A high thermal conductivity thick film substrate and its preparation method

Abstract

A high thermal conductivity thick film substrate and its preparation method belong to the field of hybrid integrated circuits. It includes a thick film substrate body, a conductive or resistive strip, a chip soldering area, a thermal conductive concave hole, a magnetron sputtering layer, a gold-tin solder layer, a copper block, a filling layer, and a backside metallization layer. The conductive or resistive strip and the chip soldering area are located on the front surface of the thick film substrate body, the backside metallization layer is located on the backside of the thick film substrate, the thermal conductive concave hole is located in the area on the backside of the thick film substrate opposite to the surface chip soldering area, the magnetron sputtering layer is a high-temperature resistant metal film layer at the bottom of the ceramic concave hole, the gold-tin solder layer is a soldering layer between the copper block and the high-temperature resistant metal film layer at the bottom of the concave hole, the copper block is located in the concave hole, and the nano-gold paste filling layer is located in the gap between the copper block and the concave hole. Laser is used to open the concave hole. Without affecting its circuit carrier function, by changing the structure of the alumina thick film substrate, the thermal conductivity efficiency of the thick film substrate is increased. It is widely used as a high thermal conductivity thick film substrate in power hybrid integrated circuits.

Description

Technical Field

[0001] The present invention belongs to the field of hybrid integrated circuits, and more particularly to the field of thick film hybrid integrated circuits. Specifically, it relates to a method for preparing a high thermal conductivity thick film substrate. Background Art

[0002] In thick film hybrid integrated circuits, the thick film substrate (hereinafter referred to as the substrate) serves as the carrier of the thick film hybrid integrated circuit. As shown in Figure 1 , circuit channels are designed on the substrate, and a series of components such as capacitors and resistors are printed. At the same time, a large number of active or passive components are mounted on the substrate. In order to make more full use of the space of the thick film substrate and improve the integration degree of the hybrid integrated circuit, a lot of buried layer circuits are made in the thick film substrate. Therefore, a large amount of heat generated during the operation of the circuit needs to be quickly dissipated from the circuit working area. Therefore, the thermal conductivity of the substrate must be considered in thick film hybrid integrated circuits. Otherwise, the accumulation of a large amount of heat will cause the burnout of local circuits, thereby triggering the failure of the entire circuit. Currently, in the thick film substrate, heat conduction often starts from the material of the thick film substrate. For example, the alumina substrate is transformed into a aluminum nitride substrate, or a silicon carbide substrate, or a composite substrate (such as a porcelain enamel metal substrate, a plasma sprayed substrate, etc.). These solutions are all improved by changing the material properties. However, the change of material properties is also accompanied by many other problems, such as a larger specific gravity than alumina, a large parasitic capacitance, difficult to form, and even highly toxic materials. On the other hand, improving the heat conduction efficiency from the structure is also the main research topic for solving the heat dissipation of the substrate. Therefore, how to improve the thermal conductivity of the alumina thick film substrate in terms of its structure is a problem that needs to be considered for this high thermal conductivity thick film substrate.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The object of the present invention is to increase the heat conduction efficiency of the thick film substrate by changing the structure of the alumina thick film substrate without affecting its function as a circuit carrier.

[0005] The inventive concept of the present invention is to open a heat conduction concave hole on the back surface of the thick film substrate chip bonding, fill it with a heat conduction material, so as to efficiently conduct the heat generated by the chip operation on the thick film substrate.

[0006] For this purpose, the present invention provides a high thermal conductivity thick film substrate, as shown in Figure 1 , Figure 2 . It includes: a thick film substrate body, a conductive strip or a resistive strip, a chip welding area, a heat conduction concave hole, a magnetron sputtering layer, a gold-tin solder layer, a copper block, a nano-gold paste filling layer, and a thick film substrate back surface metallization layer.

[0007] The conductive strip or the resistive strip and the chip welding area are located on the front surface of the thick film substrate body.

[0008] The back metalization layer of the thick film substrate is located on the back of the thick film substrate.

[0009] The heat conduction concave hole is located in the area on the back of the thick film substrate facing the surface chip welding area, and the depth of the concave hole is such that the thickness of the substrate at the chip bonding place reaches 150 μm to 200 μm.

[0010] The magnetron sputtering layer is a high-temperature resistant metal film layer at the bottom of the ceramic concave hole, with a thickness of 100 μm to 150 μm.

[0011] The Au-Sn solder layer is the welding layer between the copper block and the high-temperature resistant metal film layer at the bottom of the concave hole.

[0012] The copper block is located in the concave hole, and the gap with the concave hole wall is less than 0.1 mm.

[0013] The nano-gold paste filling layer is located in the gap between the copper block and the concave hole.

[0014] A preparation method of a high heat conduction thick film substrate according to the present invention includes:

[0015] (1) First, print and dry on the front and back (platinum-silver paste) of the thick film substrate (with a thickness of 1 mm) according to the conventional process for standby.

[0016] (2) According to the chip assembly on the thick film substrate Figure 1 Pre-drill the position of the substrate on the back of the chip.

[0017] (3) For the pre-drilled position, use a laser to open a concave hole so that the thickness at the chip bonding place reaches 200 μm.

[0018] (4) Use magnetron sputtering to deposit a Ti-Pt-Au film layer (with a thickness of 100 μm) in the ceramic concave hole. This film layer serves as both the heat sink for the concave hole on the back of the substrate under the chip and the bonding layer.

[0019] (5) Weld a bare copper block in the concave hole using Au-Sn alloy soldering technology. The size of the bare copper block is similar to the size of the concave hole, and the end of the bare copper block is exactly on the same plane as the substrate.

[0020] (6) Use nano-gold paste to fill the gap of the concave hole and dry it at 290 °C for 10 minutes.

[0021] (7) Use ultrasonic cleaning to dry the alumina thick film substrate with the changed structure.

[0022] (8) Use plasma cleaning on the alumina thick film substrate, and after cleaning, it is ready for use.

[0023] Through the above steps, a high heat conduction thick film substrate is prepared.

[0024] Advantages of the invention:

[0025] Without affecting the functions of its circuit carrier, by improving the structure of the thick film substrate, the thermal conductivity of the thick film substrate is increased, thereby improving the heat dissipation efficiency and enhancing the thermal reliability of the overall circuit; mass production can be achieved.

[0026] Application scope: Widely used as a thick film substrate with high thermal conductivity performance in power hybrid integrated circuits. Description of the drawings

[0027] Figure 1 It is a schematic plan view of the assembly surface of the thick film substrate.

[0028] Figure 2 It is a schematic longitudinal structure view of the thick film substrate of the present invention.

[0029] In the figure:

[0030] 1 is the thick film substrate body, 2 is conduction band 1, 3 is conduction band 2, 4 is chip A, 5 is chip B, 6 is the heat conduction concave hole, 7 is the magnetron sputtering area, 8 is the gold-tin soldered bare copper area, 9 is the copper block, 10 is the nano-gold paste filling area, and 11 is the platinum-silver layer on the back of the thick film substrate. Specific implementation manners

[0031] Combined with Figure 1 、 Figure 2 The embodiments of the present invention are as follows:

[0032] In a certain 54 series hybrid integrated circuit of a high-power integrated circuit, since this circuit needs to have high thermal conductivity performance, according to the chip assembly on the thick film substrate Figure 1 , so a Figure 2 thermal conduction substrate was prepared. The specific preparation steps are as follows:

[0033] (1) First, print and dry on the front and back (platinum-silver paste) of the thick film substrate (with a thickness of 1 mm) according to the conventional process for later use;

[0034] (2) According to the chip assembly drawing on the thick film substrate, pre-drill holes in the position of the substrate on the back of the chip, with a size similar to the chip size;

[0035] (3) For the position of the pre-drilled holes, use a laser to open concave holes, and the distance from the bottom of the concave holes to the chip bonding position is about 200 μm.

[0036] (4) Use magnetron sputtering to deposit a Ti-Pt-Au film layer (with a thickness of 100 μm) in the ceramic concave holes. This film layer serves as both the bottom radiator of the concave holes on the back of the substrate under the chip and the bonding layer.

[0037] (5) Weld the bare copper block in the concave hole using gold-tin alloy soldering technology (360 °C, 2 minutes of vacuum soldering, the solder piece is Au80Sn20 solder piece). The size of the bare copper block is similar to that of the concave hole (about 0.1 mm smaller). The end of the bare copper block is exactly on the same plane as the substrate; if not on the same plane, use sandpaper to grind off the excess part.

[0038] (6) Fill the gap in the concave hole with nano-gold paste and cure it at 290 °C for 10 minutes.

[0039] (7) Use ultrasonic cleaning and drying to clean the alumina thick film substrate with the changed structure.

[0040] (8) Use plasma cleaning (nitrogen-hydrogen mixed gas, hydrogen accounts for 3.5%) to clean the alumina thick film substrate, and keep it for use after cleaning. Through the above steps, a high thermal conductivity thick film substrate for a certain 54 series hybrid integrated circuit is prepared, and it has a higher thermal conductivity compared with the original substrate.

[0041] The above content is a further detailed description of the present invention in combination with the best implementation mode. It cannot be determined that the specific implementation of the present invention is limited only to these descriptions. Those skilled in the art should understand that various modifications can be made in details without departing from the scope defined by the appended claims, and all of them should be regarded as belonging to the protection scope of the present invention.

Claims

1. A high thermal conductivity thick film substrate, comprising: a thick film substrate body, a conduction band or a resistance band, a chip soldering area, a heat conduction concave hole, a magnetron sputtering layer, a gold-tin solder layer, a copper block, a nano gold paste filling layer, and a thick film substrate backside metallization layer; the conduction band or resistance band and the chip soldering area are located on the front surface of the thick film substrate body; the thick film substrate backside metallization layer is located on the backside of the thick film substrate; the heat conduction concave hole is located in the area on the backside of the thick film substrate opposite to the surface chip soldering area, and the depth of the concave hole is such that the thickness of the substrate at the chip bonding place reaches 150 μm to 200 μm; the magnetron sputtering layer is a high temperature resistant metal film layer at the bottom of the ceramic concave hole, with a thickness of 100 μm to 150 μm; the gold-tin solder layer is a soldering layer between the copper block and the high temperature resistant metal film layer at the bottom of the concave hole; the copper block is located in the concave hole, and the gap with the concave hole wall is less than 0.1 mm; the nano gold paste filling layer is located in the gap between the copper block and the concave hole; the preparation method of the high thermal conductivity thick film substrate is as follows: (1) Print a conduction band, a resistance band or a pad on the front of the thick film substrate according to the existing process, print a metal layer on the back of the thick film substrate, and dry for later use; (2) According to the chip assembly drawing on the thick film substrate, perform pre-opening in the area on the back of the thick film substrate that aligns with the front chip; (3) For the position of the pre-opening, use a laser to open a concave hole so that the thickness at the chip bonding place reaches 150 μm to 200 μm; (4) Use magnetron sputtering to deposit a high temperature resistant metal film layer in the ceramic concave hole, with a thickness of 100 μm to 150 μm; (5) Use a gold-tin alloy soldering technique to solder a bare copper block in the concave hole. The size of the bare copper block is similar to the size of the concave hole, and the end of the bare copper block is exactly on the same plane as the back of the substrate; (6) Use nano gold paste to fill the concave hole gap and dry at 250 °C to 300 °C; (7) Use ultrasonic cleaning to dry the thick film substrate with the changed structure; (8) Use plasma cleaning on the thick film substrate, and after cleaning, set aside for later use; the material of the thick film substrate is glass-ceramics, aluminum oxide, aluminum nitride or beryllium oxide.

2. A high thermal conductivity thick film substrate according to claim 1, wherein, the thickness of the thick film substrate is 1 mm.

3. A high thermal conductivity thick film substrate according to claim 1, wherein, the thick film substrate backside metal layer is a platinum-silver alloy.

4. A high thermal conductivity thick film substrate according to claim 1, wherein, the high temperature resistant metal film layer is a Ti-Pt-Au film layer, with a thickness of about 100 μm to 150 μm.

5. A high thermal conductivity thick film substrate according to claim 1, wherein, the drying conditions of the nano gold paste are: 290 °C, 10 minutes.

6. A high thermal conductivity thick film substrate according to claim 1, wherein, the soldering conditions of the bare copper block and the gold-tin alloy are: the solder is an Au80Sn20 solder, vacuum soldering at 360 °C for 2 minutes, and the distance between the bare copper block and the concave hole is less than 0.1 mm.

7. A high thermal conductivity thick film substrate according to claim 1, wherein, the gas used for plasma cleaning is a nitrogen-hydrogen mixed gas with a hydrogen proportion of 3.5%.

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