Patent Application
20240286192
This application claims the benefit of Chinese Patent Application No. 202310187970.X, filed on Feb. 23, 2023. The entire disclosure of the application referenced above is incorporated herein by reference.
The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
The present disclosure relates to silver paste, and more particularly to a method for preparing a low-temperature sintering silver paste.
Sintered silver joints have emerged as a promising candidate for high temperature bonding approaches for die attachment and other automotive applications. Sintered silver joints may be used to replace high-lead and gold-based solders due to excellent thermal conductivity, good electrical conductivity, and high melting temperature (961° C. for bulk silver as compared to about 200° C. for tin).
However, there are still some challenges preventing wider use of sintered silver joints. The sintering process poses a risk of damage to integrated circuits. Sintered joints have relatively low shear stress as compared to soldered joints. In addition, nano-silver particles are relatively expensive.
A method for preparing a silver paste includes creating a mixture of succinic acid, 1-butoxy-2-propanol, terpineol, ethanol, and ethylene glycol; ultrasonically mixing the mixture for a first predetermined period; adding silver particles; and mechanically stirring the mixture for a second predetermined period to create a silver paste.
In other features, the first predetermined period is in a range from 5 to 15 minutes. The second predetermined period is in a range from 5 to 15 minutes. Ultrasonically mixing the mixture is performed at room temperature.
In other features, the succinic acid is in a range from 0.05% to 0.2% wt., the 1-butoxy-2-propanol is in a range from 2% to 5% wt., the terpineol is in a range from 3% to 8% wt., the ethanol is in a range from 3% to 8% wt.; the ethylene glycol is in a range from 8 to 12% wt.; and the silver particles are in a range from 75 to 90% wt.
In other features, the silver particles include first particles having a size in a range from 50 nm to 150 nm, and second particles having a size in a range from 300 nm to 600 nm. A mass ratio of the first particles to the second particles is in between 5:1 and 1:3.
A method for bonding first and second components using silver paste includes applying a silver paste to a first surface of a first component. The silver paste comprises succinic acid in a range from 0.05% to 0.2% wt.; 1-butoxy-2-propanol in a range from 2% to 5% wt.; terpineol in a range from 3% to 8% wt.; ethanol in a range from 3% to 8% wt.; ethylene glycol in a range from 8 to 12% wt.; and silver particles in a range from 75% to 90% wt. The method includes baking the first component and the silver paste for a first predetermined period; arranging a second component on the silver paste located on the first component; and pressure sintering the first component, the second component, and the silver paste.
In other features, the method includes preparing the silver paste by creating a mixture of the succinic acid, the 1-butoxy-2-propanol, the terpineol, the ethanol, and the ethylene glycol; ultrasonically mixing the mixture for a first predetermined period; adding the silver particles; and mechanically stirring the mixture for a second predetermined period to create the silver paste.
In other features, the pressure sintering is performed at a pressure in a range from 1 to 10 MPa and a temperature in a range from 250° C. to 280° C. for a period in a range from 3 to 10 minutes.
In other features, the first predetermined period is in a range from 5 to 40 minutes, and the baking is performed at a temperature in a range from 50° C. to 90° C. The method includes applying the silver paste to the first component includes screen printing the silver paste on the first component. The first predetermined period is in a range from 5 to 15 minutes. The second predetermined period is in a range from 5 to 15 minutes. Ultrasonically mixing the mixture is performed at room temperature. The silver particles include first particles having a size in a range from 50 nm to 150 nm and second particles having a size in a range from 300 nm to 600 nm. A mass ratio of the first particles to the second particles is in a range from 5:1 to 1:3.
A silver paste comprises succinic acid in a range from 0.05% to 0.2% wt.; 1-butoxy-2-propanol in a range from 2% to 5% wt.; terpineol in a range from 3% to 8% wt.; ethanol in a range from 3% to 8% wt.; ethylene glycol in a range from 8 to 12% wt.; and silver particles in a range from 75% to 90% wt.
Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims, and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
In the drawings, reference numbers may be reused to identify similar and/or identical elements.
The present disclosure relates to a low-temperature, sinterable silver paste and a method for preparing the silver paste. The method involves ultrasonic mixing organic solvents and adding and stirring two or more different sizes of silver particles to produce the silver paste. The silver paste can be applied as a thin coating between first and second silver-coated surfaces, dried, and sintered to form a high-strength sintered joint. For example, the high-strength sintered joint can be used for die attaching applications. The method improves the reliability of power module packaging and allows the power density of the power electronics in electric vehicles to be increased in a cost-effective manner.
Referring now to
Referring now to
The method for preparing silver paste according to the present disclosure reduces the use of ethanol and eliminates the water bath heating used in the prior process. The method according to the present disclosure also reduces the ultrasonic dispersion period and eliminates vacuum evaporation in the prior processes. Preparation time is significantly reduced from more than 3 hours to less than or equal to 30 minutes.
Referring now to
At 218, the mixture is stirred for a second predetermined period. In some examples, the second predetermined period is in a range from 5 to 15 minutes. In some examples, the silver paste is packaged and stored at a predetermined storage temperature until usage. In some examples, the predetermined storage temperature is in a range from 0° C. to 5° C.
In some examples, the organic solvents comprise a mixture of succinic acid, 1-butoxy-2-propanol, terpineol, ethanol and ethylene glycol. In some examples, succinic acid comprises 0.05% to 0.2% wt. (e.g., 0.12% wt.). In some examples, 1-butoxy-2-propanol comprises 2% to 5% wt. (e.g., 3% wt.). In some examples, terpineol comprises 3% to 8% wt. (e.g., 4.52% wt.). In some examples, ethanol comprises 3% to 8% wt. (e.g., 4.87% wt.). In some examples, ethylene glycol comprises 8 to 12% wt. (e.g., 9.72% wt.). In some examples, the silver particles comprise 75 to 90% wt. (e.g., 77.77% wt.).
In some examples, the silver paste includes silver particles having two or more particle sizes where the second particle size is more than twice the first particle size. In some examples, the first particle size is in a range from 50 nm to 150 nm and the second particle size is in a range from 300 nm to 600 nm. In some examples, the first particle size is in a range from 50 nm to 90 nm (e.g., 70 nm) and the second particle size is in a range from 300 nm to 600 nm (e.g., 500 nm). In some examples, a mass ratio of the first particle size to the second particle size is 5:1 to 1:3 (e.g., 3:1).
In some examples, the silver particles are coated with sodium citrate. In some examples, the sodium citrate coating has a thickness in a range from 0.1 nm to 5 nm (e.g., 1 nm).
Referring now to
At 318, the first component, the second component and the silver paste are pressure sintered at a pressure in a pressure range from 1 to 10 MPa (e.g., 5 MPa) and a temperature in a predetermined temperature range from 250° C. to 280° C. (e.g., 280° C.) for a predetermined period in a range from 3 to 10 minutes (e.g., 5 minutes). In some examples, the shear strength of the sintered joint is in a range of 10 MPa to 60 MPa (e.g., 40 MPa).
The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure.
Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”
In the figures, the direction of an arrow, as indicated by the arrowhead, generally demonstrates the flow of information (such as data or instructions) that is of interest to the illustration. For example, when element A and element B exchange a variety of information, but information transmitted from element A to element B is relevant to the illustration, the arrow may point from element A to element B. This unidirectional arrow does not imply that no other information is transmitted from element B to element A. Further, for information sent from element A to element B, element B may send requests for, or receipt acknowledgements of, the information to element A.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310187970.X | Feb 2023 | CN | national |
