A fast temperature change thermoelectric cooler with good reliability and a manufacturing method thereof

Abstract

The application discloses a quick temperature change thermoelectric refrigerator with good reliability and a manufacturing method thereof, and overcomes the problem that the existing thermoelectric refrigerator is easily deformed by heat, thereby reducing the reliability of the thermoelectric refrigerator, and comprises an upper substrate and a lower substrate, and semiconductor particles are arranged between the upper substrate and the lower substrate; the upper substrate and the lower substrate each comprise a ceramic sheet and a flow guide copper sheet arranged on the surface of the ceramic sheet; the semiconductor particles are welded on the flow guide copper sheet; and the flow guide copper sheet comprises sintered flow guide copper sheets sintered and fixed on the outer circle of the ceramic sheet and glue joint flow guide copper sheets glue jointed and fixed in the middle of the ceramic sheet. The glue joint flow guide copper sheet is adopted in the area where the heat stress is concentrated, the copper sheet sintering is adopted in the area where the product strength needs to be ensured, the two are combined to reach a stable balance point of the product, and the stability of the thermoelectric refrigerator is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor cooling technology, and in particular to a reliable rapid temperature-change thermoelectric cooler and its manufacturing method. Background Technology

[0002] With the development of PCR and rapid PCR testing instruments in the medical industry, customers have increasingly higher demands for product performance limits and reliability. This has led to increasingly stringent requirements for the high reliability of TECs (Thermal-electric coolers). While the temperature change rate for typical PCR is 3-4°C / s, rapid PCR requires a rate of 7-8°C / s. When TECs undergo frequent temperature changes under such demanding operating conditions, their resistance to thermal deformation and solderability face greater challenges.

[0003] The cooling principle of TEC is the Peltier effect, which is common knowledge. Figure 8 This reflects the magnitude of thermal stress in different areas of the product when the TEC is operating. On one hand, during temperature cycling, due to the effects of thermal expansion and contraction, the different deformation trends caused by the difference in the thermal expansion coefficients of the ceramic chip and the copper conductor in the substrate, as well as the differences in the bonding force between the ceramic chip and the copper conductor and between the copper conductor and the semiconductor particles, may cause the semiconductor layer and nickel layer of the semiconductor particles to separate, leading to semiconductor particle failure, thereby reducing TEC performance and affecting TEC reliability. On the other hand, the reliability of TEC during operation is directly related to the cross-sectional area of ​​the semiconductor particles. If the flux volatilization in the solder is not properly removed during the soldering process, it will remain between the semiconductor particles and the copper conductor, forming pores. R=ρL / S, and pores reduce the effective contact area between the semiconductor particles and the copper conductor, which will inevitably lead to an increase in the thermal resistance of individual semiconductors. Under rapid temperature change conditions, this can cause individual semiconductor particles to burn out and fail, thus affecting TEC reliability. The current conventional solution is to replace the substrate made of copper and ceramic sheets sintered together (DBC substrate) with a substrate in which the current-conducting copper sheets and ceramic sheets are bonded together with adhesive to reduce the impact of thermal deformation. However, this solution still carries the risk of the current-conducting copper sheets and ceramic sheets detaching. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that thermoelectric coolers are prone to thermal deformation in the prior art, which leads to a decrease in the reliability of thermoelectric coolers. This invention provides a reliable rapid temperature change thermoelectric cooler and its manufacturing method. By using adhesive bonding of flow-guiding copper sheets in areas of concentrated thermal stress and sintering of copper sheets in areas where product strength needs to be guaranteed, the two methods are combined to achieve a stable balance point for the product and improve the stability of the thermoelectric cooler.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A reliable rapid temperature-changing thermoelectric cooler includes an upper substrate and a lower substrate, with semiconductor particles disposed between the upper and lower substrates. Both the upper and lower substrates include a ceramic sheet and a current-conducting copper sheet disposed on the surface of the ceramic sheet. The semiconductor particles are soldered onto the current-conducting copper sheet. The current-conducting copper sheet includes a sintered current-conducting copper sheet sintered and fixed to the outer ring of the ceramic sheet and an adhesive current-conducting copper sheet glued and fixed to the middle of the ceramic sheet.

[0006] The outer ring of the ceramic sheet is fixed by sintering copper sheets, which plays a role in stabilizing the product structure. The middle part of the ceramic sheet is fixed by adhesive bonding, which plays a role in releasing thermal stress. This invention achieves a balance point for product stability by using ceramic sheets bonded to copper sheets in areas of concentrated thermal stress on the substrate, and using ceramic sheets and copper sheets sintered in areas of the substrate where product strength needs to be ensured. This improves the stability of the thermoelectric cooler. At the same time, the outer ring ensures the structural strength of the product, while the current flow and semiconductor particle distribution of the inner ring can be adjusted according to actual needs, maximizing the versatility of the DBC substrate and saving on substrate molding costs.

[0007] Preferably, the current-guiding copper sheet has a groove.

[0008] The main feature is that the copper guide plate has a groove on the side where it is welded to the semiconductor particles. This solves the problem of flux evaporation causing the semiconductor particles to be squeezed and unable to escape after contact with the copper guide plate, thus avoiding pores. On the other hand, it allows the semiconductor particles and the copper guide plate to not be in complete direct contact, reducing the thermal stress generated by the semiconductor particles during operation. Furthermore, the reduced contact area between the semiconductor particles and the copper guide plate in the thermoelectric cooler increases the thermal resistance and lowers the risk of thermal short circuit.

[0009] Preferably, all the current-guiding copper sheets on the upper substrate and the current-guiding copper sheets bonded to the lower substrate are placed vertically; the sintered current-guiding copper sheets on the left and right sides of the bonded current-guiding copper sheets on the lower substrate are placed vertically, and the sintered current-guiding copper sheets on the upper and lower sides of the bonded current-guiding copper sheets on the lower substrate are placed horizontally.

[0010] The sintered copper conductive sheets on the upper and lower substrates are arranged differently to stagger the semiconductor particles, preventing short circuits and allowing current flow. Depending on the actual needs, the sintered and adhesive-bonded copper conductive sheets on the upper substrate can be placed horizontally, while the adhesive-bonded copper conductive sheets and the sintered copper conductive sheets on the top and bottom sides of the adhesive-bonded copper conductive sheets on the lower substrate can be placed horizontally, and the sintered copper conductive sheets on the left and right sides of the adhesive-bonded copper conductive sheets can be placed vertically.

[0011] Preferably, the sintered copper sheets at the first and second corners of the lower substrate are L-shaped.

[0012] Preferably, the ceramic sheet is aluminum nitride ceramic.

[0013] Aluminum nitride ceramics form the substrate of aluminum nitride material, and the ceramic sheet is aluminum nitride ceramic, which enhances the thermal stability and heat transfer efficiency of the thermoelectric cooler.

[0014] A reliable method for manufacturing a rapid temperature-change thermoelectric cooler includes the following steps: S1: The sintered copper guide sheet is sintered and fixed on the outer ring of the ceramic sheet, and the sintered copper guide sheet is etched to obtain the DBC lower substrate; S2: Adhesive-bonded copper guide sheet is bonded to the reserved middle blank area on the DBC lower substrate and processed to obtain a semi-finished high-reliability lower substrate. S3: The semi-finished high-reliability lower substrate is clamped and fixed, and grooves are processed on the surfaces of the adhesive-bonded and sintered copper flow guiding sheets to obtain the lower substrate; S4: The upper substrate is fabricated in accordance with steps S1-S3. Semiconductor particles are soldered onto the current-conducting copper sheet of the lower substrate. After the upper substrate is covered, it is sent into a heating device for soldering to obtain the thermoelectric cooler.

[0015] The outer ring of the product ensures the structural strength of the product, while the current flow and semiconductor particle distribution of the inner ring can be adjusted according to actual needs, maximizing the versatility of the DBC substrate and saving substrate molding costs.

[0016] Preferably, the copper guide sheet is pre-sintered or cut into a dumbbell shape.

[0017] Reducing the contact area between the current-conducting copper sheet and the ceramic sheet reduces the thermal stress generated by semiconductor particles during operation, reduces the thermal deformation of the current-conducting copper sheet, and improves the reliability of the thermoelectric cooler; at the same time, the middle part of the current-conducting copper sheet helps to discharge flux during soldering.

[0018] Preferably, the copper guide sheet is pre-plated with nickel before welding.

[0019] The current-conducting copper sheets here include those soldered to semiconductor particles and those soldered to wires, and are pre-nickel-plated to improve their solderability.

[0020] Preferably, a vacuum is drawn while the semiconductor particles are being soldered onto the current-guiding copper sheet of the lower substrate.

[0021] During the welding process, a vacuum is simultaneously applied to extract the volatile gases (mainly generated by the flux) to ensure that there are no weld porosity, improve the welding effect, and enhance product reliability.

[0022] Preferably, the solder is fed into the heating equipment for welding, and a vacuum is evacuated simultaneously during the heating process. Vacuum evacuation during heating is used to quickly remove the flux gas that evaporates from the solder.

[0023] Therefore, the present invention has the following beneficial effects: by using adhesive bonding of the flow-guiding copper sheet in the area of ​​thermal stress concentration of the thermoelectric cooler and copper sheet sintering in the area where product strength needs to be guaranteed, the two are combined to achieve a stable balance point for the product. Furthermore, by specially treating the shape and surface condition of the flow-guiding copper sheet, the space for the volatile flux to escape is maximized, preventing the formation of pores and ensuring good reliability. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the upper substrate structure in Embodiment 1.

[0025] Figure 2 This is a schematic diagram of the lower substrate structure in Embodiment 1.

[0026] Figure 3 This is a schematic diagram of the structure of the substrate guiding copper sheet after milling in Example 1.

[0027] Figure 4 This is an enlarged schematic diagram of the flow-guiding copper sheet after milling in Example 1.

[0028] Figure 5 This is a schematic diagram of the current-guiding copper sheet structure in Example 2.

[0029] Figure 6 This is a flowchart illustrating the steps of three methods for manufacturing thermoelectric coolers in the embodiments.

[0030] Figure 7 This is a schematic diagram of the thermoelectric cooler assembly process in Example 3.

[0031] Figure 8 This is a schematic diagram of the thermal stress in various regions of the TEC operating system.

[0032] In the figure: 1. Sintered copper guide sheet; 2. Adhesive-bonded copper guide sheet; 3. Ceramic sheet; 4. DBC lower substrate; 5. Semi-finished high-reliability lower substrate; 6. Upper substrate; 7. Semiconductor particle; 8. Groove; 9. Lower substrate; 10. First corner; 11. Second corner. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified in this application, the current-guiding copper sheets are all conventional square shapes. Example 1: This embodiment provides a reliable rapid temperature change thermoelectric cooler, including an upper substrate 6 and a lower substrate 9. Semiconductor particles 7 are provided between the upper substrate and the lower substrate. All semiconductor particles are connected and fixed by soldering. During the soldering process, a vacuum is simultaneously applied to extract volatile gases to ensure no solder pores, improve the soldering effect, and enhance the reliability of the thermoelectric cooler.

[0034] like Figure 1 As shown, the upper substrate includes a ceramic sheet 3 and a current-guiding copper sheet disposed on the surface of the ceramic sheet. Semiconductor particles are soldered onto the current-guiding copper sheet. The outer ring current-guiding copper sheet of the ceramic sheet is a sintered current-guiding copper sheet 1, which serves to stabilize the product structure. The middle current-guiding copper sheet of the ceramic sheet is an adhesive-bonded current-guiding copper sheet 2, which serves to release thermal stress. Both the sintered and adhesive-bonded current-guiding copper sheets on the upper substrate are placed vertically.

[0035] like Figure 2 As shown, the lower substrate includes a ceramic sheet 3 and a current-conducting copper sheet disposed on the surface of the ceramic sheet. Semiconductor particles are soldered onto the current-conducting copper sheet. The outer ring current-conducting copper sheet of the ceramic sheet is a sintered current-conducting copper sheet 1, which serves to stabilize the product structure. The middle current-conducting copper sheet of the ceramic sheet is an adhesive-bonded current-conducting copper sheet 2, which serves to release thermal stress. The adhesive-bonded current-conducting copper sheet on the lower substrate and the adhesive-bonded current-conducting copper sheets on the left and right sides of the adhesive-bonded current-conducting copper sheet are placed vertically, while the sintered current-conducting copper sheets on the top and bottom sides of the adhesive-bonded current-conducting copper sheet are placed horizontally. Furthermore, the sintered current-conducting copper sheets at the first corner 10 and the second corner 11 on the lower substrate are L-shaped. In this embodiment, the first corner is the lower left corner, and the second corner is the lower right corner.

[0036] The sintered current-conducting copper sheets on the upper and lower substrates are arranged differently to stagger the semiconductor particles, prevent short circuits, and enable current flow.

[0037] In this embodiment of the rapid temperature-change thermoelectric cooler, the outer ring of the ceramic plate with copper guide sheets is sintered and fixed, serving to stabilize the product structure. The middle portion of the ceramic plate with copper guide sheets is glued and fixed, serving to release thermal stress. This invention achieves a balance point for product stability by using ceramic plates glued to guide copper sheets in areas of concentrated thermal stress on the substrate, and using ceramic plates and copper sheets sintered in areas of the substrate where product strength needs to be ensured. This improves the stability of the thermoelectric cooler. Simultaneously, the outer ring of the substrate ensures product structural strength, while the current flow and semiconductor particle distribution within the inner ring can be adjusted according to actual needs, maximizing the versatility of the DBC substrate (including the upper and lower DBC substrates) and saving on mold costs for the upper and lower substrates.

[0038] In this embodiment, the current-conducting copper sheet welded to the semiconductor particles involved in cooling and the current-conducting copper sheet welded to the wire are nickel-plated before welding to improve solderability.

[0039] During the assembly of thermoelectric coolers, a vacuum is drawn simultaneously with the heating process to quickly extract the flux gas that evaporates from the solder.

[0040] In this embodiment, the ceramic sheet is aluminum nitride ceramic, which enhances the thermal stability and heat transfer efficiency of the thermoelectric cooler.

[0041] This embodiment has the following beneficial effects: (1) The rapid temperature change thermoelectric cooler in this embodiment can simultaneously take into account the characteristics of arbitrary size and high reliability. (2) In this embodiment, the outer ring of the rapid temperature change thermoelectric cooler ensures the structural strength of the product, while the current flow and semiconductor particle distribution of the inner ring can be adjusted according to actual needs, thereby maximizing the versatility of the DBC substrate and saving substrate molding costs. (3) In this embodiment, the guide copper plate of the rapid temperature change thermoelectric cooler has a groove, so that the middle area of ​​the semiconductor particle does not directly contact the guide plate, which can reduce the thermal stress generated by the semiconductor particle during operation. (4) In this embodiment, the contact area between the semiconductor particles and the current-conducting copper sheet of the rapid temperature change thermoelectric cooler is reduced, the thermal resistance of heat transfer is increased, and the risk of thermal short circuit is low.

[0042] Example 2: This embodiment, based on Embodiment 1, has a groove 8 on the current-guiding copper sheet welded to the semiconductor particles involved in cooling, such as... Figure 3 and Figure 4 As shown, in this embodiment, the groove is milled. By setting a groove on the copper guide plate, on the one hand, the problem of flux evaporation being unable to escape due to the contact and compression between the semiconductor particles and the copper guide plate, thus avoiding pores, is solved. On the other hand, it allows the semiconductor particles and the copper guide plate to not be in complete direct contact, reducing the thermal stress generated by the semiconductor particles during operation. Furthermore, the reduced contact area between the semiconductor particles and the copper guide plate in the thermoelectric cooler increases the thermal resistance, thus lowering the risk of thermal short circuit.

[0043] In this embodiment, the current-guiding copper sheet welded to the semiconductor particles involved in cooling is dumbbell-shaped, such as... Figure 5 As shown, reducing the contact area between the current-guiding copper sheet and the ceramic sheet and semiconductor particles reduces the thermal deformation of the current-guiding copper sheet, reduces the thermal stress generated by the semiconductor particles during operation, and improves the reliability of the thermoelectric cooler; at the same time, the middle part of the dumbbell-shaped current-guiding copper sheet helps the solder paste to be discharged during soldering.

[0044] Example 3: This embodiment also provides a reliable method for manufacturing a rapid temperature-change thermoelectric cooler, such as... Figure 6As shown, the process includes: First, sintering and fixing a sintered copper guide sheet to the outer ring of a ceramic sheet, and etching the sintered copper guide sheet to obtain a DBC lower substrate; Second, bonding an adhesive-bonded copper guide sheet to a pre-reserved central blank area on the DBC lower substrate and processing it to obtain a semi-finished high-reliability lower substrate; Third, clamping and fixing the semi-finished high-reliability lower substrate, and machining grooves on the surfaces of the adhesive-bonded copper guide sheet and the sintered copper guide sheet to obtain a lower substrate; Fourth, fabricating an upper substrate in the manner of steps one to three, soldering semiconductor particles onto the copper guide sheet of the lower substrate, covering it with the upper substrate, and then sending it into a heating device for soldering to obtain the thermoelectric cooler.

[0045] Simultaneously, the current-conducting copper sheet, which is welded to the semiconductor particles involved in cooling, is pre-sintered or cut into a dumbbell shape, such as... Figure 5 As shown, reducing the contact area between the current-guiding copper sheet and the ceramic sheet reduces the thermal deformation of the current-guiding copper sheet and improves the reliability of the thermoelectric cooler. A vacuum is also performed while the semiconductor particles are being soldered onto the current-guiding copper sheet on the lower substrate.

[0046] In this embodiment, both the current-conducting copper sheet welded to the semiconductor particles involved in cooling and the current-conducting copper sheet welded to the wire are pre-plated with nickel before welding to improve solderability.

[0047] During the assembly of thermoelectric coolers, a vacuum is drawn simultaneously with the heating process to quickly extract the flux gas that evaporates from the solder.

[0048] The manufacturing processes for the upper and lower substrates are the same, and the specific processes are as follows: The flow guide plate is generally made of copper. Depending on the needs, it may be nickel-plated or gold-plated. In this embodiment, a copper flow guide plate is used (other materials may also be used in other embodiments).

[0049] like Figure 7 As shown: (1) First, the sintered current-guiding copper sheet 1 is connected to the outer ring of the ceramic sheet using AMB (Active Brazing) or DBC (Copper Foil Sintering Copper Lamination) technology. Then, the sintered current-guiding copper sheet is etched as needed to form a customized sintered current-guiding copper sheet. After cleaning, the DBC substrate 4 is obtained, such as... Figure 7 As shown in step 1.

[0050] (2) Print a layer of adhesive in the reserved blank area on the DBC lower substrate. Special attention should be paid to ensuring that the printed pattern is positioned consistent with the predetermined position of the current-conducting copper sheet in the substrate design. The amount of adhesive should be controlled to avoid excessive thermal resistance and reduce heat loss. The cleaned adhesive is then used to bond the current-conducting copper sheet 2 to the blank area in the middle of the DBC lower substrate. After high-temperature curing and surface anti-oxidation treatment, a semi-finished high-reliability lower substrate 5 is obtained. Figure 7 As shown in step 2.

[0051] (3) The semi-finished high-reliability lower substrate is clamped and fixed, and milled to form the surface of the adhesive-bonded and sintered copper flow guiding sheets as shown in the figure. Figure 4 The groove shown represents the completion of the fabrication of the lower substrate 9 for the high-reliability finished product. Figure 7 As shown in step 3.

[0052] (4) The upper substrate of the high-reliability finished product is manufactured in the manner described in (1)-(3). Before assembly, a layer of solder paste is printed on both the upper substrate and the lower substrate. Then, semiconductor particles are placed at the corresponding positions on the lower substrate, such as... Figure 7 As shown in step 4.

[0053] (5) Cover with the upper substrate, clamp and fix the thermoelectric cooler with a special fixture, and send it into the heating equipment. Special attention must be paid to the fact that a vacuum must be drawn during the heating process to quickly remove the flux gas volatilized from the solder, completing the welding process and achieving the connection between the substrate and the semiconductor components. Then, the welded product is cooled and cleaned. At this point, the thermoelectric cooler in this embodiment is complete. Figure 7 As shown in step 5.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications are possible without departing from the technical solutions described in the claims.

Claims

1. A reliable rapid temperature-change thermoelectric cooler, characterized in that, The system includes an upper substrate (6) and a lower substrate (9). Semiconductor particles (7) are provided between the upper substrate (6) and the lower substrate. Both the upper substrate (6) and the lower substrate include a ceramic sheet (3) and a current-conducting copper sheet disposed on the surface of the ceramic sheet. The semiconductor particles (7) are soldered onto the current-conducting copper sheet. The current-conducting copper sheet includes a sintered current-conducting copper sheet (1) sintered and fixed on the outer ring of the ceramic sheet and an adhesive current-conducting copper sheet (2) glued and fixed in the middle of the ceramic sheet.

2. The reliable rapid temperature-change thermoelectric cooler according to claim 1, characterized in that, The current-guiding copper sheet is provided with a groove (8).

3. A reliable rapid temperature-change thermoelectric cooler according to claim 1 or 2, characterized in that, All the current-guiding copper sheets on the upper substrate (6) and the current-guiding copper sheets (2) glued on the lower substrate (9) are placed vertically; the sintered current-guiding copper sheets (1) on the left and right sides of the current-guiding copper sheets (2) glued on the lower substrate (9) are placed vertically, and the sintered current-guiding copper sheets (1) on the upper and lower sides of the current-guiding copper sheets (2) glued on the lower substrate (9) are placed horizontally.

4. A reliable rapid temperature-change thermoelectric cooler according to claim 3, characterized in that, The sintered flow-guiding copper sheets (1) at the first corner (10) and the second corner (11) on the lower substrate (9) are L-shaped.

5. A reliable rapid temperature-change thermoelectric cooler according to claim 1 or 2, characterized in that, The ceramic sheet (3) is aluminum nitride ceramic.

6. A method for manufacturing a reliable rapid temperature-change thermoelectric cooler, applied to the reliable rapid temperature-change thermoelectric cooler described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Sinter the sintered copper guide sheet (1) and fix it on the outer ring of the ceramic sheet (3). Etch the sintered copper guide sheet (1) to obtain the DBC lower substrate (4). S2: Adhesive bonding copper sheet (2) is bonded to the reserved middle blank area on the DBC lower substrate (4) and processed to obtain a semi-finished high-reliability lower substrate (5). S3: The semi-finished high-reliability lower substrate (5) is clamped and fixed, and grooves (8) are processed on the surfaces of the adhesive-bonded flow guiding copper sheet (2) and the sintered flow guiding copper sheet (1) to obtain the lower substrate (9). S4: The upper substrate (6) is fabricated in the manner of steps S1-S3. Semiconductor particles (7) are soldered onto the current-conducting copper sheet of the lower substrate (9). After the upper substrate (6) is covered, it is sent into a heating device for soldering to obtain the thermoelectric cooler.

7. A reliable rapid temperature-change thermoelectric cooler according to claim 6, characterized in that, The flow-guiding copper sheet is pre-sintered or cut into a dumbbell shape.

8. A reliable rapid temperature-change thermoelectric cooler according to claim 6, characterized in that, The flow-guiding copper sheet is pre-plated with nickel before welding.

9. A reliable rapid temperature-change thermoelectric cooler according to claim 6, 7, or 8, characterized in that, Vacuuming is performed while the semiconductor particles (7) are welded onto the current-conducting copper sheet of the lower substrate (9).

10. A reliable rapid temperature-change thermoelectric cooler according to claim 6, 7, or 8, characterized in that, The material is fed into the heating equipment for welding, and a vacuum is drawn during the heating process.

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