A power module and a method for producing the same

Abstract

The present application relates to the field of integrated circuit manufacturing, in particular to a power module and a production method thereof, by setting tin paste on both sides of the target pad of the substrate to be processed; mounting the soldering element to be processed on the target pad with tin paste, obtaining a combined substrate; performing the front heat treatment on the combined substrate; performing the middle heat treatment on the combined substrate; performing the rear heat treatment on the combined substrate; performing the wire bonding on the combined substrate after the soldering is completed, then performing the power pin assembly and the shell packaging, obtaining the finished power module. The present application divides the heat treatment of soldering into three stages, effectively solves the problems of poor solder wetting, existence of bubbles and cavities in the soldering interface, warping or cracking caused by local thermal stress concentration of the substrate, and poor growth of the intermetallic compound layer of the soldering point in the traditional soldering process, effectively guarantees the production yield, reduces the soldering element monument rate, and significantly improves the yield of the finished power module.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit manufacturing, and in particular to a power module and its manufacturing method. Background Technology

[0002] As power modules evolve towards higher power density and miniaturization, the size of surface mount resistors is decreasing, further increasing the difficulty of manual handling. Meanwhile, the reliability requirements for power modules in fields such as new energy vehicles and rail transportation are stringent. Problems with welding defects in traditional welding processes may gradually surface under long-term vibration and high-temperature cycling conditions, leading to module failure or even system malfunction.

[0003] To address these issues, the industry has attempted to introduce semi-automatic dispensing machines to replace manual solder paste application, hoping to improve soldering results by utilizing the high precision of the solder paste settings achieved by the semi-automatic dispensing machines. However, due to limitations in equipment positioning accuracy (usually above ±50μm) and insufficient stability in controlling the solder paste extrusion volume, it is still impossible to effectively reduce the resistance tombstoning rate, and the soldering yield remains poor.

[0004] Therefore, how to improve the welding yield of power modules and reduce the tombstoning rate of welded components has become an urgent problem to be solved in the existing technology. Summary of the Invention

[0005] The purpose of this invention is to provide a power module and its manufacturing method to solve the problems of low welding yield and high tombstoning rate of welded components in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides a power module manufacturing method, comprising:

[0007] Solder paste is applied to both sides of the target pads on the substrate to be processed;

[0008] The components to be soldered are mounted on the target pads that have been coated with solder paste to obtain a composite substrate;

[0009] The composite substrate is subjected to a front-end heat treatment; the front-end heat treatment includes a front-end heating stage and a front-end cooling stage, so that the solvent in the solder paste can be completely evaporated.

[0010] The combined substrate is subjected to mid-section heat treatment; the mid-section heat treatment includes multiple alternating mid-section heating and cooling stages to release the internal stress of the substrate to be treated.

[0011] The composite substrate is subjected to a post-heat treatment; the post-heat treatment includes a post-heating stage and a post-cooling stage, during which the solder paste is completely melted to complete the soldering of the components to be soldered;

[0012] The assembled substrate is wire bonded, and then the power pins are assembled and packaged to obtain the finished power module.

[0013] Optionally, in the power module production method, the front-end heating stage includes a first front-end heating stage and a second front-end heating stage.

[0014] Accordingly, the combined substrate undergoes a pre-treatment process, including:

[0015] The operating temperature is raised to the first front-end temperature at a first heating rate and kept at the first front-end temperature for a first period of time to complete the first stage of front-end heating.

[0016] The operating temperature is raised from the first front-end temperature to the second front-end temperature at a second heating rate, thus completing the second stage of the front-end heating.

[0017] The operating temperature is reduced from the second front-end temperature to the third front-end temperature, thus completing the front-end cooling stage.

[0018] Optionally, in the power module manufacturing method, the first heating rate ranges from 5°C / min to 8°C / min, including the endpoint value.

[0019] And / or, the temperature range of the first front end is 120 degrees Celsius to 150 degrees Celsius, including the endpoint value;

[0020] And / or, the first initial period ranges from 1.0 minute to 1.5 minutes, including endpoint values;

[0021] And / or, the second heating rate ranges from 8°C / min to 12°C / min, including the endpoint values;

[0022] And / or, the second front-end temperature ranges from 180 degrees Celsius to 200 degrees Celsius, including the endpoint values;

[0023] And / or, the third front-end temperature ranges from 150 degrees Celsius to 160 degrees Celsius, including the endpoint values.

[0024] Optionally, in the power module production method, the mid-section heat treatment includes a first stage of mid-section heating, a first stage of mid-section cooling, a second stage of mid-section heating, and a second stage of mid-section cooling.

[0025] Accordingly, the composite substrate undergoes a mid-section heat treatment, including:

[0026] The operating temperature is raised to the first intermediate temperature at a third heating rate, thus completing the first stage of the intermediate heating.

[0027] The operating temperature is reduced from the first intermediate temperature to the second intermediate temperature, thus completing the first stage of intermediate temperature cooling.

[0028] The operating temperature is increased from the second intermediate temperature to the third intermediate temperature at a fourth heating rate, thus completing the second stage of the intermediate temperature rise.

[0029] The operating temperature is reduced from the third intermediate temperature to the fourth intermediate temperature, completing the second stage of intermediate temperature cooling.

[0030] Optionally, in the power module production method, the third heating rate ranges from 8°C / min to 12°C / min, including the endpoint value;

[0031] And / or, the temperature range of the first intermediate section is 220 degrees Celsius to 240 degrees Celsius, including the endpoint values;

[0032] And / or, the second mid-section temperature ranges from 180 degrees Celsius to 190 degrees Celsius, including the endpoint values;

[0033] And / or, the fourth heating rate ranges from 8°C / min to 12°C / min, including the endpoint values;

[0034] And / or, the temperature range of the third intermediate section is 270 degrees Celsius to 290 degrees Celsius, including the endpoint values;

[0035] And / or, the fourth intermediate temperature ranges from 240 degrees Celsius to 260 degrees Celsius, including the endpoint values.

[0036] Optionally, in the power module manufacturing method, the composite substrate undergoes a post-processing heat treatment, including:

[0037] The operating temperature is raised to the first post-stage temperature at the fifth heating rate, thus completing the post-stage heating phase.

[0038] The operating temperature is reduced from the first rear-stage temperature to the second rear-stage temperature at a first cooling rate, thus completing the rear-stage cooling phase.

[0039] Optionally, in the power module manufacturing method, the fifth heating rate ranges from 8°C / min to 12°C / min, including the endpoint value;

[0040] And / or, the temperature range of the first downstream segment is 320 degrees Celsius to 340 degrees Celsius, including the endpoint values;

[0041] And / or, the first cooling rate ranges from 2°C / min to 5°C / min, including the endpoint values;

[0042] And / or, the temperature of the second downstream section is less than or equal to 100 degrees Celsius.

[0043] Optionally, in the power module manufacturing method, solder paste is applied to both sides of the target pads on the substrate to be processed, including:

[0044] Solder paste is applied to both sides of the target pads on the substrate to be processed using a stencil printing process; and during the stencil printing process, the squeegee's tilt angle ranges from 30 degrees to 45 degrees, including the endpoint value.

[0045] Optionally, in the power module manufacturing method, the components to be soldered include resistors and power chips;

[0046] Accordingly, the components to be soldered are mounted on the target pads on which the solder paste has been applied, to obtain a composite substrate, comprising:

[0047] Resistors and power chips are mounted on target pads that have been coated with solder paste to obtain a composite substrate.

[0048] A power module, the power module comprising a module obtained by any of the power module manufacturing methods described above.

[0049] The power module manufacturing method provided by this invention involves: applying solder paste to both sides of target pads on a substrate to be processed; mounting components to be soldered onto the target pads with the applied solder paste to obtain a combined substrate; performing a front-end heat treatment on the combined substrate, the front-end heat treatment including a front-end heating stage and a front-end cooling stage to allow the solvent in the solder paste to evaporate; performing a mid-end heat treatment on the combined substrate, the mid-end heat treatment including multiple alternating mid-end heating stages and mid-end cooling stages to release the internal stress of the substrate to be processed; performing a back-end heat treatment on the combined substrate, the back-end heat treatment including a back-end heating stage and a back-end cooling stage, during which the solder paste completely melts to complete the soldering of the components to be soldered; performing wire bonding on the soldered combined substrate, followed by power pin assembly and housing encapsulation to obtain the finished power module.

[0050] This invention effectively solves common problems in traditional welding processes by dividing the heat treatment of welding into three stages, such as poor solder wettability, bubbles and voids at the welding interface, warping or cracking of the substrate due to localized thermal stress concentration, and poor growth of the intermetallic compound layer at the solder joint. This ensures high production yield. The production method of this invention avoids problems such as cold solder joints, false solder joints, bonding failures, poor lead connections, and bubbles and cracks in the potting compound, reducing the tombstoning rate of welded components and significantly improving the yield of finished power modules. This invention also provides a power module with the aforementioned beneficial effects. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a flowchart illustrating a specific embodiment of the power module production method provided by the present invention.

[0053] Figure 2 A schematic diagram of heat treatment temperature changes in a specific embodiment of the power module production method provided by the present invention;

[0054] Figure 3 This is a schematic diagram of the stencil printing process structure for a specific embodiment of the power module production method provided by the present invention.

[0055] Figure label:

[0056] 01-Lower mold; 02-Upper mold; 03-Substrate to be processed. Detailed Implementation

[0057] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0058] The core of this invention is to provide a power module manufacturing method, the flowchart of one specific embodiment of which is shown below. Figure 1 As shown, this is referred to as Specific Implementation Method One, which includes:

[0059] S101: Apply solder paste to both sides of the target pad on the substrate 03 to be processed.

[0060] The substrate 03 to be processed can be a DBC ceramic substrate, or it can be a substrate made of other materials. This invention does not limit the application of these materials.

[0061] Preferably, this step includes:

[0062] Solder paste is applied to both sides of the target pads on the substrate 03 to be processed by stencil printing process; and during the stencil printing process, the tilt angle of the squeegee is in the range of 30 degrees to 45 degrees, including the endpoint value, such as any one of 30.0 degrees, 41.1 degrees or 45.0 degrees.

[0063] This preferred embodiment not only provides a method for applying solder paste using stencil printing, but also further defines the tilt angle of the squeegee during stencil printing. Specifically, this step involves placing the substrate 03 to be processed in a solder paste scraping fixture, specifically placing it in the groove of the lower mold 01 of a dedicated tray and covering it with the upper mold 02 for fixation; then applying an appropriate amount of solder paste to the edge of the stencil, and subsequently pushing the squeegee at a tilt angle of 30 to 45 degrees to evenly print the solder paste through the stencil holes to the resistance pad area, ensuring that the solder paste completely covers both sides of the target pad. Stencil printing ensures precise control over the quantity and positioning of the solder paste, guaranteeing the consistency of the solder joint shape from the source and improving the welding quality. (See reference...) Figure 3 , Figure 3 This is an exploded view of the structure of the substrate 03 to be processed placed in a stencil printing mold.

[0064] S102: The components to be soldered are mounted on the target pads on which the solder paste has been applied to obtain the combined substrate.

[0065] Furthermore, the placement in this step utilizes a fully automated pick-and-place machine to precisely place the components to be soldered onto the designated positions of the target pads that have been printed with solder paste, such as sequentially placing PbSn5Ag. 2.5 The component solder pads and corresponding power chips ensure precise alignment between each component to be soldered and the target pads, without offset or warping. The automated placement machine, relying on a high-precision vision and motion system, achieves accurate resistor placement, completely eliminating positional deviations caused by manual placement.

[0066] In one specific implementation, the components to be soldered include resistors and power chips;

[0067] Accordingly, this step includes:

[0068] Resistors and power chips are mounted on target pads that have been coated with solder paste to obtain a composite substrate.

[0069] In this specific embodiment, the power chip of the power module is mounted simultaneously with the resistor. This requires that solder paste be printed on the pads corresponding to both the resistor and the power chip in the previous step, thereby simplifying the production process and improving production efficiency. In other words, this invention simultaneously solders the resistor and the power chip, among other components, to the substrate 03 to be processed, reducing the multiple clamping and high-temperature treatment steps required by traditional step-by-step soldering, significantly shortening the production cycle and improving industrial production efficiency. Traditional processes require separate soldering or multiple reflow soldering of the resistor and the power chip, while this solution can complete high-quality soldering of all components in a single soldering process, reducing the transfer time and equipment usage between processes, thereby increasing output per unit time. It is also compatible with traditional process flows.

[0070] S103: Perform a front-end heat treatment on the combined substrate; the front-end heat treatment includes a front-end heating stage and a front-end cooling stage, so that the solvent in the solder paste can be completely evaporated.

[0071] In one specific implementation, the preheating stage in this step includes a first preheating stage and a second preheating stage.

[0072] Accordingly, this step includes:

[0073] A1: The operating temperature is raised to the first front-end temperature at the first heating rate, and the temperature is kept constant for the first front-end time to complete the first stage of the front-end heating.

[0074] Specifically, the first heating rate ranges from 5°C / min to 8°C / min, including endpoint values ​​such as any one of 5.0°C / min, 6.6°C / min, or 8.0°C / min; the first initial temperature ranges from 120°C to 150°C, including endpoint values ​​such as any one of 120.0°C, 136.4°C, or 15.0°C; and the first initial time ranges from 1.0 minute to 1.5 minutes, including endpoint values ​​such as any one of 1.00 minute, 1.22 minutes, or 1.50 minutes.

[0075] The above parameter ranges are all optimized ranges after extensive theoretical calculations and actual verifications. They can be adjusted accordingly based on actual conditions. The same applies to the parameters in the following text, and will not be repeated hereafter. The first stage of preheating is used to activate the solder and remove oxides from the solder pads and the surface of the components to be soldered. It also allows the solvent in the solder paste to evaporate slowly, avoiding bubbles or splashes at the solder joints caused by the rapid boiling of the solvent in the subsequent high-temperature stage.

[0076] A2: The operating temperature is raised from the first front-end temperature to the second front-end temperature at a second heating rate, thus completing the second stage of the front-end heating.

[0077] Specifically, the second heating rate ranges from 8°C / min to 12°C / min, including endpoint values ​​such as any one of 8.0°C / min, 10.4°C / min, or 12.0°C / min; the second initial temperature ranges from 180°C to 200°C, including endpoint values ​​such as any one of 180.0°C, 195.1°C, or 200.0°C.

[0078] The second stage of preheating ensures that the solder melts fully and guarantees good contact between the solder pad and the component to be soldered.

[0079] A3: The operating temperature is reduced from the second front-end temperature to the third front-end temperature, thus completing the front-end cooling stage.

[0080] Specifically, the third front-end temperature ranges from 150 degrees Celsius to 160 degrees Celsius, including endpoint values ​​such as any one of 150.0 degrees Celsius, 153.1 degrees Celsius, or 160.0 degrees Celsius.

[0081] The above parameter ranges are all optimized ranges after extensive theoretical calculations and actual verifications. They can be adjusted accordingly based on actual conditions. In the initial cooling stage, the combined substrate can be naturally cooled in a nitrogen atmosphere to ensure the stability of the solder joint structure, release the thermal stress of the substrate 03 to be treated, avoid microcracks, and improve the mechanical strength and electrical connection reliability of the welding interface.

[0082] S104: Perform mid-section heat treatment on the combined substrate; the mid-section heat treatment includes multiple alternating mid-section heating stages and mid-section cooling stages to release the internal stress of the substrate 03 to be treated.

[0083] In a preferred embodiment, the mid-section heat treatment includes a first stage of mid-section heating, a first stage of mid-section cooling, a second stage of mid-section heating, and a second stage of mid-section cooling.

[0084] Accordingly, this step includes:

[0085] B1: The operating temperature is raised to the first intermediate temperature at the third heating rate, completing the first stage of the intermediate heating.

[0086] Specifically, the third heating rate ranges from 8°C / min to 12°C / min, including endpoint values ​​such as any one of 8.0°C / min, 9.6°C / min, or 12.0°C / min; the first intermediate temperature ranges from 220°C to 240°C, including endpoint values ​​such as any one of 220.0°C, 236.4°C, or 240.0°C. This step follows the preceding cooling stage, allowing the solder (solder paste and solder pads) to remelt and fully wet the pads and component soldering surfaces, ensuring that a uniform and continuous intermetallic compound (IMC) layer is formed between the solder and the surface of the metal being soldered, thereby improving the mechanical strength and electrical and thermal conductivity of the solder joint.

[0087] B2: Reduce the operating temperature from the first intermediate temperature to the second intermediate temperature to complete the first stage of intermediate temperature reduction.

[0088] Specifically, the second intermediate temperature range is 180 degrees Celsius to 190 degrees Celsius, including endpoint values ​​such as 180.0 degrees Celsius, 188.4 degrees Celsius, or 190.0 degrees Celsius. In this step, the thermal stress of the substrate 03 to be processed is released again by cooling, while further reducing the damage to the welding interface caused by the internal stress generated by the temperature gradient.

[0089] B3: Increase the operating temperature from the second intermediate temperature to the third intermediate temperature at the fourth heating rate, thus completing the second stage of the intermediate temperature rise.

[0090] Specifically, the fourth heating rate ranges from 8°C / min to 12°C / min, including endpoint values ​​such as any one of 8.0°C / min, 11.4°C / min, or 12.0°C / min. This step ensures that the solder pads or solder paste are completely melted, forming a uniform solder layer, while promoting the stable growth of the intermetallic compound layer and ensuring the long-term reliability of the solder joint.

[0091] B4: Reduce the operating temperature from the third intermediate temperature to the fourth intermediate temperature to complete the second stage of intermediate cooling.

[0092] Specifically, the third intermediate temperature range is 270°C to 290°C, including endpoint values ​​such as 270.0°C, 274.8°C, or 290.0°C; the fourth intermediate temperature range is 240°C to 260°C, including endpoint values ​​such as 240.0°C, 255.6°C, or 260.0°C. In this step, heating is stopped, and the furnace temperature is lowered to the fourth intermediate temperature under a nitrogen atmosphere. This allows for the continued release of thermal stress accumulated during the welding process, preventing solder joint cracking or warping and cracking of the substrate 03 due to continuous temperature increases.

[0093] S105: Perform a post-heat treatment on the combined substrate; the post-heat treatment includes a post-heating stage and a post-cooling stage, during which the solder paste is completely melted to complete the soldering of the components to be soldered.

[0094] As a preferred embodiment, it includes:

[0095] C1: The operating temperature is raised to the first post-stage temperature at the fifth heating rate, completing the post-stage heating phase.

[0096] Specifically, the fifth heating rate ranges from 8°C / min to 12°C / min, including endpoint values ​​such as 8.0°C / min, 10.4°C / min, or 12.0°C / min; the first subsequent temperature ranges from 320°C to 340°C, including endpoint values ​​such as 320.0°C, 333.3°C, or 340.0°C. During the subsequent heating stage, the solder (solder pad) reaches a completely molten state, ensuring it flows sufficiently between the pad and the component to be soldered, filling all tiny gaps to form a void-free, high-density solder layer. Simultaneously, it further enhances the thickness and uniformity of the intermetallic compound layer, improving the high-temperature cycling resistance and mechanical strength of the solder joint.

[0097] C2: The operating temperature is reduced from the first rear-stage temperature to the second rear-stage temperature at a first cooling rate, thus completing the rear-stage cooling phase.

[0098] Specifically, the first cooling rate ranges from 2°C / min to 5°C / min, including endpoint values ​​such as any one of 2.0°C / min, 3.9°C / min, or 5.0°C / min; and the second subsequent temperature is less than or equal to 100°C. This step continues with natural cooling under a nitrogen atmosphere to slowly release internal stress, ensuring complete crystallization of the weld layer and preventing microcracks caused by thermal shock due to rapid cooling, ultimately achieving high-quality welding of the power chip and resistor.

[0099] Of course, the heat treatment in this invention can be performed in a vacuum welding furnace. Furthermore, throughout the entire vacuum welding process, the vacuum level inside the furnace is controlled between 10 Pa and 30 Pa to ensure the cleanliness of the welding environment, reduce the impact of oxidation on the quality of the weld joint, and at the same time, the continuous introduction of nitrogen atmosphere (flow rate controlled between 5 L / min and 10 L / min) further isolates the air, prevents the solder and welding interface from oxidizing at high temperatures, reduces bubbles and voids inside the weld joint, and improves the wettability and density of the weld joint.

[0100] One specific embodiment of this invention involves all the above-mentioned heat treatment stages, taking a total of 119.2 minutes, which can be referred to... Figure 2 , Figure 2 In this text, A1 represents the first stage of the initial heating phase, A2 represents the second stage of the initial heating phase, A3 represents the initial cooling phase, B1 represents the first stage of the middle heating phase, B2 represents the first stage of the middle cooling phase, B3 represents the second stage of the middle heating phase, B4 represents the second stage of the middle cooling phase, C1 represents the final heating phase, and C2 represents the final heating phase. For details of each stage, please refer to the preceding text; further elaboration is not provided here.

[0101] S106: Wire bonding is performed on the assembled substrate after welding, followed by power pin assembly and housing packaging to obtain the finished power module.

[0102] This step can be broken down. After the composite substrate is soldered in the previous steps, the substrate 03 to be processed, containing the power chip and resistor (i.e., the components to be soldered mentioned above), is placed in a bonding fixture, put into an ultrasonic bonding machine, and wire bonding is performed to form the internal functional circuit, including:

[0103] Several bonding wires and / or bonding metal strips are provided to perform electrical connections of power chips and realize the electrical functions of power modules by ultrasonic bonding in accordance with a bridge circuit.

[0104] Furthermore, this step specifically includes:

[0105] Several bonding wires are provided. The semi-finished power module is placed in the bonding fixture and fixed, and then placed in the ultrasonic bonding equipment. The ultrasonic frequency is set to 20-60kHz, the pressure to 0.5-1.5N, the bonding temperature to 100-150℃, and nitrogen gas is circulated (to prevent oxidation). After controlling the arc height to 1-1.5mm, the upper and lower bridges are realized according to the bridge electrical topology, and the connection between the power chip and the signal layer is realized.

[0106] Next, power pin assembly is performed. The assembled substrate after wire bonding is placed in a pin (in this specific embodiment, pin-type pins are selected as an example) soldering fixture for power pin assembly to realize internal and external electrical exchange of the power module. Specifically, this includes:

[0107] The pin-type leads (including sampling pins and control pins) are placed in a welding fixture and vacuum-welded for 10-15 minutes in a vacuum reflow soldering machine at 100℃-150℃ using any solder (preferably an active metal solder or a low melting point solder). The solder is then cooled to room temperature at a rate of 15℃ / min. The sampling pins and control pins are positioned at the corresponding sampling and control positions of the bridge circuit.

[0108] Next, the module is encapsulated. A housing is provided to encapsulate the semi-finished power module, which has been assembled with power pins, forming a cavity. Encapsulating adhesive is then poured into the cavity, dried, and cured to form the finished power module. Specifically, this includes:

[0109] S1: Place the welded semi-finished power module in a fixed mold or fixed machine tool; provide a package shell with the required packaging form, apply a strong bonding adhesive to the outline of the shell, and apply a strong bonding adhesive to the vertical projection of the package shell on the combined substrate.

[0110] S2: Place the fixed semi-finished module with the encapsulated shell in an oven and bake it in a vacuum environment at 80-100℃ for 1-1.5 hours to allow the strong bonding colloid to fully cure.

[0111] The strong bonding adhesive described in this invention is preferably epoxy resin or silicone to fill the gap between the outer shell and the heat dissipation base plate, with an adhesive layer thickness ≤100μm and an overflow amount <0.5mm (requiring precise control by a dispensing machine).

[0112] S3: Applying potting compound to the semi-finished module with the encapsulated shell: Place the semi-finished power module in the potting fixture, machine tool and production line, and encapsulate the semi-finished power module, power chip and bonding wire with the potting equipment at 3-5mm / s. Stop potting when the encapsulation compound is applied to 2 / 3-3 / 4 of the height of the encapsulation shell.

[0113] S4: Place the semi-finished power module after glue application in an oven for vacuum baking. First, bake at 40-60℃ for 15-20 minutes to slowly crosslink and reduce internal stress; then bake at 80-100℃ for 0.5-1 hour to fully cure.

[0114] The encapsulating colloid described in this invention is preferably a silicone gel, but other encapsulating materials such as epoxy resin can also be selected, which has good compatibility and cost advantages.

[0115] The present invention boasts high process compatibility and automation, making it suitable for large-scale manufacturing. The fully automated chip mounter used in the above-described embodiments for component placement, the ultrasonic bonding machine for wire bonding and pin bonding, the specialized fixtures (such as solder paste scraping fixtures, bonding fixtures, and potting fixtures) for precise positioning and fixation, and the automated operation of the potting equipment are all highly compatible with the automated processes of modern semiconductor packaging production lines. This not only reduces errors and labor intensity from manual operation but also ensures the consistency and stability of product quality, providing strong support for the large-scale, standardized production of power semiconductor devices. Furthermore, the optional implementation methods mentioned in the solder paste printing and mounting steps (such as simultaneous printing of solder paste on power chip pads and simultaneous chip mounting) further optimize the production process, allowing for flexible adjustments to maximize production efficiency according to actual needs. Moreover, the above-described embodiments employ non-contact vacuum suction and automated operation throughout, completely eliminating the risks of surface damage, micro-cracks, and electrostatic discharge that may result from tweezers, thereby ensuring the integrity of component performance and long-term reliability.

[0116] In addition, this specific implementation method has achieved significant optimization in production efficiency and process standardization, transforming the originally discrete operation that relied on individual skills into a quantifiable and reproducible automated process. This not only greatly improves welding speed and production capacity consistency, but also lays a solid foundation for process parameter optimization, quality traceability and large-scale production.

[0117] Furthermore, this specific implementation method enables precise resistor positioning, consistent solder paste volume on both sides of the resistor, controllable solder paste volume, and reduces resistor tombstoning rate to 0%, completely avoiding appearance damage and performance risks that may be caused by manual contact. It significantly improves resistor soldering efficiency and yield without damaging the appearance and performance of the resistor, further improving soldering yield and process consistency. Moreover, through automated process design, it can also reduce soldering voids, further improving product reliability and avoiding cost waste. It is suitable for large-scale standardized industrial production with high precision, high reliability, and high efficiency.

[0118] The power module manufacturing method provided by this invention involves: applying solder paste to both sides of the target pads on a substrate 03 to be processed; mounting the components to be soldered onto the target pads with the applied solder paste to obtain a combined substrate; performing a front-end heat treatment on the combined substrate, which includes a front-end heating stage and a front-end cooling stage to allow the solvent in the solder paste to evaporate; performing a mid-end heat treatment on the combined substrate, which includes multiple alternating mid-end heating stages and mid-end cooling stages to release the internal stress of the substrate 03 to be processed; performing a back-end heat treatment on the combined substrate, which includes a back-end heating stage and a back-end cooling stage, during which the solder paste completely melts to complete the soldering of the components to be soldered; performing wire bonding on the soldered combined substrate; and then assembling the power pins and encapsulating the package to obtain the finished power module. This invention effectively solves common problems in traditional welding processes by dividing the heat treatment of welding into three stages, such as poor solder wettability, bubbles and voids at the welding interface, local thermal stress concentration on the substrate leading to D-warping or cracking, and poor growth of the intermetallic compound layer at the solder joint. This ensures a high production yield. The production method of this invention avoids problems such as cold solder joints, false solder joints, bonding failures, poor lead connections, and bubbles and cracks in the potting compound, reducing the tombstoning rate of welded components and significantly improving the yield of power module products.

[0119] This invention also provides a power module, comprising a module obtained by any of the power module manufacturing methods described above. The power module manufacturing method provided by this invention involves: applying solder paste to both sides of target pads on a substrate 03; mounting components to be soldered onto the target pads with the applied solder paste to obtain a composite substrate; performing a front-end heat treatment on the composite substrate, the front-end heat treatment including a front-end heating stage and a front-end cooling stage to allow the solvent in the solder paste to evaporate; performing a mid-end heat treatment on the composite substrate, the mid-end heat treatment including multiple alternating mid-end heating stages and mid-end cooling stages to release internal stress on the substrate 03; performing a back-end heat treatment on the composite substrate, the back-end heat treatment including a back-end heating stage and a back-end cooling stage, during which the solder paste completely melts to complete the soldering of the components to be soldered; performing wire bonding on the soldered composite substrate, followed by power pin assembly and casing encapsulation to obtain the finished power module. This invention effectively solves common problems in traditional welding processes, such as poor solder wettability, bubbles and voids at the welding interface, warping or cracking caused by localized thermal stress concentration on the substrate, and poor growth of the intermetallic compound layer at the solder joint, by dividing the heat treatment of welding into three stages. This ensures a high production yield. The production method of this invention avoids problems such as cold solder joints, false solder joints, bonding failures, poor lead connections, bubbles and cracks in the potting compound, reduces the tombstoning rate of welded components, and significantly improves the yield of power module products.

[0120] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0121] It should be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0122] The power module and its manufacturing method provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of this invention.

Claims

1. A method for producing a power module, characterized in that, include: Solder paste is applied to both sides of the target pads on the substrate to be processed; The components to be soldered are mounted on the target pads that have been coated with solder paste to obtain a composite substrate; The composite substrate is subjected to a front-end heat treatment; the front-end heat treatment includes a front-end heating stage and a front-end cooling stage, so that the solvent in the solder paste can be completely evaporated. The combined substrate is subjected to mid-section heat treatment; the mid-section heat treatment includes multiple alternating mid-section heating and cooling stages to release the internal stress of the substrate to be treated. The composite substrate is subjected to a post-heat treatment; the post-heat treatment includes a post-heating stage and a post-cooling stage, during which the solder paste is completely melted to complete the soldering of the components to be soldered; The assembled substrate is wire bonded, and then the power pins are assembled and packaged to obtain the finished power module.

2. The power module manufacturing method as described in claim 1, characterized in that, The preheating stage includes a first preheating stage and a second preheating stage; Accordingly, the combined substrate undergoes a pre-treatment process, including: The operating temperature is raised to the first front-end temperature at a first heating rate and kept at the first front-end temperature for a first period of time to complete the first stage of front-end heating. The operating temperature is raised from the first front-end temperature to the second front-end temperature at a second heating rate, thus completing the second stage of the front-end heating. The operating temperature is reduced from the second front-end temperature to the third front-end temperature, thus completing the front-end cooling stage.

3. The power module manufacturing method as described in claim 2, characterized in that, The first heating rate ranges from 5°C / min to 8°C / min, including the endpoints; And / or, the temperature range of the first front end is 120 degrees Celsius to 150 degrees Celsius, including the endpoint value; And / or, the first initial period ranges from 1.0 minute to 1.5 minutes, including endpoint values; And / or, the second heating rate ranges from 8°C / min to 12°C / min, including the endpoint values; And / or, the second front-end temperature ranges from 180 degrees Celsius to 200 degrees Celsius, including the endpoint values; And / or, the third front-end temperature ranges from 150 degrees Celsius to 160 degrees Celsius, including the endpoint values.

4. The power module manufacturing method as described in claim 1, characterized in that, The intermediate heat treatment includes a first stage of intermediate heating, a first stage of intermediate cooling, a second stage of intermediate heating, and a second stage of intermediate cooling. Accordingly, the composite substrate undergoes a mid-section heat treatment, including: The operating temperature is raised to the first intermediate temperature at a third heating rate, thus completing the first stage of the intermediate heating. The operating temperature is reduced from the first intermediate temperature to the second intermediate temperature, thus completing the first stage of intermediate temperature cooling. The operating temperature is increased from the second intermediate temperature to the third intermediate temperature at a fourth heating rate, thus completing the second stage of the intermediate temperature rise. The operating temperature is reduced from the third intermediate temperature to the fourth intermediate temperature, completing the second stage of intermediate temperature cooling.

5. The power module manufacturing method as described in claim 4, characterized in that, The third heating rate ranges from 8°C / min to 12°C / min, including the endpoint values; And / or, the temperature range of the first intermediate section is 220 degrees Celsius to 240 degrees Celsius, including the endpoint values; And / or, the second mid-section temperature ranges from 180 degrees Celsius to 190 degrees Celsius, including the endpoint values; And / or, the fourth heating rate ranges from 8°C / min to 12°C / min, including the endpoint values; And / or, the temperature range of the third intermediate section is 270 degrees Celsius to 290 degrees Celsius, including the endpoint values; And / or, the fourth intermediate temperature ranges from 240 degrees Celsius to 260 degrees Celsius, including the endpoint values.

6. The power module manufacturing method as described in claim 1, characterized in that, The post-processing heat treatment of the composite substrate includes: The operating temperature is raised to the first post-stage temperature at the fifth heating rate, thus completing the post-stage heating phase. The operating temperature is reduced from the first rear-stage temperature to the second rear-stage temperature at a first cooling rate, thus completing the rear-stage cooling phase.

7. The power module manufacturing method as described in claim 6, characterized in that, The fifth heating rate ranges from 8°C / min to 12°C / min, including the endpoint values; And / or, the temperature range of the first downstream segment is 320 degrees Celsius to 340 degrees Celsius, including the endpoint values; And / or, the first cooling rate ranges from 2°C / min to 5°C / min, including the endpoint values; And / or, the temperature of the second downstream section is less than or equal to 100 degrees Celsius.

8. The power module manufacturing method as described in claim 1, characterized in that, Solder paste is applied to both sides of the target pads on the substrate to be processed, including: Solder paste is applied to both sides of the target pads on the substrate to be processed using a stencil printing process; and during the stencil printing process, the squeegee's tilt angle ranges from 30 degrees to 45 degrees, including the endpoint value.

9. The power module manufacturing method as described in claim 1, characterized in that, The components to be soldered include resistors and power chips; Accordingly, the components to be soldered are mounted on the target pads on which the solder paste has been applied, to obtain a composite substrate, comprising: Resistors and power chips are mounted on target pads that have been coated with solder paste to obtain a composite substrate.

10. A power module, characterized in that, The power module includes the module obtained by the power module manufacturing method as described in any one of claims 1 to 9.

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