Cadmium-free low-silver solder containing tin, manganese and indium

Abstract

The invention discloses cadmium-free low-silver brazing filler metal containing tin, manganese and indium. The brazing filler metal comprises the following chemical components in percentage by mass: 58.0%-76.0% of Sn, 3%-8% of Ag, 1.5%-4% of Mn, 0.5%-2.5% of In, 0.05%-0.3% of Ge, 0.8%-1.5% of Sb, 0.1%-1.6% of Ni and the balance of Ce and Ti. The composite material has the advantages of high tensile strength, good high-temperature performance, high resistance to electrochemical corrosion in a humid and hot environment, low cost and the like, and can be adapted to various scenes such as microelectronic packaging, marine equipment, dissimilar metal connection and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of metal connection materials, and in particular relates to a cadmium-free and low-silver solder containing tin, manganese and indium. Background Art

[0002] Over the past three decades, with the booming development of industries such as electronics and information technology, home appliances, automobiles, military, and building and decorative materials, the demand for solder has grown, and brazing technology has played a vital role in these emerging sectors. my country has overcome technical difficulties, such as the processing of Cu-P solder, and has successfully developed nearly 100 new solders and fluxes. Solder alloys can be categorized into over ten different types based on their alloy system, including copper-based, silver-based, aluminum-based, tin-lead-based, gold-based, nickel-based, and manganese-based. Over 200 solder alloy manufacturers in my country produce nearly 600 varieties, with an annual output of 35,000 to 40,000 tons. According to incomplete statistics, the domestic home appliance manufacturing industry alone consumes 300 tons of silver solder annually. Silver-based solders possess excellent mechanical and process properties, and possess excellent wettability for most metal materials. They can be used for brazing low-carbon steel, low-alloy structural steel, high-temperature nickel-based alloys, copper, and copper alloys. However, silver is a rare and precious metal, and its high price places a significant burden on production.

[0003] Existing cadmium-containing solders (such as Sn-Pb-Cd system): Although they have excellent wettability (spreading area ratio>1.3), the biological half-life of cadmium is as long as 10-30 years (WHO data), and the EU RoHS directive has completely banned them. High-silver cadmium-free solders (such as SAC305, Sn96.5Ag3.0Cu0.5): When the Ag content is ≥3%, the cost increases sharply (silver price is about 5.8 yuan / gram), and the coarsening of the Ag3Sn phase leads to increased brittleness (fracture toughness KIC<15MPa·m 1 / 2 ). Low-silver substitutes (such as Sn-Cu-Ni system): There are two major technical bottlenecks: 1) Liquidus temperature > 230°C cannot meet the requirements of low-temperature welding. 2) The thickness of the interface IMC layer (Cu6Sn5) is > 5μm (prone to cracks after thermal cycling). When the silver content is reduced to 3-8%, how to achieve tensile strength ≥ 220MPa (traditional low-silver solder ≤ 180MPa) through multi-scale organizational control; inhibit excessive growth of Ag3Sn phase (size control < 1μm) to avoid brittle fracture; develop low-temperature welding process (liquidust temperature ≤ 200°C) to adapt to the welding requirements of heat-sensitive components; solve the electrochemical corrosion problem in a hot and humid environment (85°C / 85% RH) to ensure that the conductivity decay is < 3% in 1000h, etc. are all problems that need to be solved urgently. Summary of the Invention

[0004] The present invention aims to provide a cadmium-free low-silver solder containing tin, manganese and indium, which solves the problems of low tensile strength, brittle fracture, and electrochemical corrosion in hot and humid environments existing in existing solders.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0006] A cadmium-free, low-silver solder containing tin, manganese and indium is characterized in that the chemical composition of the solder is as follows, by mass percentage: 58.0% to 76.0% Sn, 3% to 8% Ag, 1.5% to 4% Mn, 0.5% to 2.5% In, 0.05% to 0.3% Ge, 0.8% to 1.5% Sb, 0.1% to 1.6% Ni, and the balance is Ce+Ti.

[0007] In the present invention, Sn forms the matrix phase, and the β-Sn phase ratio is controlled to be greater than 85%. When the Sn mass percentage is less than 58%, the liquidus temperature rises suddenly, and when the Sn mass percentage is greater than 76%, the strength decreases.

[0008] In the present invention, the added Ag and Sn form an Ag3Sn strengthening phase, the size of which is controlled to be 0.5-1.2 μm. When the mass percentage of Ag is less than 3%, the eutectic reaction is insufficient, and when the mass percentage of Ag is greater than 8%, the cost increases sharply.

[0009] In the present invention, the added Mn and Sn form a nano-scale MnSn2 phase (10-20nm) to pin dislocations. When the mass percentage of Mn is less than 1.5%, the strengthening is insufficient, and when the mass percentage of Mn is greater than 8%, processing brittleness is caused.

[0010] In the present invention, the added In reduces the surface tension. For every 0.5% increase in the amount of In added, the wetting time is shortened by 0.3s.

[0011] In the present invention, the added Ge inhibits Sn oxidation and reduces welding voids (void ratio < 0.5%). Excessive addition, when the mass percentage of Ge is > 0.3%, will form a brittle GeSn phase.

[0012] In the present invention, the added Sb performs solid solution strengthening and improves the high temperature strength (strength retention rate at 250° C.>70%). When the mass percentage of Sb is>1.5%, the plasticity drops sharply.

[0013] In the present invention, the added Ni refines the interface IMC layer and suppresses Kirkendall voids. Adding 0.3% Ni can reduce the thickness of the IMC layer by 40%.

[0014] In the present invention, the added Ce+Ti forms CeTi2O5 nanoparticles (50-80nm) to purify the grain boundaries, and the Ce molar ratio needs to be controlled at 1:2 (error ±5%).

[0015] According to some preferred embodiments of the present invention, the chemical composition of the solder needs to satisfy the following mass percentage ratio: ∑[Ag+Mn+In+Ge+Sb+Ni+Ce+Ti]=24-46%.

[0016] According to some preferred embodiments of the present invention, the chemical composition of the solder is as follows in mass percentage: ∑[Ce+Ti]=0.07-3%.

[0017] According to some preferred embodiments of the present invention, the chemical composition of the solder is Ce:Ti=1:2 in molar ratio.

[0018] According to some preferred embodiments of the present invention, the chemical composition of the solder is as follows by mass percentage: 58.0% Sn, 3% Ag, 1.5% Mn, 0.5% In, 0.05% Ge, 0.8% Sb, 0.1% Ni, and the balance is Ce+Ti.

[0019] According to some preferred embodiments of the present invention, the chemical composition of the solder is as follows by mass percentage: 76.0% Sn, 8% Ag, 4% Mn, 2.5% In, 0.3% Ge, 1.5% Sb, 1.6% Ni, and the balance is Ce+Ti.

[0020] According to some preferred embodiments of the present invention, the chemical composition of the solder is as follows by mass percentage: 67.0% Sn, 5.5% Ag, 2.75% Mn, 1.5% In, 0.175% Ge, 1.15% Sb, 0.85% Ni, and the balance is Ce+Ti.

[0021] Compared with previous studies, the technical solution provided in this application creatively solves the following key technical problems: 1. Innovation of the component system: ternary synergistic strengthening mechanism, and the establishment of a Mn-In-Sb ternary synergistic model for the first time (satisfying the relationship: 0.3×(Mn%)+0.7×(In%)=Sb%±0.2). Through the synergistic effect of manganese nano-precipitation phase (MnSn2), the interfacial activation effect of indium and the solid solution strengthening of antimony, the traditional solder strength-plasticity inversion problem is broken through, and the tensile strength is achieved. ≥220MPa, while the elongation is greater than 25% (compared to SAC305 solder, the strength is increased by 23% and the plasticity is increased by 40%). 2. Rare earth composite control technology: Innovative use of Ce-Ti binary composite addition (molar ratio 1:2, error ±5%) to form 5-8nm CeTi2O5 nanoclusters, achieving grain boundary purification through the following mechanisms: Pinning grain boundary migration: inhibiting Ag3Sn phase coarsening (size ≤ 1.2μm), capturing oxygen impurities: reducing the oxygen content of the solder to ≤ 12ppm (a 67% reduction), and increasing the recrystallization temperature: reducing the processing annealing temperature by 50°C (300°C → 250°C).

[0022] The beneficial effects of the present invention are:

[0023] (1) By adding Mn element (1.5-4%), nano-scale MnSn2 phase (10-20 nm) is formed, which can pin dislocations and refine grains, making the solder tensile strength ≥220 MPa, far exceeding the 180 MPa of traditional low-silver solder.

[0024] (2) Optimization of high temperature performance: The solid solution strengthening effect of Sb (0.8-1.5%) combined with the cryogenic treatment process (-196°C) makes the high temperature strength retention rate of the brazing material at 250°C greater than 70%, making it suitable for welding high temperature components in aerospace.

[0025] (3) Anti-electrochemical corrosion: The added Ce+Ti forms CeTi2O5 nanoparticles (50-80nm), and the conductivity decay is less than 3% in a hot and humid environment (85℃ / 85%RH) for 1000h, and the corrosion rate in the salt spray test is reduced by 60%. DETAILED DESCRIPTION

[0026] The present application is described in further detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0027] 1. Main raw materials:

[0028] Commercially available Sn (99.99A grade tin ingots from Yunnan Tin Group (GB / T728-2010)), silver (Heraeus Ag9999 grade silver foil (YS / T 201-2015)), manganese (Xiangtan Electrochemical electrolytic manganese flakes (Mn ≥ 99.8%, GB / T 2774-2016)), indium (Zhuzhou Keneng high-purity indium pellets (In ≥ 99.995%, YS / T 264-2012)), germanium (Zhongge Technology Zone Melting Germanium Ingots (Ge ≥ 99.999%, GB / T 11069-2014)), antimony (Sb 99.9 grade antimony ingots from Xikuangshan Shanxing Antimony Industry (GB / T4062-2012)), and nickel (carbonyl nickel powder from Jinchuan Group (Ni ≥ 99.9%, ASTM D 1667) were used. B330)), cerium (Ce) and titanium (Ti) (Baotou Steel rare earth Ce-Ti master alloy (Ce = 1:2 molar ratio))

[0029] 2. Example

[0030] Example 1

[0031] The following process steps are used to prepare the solder:

[0032] S1: Vacuum induction melting: Equipment: ZG-0.01 vacuum furnace (ultimate vacuum degree 5×10-4Pa), melting sequence: melt 67g Sn (450℃ for 20min), add 5.5g silver and 2.75g manganese (heated to 480℃), then add 1.5g indium, 1.15g antimony, 0.85g nickel (electromagnetic stirring, frequency 20Hz), and finally add 0.175g germanium and 0.69g Ce-Ti master alloy. Finally, the melt is purified and degassed by introducing argon (speed 1200rpm, time 15min).

[0033] S2: Directional solidification: Cooling medium: Ga-In-Sn liquid alloy (thermal conductivity > 40 W / m·K), solidification parameters: first stage (T > 230°C): cooling rate 5°C / min to promote dendrite refinement, second stage (T < 230°C): cooling rate 20°C / min to suppress element segregation.

[0034] S3: Plastic processing, hot rolling: 480℃ for cogging, total deformation 80% (pass reduction 10-15%), warm rolling: 180℃ for rolling to target thickness, final rolling temperature strictly controlled at 120±5℃; annealing: continuous annealing furnace (300℃×2min, protective gas H2 / N2=5 / 95).

[0035] S4: Surface treatment, chemical nickel plating: thickness 1-2μm, plating solution formula: NiSO4 (30g / L) + NaH2PO2 (25g / L) + C3H6O3 (15g / L), passivation treatment: chromate conversion film (film weight 0.2~0.4g / m 2 , hexavalent chromium content <0.1μg / cm 2 ).

[0036] Example 2

[0037] S1: Vacuum induction melting: Equipment: ZG-0.01 vacuum furnace (maximum vacuum degree 5×10 -4 Pa), smelting sequence: melt 76g Sn (450℃ for 20min), add 8g silver and 4g manganese (heated to 480℃), then add 2.5g indium, 1.5g antimony, 1.6g nickel (electromagnetic stirring at 20Hz), and finally add 0.3g germanium and 0.69g Ce-Ti master alloy. Finally, the melt is purified and degassed by argon rotation (speed 1200rpm, time 15min).

[0038] S2: Directional solidification: Cooling medium: Ga-In-Sn liquid alloy (thermal conductivity > 40 W / m·K), solidification parameters: first stage (T > 230°C): cooling rate 5°C / min to promote dendrite refinement, second stage (T < 230°C): cooling rate 20°C / min to suppress element segregation.

[0039] S3: Plastic processing, hot rolling: 480℃ for cogging, total deformation 80% (pass reduction 10-15%), warm rolling: 180℃ for rolling to target thickness, final rolling temperature strictly controlled at 120±5℃; annealing: continuous annealing furnace (300℃×2min, protective gas H2 / N2=5 / 95).

[0040] S4: Surface treatment, chemical nickel plating: thickness 1-2μm, plating solution formula: NiSO4 (30g / L) + NaH2PO2 (25g / L) + C3H6O3 (15g / L), passivation treatment: chromate conversion film (film weight 0.2~0.4g / m 2 , hexavalent chromium content <0.1μg / cm 2 ).

[0041] Example 3

[0042] S1: Vacuum induction melting: Equipment: ZG-0.01 vacuum furnace (maximum vacuum degree 5×10 -4 Pa), smelting sequence: melt 58g Sn (450℃ for 20min), add 3g silver and 1.5g manganese (heated to 480℃), then add 0.5g indium, 0.8g antimony, 0.1g nickel (electromagnetic stirring at 20Hz), and finally add 0.05g germanium and 0.69g Ce-Ti master alloy. Finally, the melt is purified and degassed by argon rotation (speed 1200rpm, time 15min).

[0043] S2: Directional solidification: Cooling medium: Ga-In-Sn liquid alloy (thermal conductivity > 40 W / m·K), solidification parameters: first stage (T > 230°C): cooling rate 5°C / min to promote dendrite refinement, second stage (T < 230°C): cooling rate 20°C / min to suppress element segregation.

[0044] S3: Plastic processing, hot rolling: 480℃ for cogging, total deformation 80% (pass reduction 10-15%), warm rolling: 180℃ for rolling to target thickness, final rolling temperature strictly controlled at 120±5℃; annealing: continuous annealing furnace (300℃×2min, protective gas H2 / N2=5 / 95).

[0045] S4: Surface treatment, chemical nickel plating: thickness 1-2μm, plating solution formula: NiSO4 (30g / L) + NaH2PO2 (25g / L) + C3H6O3 (15g / L), passivation treatment: chromate conversion film (film weight 0.2~0.4g / m 2 , hexavalent chromium content <0.1μg / cm 2 ).

[0046] Comparative Example 1

[0047] S1: Vacuum induction melting: Equipment: ZG-0.01 vacuum furnace (maximum vacuum degree 5×10 -4 Pa), melting sequence: melt 76g Sn (450℃ for 20min), add 8g silver, then add 2.5g indium, 1.5g antimony, 1.6g nickel in sequence (electromagnetic stirring, frequency 20Hz), and finally add 0.3g germanium and 0.69g Ce-Ti master alloy. Finally, the melt is purified and degassed by introducing argon (speed 1200rpm, time 15min).

[0048] S2: Directional solidification: Cooling medium: Ga-In-Sn liquid alloy (thermal conductivity > 40 W / m·K), solidification parameters: first stage (T > 230°C): cooling rate 5°C / min to promote dendrite refinement, second stage (T < 230°C): cooling rate 20°C / min to suppress element segregation.

[0049] S3: Plastic processing, hot rolling: 480℃ for cogging, total deformation 80% (pass reduction 10-15%), warm rolling: 180℃ for rolling to target thickness, final rolling temperature strictly controlled at 120±5℃; annealing: continuous annealing furnace (300℃×2min, protective gas H2 / N2=5 / 95).

[0050] S4: Surface treatment, chemical nickel plating: thickness 1-2μm, plating solution formula: NiSO4 (30g / L) + NaH2PO2 (25g / L) + C3H6O3 (15g / L), passivation treatment: chromate conversion film (film weight 0.2~0.4g / m 2 , hexavalent chromium content <0.1μg / cm 2 ).

[0051] Comparative Example 2

[0052] S1: Vacuum induction melting: Equipment: ZG-0.01 vacuum furnace (maximum vacuum degree 5×10 -4 Pa), smelting sequence: melt 76g Sn (450℃ for 20min), add 8g silver and 1g manganese (heated to 480℃), then add 2.5g indium and 1.6g nickel (electromagnetic stirring at 20Hz), and finally add 0.3g germanium and 0.69g Ce-Ti master alloy. Finally, the melt is purified and degassed by argon rotation (speed 1200rpm, time 15min).

[0053] S2: Directional solidification: Cooling medium: Ga-In-Sn liquid alloy (thermal conductivity > 40 W / m·K), solidification parameters: first stage (T > 230°C): cooling rate 5°C / min to promote dendrite refinement, second stage (T < 230°C): cooling rate 20°C / min to suppress element segregation.

[0054] S3: Plastic processing, hot rolling: 480℃ for cogging, total deformation 80% (pass reduction 10-15%), warm rolling: 180℃ for rolling to target thickness, final rolling temperature strictly controlled at 120±5℃; annealing: continuous annealing furnace (300℃×2min, protective gas H2 / N2=5 / 95).

[0055] S4: Surface treatment, chemical nickel plating: thickness 1-2μm, plating solution formula: NiSO4 (30g / L) + NaH2PO2 (25g / L) + C3H6O3 (15g / L), passivation treatment: chromate conversion film (film weight 0.2~0.4g / m 2 , hexavalent chromium content <0.1μg / cm 2 ).

[0056] Comparative Example 3

[0057] S1: Vacuum induction melting: Equipment: ZG-0.01 vacuum furnace (maximum vacuum degree 5×10 -4 Pa), smelting order: melt 76g Sn (450℃ for 20min), add 8g silver and 1g manganese (heated to 480℃), then add 2.5g indium, 1.5g antimony, 1.6g nickel (electromagnetic stirring, frequency 20Hz), and finally add 0.3g germanium. Finally, the melt is purified and degassed by passing argon gas (speed 1200rpm, time 15min).

[0058] S2: Directional solidification: Cooling medium: Ga-In-Sn liquid alloy (thermal conductivity > 40 W / m·K), solidification parameters: first stage (T > 230°C): cooling rate 5°C / min to promote dendrite refinement, second stage (T < 230°C): cooling rate 20°C / min to suppress element segregation.

[0059] S3: Plastic processing, hot rolling: 480℃ for cogging, total deformation 80% (pass reduction 10-15%), warm rolling: 180℃ for rolling to target thickness, final rolling temperature strictly controlled at 120±5℃; annealing: continuous annealing furnace (300℃×2min, protective gas H2 / N2=5 / 95).

[0060] S4: Surface treatment, chemical nickel plating: thickness 1-2μm, plating solution formula: NiSO4 (30g / L) + NaH2PO2 (25g / L) + C3H6O3 (15g / L), passivation treatment: chromate conversion film (film weight 0.2~0.4g / m 2 , hexavalent chromium content <0.1μg / cm 2 ).

[0061] Table 1: Test results of various embodiments and comparative examples

[0062]

[0063]

[0064] As can be seen in Table 1, the brazing filler metal prepared in Example 1 of the present invention achieved an excellent tensile strength of 238 MPa. However, in Comparative Example 1, which lacked the addition of Mn, its tensile strength decreased significantly compared to the other examples. Furthermore, the corrosion resistance (salt spray) of Comparative Example 3 (without the Ce-Ti master alloy) was inferior to that of Examples 1 and 2, indicating that the addition of the Ce+Ti alloy reduced the corrosion rate.

[0065] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A cadmium-free low-silver solder containing tin, manganese and indium, characterized in that: The chemical composition of the solder is as follows by mass percentage: 58.0% to 76.0% Sn, 3% to 8% Ag, 1.5% to 4% Mn, 0.5% to 2.5% In, 0.05% to 0.3% Ge, 0.8% to 1.5% Sb, 0.1% to 1.6% Ni, and the balance is Ce+Ti.

2. The solder according to claim 1, wherein The chemical composition of the solder must meet the following mass percentage ratio: ∑[Ag+Mn+In+Ge+Sb+Ni+Ce+Ti]=24-46%.

3. The solder according to claim 1, wherein The chemical composition of the solder is as follows: ∑[Ce+Ti]=0.07-3% by mass percentage.

4. The solder according to claim 1, wherein The chemical composition of the solder is Ce:Ti=1:2 in molar ratio.

5. The solder according to claim 1, wherein The chemical composition of the solder is as follows in terms of mass percentage: 58.0% Sn, 3% Ag, 1.5% Mn, 0.5% In, 0.05% Ge, 0.8% Sb, 0.1% Ni, and the balance is Ce+Ti. The solder according to claim 1 , wherein The chemical composition of the solder is as follows in terms of mass percentage: 76.0% Sn, 8% Ag, 4% Mn, 2.5% In, 0.3% Ge, 1.5% Sb, 1.6% Ni, and the balance is Ce+Ti.

7. The solder according to claim 1, wherein The chemical composition of the solder is as follows in mass percentage: 67.0% Sn, 5.5% Ag, 2.75% Mn, 1.5% In, 0.175% Ge, 1.15% Sb, 0.85% Ni, and the balance is Ce+Ti.

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