阅读说明：本技术 一种可实现芯片垂直堆叠的Sn基钎料及其键合方法 (Sn-based brazing filler metal capable of realizing vertical chip stacking and bonding method thereof ) 是由 张亮 李志豪 郭永环 何鹏 李木兰 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种可实现芯片垂直堆叠的Sn基钎料及其键合方法,其成分包括氧化铝纳米纤维、纳米钯颗粒、Bi和Sn。本发明利用氧化铝纳米纤维、纳米钯颗粒、Bi和Sn四者耦合作用强化焊点,添加氧化铝纳米纤维会将富Bi和IMC晶粒紧紧缠绕在一起,而纳米钯颗粒会聚集在富Bi和IMC晶粒晶界处,具有钉扎氧化铝纳米纤维和晶界的作用,氧化铝纳米纤维和纳米钯颗粒耦合强化焊点,因此焊点在服役期间仍然保持较高的强度和使用寿命,且具有良好的润湿性和较高的焊点力学性能,能够满足高密度封装以及三维封装电子器件芯片垂直堆叠的高可靠性需求,可用于波峰焊、回流焊以及其他钎焊方法。(The invention discloses a Sn-based brazing filler metal capable of realizing vertical chip stacking and a bonding method thereof. The invention utilizes the coupling effect of the alumina nano fiber, the nano palladium particles, the Bi and the Sn to strengthen the welding spot, the added alumina nano fiber can tightly wind the Bi-rich crystal grains and the IMC crystal grains together, the nano palladium particles can be gathered at the crystal grain boundary of the Bi-rich crystal grains and the IMC crystal grains, and the alumina nano fiber and the nano palladium particles have the function of pinning the alumina nano fiber and the crystal grain boundary, so the welding spot is strengthened by the coupling of the alumina nano fiber and the nano palladium particles, the welding spot still has higher strength and service life during service, and has good wettability and higher welding spot mechanical property, can meet the high reliability requirement of high-density packaging and vertical stacking of three-dimensional packaging electronic device chips, and can be used for wave soldering, reflow soldering and other soldering methods.)

1. The Sn-based solder capable of realizing vertical chip stacking is characterized by comprising the following components in percentage by mass: 1.0-5.0% of alumina nano-fiber, 3.0-15.0% of nano-palladium particles, 50-60% of Bi and the balance of Sn.

2. The Sn-based solder capable of realizing vertical chip stacking according to claim 1, wherein the ratio of the addition amount of the alumina nanofibers and the nano palladium particles is 1: 3.

3. the Sn-based solder capable of realizing vertical chip stacking according to claim 1, wherein the Sn-based solder comprises the following components in percentage by mass: the content of the alumina nano-fiber is 3.0 percent, the content of the nano-palladium particles is 9.0 percent, the content of Bi is 50 percent, and the balance is Sn.

4. The Sn-based solder capable of realizing vertical chip stacking according to claim 1, wherein the Sn-based solder comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.0 percent, the content of the nano-palladium particles is 3.0 percent, the content of Bi is 56 percent, and the balance is Sn.

5. The Sn-based solder capable of realizing vertical chip stacking according to claim 1, wherein the Sn-based solder comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.0 percent, the content of the nano-palladium particles is 3.0 percent, the content of Bi is 58 percent, and the balance is Sn.

6. The method for bonding the Sn-based solder capable of realizing the vertical stacking of the chips as claimed in claim 1, wherein the Sn powder, the Bi powder, the nano palladium particles and the alumina nano fibers are mixed with the rosin resin, the thixotropic agent, the stabilizer, the active auxiliary agent, the active agent and the solvent to prepare the solder paste, the salient points are prepared on the surface of the metal layer of the chip by a jet printing technology, and the vertical stacking interconnection of the chips is realized by adopting instantaneous liquid phase bonding.

Technical Field

The invention relates to a Sn-based brazing filler metal and a bonding method thereof, in particular to the Sn-based brazing filler metal capable of realizing vertical chip stacking and the bonding method thereof, and belongs to the technical field of chip-scale packaging.

Background

With the development of moore's law, the miniaturization and multi-functionalization of electronic devices has become an engine for the development of the integrated circuit industry. The vertical stacking and interconnection of the chips in the three-dimensional space successfully pushes the development of electronic products to the direction of miniaturization, integration and multi-functionalization. The stacking technology is mainly applied to various hardware including a 3D stacked memory, a Graphic Processing Unit (GPU), a Field Programmable Gate Array (FPGA) and a CMOS Image Sensor (CIS), and the total value of the chip stacking technology market is predicted to exceed $ 55 billion by 2023 according to research reports of research institution YOLE, and the annual growth rate is 27%. Therefore, the technology of stacking chips in three-dimensional space and the related reliability problem will become important research issues in the industry.

In order to realize vertical stacking of chips in three-dimensional space, researchers in the industry propose to realize vertical stacking of chips by using a high-melting-point intermetallic compound (IMC), which is mainly formed by a liquid-solid interdiffusion reaction between Sn (melting point 231 ℃) as an interconnection material and a metal layer (UBM) or a copper Pillar (Cu pilar) under a certain pressure and temperature (higher than the melting point of Sn) to form the high-melting-point intermetallic compound (IMC), for example, Cu₆Sn₅Melting point 415 ℃ and Cu₃Sn is 676 ℃, and the requirements of three-dimensional packaging chip stacking on low-temperature bonding and high-temperature service are met. However, the welding spots are mostly brittle intermetallic compound welding spots, and the welding spots of the three-dimensional packaging device are easy to become stress concentration areas due to changes of service environments during service, so that the brittle intermetallic compound is easy to crack and the welding spots fail. Therefore, the high performance requirement of vertically stacking chips by using the high performance Sn-based solder is the premise of meeting the reliability of vertically stacking chips.

In the prior art, a series of Sn-based lead-free solders mainly adopting addition of alloy elements or nanoparticles to improve the performance of solders and welding spots appear, and selected elements generally comprise: bi. Ni, Co, Sb, etc. For example, the Sn-based lead-free solder disclosed in U.S. Pat. No. 10434608B2 includes (1.2-4.5%) Ag, (0.25-0.75%) Cu, (1.0-5.8%) Bi, (0.01-0.15%) Ni, and the balance Sn, and the wettability, solder joint shear property, and thermal fatigue resistance of the solder are enhanced to some extent by optimizing the content of alloy elements, which is mainly directed to conventional SMT (Surface Mounted Technology) solder joints, the solder joints are composed of an intermetallic compound layer and a solder base, and the conventional SMT solder joints occupy most of the solder joints due to a short soldering time, but for micro solder joints of high-density packages and three-dimensional packages, the intermetallic compound occupies most of the solder joints, which results in completely different properties, and thus the solder is not suitable for high-density packages and three-dimensional packaged electronic devices. The Sn-based lead-free solder disclosed in Chinese patent ZL201810286715.6 comprises (3.0-3.1%) Ag, (0.7-1.0%) Cu, (3.0-5.0%) Sb, (3.1-4.5%) Bi, (0.01-0.03%) Ni, (0.008-0.15%) Co and the balance of Sn, and the Sn-based lead-free solder can inhibit the expansion of solder joint cracks under severe environments with large temperature difference and load vibration by adding a certain amount of Ag, Cu, Sb, Bi, Ni and Co, mainly comprises trace amounts of Sb and Bi and trace amounts of Ni and Co added into the Sn-Ag-Cu solder, but aiming at a three-dimensional packaging all-intermetallic compound solder joint, the solder needs to be completely converted into an intermetallic compound for a long time, and the components Sb, Ni and Co can also be completely converted into the intermetallic compound, so the solder is not suitable for high-density packaging and three-dimensional packaging electronic devices.

Disclosure of Invention

Aiming at the problems, the invention provides the Sn-based brazing filler metal capable of realizing the vertical stacking of the chips, which can obviously improve the vertical stacking interconnection strength of the chips, has good wettability and higher welding spot mechanical property, can meet the high reliability requirement of the vertical stacking of the chips of high-density packaging and three-dimensional packaging electronic devices, and can be used for wave soldering, reflow soldering and other brazing methods.

In order to achieve the purpose, the Sn-based solder capable of realizing vertical chip stacking comprises the following components in percentage by mass: 1.0-5.0% of alumina nano-fiber, 3.0-15.0% of nano-palladium particles, 50-60% of Bi and the balance of Sn.

As a further improvement of the invention, the adding amount ratio of the alumina nano-fiber and the nano-palladium particle is 1: 3.

as an implementation mode of the invention, the Sn-based solder capable of realizing vertical chip stacking comprises the following components in percentage by mass: the content of the alumina nano-fiber is 3.0 percent, the content of the nano-palladium particles is 3.0 percent, the content of Bi is 58 percent, and the balance is Sn.

As an implementation mode of the invention, the Sn-based solder capable of realizing vertical chip stacking comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.0 percent, the content of the nano-palladium particles is 3.0 percent, the content of Bi is 56 percent, and the balance is Sn.

As an implementation mode of the invention, the Sn-based solder capable of realizing vertical chip stacking comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.0 percent, the content of the nano-palladium particles is 3.0 percent, the content of Bi is 58 percent, and the balance is Sn.

A method for bonding Sn-based brazing filler metal capable of realizing vertical chip stacking comprises the steps of mixing Sn powder, Bi powder, nano palladium particles and alumina nano fibers with rosin resin, a thixotropic agent, a stabilizer, an active auxiliary agent, an active agent and a solvent to prepare a soldering paste, preparing salient points on the surface of a metal layer of a chip by a spray printing technology, and realizing vertical chip stacking interconnection by adopting instantaneous liquid phase bonding.

Compared with the prior art, the Sn-based brazing filler metal capable of realizing vertical chip stacking strengthens a welding spot by utilizing the coupling effect of the alumina nano-fiber, the nano-palladium particle, the Bi and the Sn, the Bi content is 50-60%, the melting temperature of the brazing filler metal is mainly reduced, the temperature is controlled to be about 150 ℃, after the chip vertical stacking is realized through low-temperature bonding, the welding spot is completely composed of an intermetallic compound (IMC) and a Bi-rich phase, the Bi-rich phase and IMC crystal grain boundaries can become a weak area of the whole welding spot in a long-time service process, the alumina nano-fiber is added to form a similar net structure and is distributed in the internal tissue of the welding spot, the alumina nano-fiber can tightly wind the Bi-rich and IMC crystal grains together, the nano-palladium particle can be gathered at the Bi-rich and IMC crystal grain boundaries, the function of pinning the alumina nano-fiber and the crystal boundaries is realized, the alumina nano-fiber and the nano-palladium particle are coupled to strengthen the welding spot, therefore, the solder joint still keeps higher strength and service life during service, has good wettability and higher solder joint mechanical property, can meet the high reliability requirement of high-density packaging and vertical stacking of three-dimensional packaging electronic device chips, and can be used for wave soldering, reflow soldering and other soldering methods.

Drawings

FIG. 1 is a schematic diagram of the modification mechanism of the present invention;

FIG. 2 is a graph of the shear performance of 9 experimental examples of different alumina nanofiber contents with other components unchanged according to the present invention;

FIG. 3 is a graph of the shear performance of the Sn-58Bi-1.0 alumina nanofiber-3.0 nano-palladium particles of the present invention versus a lead-free solder (Sn-58Bi) that does not contain alumina nanofibers and nano-palladium particles during solder joint service.

Detailed Description

The Sn-based solder capable of realizing vertical chip stacking is coupled by adopting the aluminum oxide nano-fibers, the nano-palladium particles, the Bi and the Sn in a trace amount, so that the strength of vertical chip stacking interconnection can be obviously improved.

The mechanism of the invention is as follows: in order to realize the high-reliability interconnection of the vertical stacking of chips, the welding spot is strengthened by utilizing the coupling effect of the alumina nano-fiber, the nano-palladium particles, Bi and Sn, a simple modification mechanism schematic diagram is shown in figure 1, the Bi content is 50-60%, the melting temperature of the brazing filler metal is mainly reduced, the temperature is controlled to be about 150 ℃, after the vertical stacking of the chips is realized through low-temperature bonding, the welding spot is completely composed of an intermetallic compound (IMC) and a Bi-rich phase, a Bi-rich phase and an IMC crystal grain boundary can become a weak area of the whole welding spot in the long-time service process, the alumina nano-fiber is added to form a similar net structure and is distributed in the internal tissue of the welding spot, the alumina nano-fiber can tightly wind the Bi-rich and IMC crystal grains together, the nano-palladium particles can be gathered at the Bi-rich and IMC crystal grain boundary, the function of pinning the alumina nano-fiber and the crystal grain boundary is realized, the alumina nano-fiber and the nano-palladium particles are coupled to strengthen the welding spot, the strength and service life of the welding spot are still high during service. The coupling effect of the alumina nano-fiber and the nano-palladium particles is considered, the strengthening effect is exerted to the maximum extent, wherein the adding amount ratio of the alumina nano-fiber to the nano-palladium particles is controlled to be 1: 3.

the present invention will be described in detail with reference to examples. The materials used in the following 16 examples are Sn powder, Bi powder, nano-palladium particles, and alumina nanofibers, and the bonding method is: sn powder, Bi powder, nano palladium particles and alumina nano fibers are mixed with rosin resin, a thixotropic agent, a stabilizer, an active auxiliary agent, an active agent and a solvent to prepare soldering paste, salient points are prepared on the surface of a metal layer of a chip by a spray printing technology, and the vertical stacking interconnection of the chip is realized by adopting instantaneous liquid phase bonding.

Example 1:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.0 percent, the content of the nano-palladium particles is 3.0 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 138.4 ℃, and the liquidus temperature is about 140.3 ℃.

Example 2:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.1 percent, the content of the nano-palladium particles is 3.3 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 138.5 ℃, and the liquidus temperature is about 140.6 ℃.

Example 3:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.2 percent, the content of the nano-palladium particles is 3.6 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 138.7 ℃, and the liquidus temperature is about 140.9 ℃.

Example 4:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.3 percent, the content of the nano-palladium particles is 3.9 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 139.0 ℃, and the liquidus temperature is about 141.1 ℃.

Example 5:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.4 percent, the content of the nano-palladium particles is 4.2 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 139.5 ℃, and the liquidus temperature is about 141.5 ℃.

Example 6:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.5 percent, the content of the nano-palladium particles is 4.5 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 140 ℃, and the liquidus temperature is about 142.1 ℃.

Example 7:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.6 percent, the content of the nano-palladium particles is 4.8 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 141 ℃, and the liquidus temperature is about 143.2 ℃.

Example 8:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.7 percent, the content of the nano-palladium particles is 5.1 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 142.5 ℃, and the liquidus temperature is about 145.1 ℃.

Example 9:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.7 percent, the content of the nano-palladium particles is 5.1 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 143.6 ℃, and the liquidus temperature is about 147.0 ℃.

Example 10:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.8 percent, the content of the nano-palladium particles is 5.4 percent, the content of Bi is 56 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 147.1 ℃, and the liquidus temperature is about 150 ℃.

Example 11:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.0 percent, the content of the nano-palladium particles is 3.0 percent, the content of Bi is 50 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 144.2 ℃, and the liquidus temperature is about 154.0 ℃.

Example 12:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.1 percent, the content of the nano-palladium particles is 3.3 percent, the content of Bi is 50 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 144.3 ℃, and the liquidus temperature is about 155.0 ℃.

Example 13:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.3 percent, the content of the nano-palladium particles is 3.9 percent, the content of Bi is 50 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 144.7 ℃, and the liquidus temperature is about 156.1 ℃.

Example 14:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 1.4 percent, the content of the nano-palladium particles is 4.2 percent, the content of Bi is 50 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 145.9 ℃, and the liquidus temperature is about 158.0 ℃.

Example 15:

the Sn-based brazing filler metal comprises the following components in percentage by mass: the content of the alumina nano-fiber is 3.0 percent, the content of the nano-palladium particles is 9.0 percent, the content of Bi is 59 percent, and the balance is Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 188.7 ℃, and the liquidus temperature is about 205.5 ℃.

Example 16:

the Sn-based brazing filler metal comprises the following components in percentage by mass: 5.0 percent of alumina nano fiber, 15 percent of nano palladium particles, 60 percent of Bi and the balance of Sn.

And (3) detecting the temperature performance of the brazing filler metal: on the premise of considering test errors, the solidus temperature is about 190.5 ℃, and the liquidus temperature is about 215.5 ℃.

In the 16 embodiments, the solidus temperature and the liquidus temperature of the embodiment 1 are both lower than those of the other embodiments, so that the lower melting temperature can be obtained and the lower welding temperature can be realized.

In addition, under the condition that other components are not changed, the shearing strength of welding spots is different according to different alumina nanofiber contents, 9 groups of typical experimental examples of the lead-free solder containing alumina nanofibers, nano palladium particles, Bi and Sn shown in the following table 1 are selected, the welding spot shearing performance of the 9 groups of experimental examples is shown in fig. 2, and as can be seen from fig. 2, the welding spot shearing performance of the 6 th group of experimental examples reaches the maximum value.

TABLE 1 typical composition of 9 groups of experimental alloy examples containing alumina nanofibers, nano-palladium particles, Bi and Sn

In order to verify that the lead-free solder has excellent welding spot shearing performance and longer fatigue life in service period, the Sn-58Bi-1.0 alumina nanofiber-3.0 nano palladium particles are selected to carry out a thermal cycle experiment on the lead-free solder (Sn-58Bi) without the alumina nanofiber and the nano palladium particles, the working condition of the welding spot in service period is simulated, the shearing performance of the Sn-58Bi-1.0 alumina nanofiber-3.0 nano palladium particles in the service period of the welding spot is shown in figure 3, as can be seen from figure 3, the welding spot shearing performance of the Sn-58Bi-1.0 alumina nanofiber-3.0 nano palladium particles is also obviously greater than that of the lead-free solder (Sn-58Bi) without the alumina nanofiber and the nano palladium particles, namely, the alumina nano-fiber, the nano-palladium particle, and the Bi and Sn of the invention are coupled, so that the shear strength of the welding spot can be obviously improved.