CN-122021177-A - Construction method of sintered nano silver constitutive model based on nano indentation test

CN122021177ACN 122021177 ACN122021177 ACN 122021177ACN-122021177-A

Abstract

A method for constructing a sintered nano silver constitutive model based on a nano indentation test comprises the steps of preparing a sintered nano silver sample, carrying out nano indentation test under different loading rates, recording a load-displacement curve, establishing a unified creep-plasticity constitutive model, establishing a finite element model, embedding the constitutive model into the finite element model through a user-defined material subroutine, simulating nano indentation process under different loading rates, recording the load-displacement curve, comparing and analyzing the obtained load-displacement curve, and verifying the accuracy of the model. According to the invention, through accurately describing the mechanical behavior of the sintered nano silver at different loading rates, the data blank of the mechanical property of the sintered nano silver at high loading rates is filled, a constitutive model capable of capturing the microscopic mechanical behavior of the sintered nano silver is established, and effective simulation means and theoretical support are provided for reliability evaluation of electronic packaging materials.

Inventors

LIU LU
WANG NAN
Yu Huachen
LEI MINGQI
Huang Shoukun
CAI ZHIKUANG
WANG ZIXUAN

Assignees

南京邮电大学
南京邮电大学南通研究院有限公司

Dates

Publication Date: 20260512
Application Date: 20260213

Claims (10)

1. A method for constructing a sintered nano silver constitutive model based on a nano indentation test is characterized by comprising the following steps: step 1, preparing a sintered nano silver sample; step 2, carrying out nanoindentation experiments at different loading rates, and recording load-displacement curves; step 3, establishing a unified creep-plastic constitutive model; Step 4, establishing a finite element model, embedding the constitutive model into the finite element model through a user-defined material subroutine, simulating nanoindentation processes at different loading rates, and recording a load-displacement curve; and 5, comparing and analyzing the load-displacement curves obtained in the step 2 and the step 4, and verifying the accuracy of the model.
2. The method for constructing the sintered nano silver constitutive model based on the nano indentation test of claim 1, wherein the sintered nano silver sample in the step 1 is prepared by adopting high-purity nano silver paste through a gradient heating sintering process.
3. The method for constructing a sintered nano silver constitutive model based on a nano indentation test as claimed in claim 1, wherein the loading rate in the step 2 comprises 1mN/s, 2mN/s, 4mN/s and 8mN/s, and the average value is obtained by repeating five times at each rate.
4. The method for constructing a sintered nanosilver constitutive model based on a nanoindentation test as claimed in claim 1, wherein said unified creep-plastic constitutive model in step 3 is based on UCP model, in which model the total strain rate is Decomposition into elastic strain rate Inelastic strain rate And thermal strain rate The relation is as follows: 。
5. the method for constructing a sintered nanosilver constitutive model based on a nanoindentation test as claimed in claim 4, wherein the elastic strain rate is as follows The definition is as follows: wherein Is a component of the stress-tension, Is the modulus of elasticity of the material, Is poisson's ratio.
6. The method for constructing a sintered nanosilver constitutive model based on a nanoindentation test as claimed in claim 4, wherein the inelastic strain rate in step 3 The following is followed: wherein 、、 Is a material constant which is a function of the material, In order to exhibit the activation energy, In order to be a universal gas constant, The temperature is set to be the absolute temperature, In order for the resistance to be strong, In order to deform the direction of the load, In order to be a viscous overstress, Is the stress index.
7. The method for constructing a sintered nanosilver constitutive model based on a nanoindentation test as claimed in claim 6, wherein the viscous overstress is characterized by Wherein As a function of the deflection stress tensor, Is the radius of the yielding surface.
8. The method for constructing a sintered nanosilver constitutive model based on a nanoindentation test as claimed in claim 7, wherein the radius of the yielding surface is as follows Wherein In order for the initial yield stress to be the same, Is a saturation value, and is set to be a saturation value, Is a material constant which is a function of the material, To accumulate equivalent plastic strain.
9. The method for constructing the sintered nano silver constitutive model based on the nano indentation test of claim 1, wherein in the step 4, a nano indentation model is established by utilizing finite element software Abaqus, a finite element model is established, the constitutive model is embedded into the finite element model through a user-defined material subroutine, nano indentation processes under different loading rates are simulated, the simulated loading rates comprise four loading rates of 1mN/s, 2mN/s, 4mN/s and 8mN/s, and a load-displacement curve is recorded.
10. The method for constructing a sintered nanosilver constitutive model based on a nanoindentation test as claimed in claim 1, wherein the accuracy of establishing the UCP constitutive model is evaluated by comparing the load-displacement curves of the simulation and experiment obtained in the step 2 and the step 4 in the step 5, and the effectiveness of the model is proved to obtain a UCP model describing the effectiveness and applicability of the sintered nanosilver in terms of viscoplastic deformation behavior.

Description

Construction method of sintered nano silver constitutive model based on nano indentation test Technical Field The invention belongs to the field of mechanical property tests and constitutive models, and particularly relates to a method for constructing a sintered nano silver constitutive model based on a nano indentation test. Background With the continuous development of microelectronic devices with higher integration and smaller size, the sizes of welding spots and interfaces in packaging structures are continuously reduced, and increasingly strict requirements are put on the mechanical properties of materials under microscale. The sintered nano silver is used as a high-performance lead-free interconnection material, and has excellent heat conductivity, electric conductivity, higher melting point and good mechanical property, so that the sintered nano silver has great application potential in the field of high-temperature and high-power electronic packaging. However, the research on the mechanical behavior of the micro-welding spot under the high loading rate is insufficient at present, and is mainly limited by the defects of the traditional experimental method, the quasi-static test equipment is difficult to cover the high strain rate range in the actual working condition, and the size effect, the interface effect and the porous structure of the micro-welding spot enable the macroscopic test result to be unable to be directly extrapolated. Meanwhile, a constitutive model capable of accurately describing the viscoplastic deformation of the material in a wide strain rate and wide temperature range and correlating microstructure characteristics is lacking. Therefore, the system research on the dynamic mechanical response and the establishment of an accurate constitutive model have become key challenges for promoting the reliable application of the system. Disclosure of Invention Aiming at the problems, the invention aims to provide a test and constitutive model modeling method capable of accurately representing the mechanical behavior of sintered nano silver under various loading rate conditions. A method for constructing a sintered nano silver constitutive model based on a nano indentation test comprises the following steps: step 1, preparing a sintered nano silver sample; step 2, carrying out nanoindentation experiments at different loading rates, and recording load-displacement curves; step 3, establishing a unified creep-plastic constitutive model; Step 4, establishing a finite element model, embedding the constitutive model into the finite element model through a user-defined material subroutine, simulating nanoindentation processes at different loading rates, and recording a load-displacement curve; and 5, comparing and analyzing the load-displacement curves obtained in the step 2 and the step 4, and verifying the accuracy of the model. Compared with the prior art, the method has the advantages that (1) the mechanical properties of the sintered nano silver under different loading rates are obtained through a nano indentation experimental system, a unified creep-plastic constitutive model is established, the viscoplastic behavior of the sintered nano silver can be accurately described, and (2) the method combines finite element simulation to realize the accurate simulation of the nano indentation process, and is compared with a load-displacement curve obtained through a nano indentation experiment under laboratory conditions, so that the viscoplastic deformation behavior of the sintered nano silver under various loading conditions can be accurately captured, the method can be used for predicting mechanical response and reliability in electronic packaging, and theoretical support is provided for engineering application. Drawings FIG. 1 is a flow chart of a method for constructing a constitutive model in a specific embodiment of the invention. Fig. 2 is a graph showing sintering temperature of nano-silver paste according to an embodiment of the present invention. FIG. 3 is a schematic diagram of a triangular pyramid Berkovich indenter in accordance with an embodiment of the present invention. FIG. 4 is a finite element model mesh schematic diagram in accordance with an embodiment of the present invention. FIG. 5 is a finite element model boundary condition constraint diagram in accordance with an embodiment of the present invention. FIG. 6 is a graph of nanoindentation experiments versus simulated load-displacement in accordance with embodiments of the invention. Detailed Description The technical scheme of the invention is further described in detail below with reference to the attached drawings. The method for constructing the sintered nano silver constitutive model based on the nano indentation test in the embodiment is shown in fig. 1, and the specific steps are as follows. Step 1, preparing a sintered nano silver sample, selecting commercial nano silver paste with high purity of 99.9%, heating in a