Power module and preparation method thereof

Abstract

The invention relates to the technical field of electronic materials, in particular to a power module and a preparation method of the power module. The power module comprises a lining plate, a chip and a packaging body, the chip is arranged on the lining plate, the packaging body comprises a first packaging body and a second packaging body, the first packaging body is arranged on the lining plate and wraps the chip, the second packaging body is arranged on the lining plate and wraps the first packaging body, and the first packaging body is arranged on the lining plate and wraps the second packaging body. The first packaging body is made of first epoxy resin glue, the second packaging body is made of second epoxy resin glue, and the curing shrinkage rate of the first epoxy resin glue is smaller than that of the second epoxy resin glue. Epoxy resin glue with different curing shrinkage rates is used in cooperation, the cracking or falling-off phenomenon occurring in the curing process can be reduced, and the cracking problem of the product in the power cycle process is solved.

Description

Technical Field

[0001] The present application relates to the technical field of electronic materials, and in particular to a power module and a method for preparing the power module. Background Art

[0002] In the field of electronic materials technology, power module is an important electronic component, which is a module that integrates multiple electronic components (such as MOS, diodes, etc.) in one package. Power modules are widely used in power electronics, new energy, rail transportation and other fields. Their performance and reliability directly affect the stability and service life of the entire system. In the manufacturing process of power modules, epoxy resin glue is a commonly used filling material, which can not only enhance the mechanical strength of the power module, but also improve the thermal conductivity and electrical insulation performance of the module.

[0003] In the related art, an epoxy resin glue is usually used to fill the power module. This solution is simple to operate and has low cost, but some problems may arise in actual application.

[0004] First, the reliability of the power module is insufficient. In actual applications, the power module may experience multiple power cycles (i.e., frequent switching of current). It is found during use that multiple power cycles will cause fatigue and cracking of the epoxy resin glue, thus affecting the reliability and service life of the power module.

[0005] Second, epoxy resin glue is prone to cracking during the curing process. During the curing process, due to factors such as temperature changes and stress concentration, the epoxy resin glue may crack or fall off, thereby affecting the performance and reliability of the power module.

[0006] Therefore, the power module of the existing technical solution has technical problems such as poor power cycle reliability and easy cracking of epoxy resin glue during the curing process, which seriously limits the performance and reliability of the power module. Summary of the invention

[0007] The present application provides a power module and a method for preparing the power module to solve the above-mentioned technical problems.

[0008] In a first aspect, the present application provides a power module, which includes a backing plate, a chip and a package, wherein the chip is arranged on the backing plate, and the package includes a first package and a second package, wherein the first package is arranged on the backing plate and covers the chip, and the second package is arranged on the backing plate and covers the first package, the material of the first package is a first epoxy resin glue, the material of the second package is a second epoxy resin glue, and the curing shrinkage rate of the first epoxy resin glue is less than the curing shrinkage rate of the second epoxy resin glue.

[0009] Furthermore, the power module further includes bonding wires, the bonding wires are connected to the chip, and the first package body covers the chip and the bonding wires at the same time.

[0010] Furthermore, a surface of the first packaging body facing away from the backing plate is a curved surface.

[0011] Furthermore, a forming angle between the first packaging body and the liner is less than 90°.

[0012] Furthermore, the curing shrinkage rate of the first epoxy resin glue is 0.03% to 0.25%, and the curing shrinkage rate of the second epoxy resin glue is 0.50% to 1.15%.

[0013] Furthermore, the power module further comprises a substrate, at least one of the lining plates is fixed on the substrate, and a side of the lining plate facing away from the chip is connected to the substrate.

[0014] Furthermore, the power module further comprises a shell, the shell is covered on the outside of the packaging body and the lower part of the shell is connected to the substrate.

[0015] In a second aspect, the present application further provides a method for preparing a power module, which is used to prepare the power module provided in the first aspect of the present application. The method for preparing the power module comprises:

[0016] placing a chip and bonding wires on a backing plate;

[0017] Injecting a first epoxy resin glue onto the backing plate to cover the chip and the bonding wire;

[0018] Curing the first epoxy resin glue to form a first packaging body;

[0019] Injecting a second epoxy resin glue into the backing plate to cover the first packaging body;

[0020] The second epoxy resin glue is cured to form a second packaging body.

[0021] Furthermore, in the method for preparing the power module, the curing process of the first epoxy resin glue and the second epoxy resin glue both adopts a step temperature curing process.

[0022] Furthermore, in the preparation method of the power module, the step temperature curing process includes: after vacuuming to remove bubbles in the epoxy resin glue, keeping the device at a certain temperature for a certain time, then raising the temperature to the curing temperature, and curing the epoxy resin glue at the curing temperature.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] First, the power cycle reliability of the power module can be increased. Due to the use of the first epoxy resin glue with a low curing shrinkage rate, after the power module has undergone multiple power cycles (i.e., frequent on-off current), the stress caused by slight changes on the chip surface can be better alleviated, reducing fatigue and cracking in the package. This design can greatly improve the reliability of the power module, especially when the power module works in a high-power environment, frequent power cycles will not cause damage to the package or chip shedding, thereby extending the service life of the power module.

[0025] Secondly, this solution can improve problems such as cracking that occur during the curing process of epoxy resin glue. Since two epoxy resin glues with different curing shrinkage rates are used, the first epoxy resin glue with a low curing shrinkage rate can be cured first during the curing process of the epoxy resin glue, reducing the volume of the package body that is in direct contact with the chip, thereby reducing the impact of factors such as temperature changes and stress concentration on the first epoxy resin glue. The first epoxy resin glue has a low shrinkage rate and will not produce excessive volume changes during the curing process. Therefore, it can effectively reduce the concentration of stress in the first package body, especially the stress concentration at the contact surface between the chip and the first package body, avoid cracking problems caused by uneven stress, and reduce the risk of cracking or falling off during the curing process of the first epoxy resin glue, thereby improving problems such as cracking that are prone to occur during the curing process of the epoxy resin glue.

[0026] Thirdly, since the curing shrinkage rate of the first epoxy resin glue is lower than that of the second epoxy resin glue, the second epoxy resin glue will produce a greater degree of volume shrinkage relative to the first epoxy resin glue during the curing process, so that the second package can form a tight coating effect on the first package, thereby improving the integrity between the first package and the second package, and reducing the phenomenon of separation of the first package from the chip and the liner.

[0027] Fourthly, although the present technical solution uses two epoxy adhesives with different shrinkage rates, overall, the present embodiment is simple to operate and does not require the addition of complex process steps. Therefore, the process cost is low and it is easy to promote and implement. In addition, the cost of epoxy resin adhesive with a high curing shrinkage rate is relatively lower, and the second package occupies a larger volume in the package, which can significantly reduce material costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0030] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0031] Figure 1 A schematic cross-sectional structure diagram of a power module provided in some embodiments of the present application;

[0032] Figure 2 A schematic diagram of force analysis of a first package body in a power module provided in an embodiment of the present application;

[0033] Figure 3 A schematic cross-sectional structure diagram of a power module provided in some embodiments of the present application;

[0034] Figure 4 This is a schematic diagram of the cross-sectional structure of the power module provided in Comparative Examples 1-2 of the present application.

[0035] In the figure:

[0036] 1. Backing plate; 2. Chip; 3. Package; 301. First package; 302. Second package; 4. Bonding wire; 5. Substrate; 6. Shell. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] The disclosure below provides many different embodiments or examples to implement different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or letters in different examples. This repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed.

[0039] like Figure 1 and 3 As shown, the main structure of a power module of an embodiment of the present invention includes a backing plate 1, a chip 2 and a package 3. The chip 2 is arranged on the backing plate 1, and the package 3 includes a first package 301 and a second package 302. The first package 301 is arranged on the backing plate 1 and covers the chip 2. The second package 302 is arranged on the backing plate and covers the first package 301. The material of the first package 301 is a first epoxy resin glue, and the material of the second package 302 is a second epoxy resin glue. The curing shrinkage rate of the first epoxy resin glue is less than the curing shrinkage rate of the second epoxy resin glue.

[0040] It should be noted that the epoxy resin glue is a multi-component mixture before curing, which contains epoxy resin, stabilizer, curing agent, coupling agent and necessary filler components, etc. The factors affecting the curing shrinkage rate of the epoxy resin glue include but are not limited to the types and ratios of the components of the epoxy resin glue, the choice of curing process, the curing temperature and the curing time, etc. Those skilled in the art can obtain the required curing shrinkage rate of the epoxy resin glue by adjusting and optimizing the aforementioned influencing factors. In the above embodiment, two epoxy resin glues with different curing shrinkage rates are used to fill the power module, and the first epoxy resin glue with a low curing shrinkage rate is used to fill and cover the chip 2 to form a first package 301, and then the second epoxy resin glue with a higher curing shrinkage rate is used to fill other areas of the module to form a second package 302.

[0041] On the one hand, this solution can increase the power cycle reliability of the power module. Due to the use of the first epoxy resin glue with a low curing shrinkage rate, after the power module has undergone multiple power cycles (i.e., frequent on and off current), the stress caused by slight changes on the surface of the chip 2 can be well alleviated, reducing fatigue and cracking in the package 3. This design can greatly improve the reliability of the power module, especially when the power module works in a high-power environment, frequent power cycles will not cause damage to the package 3 or the chip 2 to fall off, thereby extending the service life of the power module.

[0042] Secondly, this solution can improve problems such as cracking that occur during the curing process of epoxy resin glue. Since two epoxy resin glues with different curing shrinkage rates are used, the first epoxy resin glue with a low curing shrinkage rate can be cured first during the curing process of epoxy resin glue, reducing the volume of the package 3 that is in direct contact with the chip 2, thereby reducing the impact of factors such as temperature changes and stress concentration on the first epoxy resin glue. The first epoxy resin glue has a low shrinkage rate and will not produce excessive volume changes during the curing process. Therefore, it can effectively reduce the concentration of stress in the first package 301, especially the stress concentration at the contact surface between the chip 2 and the first package 301, avoid cracking problems caused by uneven stress, reduce the risk of cracking or falling off during the curing process of the first epoxy resin glue, and thus improve the problem of cracking that is easy to occur during the curing process of the epoxy resin glue.

[0043] Thirdly, since the curing shrinkage rate of the first epoxy resin glue is lower than that of the second epoxy resin glue, the second epoxy resin glue will produce a greater degree of volume shrinkage during the curing process than the first epoxy resin glue, so that the second package 302 can form a tight coating effect on the first package 301, thereby improving the integrity between the first package 301 and the second package 302 and reducing the phenomenon of separation between the first package 301 and the chip 2 and the liner.

[0044] Fourthly, although the present technical solution uses two epoxy adhesives with different shrinkage rates, in general, the present embodiment is simple to operate and does not require the addition of complex process steps. Therefore, the process cost is low and it is easy to promote and implement. Moreover, the cost of epoxy resin adhesive with a high curing shrinkage rate is relatively lower. The second package body 302 occupies a larger volume in the package body 3, which can significantly reduce material costs.

[0045] In some embodiments, the power module further includes a bonding wire 4, the bonding wire 4 is connected to the chip 2, and the first package 301 simultaneously covers the chip 2 and the bonding wire 4. ###Specific embodiment: The bonding wire 4 is used to connect the chip 2 with other electrical components of the power module. The bonding wire 4 can be connected to the contact point of the chip 2 by ultrasonic welding or other methods, and realize the signal transmission or power connection of the power module through electrical connection. Since the bonding wire 4 is directly connected to the chip 2, the stable connection of the contact point of the bonding wire 4 is crucial to the performance of the power module, especially during the power cycle, the reliability and stability of the bonding wire 4 are crucial to the long-term operation of the power module. Therefore, in this embodiment, the first package 301 not only provides mechanical strength to protect the chip 2 and the bonding wire 4 and its contact points, but also avoids excessive stress during the curing process through the first epoxy resin glue with a lower curing shrinkage rate, reduces the impact on the bonding wire 4 and its contact points, and thus maintains the stable connection of the bonding wire 4. When the power module faces multiple power cycles, it can maintain a stable working state and avoid the bonding wire 4 from loosening or breaking due to changes in thermal stress and electrical stress. In addition, by covering the bonding wire 4, the first package body 301 also provides additional electrical insulation to prevent electrical short circuit or failure caused by corrosion of the bonding wire 4 by the external environment (such as moisture, corrosive gas, etc.) during the use of the power module.

[0046] In some embodiments, the surface of the first package body 301 facing away from the backing plate 1 is a curved surface. The specific shape of the curved surface includes but is not limited to a circular arc surface, an elliptical arc surface, a parabola, or a curved surface of other shapes. Figure 2 As shown, the curing shrinkage stress along the tangent direction on the curved surface can be decomposed into horizontal component stress and vertical component stress. The horizontal component stresses F1 and F2 at the symmetrical positions on both sides will offset each other. The resultant force formed by the tangential stresses F1 and F2 at the symmetrical positions on both sides will be directed toward the inside of the first package body 301, thereby reducing the outward shrinkage stress formed in the tangential direction, thereby improving the cracking problem that occurs during the product curing process.

[0047] The curved surface design of the first package body 301 enables the curing shrinkage stress along the tangent direction to be effectively decomposed into a horizontal stress component and a vertical stress component. At the symmetrical positions on both sides of the curved surface, the horizontal stress components will offset each other, which can effectively reduce the stress accumulation in the horizontal direction. In the vertical direction, the resultant force formed by the tangential stress of the curved surface will be directed toward the inside of the first package body 301, which means that during the curing process, the first package body 301 will not be stretched or cracked due to the action of the external shrinkage stress.

[0048] Since the curved surface design helps to divert the contraction stress in the tangential direction to the inside of the first package body 301 and reduces the outward contraction stress, the stress concentration and cracking problems that may occur during the curing process are significantly reduced. Especially when the first epoxy resin glue is cured, temperature changes and stress concentration are the main factors leading to cracks. The curved surface shape can effectively alleviate these problems and improve the curing quality, thereby improving the long-term reliability and stability of the power module.

[0049] In addition, since the power module will experience drastic temperature changes during operation, the curved surface design helps reduce the impact of thermal stress during curing and use. In particular, during cooling or heating, the package 3 with a curved surface structure can disperse heat more evenly, avoiding local stress accumulation, thereby improving the module's ability to resist thermal stress.

[0050] In addition, the above-mentioned configuration of the first package body 301 enables a curved interface to be formed inside the package body 3, which can provide better dispersion capability at the interface when subjected to external impact or pressure, reduce the external force directly acting on the local area of ​​the first package body 301, and improve the mechanical strength and impact resistance of the power module. This is crucial for the long-term use of the module in practical applications, especially in environments with large vibrations or need to withstand external impacts.

[0051] In some embodiments, the molding angle between the first package body 301 and the liner 1 is less than 90°. The molding angle refers to the angle between the interface between the first package body 301 and the liner 1 at the contact point between the first package body 301 and the liner 1 and the tangent line of the surface of the first package body 301. When the molding angle is greater than 90°, the resultant force of the tangential stress at the corresponding positions on both sides will be outward, which will have an adverse effect on reducing the shedding and cracking of the first package body 301. By reducing the molding angle, the surface of the package body 3 can be made smoother, reducing stress concentration, which helps to reduce the cracking and detachment of the first package body 301 caused by stress concentration during the curing process, thereby improving the reliability of the power module.

[0052] Preferably, the curing shrinkage rate of the first epoxy resin glue is 0.03% to 0.25%, and the curing shrinkage rate of the second epoxy resin glue is 0.50% to 1.15%.

[0053] In some embodiments, Figure 3As shown, the power module also includes a substrate 5, at least one of the lining plates 1 is fixed on the substrate 5, and the side of the lining plate 1 facing away from the chip 2 is connected to the substrate 5. The substrate 5 can be a material with good thermal conductivity, such as a metal substrate 5, a ceramic substrate 5 or other materials suitable for thermal management, to help the power module dissipate heat more effectively. The connection between the lining plate 1 and the substrate 5 can be achieved by welding, bonding or mechanical fixing to ensure that the lining plate 1 is stably fixed on the substrate 5, thereby enhancing the overall stability and heat dissipation effect of the power module. In this design, the lining plate 1 acts as a support and heat-conducting medium to conduct the heat generated by the chip 2 to the substrate 5, thereby optimizing the heat dissipation path and improving the working stability of the power module.

[0054] In some embodiments, Figure 3 As shown, the power module further includes a housing 6, which is disposed outside the package body 3 and the lower portion of the housing 6 is connected to the substrate 5. The lower portion of the housing 6 and the substrate 5 can be fixedly bonded in a gas-tight manner using a sealant, and a second epoxy resin glue is encapsulated in the accommodating cavity formed by the substrate 5 and the housing 6 to form a second package body 302 as a sealing structure.

[0055] The present application also provides a method for preparing a power module, which is used to prepare the power module of the above-mentioned embodiment of the present application. The method for preparing a power module includes the following steps 1-5.

[0056] Step 1: Place chip 2 and bonding wire 4 on substrate 1. Install chip 2 and bonding wire 4 on substrate 1. Chip 2 is usually connected to substrate 1 through bonding wire 4 to ensure electrical connection. This step ensures that the core components of the power module are correctly installed.

[0057] Step 2: Inject the first epoxy resin glue onto the backing plate 1 to cover the chip 2 and the bonding wire 4. After the chip 2 and the bonding wire 4 are installed, inject the first epoxy resin glue onto the backing plate 1 to ensure that it completely covers the chip 2, the bonding wire 4 and the bonding point.

[0058] Step 3: Curing the first epoxy resin glue to form a first package 301. The first epoxy resin glue is cured, usually at a suitable temperature, so that the first epoxy resin glue forms a solid first package 301, which not only provides mechanical support, but also increases thermal conductivity and electrical insulation performance.

[0059] Step 4: inject the second epoxy resin glue onto the backing plate 1 to cover the first package body 301. After the first package body 301 is cured, inject the second epoxy resin glue onto the backing plate 1 to cover the cured first package body 301.

[0060] Step 5: Curing the second epoxy resin adhesive to form a second packaging body 302. The second epoxy resin adhesive is cured, usually at a suitable temperature, so that the second epoxy resin adhesive forms a solid second packaging body 302.

[0061] The preparation method of the power module adopts two epoxy resin glues with different curing shrinkage rates, which can effectively improve the reliability of the power module in frequent power cycles and reduce cracking or falling off problems. The epoxy resin glues with different shrinkage rates make the glue layer with low shrinkage rate cure preferentially during the curing process, reducing stress concentration and reducing the risk of cracking. Since the second epoxy resin glue has a higher shrinkage rate during the curing process, it will tightly wrap the first package body 301, enhance the mechanical strength of the power module, and reduce the risk of detachment between components. By using epoxy resin glues with different curing shrinkage rates, not only can the reliability and performance of the module be improved, but also the material cost can be effectively reduced, especially using the second epoxy resin glue with a high curing shrinkage rate to cover a large area.

[0062] In some embodiments, in the method for preparing a power module, the curing process of the first epoxy resin glue and the second epoxy resin glue both adopt a step temperature curing process. Specifically, the step temperature curing process includes: after vacuuming to remove bubbles in the epoxy resin glue, keeping the device at a certain temperature for a certain time, then raising the temperature to the curing temperature, and curing the epoxy resin glue at the curing temperature.

[0063] Before curing the epoxy resin glue, the epoxy resin glue is first vacuumed to remove any bubbles that may exist in it. The presence of bubbles may affect the adhesion and mechanical properties of the colloid, so removing bubbles is a very important step. Vacuuming can not only remove bubbles, but also ensure the uniformity and high-density filling of the epoxy resin glue.

[0064] The epoxy resin glue that has been treated for bubbles is kept warm at a certain temperature, usually at a lower temperature, to ensure the initial curing of the resin glue. The purpose of this stage is to allow the epoxy resin glue to gradually heat up and begin to gradually cure at a lower temperature to avoid stress concentration and cracking caused by sudden temperature changes. After a period of insulation, the temperature is raised to the required curing temperature to accelerate the curing reaction. The temperature increase process should be gentle to avoid stress concentration of the epoxy resin glue due to excessive temperature fluctuations. Finally, at the set curing temperature, it is maintained for a period of time to allow the epoxy resin glue to fully cure. This process ensures that the epoxy resin glue fully reacts and achieves the best mechanical strength and electrical insulation properties. At this temperature, the molecular chains of the epoxy resin glue undergo a cross-linking reaction to form a solid three-dimensional network structure, providing good protection and thermal conductivity.

[0065] The step temperature curing process can effectively control the temperature gradient during the curing process. By increasing the temperature in stages, it avoids thermal stress caused by rapid temperature changes, thereby reducing the risk of cracking or falling off during the curing process of the epoxy resin glue, thereby improving the reliability of the power module. By gradually increasing the temperature, it is ensured that the epoxy resin glue can be evenly distributed and thoroughly cured during the curing process, avoiding defects caused by uneven curing and improving the curing quality. In terms of the selection of curing temperature and time, low-temperature curing should be preferred to prolong the gelation time. The cooling process after the curing is completed should be slow, so that the cross-linked epoxy resin glue slowly cools and shrinks, avoiding high temperature and short-time curing conditions that lead to uneven temperature fields during the cross-linking reaction, uneven temperature fields forming uneven cured products, and inconsistent degrees of curing reactions of epoxy glue, resulting in product stratification, cracks and other abnormalities.

[0066] Example 1

[0067] A method for preparing a power module.

[0068] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0069] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0070] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 120°C, keep warm for about 0.5 hours, then raise the temperature to 165°C and cure for about 3 hours to obtain a first package body 301. The curing shrinkage rate of the first epoxy resin glue is 0.08%.

[0071] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0072] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 1 hour, then raise the temperature to 180°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.78%.

[0073] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0074] The property parameters of the first epoxy resin glue and the second epoxy resin glue in this embodiment are shown in Table 1.

[0075] Table 1

[0076]

[0077] The power module is prepared by the preparation method of this embodiment, and whether the package body 3 is cracked or falls off in the curing step during each preparation process is recorded. The proportion of the package body 3 cracking or falling off in the curing step of this embodiment is 0.

[0078] The power module with no cracks in the package body 3 prepared in this embodiment was subjected to a temperature shock test TST 500Cycle reliability test, and the package body 3 passed the test without cracks.

[0079] Example 2

[0080] A method for preparing a power module.

[0081] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0082] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0083] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 110°C, keep warm for about 0.5 hours, then raise the temperature to 150°C and cure for about 3 hours to obtain a first package body 301. The curing shrinkage rate of the first epoxy resin glue is 0.03%.

[0084] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0085] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 125°C, keep warm for about 1 hour, then raise the temperature to 160°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.5%.

[0086] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0087] The power module was prepared by the preparation method of this embodiment, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this embodiment was 0.1%.

[0088] The power module with no cracks in the package body 3 prepared in this embodiment was subjected to a TST 500Cycle reliability test, and the package body 3 passed the test without cracks.

[0089] Example 3

[0090] A method for preparing a power module.

[0091] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0092] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0093] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 115°C, keep warm for about 0.5 hours, then raise the temperature to 155°C and cure for about 3 hours to obtain a first package 301. The curing shrinkage rate of the first epoxy resin glue is 0.05%.

[0094] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0095] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 125°C, keep warm for about 1 hour, then raise the temperature to 170°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.65%.

[0096] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0097] The power module is prepared by the preparation method of this embodiment, and whether the package body 3 is cracked or falls off in the curing step during each preparation process is recorded. The proportion of the package body 3 cracking or falling off in the curing step of this embodiment is 0.

[0098] The power module with no cracks in the package body 3 prepared in this embodiment was subjected to a TST 500Cycle reliability test, and the package body 3 passed the test without cracks.

[0099] Example 4

[0100] A method for preparing a power module.

[0101] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0102] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0103] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 140°C, keep warm for about 0.5 hours, then raise the temperature to 170°C and cure for about 3 hours to obtain a first package 301. The curing shrinkage rate of the first epoxy resin glue is 0.11%.

[0104] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0105] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 1 hour, then raise the temperature to 180°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.84%.

[0106] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0107] The power module was prepared by the preparation method of this embodiment, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this embodiment was 0.1%.

[0108] The power module with no cracks in the package body 3 prepared in this embodiment was subjected to a TST 500Cycle reliability test, and the package body 3 passed the test without cracks.

[0109] Example 5

[0110] A method for preparing a power module.

[0111] Step 1, SMD or weld chip 2 on AMB liner 1, and obtain semi-finished product after reflow; weld AMB liner 1 to copper substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to copper substrate 5 through sealant, and bond bonding wire 4 to chip 2 and AMB liner 1, and make PLASMA of the obtained module.

[0112] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0113] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 125°C, keep warm for about 0.5 hours, then raise the temperature to 170°C and cure for about 3 hours to obtain a first package 301. The curing shrinkage rate of the first epoxy resin glue is 0.15%.

[0114] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0115] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 135°C, keep warm for about 1 hour, then raise the temperature to 185°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.99%.

[0116] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0117] The power module is prepared by the preparation method of this embodiment, and whether the package body 3 is cracked or falls off in the curing step during each preparation process is recorded. The proportion of the package body 3 cracking or falling off in the curing step of this embodiment is 0.

[0118] The power module with no cracks in the package body 3 prepared in this embodiment was subjected to a TST 500Cycle reliability test, and the package body 3 passed the test without cracks.

[0119] Example 6

[0120] A method for preparing a power module.

[0121] Step 1, SMD or weld chip 2 on AMB liner 1, and obtain semi-finished product after reflow; weld AMB liner 1 to copper substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to copper substrate 5 through sealant, and bond bonding wire 4 to chip 2 and AMB liner 1, and make PLASMA of the obtained module.

[0122] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0123] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 0.5 hours, then raise the temperature to 175°C and cure for about 3 hours to obtain a first package 301. The curing shrinkage rate of the first epoxy resin glue is 0.25%.

[0124] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0125] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 140°C, keep warm for about 1 hour, then raise the temperature to 190°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 1.15%.

[0126] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0127] The power module was prepared by the preparation method of this embodiment, and it was recorded whether the package 3 cracked or fell off during the curing step during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this embodiment was 0.05%.

[0128] The power module with no cracks in the package body 3 prepared in this embodiment was subjected to a TST 500Cycle reliability test, and the package body 3 passed the test without cracks.

[0129] Comparative Example 1

[0130] A method for preparing a power module.

[0131] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0132] Step 2: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6. The injection amount is the size of the space in the product cavity. The second epoxy resin glue is the same as that in Example 1.

[0133] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 1 hour, then raise the temperature to 180°C and cure for about 1.5 hours to obtain package 3. The curing shrinkage rate of the epoxy resin glue is 0.78%.

[0134] Step 4: Take the power module out of the oven and cool it to room temperature. Figure 4 shown.

[0135] The power module was prepared by the preparation method of this comparative example, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 3.7%.

[0136] The power module with no cracks in the package body 3 prepared in this comparative example was subjected to TST 500 Cycle reliability test. The package body 3 was cracked and failed the test.

[0137] Comparative Example 2

[0138] A method for preparing a power module.

[0139] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0140] Step 2: Use a precision syringe to inject the first epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6. The injection amount is the size of the space in the product cavity. The first epoxy resin glue is the same as that in Example 1.

[0141] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 120°C, keep warm for 0.5 hours, then raise the temperature to 165°C, and cure for about 1.5 hours to obtain package 3. The curing shrinkage of the epoxy resin glue is 0.08%.

[0142] Step 4: Take the power module out of the oven and cool it to room temperature. Figure 4 shown.

[0143] The power module was prepared by the preparation method of this comparative example, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 0.9%.

[0144] The power module with no cracks in the package body 3 prepared in this comparative example was subjected to TST 500 Cycle reliability test. The package body 3 was cracked and failed the test.

[0145] Comparative Example 3

[0146] A method for preparing a power module.

[0147] Step 1, SMD or weld chip 2 on AMB liner 1, and obtain semi-finished product after reflow; weld AMB liner 1 to copper substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to copper substrate 5 through sealant, and bond bonding wire 4 to chip 2 and AMB liner 1, and make PLASMA of the obtained module.

[0148] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0149] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 0.5 hours, then raise the temperature to 180°C and cure for about 3 hours. The curing shrinkage of the first epoxy resin glue is 0.27%.

[0150] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0151] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 145°C, keep warm for about 1 hour, then raise the temperature to 195°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 1.3%.

[0152] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0153] The power module was prepared by the preparation method of this comparative example, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 0.65%.

[0154] The power module with no cracks in the package body 3 prepared in this comparative example was subjected to TST 500 Cycle reliability test. The package body 3 was cracked and failed the test.

[0155] Comparative Example 4

[0156] A method for preparing a power module.

[0157] Step 1, SMD or weld chip 2 on AMB liner 1, and obtain semi-finished product after reflow; weld AMB liner 1 to copper substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to copper substrate 5 through sealant, and bond bonding wire 4 to chip 2 and AMB liner 1, and make PLASMA of the obtained module.

[0158] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0159] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 105°C, keep warm for about 0.5 hours, then raise the temperature to 145°C and cure for about 3 hours. The curing shrinkage of the first epoxy resin glue is 0.02%.

[0160] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0161] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 120°C, keep warm for about 1 hour, then raise the temperature to 155°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.26%.

[0162] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0163] The power module was prepared by the preparation method of this comparative example, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 0.

[0164] The power module without cracks in the package body 3 prepared in this comparative example was subjected to TST 500 Cycle reliability test. The package body 3 was cracked and failed the test.

[0165] Comparative Example 5

[0166] A method for preparing a power module.

[0167] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0168] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0169] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 110°C, keep warm for about 0.5 hours, then raise the temperature to 150°C and cure for about 3 hours to obtain a first package body 301. The curing shrinkage rate of the first epoxy resin glue is 0.03%.

[0170] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0171] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 1 hour, then raise the temperature to 180°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.84%.

[0172] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0173] The power module was prepared by the preparation method of this comparative example, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 1.82%.

[0174] The power module with no cracks in the package 3 prepared in this comparative example was subjected to a TST 500Cycle reliability test, and the package 3 passed the test without cracks.

[0175] Comparative Example 6

[0176] A method for preparing a power module.

[0177] Step 1, SMD or weld chip 2 on DBC liner 1, and obtain semi-finished product after reflow; weld DBC liner 1 to AlSiC substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to AlSiC substrate 5 through sealant, and bond bonding wire 4 to chip 2 and DBC liner 1, and make PLASMA of the obtained module.

[0178] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0179] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 115°C, keep warm for about 0.5 hours, then raise the temperature to 155°C and cure for about 3 hours to obtain a first package 301. The curing shrinkage rate of the first epoxy resin glue is 0.05%.

[0180] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0181] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 135°C, keep warm for about 1 hour, then raise the temperature to 185°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.99%.

[0182] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0183] The power module was prepared by the preparation method of this comparative example, and it was recorded whether the package 3 cracked or fell off during the curing step during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 2.47.

[0184] The power module with no cracks in the package 3 prepared in this comparative example was subjected to a TST 500Cycle reliability test, and the package 3 passed the test without cracks.

[0185] Comparative Example 7

[0186] A method for preparing a power module.

[0187] Step 1, SMD or weld chip 2 on AMB liner 1, and obtain semi-finished product after reflow; weld AMB liner 1 to copper substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to copper substrate 5 through sealant, and bond bonding wire 4 to chip 2 and AMB liner 1, and make PLASMA of the obtained module.

[0188] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0189] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 0.5 hours, then raise the temperature to 175°C and cure for about 3 hours to obtain a first package 301. The curing shrinkage rate of the first epoxy resin glue is 0.25%.

[0190] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0191] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 1 hour, then raise the temperature to 180°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.84%.

[0192] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0193] The power module was prepared by the preparation method of this comparative example, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 0.45%.

[0194] The power module with no cracks in the package body 3 prepared in this comparative example was subjected to TST 500 Cycle reliability test. The package body 3 was cracked and failed the test.

[0195] Comparative Example 8

[0196] A method for preparing a power module.

[0197] Step 1, SMD or weld chip 2 on AMB liner 1, and obtain semi-finished product after reflow; weld AMB liner 1 to copper substrate 5, and reflow in formic acid furnace; then check voids by X-RAY; assemble housing 6 to copper substrate 5 through sealant, and bond bonding wire 4 to chip 2 and AMB liner 1, and make PLASMA of the obtained module.

[0198] Step 2: Use a precision syringe to inject the first epoxy resin glue in an amount sufficient to cover the chip 2 and the bonding wire 4. The surface of the first epoxy resin glue naturally forms a curved surface structure under the action of surface tension.

[0199] Step 3: Place the module obtained in step 2 into a vacuum drying oven, evacuate to remove bubbles in the first epoxy resin glue, then place the power module into an oven preheated to 130°C, keep warm for about 0.5 hours, then raise the temperature to 175°C and cure for about 3 hours to obtain a first package 301. The curing shrinkage rate of the first epoxy resin glue is 0.25%.

[0200] Step 4: Use a precision syringe to inject the second epoxy resin glue into the cavity surrounded by the substrate 5 and the shell 6 to cover the first packaging body 301. The injection amount is the size of the remaining space in the product cavity.

[0201] Step 5: Place the module obtained in step 4 into a vacuum drying oven, evacuate to remove bubbles in the second epoxy resin glue, then place the power module into an oven preheated to 125°C, keep warm for about 1 hour, then raise the temperature to 170°C and cure for about 1.5 hours to obtain a second package 302. The curing shrinkage rate of the second epoxy resin glue is 0.65%.

[0202] Step 6: Take the power module out of the oven and cool it to room temperature. Figure 3 shown.

[0203] The power module was prepared by the preparation method of this comparative example, and whether the package 3 cracked or fell off during the curing step was recorded during each preparation process. The proportion of the package 3 cracking or falling off during the curing step of this comparative example was 0.27%.

[0204] The power module with no cracks in the package body 3 prepared in this comparative example was subjected to TST 500 Cycle reliability test. The package body 3 was cracked and failed the test.

[0205] Table 2 Curing shrinkage parameters of epoxy resin glue in various embodiments and comparative examples and test results of the prepared power module

[0206]

[0207] It can be seen from the material parameters and test index results of each embodiment and comparative example in Table 2 that epoxy resin glue with different curing shrinkage rates is used in each embodiment, the curing shrinkage rate of the first epoxy resin glue is 0.03% to 0.25%, and the curing shrinkage rate of the second epoxy resin glue is 0.50% to 1.15%, which can not only reduce the cracking or falling off phenomenon during the curing process, but also solve the problem of power cycle reliability cracking of the product. When the curing shrinkage rate exceeds the above range, it is difficult to meet the requirements of at least one test index of the power module, such as comparative examples 3-4.

[0208] For comparison 1, which only uses epoxy resin glue with a higher curing shrinkage rate, although the obtained package module can pass the reliability test of the temperature shock test (TST 500Cycle), the package body is more likely to crack or fall off during the curing step in the preparation process; for comparison 2, which only uses epoxy resin glue with a lower curing shrinkage rate, although the proportion of cracking or falling off of the package body in the curing step in the preparation process is relatively low, it cannot pass the reliability test of the temperature shock test (TST 500Cycle). It can be seen that the epoxy resin glue with a lower curing shrinkage rate helps to reduce the possibility of cracking or falling off of the package body during the curing stage, but the reliability of long-term use is not improved. The epoxy resin glue with a higher curing shrinkage rate helps to improve the reliability of the device in long-term use, but the package body is more likely to crack or fall off during the curing stage. In Examples 1-6 of the present application, the use of different epoxy resin glues with differentiated curing shrinkage rates can not only reduce the cracking or falling off phenomenon occurring during the curing process, but also optimize the long-term use reliability of the product.

[0209] The researchers further compared Examples 5-8 with Examples 1-6 and found that:

[0210] 1. The ratio of the curing shrinkage rate of the first epoxy resin glue to the curing shrinkage rate of the second epoxy resin glue should not be too large. For example, the ratios of the two in Comparative Examples 7 and 8 are 0.298 and 0.385, respectively, indicating that the curing shrinkage rate of the first epoxy resin glue is relatively close to the curing shrinkage rate of the second epoxy resin glue. The second epoxy resin glue has a lower coating force than the volume shrinkage degree of the first epoxy resin glue during the curing process, so that the coating effect of the second package body 302 on the first package body 301 is not good. There will be a certain degree of stratification or gap between the first package body 301 and the second package body 302, and the integrity is not good. After being subjected to continuous temperature shock during long-term use, the reliability is poor.

[0211] 2. The ratio of the curing shrinkage rate of the first epoxy resin glue to the curing shrinkage rate of the second epoxy resin glue should not be too small. For example, the ratios of the two in Comparative Examples 5 and 6 are 0.036 and 0.051, respectively, indicating that there is a large difference between the curing shrinkage rate of the first epoxy resin glue and the curing shrinkage rate of the second epoxy resin glue. The volume shrinkage of the second epoxy resin glue during the curing process is too large compared with that of the first epoxy resin glue, so that the second package 302 forms a large coating stress on the first package 301. During the curing process, the large coating stress exceeds the bearing capacity of the first package, and the proportion of cracking or falling off of the first package 301 will be increased during the curing process of the second epoxy resin glue.

[0212] 3. In summary, the ratio of the curing shrinkage of the first epoxy resin glue to the curing shrinkage of the second epoxy resin glue is preferably 0.060-0.217, so that the second package body 302 can form a good covering effect on the first package body 301 while avoiding excessive stress caused by the second package body 302 on the first package body during the curing process.

[0213] It should be understood that the terms used herein are only for the purpose of describing specific example embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "one", "an" and "said" as used herein may also be meant to include plural forms. The terms "include", "comprise", "contain", and "have" are inclusive, and therefore specify the existence of stated features, steps, operations, elements and / or parts, but do not exclude the existence or addition of one or more other features, steps, operations, elements, parts, and / or combinations thereof. The method steps, processes, and operations described herein are not interpreted as necessarily requiring them to be performed in the specific order described or illustrated, unless the execution order is clearly indicated. It should also be understood that additional or alternative steps may be used.

[0214] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A power module, characterized in that: It includes a backing plate, a chip and a packaging body, the chip is arranged on the backing plate, the packaging body includes a first packaging body and a second packaging body, the first packaging body is arranged on the backing plate and covers the chip, the second packaging body is arranged on the backing plate and covers the first packaging body, the material of the first packaging body is a first epoxy resin glue, the material of the second packaging body is a second epoxy resin glue, and the curing shrinkage rate of the first epoxy resin glue is less than the curing shrinkage rate of the second epoxy resin glue.

2. The power module according to claim 1, characterized in that: The power module further includes bonding wires, the bonding wires are connected to the chip, and the first package body covers the chip and the bonding wires at the same time.

3. The power module according to claim 1, characterized in that: The surface of the first packaging body facing away from the backing plate is a curved surface.

4. The power module according to claim 1, characterized in that: A forming angle between the first packaging body and the liner is less than 90°.

5. The power module according to claim 1, characterized in that: The curing shrinkage rate of the first epoxy resin glue is 0.03% to 0.25%, and the curing shrinkage rate of the second epoxy resin glue is 0.50% to 1.15%.

6. The power module according to any one of claims 1 to 5, characterized in that: It also includes a substrate, at least one of the lining plates is fixed on the substrate, and a side of the lining plate facing away from the chip is connected to the substrate.

7. The power module according to claim 6, characterized in that: It also includes a shell, which is arranged on the outside of the packaging body and the lower part of the shell is connected to the substrate.

8. A method for preparing a power module, for preparing the power module according to any one of claims 1 to 7, characterized in that: The preparation method comprises: placing a chip and bonding wires on a backing plate; Injecting a first epoxy resin glue onto the backing plate to cover the chip and the bonding wire; Curing the first epoxy resin glue to form a first packaging body; Injecting a second epoxy resin glue into the backing plate to cover the first packaging body; The second epoxy resin glue is cured to form a second packaging body.

9. The method for preparing a power module according to claim 8, characterized in that: The curing process of the first epoxy resin glue and the second epoxy resin glue both adopts a step temperature curing process.

10. The method for preparing a power module according to claim 9, characterized in that: The step temperature curing process includes: after vacuuming to remove bubbles in the epoxy resin glue, keeping the device at a certain temperature for a certain time, and then raising the temperature to the curing temperature, and curing the epoxy resin glue at the curing temperature.

Images