A pressure-free, low-temperature sintering method and its application

Abstract

The present invention discloses a pressure-free, low-temperature sintering method and its application, belonging to the field of electronic packaging technology. The present invention mainly includes the following steps: S1 pretreatment: after cleaning the surface of the pad and the lead, the sintering material is activated, coated on the bonding surface of the pad and the lead, fixed, and then the pad is fixed on the sintering plate; S2 precuring treatment: placing the sintering plate in (1) in an oven, under the protection of a nitrogen atmosphere, heating to 30-100°C, maintaining for 30-60 minutes, and cooling to room temperature; S3 sintering treatment: placing the sintering plate that has been precured in (2) in a high-temperature furnace, under the protection of an inert gas atmosphere, heating to 100-150°C, maintaining for 30-60 minutes, and then heating to 150-250°C, maintaining for 60-120 minutes, and cooling to room temperature. The sintering process can improve the sintering efficiency and the sintering quality.

Description

Technical Field

[0001] The invention relates to the technical field of electronic packaging, and in particular to a pressure-free, low-temperature sintering method and application thereof. Background Art

[0002] The main purpose of electronic packaging is: (1) to protect the IC chip; (2) to provide interconnection between the IC chip and other electronic components to achieve the transmission of electrical signals. Generally, large-scale and ultra-large-scale integrated circuits can be divided into four packaging levels. Chip-level interconnection technology belongs to the first-level packaging and is widely used in the field of electronic packaging. The selection of appropriate chip functional and structural bonding materials is very important for electronic device packaging. It is not only related to the effective combination between the chip and the substrate, but also crucial to the thermal adaptability of the entire packaged device.

[0003] It is known that tin-lead soldering and wire bonding are widely used in IC packaging and effective electrical interconnection. The operation is controllable and has been put into large-scale automated production. The local temperature of this interconnection and assembly method is relatively high, and the melting temperature of the solder or solder wire must be reached, which can easily lead to oxidation of the surface of the components or high-temperature damage and shedding. When electronic components experience thermal shocks of temperature rise and fall, the ability of solder-connected devices to resist large-scale temperature cycles is limited, especially when used in an environment above 200°C, the device failure rate increases sharply. At the same time, lead-containing solders are highly environmentally toxic and related applications have been stopped.

[0004] Wire bonding can replace welding wires to a certain extent, but due to the high temperature (>200℃), high mechanical vibration and high humidity environment in the application scenario, the life of wire bonding is greatly reduced. In order to meet the needs of high temperature measurement, it is necessary to find an interconnection solution that is suitable for high temperature environments.

[0005] As a substitute for lead-containing solder, sintered materials have an elastic modulus that is superior to that of tin-lead solder, and can be sintered at low temperatures to enable applications in high-temperature environments. Components connected by sintered materials are more resistant to high-temperature thermal shock and mechanical strain, have better fatigue tolerance, and can meet application requirements in high-temperature and high-mechanical vibration environments.

[0006] At present, the commonly used sintering processes are pressure sintering and pressureless sintering. Pressure sintering means that the sintered material is sintered in a high-pressure environment of ~20MPa. Compared with pressureless sintering, the sintered bonding layer of pressure sintering is denser, the probability of cracks and delamination in the sintered matrix is ​​lower, and the component bonding strength is higher. However, pressure-assisted sintering has high requirements for equipment, which not only increases the equipment cost, but also easily causes device damage. In order to ensure the high bonding strength of sintered lead components in harsh industrial environments, reduce the equipment cost and operation difficulty of the sintering process, and achieve effective interconnection by optimizing the pressureless sintering process.

[0007] Therefore, in order to solve the above problems, it is necessary to conduct further in-depth research on the pressureless, low-temperature sintering process. Summary of the invention

[0008] In view of this, one of the objects of the present invention is to provide a pressure-free, low-temperature sintering method; a second object of the present invention is to provide an application of a pressure-free, low-temperature sintering method in a composite device.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A pressure-free, low-temperature sintering method, the method comprising the following steps:

[0011] (1) Pretreatment: Clean the surface of the pad and the lead, activate the sintering material, apply it to the bonding surface of the pad and the lead, fix it, and then fix the pad on the sintering board;

[0012] (2) Pre-curing treatment: Place the sintered plate in step (1) in an oven, heat it to 30-100° C. under a nitrogen atmosphere, maintain it for 30-60 min, and then cool it to room temperature;

[0013] (3) Sintering treatment: Place the sintered plate that has undergone pre-curing treatment in step (2) in a high-temperature furnace, and heat it to 100-150° C. under the protection of an inert gas atmosphere. Keep it for 30-60 minutes, then heat it to 150-250° C., keep it for 60-120 minutes, and then cool it to room temperature.

[0014] Preferably, in step (1), the cleaning is any one of alternating ultrasonic cleaning with anhydrous ethanol and acetone solutions, plasma solution cleaning, acid-base solution cleaning or deionized water rinsing.

[0015] Preferably, in step (1), the activation treatment time is 30 to 200 minutes.

[0016] Preferably, in step (1), the sintering material comprises metal nanoparticles, a polymer adhesive and a stabilizer.

[0017] Preferably, the viscosity of the sintered material is less than 15000 mPa.s.

[0018] Preferably, the metal nanoparticles are any one or more of silver, gold or platinum.

[0019] Preferably, the average particle size of the metal nanoparticles is 7.5-10 μm.

[0020] Preferably, the mass percentage of the metal nanoparticles is 85-99%.

[0021] Application of the above method in preparing a composite device.

[0022] Preferably, the combined device consists of a pad and a lead; the pad and the lead are fixedly connected by a sintered material.

[0023] The beneficial effects of the present invention are as follows: the present invention provides a pressure-free, low-temperature sintering method and its application, the method includes pretreatment, precuring treatment and sintering treatment, can realize the bonding of components of different shapes such as surface-to-surface, surface-to-line, etc., adopts low temperature, can reduce the failure rate of devices, and can obtain a dense sintered bonding layer without external pressure, which greatly simplifies the operation difficulty and reduces the cost. Compared with pressure sintering, this method can realize large-scale industrial application. Selecting materials with similar properties of metal nanoparticles in the sintering material can realize metal diffusion connection at the bonding interface during the sintering process, improve the bonding strength, and the combined device sintered by this method can resist high-temperature fatigue strain and mechanical vibration.

[0024] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0026] Figure 1 This is a flow chart of the pressure-free, low-temperature sintering method in Example 1;

[0027] Figure 2 It is a schematic structural diagram of the combination of the pad, lead, sintering material and sintering plate in Example 1;

[0028] Figure 3 This is a SEM image of the sintered material in Example 1 after sintering;

[0029] Reference numerals: 1 is a pad, 2 is a sintering plate, 3 is a lead, and 4 is a sintering material. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0031] Example 1

[0032] The pressure-free, low-temperature sintering method has a process such as Figure 1 As shown, the specific steps include:

[0033] S1 pretreatment: After the pad 1 and the lead 3 are ultrasonically cleaned alternately with anhydrous ethanol and acetone solutions, they are finally soaked and cleaned with deionized water, and the sintered material 4 is activated for 115 minutes, coated on the bonding surface of the pad 1 and the lead 3, and fixed, the pad is fixed on the sintering plate 2 (its structural schematic diagram is shown in FIG. Figure 2 shown);

[0034] S2 pre-curing treatment: placing the sintered plate 2 in step S1 in an oven, heating it to 65°C under a nitrogen atmosphere, maintaining it for 45 minutes, and then cooling it to room temperature;

[0035] S3 sintering treatment: the sintered plate 2 pre-cured in step S2 is placed in a high temperature furnace, and under the protection of an inert gas atmosphere, the temperature is raised to 125° C., maintained for 45 minutes, then raised to 200° C., maintained for 90 minutes, and then cooled to room temperature.

[0036] Example 2

[0037] The pressure-free, low-temperature sintering method specifically includes the following steps:

[0038] (1) Pretreatment: The pad 1 and the lead 3 are ultrasonically cleaned alternately with anhydrous ethanol and acetone solutions, and then soaked and cleaned with deionized water. The sintered material 4 is activated for 30 minutes, coated on the bonding surface of the pad 1 and the lead 3, and fixed, and then the pad is fixed on the sintered plate 2;

[0039] (2) Pre-curing treatment: Place the sintered plate 2 in step (1) in an oven, heat to 30° C. under a nitrogen atmosphere, maintain for 30 min, and then cool to room temperature;

[0040] (3) Sintering treatment: The sintered plate 2 that has undergone pre-curing treatment in step (2) is placed in a high-temperature furnace, and under the protection of an inert gas atmosphere, the temperature is raised to 100° C., maintained for 30 min, then raised to 150° C., maintained for 60 min, and then cooled to room temperature.

[0041] Example 3

[0042] The pressure-free, low-temperature sintering method specifically includes the following steps:

[0043] S1 pretreatment: After the pad 1 and the lead 3 are ultrasonically cleaned alternately with anhydrous ethanol and acetone solutions, they are finally soaked and cleaned with deionized water. The sintered material 4 is activated for 200 minutes, coated on the bonding surface of the pad 1 and the lead 3, and fixed, and then the pad is fixed on the sintered plate 2;

[0044] S2 pre-curing treatment: placing the sintered plate 2 in step S1 in an oven, heating it to 100°C under a nitrogen atmosphere, maintaining it for 60 minutes, and then cooling it to room temperature;

[0045] S3 sintering treatment: the sintered plate 2 pre-cured in step S2 is placed in a high temperature furnace, and under the protection of an inert gas atmosphere, the temperature is raised to 150° C., maintained for 60 minutes, then raised to 250° C., maintained for 120 minutes, and then cooled to room temperature.

[0046] Performance Testing

[0047] Figure 3 This is a SEM picture of the sintered material in Example 1 after sintering. The results show that the sintered material is dense and has no obvious holes, which proves that there is a tight sintering transition layer between the sintered material and the bonding surface of the pad, which can ensure the effective connection between the pad and the lead.

[0048] Similarly, after testing, the sintered material also has the performance of the sintered material in Example 1 after sintering under other conditions, and has good application prospects.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A pressure-free, low-temperature sintering method, the method comprising the following steps: S1 pretreatment: clean the surface of the pad and lead, activate the sintering material, apply it to the bonding surface of the pad and lead, and fix the pad on the sintering board after pre-fixation; The sintering material comprises metal nanoparticles, a polymer adhesive and a stabilizer, wherein the average particle size of the metal nanoparticles is 7.5 to 10 μm, and the mass percentage of the metal nanoparticles is 85 to 99%; S2 pre-curing treatment: placing the sintered plate in step S1 in an oven, heating it to 30-100°C under a nitrogen atmosphere, maintaining it for 30-60 minutes, and then cooling it to room temperature; S3 sintering treatment: Place the sintered plate that has undergone pre-curing treatment in step S2 in a high-temperature furnace, and under the protection of an inert gas atmosphere, heat it to 100-150°C, maintain it for 30-60 minutes, then heat it to 150-250°C, maintain it for 60-120 minutes, and then cool it to room temperature.

2. The method according to claim 1, characterized in that In step S1, the cleaning is any one of alternating ultrasonic cleaning with anhydrous ethanol and acetone solutions, plasma solution cleaning, acid-base solution cleaning or deionized water rinsing.

3. The method according to claim 1, characterized in that In step S1, the activation treatment time is 30 to 200 minutes.

4. The method according to claim 1, characterized in that: The viscosity of the sintered material is less than 15000 mPa.s.

5. The method according to claim 1, characterized in that The metal nanoparticles are any one or more of silver, gold or platinum.

6. Use of the method according to any one of claims 1 to 5 in preparing a composite device.

7. The use according to claim 6, characterized in that: The combined device consists of a pad and a lead; the pad and the lead are fixedly connected via a sintering material.

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