titanium (Ti): 1%-7%, silicon (Si): 0.05%-1%, and the balance is aluminum (Al).

[0006] As a preferred option, titanium (Ti) is replaced with zirconium (Zr).

[0007] Preferably, silicon (Si) is replaced with boron (B).

[0008] This invention uses Al, a low-melting-point element, as the main element, and adds Ti or Zr active elements. Since the melting points of Ti and Zr are very different from those of Al, Ti and Zr are difficult to completely and uniformly dissolve in Al, and are also prone to causing Al to volatilize, making it difficult to control the chemical composition ratio.

[0009] This invention incorporates the high-melting-point transition element Ni, and utilizes the miscibility of Ni with Ti and Zr, as well as the miscibility of Ni with Al, to achieve compositional homogenization of the AlNiTi(Zr) active metal. To ensure the soldering activity of the silver-free solder, 0.05%-1% by mass of self-fluxing elements Si and B are added to provide the silver-free solder with antioxidant properties.

[0010] The solder contains 5%-28% nickel by mass and 1%-7% Ti or Zr by mass, which ensures the wettability of the silver-free solder on the ceramic substrate under low-temperature soldering conditions.

[0011] To achieve wettability of silver-free solder on ceramic substrates under low-temperature soldering conditions, the present invention adds nickel at a mass percentage of 5%-28% and Ti or Zr at a mass percentage of 1%-7%.

[0012] Therefore, the present invention can meet the requirements for reliable connection of AMB ceramic substrates and effectively avoid abnormal grain growth of copper foil, greatly reducing the material cost of solder.

[0013] As a preferred option, the following steps are included:

[0014] The elements of the low-temperature silver-free solder are added to a crucible according to their percentages and heated. When the temperature inside the crucible reaches 800℃-880℃, the elements melt into an alloy. The alloy is then atomized into spherical powder using a vacuum atomization device. Powder with a particle size of less than 48 micrometers is sieved from the powdered alloy using a 300M-340M sieve to obtain the prepared low-temperature silver-free solder.

[0015] As a preferred option, the elements in the low-temperature silver-free solder are added to a crucible according to their percentages and heated until the temperature inside the crucible reaches 800℃-880℃, at which point the elements melt into an alloy. This process can be replaced by the following steps:

[0016] First, add 5%-15% Al and all other elements to the crucible. After all elements have completely melted into an alloy, wait for the temperature of the alloy melt to drop to 680℃-750℃ before adding the remaining percentage of Al.

[0017] First, add a portion of Al. After all elements have completely melted into an alloy, wait for the temperature of the alloy melt to drop to 680℃-750℃, and then add the remaining percentage of Al. This can achieve uniform melting of AlNiTi(Zr) silver-free solder and ensure the composition ratio of the silver-free solder.

[0018] A method for soldering AMB ceramic substrates using a low-temperature silver-free solder includes the following steps:

[0019] 6-1. Low-temperature silver-free solder is made into solder paste by mixing 10%-15% ethyl cellulose and terpineol in an organic solvent. The solder paste is then transferred to the upper and lower surfaces of a zirconium oxide substrate, an aluminum nitride substrate, or a silicon nitride substrate using screen printing.

[0020] 6-2. Place two copper foils on the upper and lower surfaces of the ceramic substrate respectively, and apply a certain pressure to both copper foils to make them stably adhere to the solder paste on the upper and lower surfaces of the ceramic substrate. Place the ceramic substrate into a vacuum brazing furnace.

[0021] 6-3, Brazing: Evacuate the vacuum brazing furnace to 1.0 x 10⁻² Pa, raise the temperature in the vacuum brazing furnace to 350℃-500℃ at a heating rate of 3℃ / min, and hold for 0.5h-2h; raise the temperature in the vacuum brazing furnace to 750℃-800℃ at a heating rate of 5℃ / min, and hold for 5min-20min. When the solder paste melts, weld the two copper foils to the upper and lower surfaces of the ceramic substrate respectively. After holding at the temperature, allow the ceramic substrate to cool to room temperature with the furnace, and remove the ceramic substrate from the vacuum brazing furnace. The brazing is then complete.

[0022] As a preferred option, the following steps are included:

[0023] Step 6-1 is replaced by the following steps:

[0024] The alloy melted in the crucible is made into a plate-shaped alloy ingot. The alloy ingot is then processed into foil-shaped alloy sheets with a width of 125mm-140mm and a thickness of 0.05mm-0.25mm using a high-precision rolling mill. The two foil-shaped alloy sheets are flattened and placed on the upper and lower surfaces of a ceramic substrate, respectively.

[0025] In order to improve the processability and applicability of solder, this invention processes silver-free solder into foil or powder form.

[0026] Preferably, the process also includes the following steps: heating the alloy ingot to 420℃-480℃, holding it at that temperature for 1h-4h, and then using a high-precision rolling mill to process the alloy ingot into a width of 125mm-140mm.

[0027] Therefore, the present invention has the following beneficial effects: it can meet the requirements for reliable connection of AMB ceramic substrates and effectively avoid abnormal grain growth of copper foil, greatly reducing the material cost of solder; compared with other solders, it has a lower melting point, which reduces the welding temperature and saves more energy; it does not contain silver, so the solder cost is low, and the effect after welding is comparable to or even slightly better than that of silver-copper-titanium solder. Attached Figure Description

[0028] Figure 1 This is an ultrasonic scanning detection void ratio map according to Embodiment 1 of the present invention;

[0029] Figure 2 This is an ultrasonic scanning detection void ratio map of Embodiment 3 of the present invention;

[0030] Figure 3 This is an ultrasonic scanning detection void ratio map according to Embodiment 7 of the present invention;

[0031] Figure 4 This is a diagram of void ratio detected by ultrasonic scanning, as shown in Comparative Example 1.

[0032] Figure 5 This is a diagram of void ratio detected by ultrasonic scanning, as shown in Comparative Example 2.

[0033] Figure 6 This is a weld layer interface diagram of Example 3;

[0034] Figure 7 This is a welding interface diagram of Comparative Example 2. Detailed Implementation

[0035] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0036] Example 1

[0037] A low-temperature silver-free solder for soldering AMB ceramic substrates, wherein the mass percentages of the components in the low-temperature silver-free solder are: nickel (Ni): 5%, titanium (Ti): 7%, silicon (Si): 0.05%, and the balance is aluminum (Al); the process includes the following steps:

[0038] First, 10% Al and all other elements are added to a crucible. After the temperature inside the crucible reaches 840℃, the elements melt into an alloy liquid. After the temperature of the alloy liquid drops to 720℃, the remaining percentage of Al is added. The alloy is then atomized into spherical powder using a vacuum atomization device. Powder with a particle size of less than 48 micrometers is sieved from the powdered alloy using a 300M sieve to obtain the prepared low-temperature silver-free solder.

[0039] A method for soldering AMB ceramic substrates using a low-temperature silver-free solder includes the following steps:

[0040] 6-1. Low-temperature silver-free solder is prepared by mixing 13% ethyl cellulose and terpineol in an organic solvent to make solder paste. The solder paste is then transferred to the upper and lower surfaces of a zirconium oxide substrate, an aluminum nitride substrate, or a silicon nitride substrate using screen printing.

[0041] 6-2. Place two copper foils on the upper and lower surfaces of the ceramic substrate respectively, and apply a certain pressure to both copper foils to make them stably adhere to the solder paste on the upper and lower surfaces of the ceramic substrate. Place the ceramic substrate into a vacuum brazing furnace.

[0042] 6-3, Brazing: Evacuate the vacuum in the vacuum brazing furnace to 1.0 x 10⁻⁶. -2 Pa, raise the temperature in the vacuum brazing furnace to 450℃ at a heating rate of 3℃ / min, and hold for 1 hour; raise the temperature in the vacuum brazing furnace to 780℃ at a heating rate of 5℃ / min, and hold for 10 minutes. The solder paste melts and the two copper foils are welded to the upper and lower surfaces of the ceramic substrate respectively. After the holding period, allow the ceramic substrate to cool to room temperature with the furnace, and remove the ceramic substrate from the vacuum brazing furnace. The brazing is then complete.

[0043] Example 2

[0044] The mass percentages of the components in the low-temperature silver-free solder in Example 2 are: nickel (Ni): 28%, titanium (Ti): 1%, silicon (Si): 1%, and the balance is aluminum (Al);

[0045] The alloy melted in the crucible is made into a plate-shaped alloy ingot. The alloy ingot is heated to 450°C and held for 3 hours. Then, the alloy ingot is processed into a foil-shaped alloy with a width of 130 mm and a thickness of 0.06 mm using a high-precision rolling mill. The two foil-shaped alloys are flattened and placed on the upper and lower surfaces of the ceramic substrate, respectively. The other methods in Example 2 are the same as those in Example 1.

[0046] Example 3

[0047] The mass percentages of each component in the low-temperature silver-free solder in Example 3 are: Nickel (Ni): 20%, Titanium (Ti): 5%, Silicon (Si): 0.08%; the other methods in Example 3 are the same as those in Example 1.

[0048] Example 4

[0049] The mass percentages of each component in the low-temperature silver-free solder in Example 2 are: nickel (Ni): 28%, zirconium (Zr): 1%, silicon (Si): 1%, and the balance is aluminum (Al); the other methods in Example 4 are the same as those in Example 1.

[0050] Example 5

[0051] The mass percentages of each component in the low-temperature silver-free solder in Example 2 are: nickel (Ni): 6%, zirconium (Zr): 7%, silicon (Si): 0.08%, and the balance is aluminum (Al); the other methods in Example 5 are the same as those in Example 1.

[0052] Example 6

[0053] The mass percentages of each component in the low-temperature silver-free solder in Example 2 are: nickel (Ni): 10%, zirconium (Zr): 4%, silicon (Si): 0.2%, and the balance is aluminum (Al); the other methods in Example 6 are the same as those in Example 1.

[0054] Example 7

[0055] The mass percentages of each component in the low-temperature silver-free solder are: nickel (Ni): 20%, titanium (Ti): 5%, boron (B): 0.05%, and the balance is aluminum (Al); the other methods in Example 7 are the same as those in Example 1.

[0056] Example 8

[0057] The mass percentages of each component in the low-temperature silver-free solder are: nickel (Ni): 18%, titanium (Ti): 4%, boron (B): 1%, and the balance is aluminum (Al); the other methods in Example 8 are the same as those in Example 1.

[0058] Example 9

[0059] The mass percentages of each component in the low-temperature silver-free solder are: nickel (Ni): 25%, titanium (Ti): 1%, boron (B): 0.08%, and the balance is aluminum (Al); the other methods in Example 9 are the same as those in Example 1.

[0060] Welding performance analysis:

[0061] Alloy powder was prepared using the AlNi5Ti7Si0.05 alloy from Example 1, and then used for brazing at a temperature of 780°C for 10 minutes.

[0062] like Figure 1 As shown, the void ratio of the prepared AMB ceramic substrate after welding was 0.5% as measured by an ultrasonic scanner, and the peel strength was 22 N / mm as measured by a peel strength tester.

[0063] Alloy powder was prepared using the AlNi20Ti5Si0.08 alloy from Example 3, and then used for brazing at a temperature of 780°C for 10 minutes.

[0064] like Figure 2 As shown, the void ratio of the prepared AMB ceramic substrate after welding was 0.12% as measured by an ultrasonic scanner, and the peel strength was 23 N / mm as measured by a peel strength tester.

[0065] Figure 6 This is a metallographic image of the weld layer interface observed using a metallographic microscope in Example 3, which shows that the solder and the weld layer are tightly bonded.

[0066] Alloy powder was prepared using the AlNi20Ti5Si0.05 alloy from Example 7, and then used for brazing at a temperature of 780°C for 10 minutes.

[0067] like Figure 3 As shown, the void ratio of the prepared AMB ceramic substrate after welding was 0.08% as measured by an ultrasonic scanner, and the peel strength was 25 N / mm as measured by a peel strength tester.

[0068] Figure 7 This is a metallographic microscopy image of the weld interface observed in Comparative Example 2. It shows unmelted alloy powder, an uneven weld layer, and a loose bond between the ceramic and copper foil.

[0069] Comparative Example 1: AMB ceramic substrate was welded using silver-copper-titanium solder. The process was the same as in Example 1, with a welding temperature of 900°C and a holding time of 10 minutes.

[0070] like Figure 4 As shown, the AMB ceramic substrate prepared in Comparative Example 1 had a void ratio of 0.8% and a peel strength of 15 N / mm after welding. This indicates that the welding temperature using silver-copper-titanium solder is high, the peel strength is low, and the connection between the copper foil and the AMB ceramic substrate is unreliable.

[0071] Comparative Example 2: AMB ceramic substrate was soldered using silver-copper-titanium solder. The process was the same as in Example 1, and the soldering temperature and time were set the same as in Example 1. The solder did not completely melt.

[0072] like Figure 5 As shown, the void ratio of the sample prepared in Comparative Example 2, measured using an ultrasonic scanner, was 11.5%, indicating that a reliable connection could not be achieved between the copper foil and the ceramic substrate. This demonstrates that it is impossible to successfully weld the copper foil to the AMB ceramic substrate using silver-copper-titanium solder at the same welding temperature.

[0073] in, Figures 1-5 The original background color in the image is black. Figures 1-5 The black background is changed to gray, the white dots represent the cavitary areas of the ultrasound scan, and the other areas are normal areas without cavities.

[0074] As can be seen, compared with other solders, the present invention has a lower melting point, which reduces the welding temperature and saves more energy; without the addition of silver, the cost of the solder is low, and the effect after welding is comparable to or even slightly better than that of silver-copper-titanium solder.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-temperature silver-free solder for soldering AMB ceramic substrates, characterized in that, The mass percentages of each component in the low-temperature silver-free solder are: Nickel (Ni): 5%-28%, Titanium (Ti): 1%-7%, Silicon (Si): 0.05%-1%, with the balance being Aluminum (Al); the process includes the following steps: First, add 5%-15% Al and all other elements to the crucible. After all elements are completely melted into an alloy, wait for the temperature of the alloy melt to drop to 680℃-750℃, and then add the remaining percentage of Al. Use a vacuum atomization device to atomize the alloy into spherical powder. Use a 300M-340M sieve to sieve out powder with a particle size of less than 48 micrometers from the powdered alloy to obtain the prepared low-temperature silver-free solder.

2. The low-temperature silver-free solder for soldering AMB ceramic substrates according to claim 1, characterized in that, Titanium (Ti) is replaced with zirconium (Zr).

3. The low-temperature silver-free solder for soldering AMB ceramic substrates according to claim 1, characterized in that, Silicon (Si) is replaced with boron (B).

4. A welding method based on the low-temperature silver-free solder for AMB ceramic substrate welding as described in claim 1, characterized in that, Includes the following steps: 4-1. Low-temperature silver-free solder is made into solder paste by mixing 10%-15% of ethyl cellulose and terpineol in a mixed organic solvent. The solder paste is then transferred to the upper and lower surfaces of a zirconium oxide substrate, aluminum nitride substrate, or silicon nitride substrate using screen printing. 4-2. Place two copper foils on the upper and lower surfaces of the ceramic substrate respectively, and apply a certain pressure to both copper foils to make them stably adhere to the solder paste on the upper and lower surfaces of the ceramic substrate. Place the ceramic substrate into a vacuum brazing furnace. 4-3, Brazing: Evacuate the vacuum in the vacuum brazing furnace to 1.0 x 10⁻⁶. -2 Pa, raise the temperature in the vacuum brazing furnace to 350℃-500℃ at a heating rate of 3℃ / min, and hold for 0.5h-2h; raise the temperature in the vacuum brazing furnace to 750℃-800℃ at a heating rate of 5℃ / min, and hold for 5min-20min. The solder paste melts and the two copper foils are welded to the upper and lower surfaces of the ceramic substrate respectively. After the holding period, allow the ceramic substrate to cool to room temperature with the furnace, and remove the ceramic substrate from the vacuum brazing furnace. The brazing is then complete.

5. The welding method for low-temperature silver-free solder for AMB ceramic substrate welding according to claim 4, characterized in that, Includes the following steps: Step 4-1 is replaced by the following steps: The alloy melted in the crucible is made into a plate-shaped alloy ingot. The alloy ingot is then processed into foil-shaped alloy sheets with a width of 125mm-140mm and a thickness of 0.05mm-0.25mm using a high-precision rolling mill. The two foil-shaped alloy sheets are flattened and placed on the upper and lower surfaces of a ceramic substrate, respectively.

6. The welding method for low-temperature silver-free solder for AMB ceramic substrate welding according to claim 5, characterized in that, The process also includes the following steps: heating the alloy ingot to 420℃-480℃, holding it at that temperature for 1-4 hours, and then using a high-precision rolling mill to process the alloy ingot into a width of 125mm-140mm.

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