Low-modulus low-temperature sintered elargol as well as preparation method and application thereof

Abstract

The invention relates to the technical field of semiconductor packaging, and discloses a low-modulus low-temperature sintering silver colloid and a preparation method and application thereof.The low-modulus low-temperature sintering silver colloid comprises, by mass, 0.2%-3.0% of curable resin composition, 9.5%-14% of diluent, 40%-50% of silver powder 1, 20%-35% of silver powder 2 and 10%-25% of sinterable silver powder 3; the particle size of the silver powder 1 is 3.0-8.0 [mu] m, the particle size of the silver powder 2 is 0.5-2.5 [mu] m, and the particle size of the sinterable silver powder 3 is 0.3-2.3 [mu] m. The micron silver powder adopted in the method is mild in reaction and controllable in agglomeration speed in the sintering process, internal high stress and defects caused by rapid agglomeration and heat release of the nano silver powder are avoided, and the obtained sintered silver layer shows the excellent performance that the normal-temperature modulus is smaller than or equal to 6.5 GPa.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor packaging, in particular to a low-modulus low-temperature sintering silver glue, a preparation method and application thereof. BACKGROUND

[0002] With the development of semiconductor chips towards higher power density, smaller size and stronger integration, the heat generated per unit area rises sharply, which poses unprecedented challenges to the connecting materials between chips and substrates. The traditional tin-based eutectic solder has a generally low thermal conductivity (usually less than 60 W / m·K), which has become a key bottleneck limiting the heat dissipation capacity of high-power devices, and is prone to cause excessive chip junction temperature, affecting performance and service life.

[0003] To solve this fundamental problem, sintered silver technology has become an ideal alternative due to its excellent thermal conductivity (thermal conductivity can reach 150~250 W / m·K). This technology forms a high-thermal-conductivity silver skeleton by forming a firm metallurgical bond between silver particles under heating conditions, which can significantly reduce the thermal interface resistance and improve overall heat dissipation efficiency. Currently, the core direction of the development of this technology is to achieve "low temperature" and "pressureless" sintering, that is, to reduce the process temperature to below 300℃ under the premise of ensuring performance, and to eliminate the expensive and complex pressing step, so as to be compatible with more heat-sensitive components, simplify the production process and reduce costs.

[0004] Currently, the mainstream low-temperature pressureless sintering silver technology route is highly dependent on nano-silver materials. For example, there have been reports or products that can start and complete sintering at a temperature range of 180~230℃ without applying external force. This advantage is due to the large specific surface area and high surface activity of nano-silver particles, which can cause significant atomic diffusion and bonding at relatively low temperatures.

[0005] However, the technology route with nano-silver as the core exposes the following two key defects in practice: 1. High cost, the preparation process of nano-silver powder is complex, so that the raw material cost is much higher than that of traditional micron silver powder, which makes the final product expensive, and seriously restricts its popularization in cost-sensitive large-scale application scenarios; 2. Long-term reliability is challenged, the extremely high surface energy of nano-silver is a double-edged sword in the sintering process, on the one hand, it promotes low-temperature sintering; on the other hand, it is also easy to cause the particles to fuse and aggregate with each other too fast and too violent during sintering. This unbalanced combination process is easy to form local stress concentration and micro defects in the sintered body, and at the same time makes the silver layer after sintering too hard (i.e. "high modulus"). In the temperature cycle generated by the actual work of the chip, this hard and brittle connecting layer cannot effectively buffer the stress generated by the mismatch of the thermal expansion coefficients between the chip and the substrate, and this stress will be directly transmitted to the chip itself, increasing the risk of chip cracking or connection interface failure, which threatens the long-term reliability of the packaging structure.

[0006] Therefore, there is an urgent need in the art for an innovative material solution that not only retains the process advantages of low-temperature pressureless sintering and high thermal conductivity, but also significantly reduces material costs and effectively improves the mechanical properties of the sintered body (especially reduces the modulus), thereby improving the heat dissipation capability while ensuring the firmness and reliability of the packaging connection. SUMMARY

[0007] The purpose of the present application is to solve the problems in the background art, and to provide a low-modulus low-temperature sintering silver paste, its preparation method and application, which is suitable for epoxy and acrylate double systems, and significantly reduces the cost by using micron silver powder. By adjusting the material components and structure, the problem of high internal stress and high modulus caused by excessive or uneven sintering densification is avoided, so as to obtain a sintered silver connecting layer with lower modulus, smaller stress and better toughness, which can better buffer the thermal mismatch stress and enhance the long-term reliability of the packaging structure. The sintered silver paste can still realize efficient densification under the condition of lower process temperature (such as 200-230℃) and without external pressure, and finally form an interconnection layer with high thermal conductivity, high electrical conductivity and good bonding strength, which meets the stringent requirements of high-performance semiconductor packaging.

[0008] The technical solution of the present application is: a low-modulus low-temperature sintering silver paste, characterized in that it comprises the following components by mass percentage: Curable resin composition 0.2%-3.0%, Diluent 9.5%-14%, Silver powder 1 40%-50%, Silver powder 2 20%-35%, Sinterable silver powder 3 10%-25%; The particle size of the silver powder 1 is 3.0-8.0 μm, the particle size of the silver powder 2 is 0.5-2.5 μm, and the particle size of the sinterable silver powder 3 is 0.3-2.3 μm. In the present application, the particle size is the median particle size D 50 The sum of the mass percentages of the above components is 100%.

[0009] More preferably, the components include, by mass percentage: the curable resin composition 0.5%-1.0%, the diluent 10%-11%, the silver powder 1 40%-50%, the silver powder 2 21%-31%, and the sinterable silver powder 3 15%-18%.

[0010] Preferably, the diluent is one or more of ethylene glycol butyl ether, diethylene glycol, heptanol, and terpineol, and the curable resin composition is the epoxy system composition I or the acrylate system composition II, The epoxy system composition I includes an epoxy resin, an epoxy diluent, a silane coupling agent I, and a curing agent I, The mass ratio of the epoxy resin, the epoxy diluent, the silane coupling agent I, and the curing agent I is (0.1-1.0):(0.1-0.5):(0.01-0.10):(0.01-0.05).

[0011] More preferably, the mass ratio of the epoxy resin, the epoxy diluent, the silane coupling agent I, and the curing agent I is (0.5-1.0):(0.2-0.5):(0.05-0.10):(0.01-0.02).

[0012] More preferably, in the epoxy system composition I, the epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and epoxidized polybutadiene; the epoxy diluent is one or more of aliphatic glycidyl ether, alicyclic glycidyl ether, and phenyl glycidyl ether; the silane coupling agent I is one or more of KH-550 and KH-560; and the curing agent I is one or more of aliphatic amine, alicyclic amine, adipic acid, and methyl imidazole.

[0013] More preferably, the acrylate system composition II includes an acrylate monomer, a polybutadiene derivative, a silane coupling agent II, and a curing agent II, The mass ratio of the acrylate monomer, the polybutadiene derivative, the silane coupling agent II, and the curing agent II is (0.1-1.0):(0.1-0.5):(0.01-0.10):(0.01-0.05).

[0014] More preferably, the mass ratio of the acrylate monomer, the polybutadiene derivative, the silane coupling agent II, and the curing agent II is (0.3-0.5):(0.2-0.3):(0.05-0.10):(0.01-0.02).

[0015] More preferably, in the acrylate system composition II, the acrylate monomer is one or more of methyl methacrylate MMA, ethyl methacrylate EMA, hexanediol diacrylate HDDA, pentaerythritol triacrylate PETA; the polybutadiene derivative is one or more of maleated polybutadiene MLBP, hydroxyl-terminated polybutadiene HTPB.

[0016] More preferably, in the acrylate system composition II, the silane coupling agent II is one or more of KH570, KH602; the curing agent II is one or more of benzoyl peroxide BPO, tert-butyl peroxybenzoate TBPB, dicumyl peroxide DCP.

[0017] Preferably, the specific surface area of the silver powder 1 is 0.3-1.0 m 2 / g, the specific surface area of the silver powder 2 is 1.0-2.2 m 2 / g, and the specific surface area of the sinterable silver powder 3 is 2.0-3.5 m 2 / g. More preferably, the sintering peak temperature of the sinterable silver powder 3 is 210-220℃.

[0018] Preferably, the low-modulus low-temperature sintering silver glue has the following properties: thermal conductivity ≥175 W / (m·K); modulus ≤6.5 GPa at room temperature, and modulus ≤7.5 GPa at high temperature 250±2℃.

[0019] resistivity ≤2.2 μΩ·cm; shear force ≥3.0 kg·f on a 1mm×1mm chip at room temperature, and shear force ≥2.5 kg·f on a 1mm×1mm chip at 200±2℃. 200±2℃ means 198-202℃, and 250±2℃ means 248-252℃.

[0020] The application also provides a preparation method of the low-modulus low-temperature sintering silver glue as described above, which comprises: mixing a curable resin composition and a diluent, then sequentially adding the silver powder 1, the silver powder 2, and the sinterable silver powder 3, fully stirring each time until uniform, and finally placing the mixture in a vacuum homogenizer to obtain the low-modulus low-temperature sintering silver glue.

[0021] The application also provides an application of the low-modulus low-temperature sintering silver glue as described above, which is applied to chip packaging.

[0022] The application has the following beneficial effects: 1. Relative to non-sintered ordinary conductive adhesive, the sintered silver adhesive of the present application can form a dense silver sintering network in the epoxy or acrylate system, so that firm metallurgical bonding between silver particles is generated. This gives the material extremely low volume resistivity (≤2.2 μΩ•cm) and excellent thermal conductivity (≥175 W / (m•K)), which can significantly reduce the connection resistance and thermal resistance, and meet the core demand of high-power, high-frequency semiconductor devices for high-efficiency conduction and heat dissipation.

[0023] 2. Thanks to the sintering connection between silver particles, the silver adhesive of the present application exhibits strong adhesion at room temperature and high temperature. Its shear strength tested on standard chips at room temperature and high temperature of 200℃ is far superior to that of conventional conductive adhesive (such as ≥3.0 kg•f at room temperature). This strong mechanical interlocking capability ensures the physical stability of the packaging structure in harsh environments, greatly improving the long-term use reliability of the product.

[0024] 3. Unlike conventional sintered silver adhesives on the market that rely on expensive nano-silver powder, the present application creatively uses a combination of specially designed and proportioned micron silver powder as a functional phase. While retaining the necessary sintering activity, the production difficulty and procurement cost of the core raw material are greatly reduced, enabling the product to achieve high performance while having a significant cost advantage, which is conducive to large-scale commercial application.

[0025] 4. The micron silver powder used in the present application has a mild reaction and controllable agglomeration speed during sintering, avoiding the internal high stress and defects caused by the rapid agglomeration and heat release of nano-silver powder. Therefore, the obtained sintered silver layer exhibits a lower modulus (≤6.5 GPa at room temperature). This low modulus and high toughness characteristic enables it to effectively absorb and release the stress generated between the chip and the substrate due to the mismatch of thermal expansion and contraction, fundamentally improving the fatigue resistance and service life of the package under temperature cycling conditions.

[0026] 5. The core silver powder formula of the present application can be compatible with both epoxy and acrylate resin systems, and can complete high-quality sintering at a low temperature of 200-230℃ without pressure. This provides users with the freedom to choose resin systems according to specific process or product performance preferences. The unified low-temperature pressureless sintering process also reduces the dependence on expensive special equipment, simplifies the production process, and broadens the application potential in power semiconductors, radio frequency packaging, advanced integration and other scenarios. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 is a micrograph of the conductive silver adhesive of Comparative Example 1, Fig. 2 is a micrograph of the conductive silver adhesive of Comparative Example 4, Fig. 3 is a micrograph of the conductive silver adhesive of Example 2. DETAILED DESCRIPTION

[0028] The concept and the technical effects of the present application will be described clearly and completely in combination with the embodiments, so that the purpose, features and effects of the present application can be fully understood. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application. If the specific conditions are not mentioned in the embodiments, the conventional conditions or the conditions suggested by the manufacturers are adopted. If the reagents or instruments are not mentioned by the manufacturers, they are the conventional products that can be purchased in the market.

[0029] The raw material specifications of the embodiments and the comparative examples of the present application are as follows: Epoxy resin, one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and epoxidized polybutadiene LEPB.

[0030] Epoxy diluent, alicyclic glycidyl ether EHPE-3150.

[0031] Silane coupling agent I, KH-550.

[0032] Curing agent I, methyl imidazole.

[0033] Acrylate monomer, one or more of methyl methacrylate MAA, ethyl methacrylate EMA, hexanediol diacrylate HDDA, and pentaerythritol triacrylate PETA.

[0034] Polybutadiene derivative, maleated polybutadiene MLBP.

[0035] Silane coupling agent II, methacryloyloxysilane KH570.

[0036] Curing agent II, one or more of benzoyl peroxide BPO, tert-butyl peroxybenzoate TBPB, and dicumyl peroxide DCP.

[0037] Diluent, one or more of ethylene glycol butyl ether, diethylene glycol, heptanol, and terpinen-4-ol.

[0038] Silver powder 1, silver powder of EA 0018 model produced by Metalor Company in the United States, D 50 with a particle size of 5.5 μm and a specific surface area of 0.81 m 2 / g.

[0039] Silver powder 2, silver powder of C0083P model produced by Metalor Company in the United States, D 50 with a particle size of 0.8 μm and a specific surface area of 1.72 m 2 / g.

[0040] Sinterable silver powder 3, Technic, USA, model 41-174 silver powder, D 50 Particle size 2.0 μm, specific surface area 3.0 m 2 Initial sintering temperature 197.6 °C, sintering peak temperature 214.9 °C, end sintering temperature 226.51 °C.

[0041] The low modulus low temperature sintering silver glue of the present application comprises the following components by mass percentage: 0.2%~3.0% of the curable resin composition, 9.5%~14% of the diluent, 40%~50% of silver powder 1, 20%~35% of silver powder 2, and 10%~25% of sinterable silver powder 3. The curable resin composition is epoxy system composition I or acrylate system composition II, which can be compatible with both epoxy resin and acrylate resin systems.

[0042] The following specific examples further illustrate the present application. Examples 1-3 are low modulus low temperature sintering silver glue when the curable resin composition is epoxy system composition I, and the formulations of the examples and comparative examples are shown in Table 1, wherein the data are mass percentages; Examples 4-6 are low modulus low temperature sintering silver glue when the curable resin composition is acrylate system composition II, and the formulations of the examples and comparative examples are shown in Table 2, wherein the data are mass percentages.

[0043] Table 1 Sintering silver glue formulation of epoxy system

[0044] Example 1 This example provides a low modulus low temperature sintering silver glue, and the raw materials include 0.76% of epoxy system composition I, 10.24% of diluent (a mixture of diethylene glycol and heptanol in a mass ratio of 1:1), 40% of silver powder 1, 31% of silver powder 2, and 18% of sinterable silver powder 3 by mass percentage.

[0045] Epoxy system composition I is a mixture of bisphenol F epoxy resin, epoxy diluent (alicyclic glycidyl ether), silane coupling agent I (KH-550), and curing agent I (methyl imidazole) in a mass ratio of 0.5:0.2:0.05:0.01.

[0046] Sample preparation: according to the order and mass percentage in the above table, epoxy resin, epoxy diluent, silane coupling agent I, curing agent I, and diluent were sequentially added to the container and fully stirred until uniform. Then silver powder 1, silver powder 2, and sinterable silver powder 3 were added one by one, and each kind of silver powder needed to be fully stirred until uniform before adding the next one. The mixture was placed in a homogenizer for homogenization, and fully mixed under vacuum to remove air bubbles, thereby obtaining the low modulus low temperature sintering silver of this example.

[0047] Example 2 The present example provides a low modulus low temperature sintering silver glue, raw materials including epoxy system composition I is 0.76%, diluent 10.24% (diethylene glycol, heptanol mixed in a mass ratio of 1:1), silver powder 1 is 45%, silver powder 2 is 26%, and sinterable silver powder 3 is 18% by mass percentage.

[0048] The epoxy system composition I is a mixture of bisphenol F epoxy resin, epoxy diluent (alicyclic glycidyl ether), silane coupling agent I (KH-550), and curing agent I (methyl imidazole) in a mass ratio of 0.5:0.2:0.05:0.01.

[0049] Sample preparation: according to the above table order and mass percentage, epoxy resin, epoxy diluent, silane coupling agent I, curing agent I, diluent I were added in the container in turn, and fully stirred until uniform. Then silver powder 1, silver powder 2, and sinterable silver powder 3 were added one by one, and each silver powder needed to be fully stirred until uniform before adding the next one. The mixture was placed in a homogenizer for homogenization, and fully mixed under vacuum to remove bubbles, thus obtaining the low modulus low temperature sintering silver of the present example.

[0050] Example 3 The present example provides a low modulus low temperature sintering silver glue, raw materials including epoxy system composition I is 0.76%, diluent 10.24% (diethylene glycol, heptanol mixed in a mass ratio of 1:1), silver powder 1 is 45%, silver powder 2 is 26%, and sinterable silver powder 3 is 18% by mass percentage.

[0051] The epoxy system composition I is a mixture of bisphenol A epoxy resin, epoxy diluent (alicyclic glycidyl ether), silane coupling agent I (KH-550), and curing agent I (methyl imidazole) in a mass ratio of 0.5:0.2:0.05:0.01.

[0052] Sample preparation: according to the above table order and mass percentage, epoxy resin, epoxy diluent, silane coupling agent I, curing agent I, diluent were added in the container in turn, and fully stirred until uniform. Then silver powder 1, silver powder 2, and sinterable silver powder 3 were added one by one, and each silver powder needed to be fully stirred until uniform before adding the next one. The mixture was placed in a homogenizer for homogenization, and fully mixed under vacuum to remove bubbles, thus obtaining the low modulus low temperature sintering silver of the present example.

[0053] Comparative Example 1 The present comparative example provides a comparative sintering silver glue without adding sinterable silver powder 3, raw materials including epoxy system composition I is 20.15%, diluent 0.85% (diethylene glycol, heptanol mixed in a mass ratio of 1:1), silver powder 1 is 45%, and silver powder 2 is 34% by mass percentage.

[0054] Epoxy system composition I is bisphenol A epoxy resin, epoxy diluent (alicyclic glycidyl ether), silane coupling agent I (KH-550), curing agent I (methyl imidazole) are mixed in a mass ratio of 16:4:0.1:0.05. The preparation process refers to Example 1.

[0055] Comparative Example 2 This comparative example provides a comparative sintered silver paste without adding sinterable silver powder 3, and the raw materials include epoxy system composition I 0.76%, diluent 10.24% (diethylene glycol, heptanol mixed in a mass ratio of 1:1), silver powder 1 45%, silver powder 2 44% by mass percentage.

[0056] Epoxy system composition I is bisphenol A epoxy resin, epoxy diluent (alicyclic glycidyl ether), silane coupling agent I (KH-550), curing agent I (methyl imidazole) are mixed in a mass ratio of 0.5:0.2:0.05:0.01. The preparation process refers to Example 1.

[0057] Comparative Example 3 This comparative example provides a comparative sintered silver paste with an excess of organic phase, and the raw materials include epoxy system composition I 4.15%, diluent 9.85% (diethylene glycol, heptanol mixed in a mass ratio of 1:1), silver powder 1 45%, silver powder 2 26%, sinterable silver powder 3 15% by mass percentage.

[0058] Epoxy system composition I is bisphenol A epoxy resin, epoxy diluent (alicyclic glycidyl ether), silane coupling agent I (KH-550), curing agent I (methyl imidazole) are mixed in a mass ratio of 3:1:0.1:0.05. The preparation process refers to Example 1.

[0059] Table 2 Sintered silver paste formula of acrylate system

[0060] Example 4 This example provides a low modulus low temperature sintered silver paste, and the raw materials include acrylate system composition II 0.56%, diluent 10.44% (terpineol), silver powder 1 50%, silver powder 2 24%, sinterable silver powder 3 15% by mass percentage.

[0061] Acrylate system composition II is acrylate (ethyl methacrylate EMA), polybutadiene derivative (maleic anhydride polybutadiene MLBP), silane coupling agent II (KH570), curing agent II (BPO) are mixed in a mass ratio of 0.3:0.2:0.05:0.01.

[0062] The acrylate monomer, polybutadiene derivative, silane coupling agent II, curing agent II, diluent are stirred well to be uniform. Then the silver powder 1, silver powder 2, sinterable silver powder 3 are added one by one, and each kind of silver powder needs to be stirred well to be uniform before adding the next one. The above mixture is placed in a homogenizer for homogenization, and is mixed well in vacuum state to remove bubbles, so that the acrylate low-temperature sintering silver of the example is obtained.

[0063] Example 5 The example provides a low-modulus low-temperature sintering silver glue, and raw materials include acrylate system composition II 0.56%, diluent 10.44% (terpineol), silver powder 1 50%, silver powder 2 21%, and sinterable silver powder 3 18% by mass percentage.

[0064] The acrylate system composition II is acrylate (ethyl methacrylate EMA), polybutadiene derivative (maleated polybutadiene MLBP), silane coupling agent II (KH570), and curing agent II (BPO) mixed in a mass ratio of 0.3:0.2:0.05:0.01.

[0065] The acrylate low-temperature sintering silver glue is prepared according to the preparation method of Example 4.

[0066] Example 6 The example provides a low-modulus low-temperature sintering silver glue, and raw materials include acrylate system composition II 0.56%, diluent 10.44% (terpineol), silver powder 1 50%, silver powder 2 21%, and sinterable silver powder 3 18% by mass percentage.

[0067] The acrylate system composition II is acrylate (ethyl methacrylate EMA), polybutadiene derivative (maleated polybutadiene MLBP), silane coupling agent II (KH570), and curing agent II (BPO) mixed in a mass ratio of 0.3:0.2:0.05:0.01.

[0068] The acrylate low-temperature sintering silver glue is prepared according to the preparation method of Example 4.

[0069] Comparative Example 4 The comparative example provides a comparative sintering silver glue without adding silver powder 3, and raw materials include acrylate system composition II 13.15%, diluent (terpineol) 0.85%, silver powder 1 50%, and silver powder 2 36% by mass percentage.

[0070] The acrylate system composition II is acrylate (EMA), polybutadiene derivative (MLBP), silane coupling agent II (KH570), and curing agent II (BPO) mixed in a mass ratio of 11:2:0.1:0.05.

[0071] Comparative sintered silver paste preparation process refers to example 4.

[0072] Comparative example 5 This comparative example provides a comparative sintered silver paste without adding silver powder 3, the raw materials include acrylic ester system composition II 4.15% by mass percentage, diluent (terpineol) 9.85%, silver powder 1 50%, silver powder 2 36%.

[0073] The acrylic ester system composition II is a mixture of acrylic ester (EMA), polybutadiene derivative (MLBP), silane coupling agent II (KH570), and curing agent II (BPO) in a mass ratio of 3:1:0.1:0.05.

[0074] Comparative sintered silver paste preparation process refers to example 4.

[0075] Comparative example 6 This comparative example provides a comparative sintered silver paste without adding silver powder 3, the raw materials include acrylic ester system composition II 0.56% by mass percentage, diluent (terpineol) 10.44%, silver powder 1 50%, silver powder 2 39%.

[0076] The acrylic ester system composition II is a mixture of acrylic ester (EMA), polybutadiene derivative (MLBP), silane coupling agent II (KH570), and curing agent II (BPO) in a mass ratio of 0.3:0.2:0.05:0.01.

[0077] Comparative sintered silver paste preparation process refers to example 4.

[0078] Comparative example 7 This comparative example provides a comparative sintered silver paste with an excess of organic phase, the raw materials include acrylic ester system composition II 4.15% by mass percentage, diluent (terpineol) 9.85%, silver powder 1 50%, silver powder 2 21%, silver powder 3 15%.

[0079] The acrylic ester system composition II is a mixture of acrylic ester (EMA), polybutadiene derivative (MLBP), silane coupling agent II (KH570), and curing agent II (BPO) in a mass ratio of 3:1:0.1:0.05.

[0080] Comparative sintered silver paste preparation process refers to example 4.

[0081] Comparative example 8 This comparative example provides a comparative sintered silver paste with insufficient silver powder 3, the raw materials include acrylic ester system composition II 0.56% by mass percentage, diluent (terpineol) 10.44%, silver powder 1 50%, silver powder 2 31%, silver powder 3 8%.

[0082] The acrylate system composition II is obtained by mixing acrylate (EMA), polybutadiene derivative (MLBP), silane coupling agent II (KH570), and curing agent II (BPO) in a mass ratio of 0.3:0.2:0.05:0.01.

[0083] The comparative sintered silver adhesive was prepared according to the preparation process of Example 4.

[0084] Performance test 1. Conductive performance test, the test steps are as follows: Sample preparation The conductive adhesive prepared in the examples and the comparative examples was used to prepare a strip with a thickness of 0.005 cm and a width of 0.3 cm on a glass slide, and was placed in an oven for curing. The curing conditions were set as follows: 1 h for temperature rising from room temperature to 130℃, 0.5 h for constant temperature at 130℃, 1 h for temperature rising to 220℃, 0.5 h for constant temperature at 220℃, and 0.5 h for temperature dropping to 100℃. After the curing was completed, the sample was placed at room temperature.

[0085] Resistivity test A micro-ohmmeter "Mettler-RN2511N" was used to test the resistance of each sample by two-point probe method, and the resistivity was calculated according to the following formula: ρ = RS / L Wherein: ρ is the resistivity, unit is Ω·cm; R is the resistance, unit is Ω; S is the test cross-sectional area, unit is cm 2 ; L is the length of the material, unit is cm.

[0086] The test results are shown in Tables 3 and 4.

[0087] Table 3 Resistivity test results of epoxy system silver adhesive

[0088] As shown in Table 3, the comparative example 1 is a conventional epoxy conductive adhesive, and the resistivity is high due to the high proportion of organic phase. The comparative example 2 has too little organic phase content and does not contain sintering components, so it cannot form a material after curing and cannot test the resistivity. The organic phase content of the comparative example 3 is still about 4%, but the resistivity is only one tenth of that of the comparative example 1 due to the introduction of sintering components. The conductivities of Examples 1-3 are one order of magnitude smaller than that of the comparative example 3 and nearly two orders of magnitude smaller than that of the comparative example 1, based on the comparative example 3. It can be seen that the examples of the present application all achieve high sintering effect.

[0089] Table 4 Resistivity test results of acrylate system silver adhesive

[0090] As shown in Table 4, Comparative Example 4 is a conventional conductive adhesive with a large proportion of organic phase resin. Comparative Example 5 and Comparative Example 6 have a small proportion of resin and do not contain sinterable silver powder, so after curing, they cannot rely on the resin to form a whole piece like conventional conductive adhesives, nor do they have the effect of silver powder sintering. When testing the resistivity, the probe was broken by light pressing and could not be tested. Compared with Comparative Example 4 and Comparative Example 5, Comparative Example 7 has less than 5% resin content and its resistivity is significantly lower than that of Comparative Example 4 due to the introduction of sinterable silver powder. Although the proportion of organic phase in Comparative Example 8 is further reduced, the proportion of sinterable silver powder is small, and the resistivity is reduced to a limited extent. Compared with Comparative Example 4 and Comparative Example 6, the resin content of Comparative Example 8 and the present application is less than 1%, and sinterable silver powder is introduced. After curing, the present application relies on sintering, and the resistivity of the present application is significantly lower than that of Comparative Example 4. Compared with Comparative Example 8, the resistivity of the present application is 40 times smaller. Compared with Comparative Example 7, the present application has less raw material resin, increased silver content, and increased sinterable silver powder content, and its resistivity is one order of magnitude smaller.

[0091] 2. Adhesion test, test steps as follows: Take the conductive adhesive prepared from each comparative example and example, 1mm x 1mm back silver chip, copper plated silver frame. Take an appropriate amount of conductive adhesive and adhere the chip to the frame, and place it in an oven for curing. The curing conditions are set as follows: 1h from room temperature to 130℃, 0.5h at 130℃, 1h from 130℃ to 220℃, 0.5h at 220℃, 0.5h from 220℃ to 100℃. After curing, place it at room temperature.

[0092] The shear force was tested using a wire bonding push-pull force tester "HAWK-8200S", and the room temperature shear force was tested at room temperature (25±1℃), and the high temperature shear force was tested at 200±2℃. The test results of the epoxy system silver adhesive are shown in Tables 5-6, and the test results of the acrylate system silver adhesive are shown in Tables 7-8.

[0093] Table 5 Room temperature shear force test results of epoxy system silver adhesive

[0094] Table 6 High temperature shear force test results of epoxy system silver adhesive

[0095] As shown in Tables 5~6 above. Comparative Example 1 has higher shear force at room temperature due to the epoxy system and much higher organic phase ratio than other examples, but the shear force at high temperature drops significantly, only one fourth of that at room temperature. Comparative Example 2 has no shear force data because it has less organic phase content and shows no adhesion after curing. Comparative Example 3 reduces the organic phase composition and introduces sinterable silver powder, so although its shear force at room temperature decreases slightly, its shear force at high temperature is more than doubled compared with Comparative Example 1. The inventive examples have more than three times the shear force at high temperature compared with Comparative Example 1, indicating that sintering is obvious and shows excellent stability at high temperature; compared with Comparative Example 3, the inventive examples increase the sinterable composition and reduce the organic phase, so the shear force at high temperature also increases significantly, which also indicates that the sintering of the inventive examples is more complete.

[0096] Table 7 Shear force test results of acrylate system silver paste at room temperature

[0097] Table 8 Shear force test results of acrylate system silver paste at high temperature

[0098] From Tables 7~8 above, it can be seen that Comparative Examples 5 and 6 do not show adhesion due to the inability to sinter, and the chips fall off after curing, so there is no data. The shear force at room temperature and high temperature of Comparative Example 7 and the inventive examples is higher than that of Comparative Example 4, and the organic phase content is much lower than that of Comparative Example 4, so the sintering effect exists. Comparative Example 8 relies on the dual action of organic phase and adhesion, and the sintering ratio of the inventive examples is increased, so the shear force at high temperature of the inventive examples 4, 5 and 6 is increased by more than 37% compared with Comparative Example 7. This phenomenon also conforms to the nature that sintering shows more stability at high temperature. Compared with Comparative Example 8, the sinterable silver powder ratio of each inventive example is increased, and the advantages in shear force at room temperature and high temperature are obvious; this also proves that the more complete the sintering, the stronger the adhesion, i.e. the more reliable the adhesion.

[0099] 3. SEM electron microscope analysis, take the conductive adhesive samples of Comparative Example 4, Comparative Example 7 and Example 5 of the acrylate system, and cure them into 0.5 cm thick, 2x2 cm sized blocks (the curing conditions are set as 1 h from room temperature to 130℃, 0.5 h at 130℃, 1 h from 130℃ to 220℃, 0.5 h at 220℃, and 0.5 h from 220℃ to 100℃). Polish to a smooth surface. Use a scanning electron microscope "Czech TESCAN MIRA LMS" to observe the morphology. The results are shown in Figs. 1-3 .

[0100] From Fig. 1 it can be seen that the ordinary silver paste of Comparative Example 4 is uniformly distributed after curing, and the silver particles and organic phase are combined by the curing of the organic phase, and the particles are dispersed. FromFig. 2 It can be seen that the silver glue of Comparative Example 7 after curing presents a block shape, and the silver particles are fused with each other, but the organic phase is still dispersed therein. Example 5 of the present application presents a whole silver block shape due to almost no organic phase. It can be seen from the comparison that the addition of the sinterable silver powder changes the interaction of the silver particles in the curing system, and further increasing the proportion of the sinterable silver powder and reducing the organic phase, the sintering phenomenon is more obvious.

[0101] 4. Thermal conductivity test, the thermal conductivity of the sample is tested by laser flash method.

[0102] The sample is taken, cured into a 11mmx11mmx2-3mm bubble-free glue block, polished to be flat and smooth. The conductive glue of the sample is tested by a laser flash instrument "Germany NETZSCH LFA457". The results of the epoxy system silver glue are shown in Table 9 below, and the results of the acrylate system silver glue are shown in Table 10 below.

[0103] Table 9 Thermal conductivity test results of epoxy system silver glue

[0104] It can be seen from Table 9 that the thermal conductivity of the examples of the present application is increased by more than 65 times compared with Comparative Example 1 of the conventional epoxy conductive glue. It can be seen that the examples of the present application all achieve a high sintering degree, and the effect of sintering on the thermal conductivity increases exponentially.

[0105] Table 10 Thermal conductivity test results of acrylate system silver glue

[0106] It can be seen from Table 10 that the thermal conductivity of the ordinary conductive silver glue is as shown in Comparative Example 4, the thermal conductivity of the partially sintered silver glue of Comparative Example 8 is increased by more than 10 times, and the thermal conductivity of the fully sintered silver glue of the examples of the present application can all reach more than 180W / (m·K), basically meeting the needs of all high thermal conductivity.

[0107] 5. Modulus analysis: DMA three-point bending mode test is adopted. The sample is made into a long block with a size of 45mmx10mmx2mm and flat top and bottom. The modulus of the sample is tested by a dynamic thermal mechanical analyzer "TA Q800 / Mettler". The results of the epoxy system silver glue are shown in Table 11 below, and the results of the acrylate system silver glue are shown in Table 12 below. (Note: the product name of commercially available 1 is Jingcheng CT2700RST, and the product name of commercially available 2 is Namics H9890-6A) Table 11 Modulus test results of epoxy system silver glue

[0108] As can be seen from Table 11, the modulus at room temperature (25°C) and the modulus at high temperature (250°C) of Examples 1-3 of the present application are substantially reduced compared to commercially available sinterable silver paste. This property can significantly reduce the internal stress of the silver paste after curing.

[0109] Table 12 Modulus test results of acrylate based silver paste

[0110] As can be seen from Table 12, the modulus at room temperature (25°C) and the modulus at high temperature (250°C) of Example 8, which is a semi-sintered product, and Examples 1-3, which are fully sintered products, are substantially reduced compared to commercially available sinterable silver paste. The fully sintered product of Examples 1-3 has the lowest modulus at room temperature.

Claims

1. A low-modulus, low-temperature sintered silver paste, characterized in that, Includes the following components by mass percentage: Curable resin composition 0.2%~3.0%, Diluent 9.5%~14%, Silver powder 1 40%~50%, Silver powder 2 20%~35%, Sinterable silver powder 3 10%~25%; The silver powder 1 has a particle size of 3.0~8.0 μm, the silver powder 2 has a particle size of 0.5~2.5 μm, and the sinterable silver powder 3 has a particle size of 0.3~2.3 μm.

2. The low-modulus, low-temperature sintered silver paste as described in claim 1, characterized in that, The diluent is one or more of ethylene glycol butyl ether, diethylene glycol, heptanol, and terpineol; the curable resin composition is epoxy system composition I or acrylate system composition II. The epoxy system composition I includes epoxy resin, epoxy diluent, silane coupling agent I, and curing agent I. The mass ratio of epoxy resin, epoxy diluent, silane coupling agent I, and curing agent I is (0.1~1.0):(0.1~0.5):(0.01~0.10):(0.01~0.05).

3. The low-modulus, low-temperature sintered silver paste as described in claim 2, characterized in that, In the epoxy system composition I, the epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and epoxidized polybutadiene; the epoxy diluent is one or more of aliphatic glycidyl ether, alicyclic glycidyl ether, and phenyl glycidyl ether; the silane coupling agent I is one or more of KH-550 and KH-560; and the curing agent I is one or more of aliphatic amine, alicyclic amine, adipic acid, and methylimidazole.

4. The low-modulus, low-temperature sintered silver paste as described in claim 2, characterized in that, The acrylate system composition II includes acrylate monomers, polybutadiene derivatives, silane coupling agent II, and curing agent II. The mass ratio of acrylate monomer, polybutadiene derivative, silane coupling agent II, and curing agent II is (0.1~1.0):(0.1~0.5):(0.01~0.10):(0.01~0.05).

5. The low-modulus, low-temperature sintered silver paste as described in claim 4, characterized in that, In the acrylate system composition II, the acrylate monomer is one or more of methyl methacrylate (MMA), ethyl methacrylate (EMA), hexanediol diacrylate (HDDA), and pentaerythritol triacrylate (PETA); the polybutadiene derivative is one or more of maleic anhydride polybutadiene (MLBP) and hydroxyl-terminated polybutadiene (HTPB).

6. The low-modulus, low-temperature sintered silver paste as described in claim 5, characterized in that, In the acrylate system composition II, the silane coupling agent II is one or more of KH570 and KH602; the curing agent II is one or more of benzoyl peroxide BPO, tert-butyl peroxide TBPB, and dicumyl peroxide DCP.

7. The low-modulus, low-temperature sintered silver paste as described in claim 1, characterized in that, The silver powder 1 has a specific surface area of ​​0.3~1.0 m². 2 / g, silver powder 2 specific surface area 1.0~2.2 m² 2 / g, sinterable silver powder with a specific surface area of ​​2.0~3.5m² 2 / g.

8. The low-modulus, low-temperature sintered silver paste as described in claim 1, characterized in that, The properties of the low-modulus, low-temperature sintered silver paste are as follows: Thermal conductivity ≥175 W / (m·K); The modulus at room temperature is ≤6.5 GPa, and the modulus at a high temperature of 250±2 ℃ is ≤7.5 GPa. Resistivity ≤ 2.2 μΩ·cm; At room temperature, the shear force on a 1mm×1mm chip is ≥3.0 kg·f; at 200±2℃, the shear force on a 1mm×1mm chip is ≥2.5 kg·f.

9. A method for preparing low-modulus low-temperature sintered silver paste as described in any one of claims 1 to 8, characterized in that, include: The curable resin composition and diluent are mixed, and then silver powder 1, silver powder 2 and sinterable silver powder 3 are added in sequence. Each silver powder must be thoroughly stirred until uniform before adding. Finally, the mixture is placed in a vacuum homogenizer for homogenization to obtain low-modulus low-temperature sintered silver paste.

10. An application of the low-modulus low-temperature sintered silver paste as described in any one of claims 1 to 8, characterized in that, Used in chip packaging.

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