Microwave transceiver module assembly process method based on ceramic substrate stacking assembly

Abstract

The invention discloses a microwave transceiver module assembly process method based on ceramic substrate stacking assembly. The microwave transceiver module assembly process method comprises the following steps: welding a shell; welding a first electronic component on the bottom metal heat sink, and welding a load chip through the ceramic substrate; assembling a second electronic component on the upper surface of the second layer of ceramic substrate; implanting a high-melting-point solder ball array on the back surface of the second-layer ceramic substrate, and coating the solder paste on the high-melting-point solder ball array by using silk-screen printing to obtain an assembled second-layer ceramic substrate; assembling the assembled second layer of ceramic substrate on a bonding pad corresponding to the ceramic substrate at the bottom of the shell in an inverted buckling manner, and realizing interconnection through reflow soldering; after the third layer of ceramic substrate is assembled by a similar method, the third layer of ceramic substrate and the corresponding bonding pad on the second layer of ceramic substrate are interconnected through reflow soldering; and finally, packaging the metal shell cover plate. The invention provides a new scheme for completing the assembly of the multi-layer ceramic substrate in a deep body, the production efficiency can be improved, and the assembly cost can be reduced.

Description

Technical Field

[0001] The invention relates to a microwave transceiver module assembly process method, and in particular to a microwave transceiver module assembly process method based on ceramic substrate stacking assembly. Background Art

[0002] Microwave transceiver modules are widely used in communication systems and are an important part of wireless transceiver systems. They are mainly assembled from the transmitting part, receiving part, power control and shell, etc. The electronic components in the current transceiver modules, including power amplifier chips, radio frequency chips, power chips, etc., are assembled in a plane in a shell, and then walled off different parts to prevent internal electromagnetic interference, and finally hermetically sealed, thereby realizing the entire process.

[0003] However, as devices and modules continue to develop in the direction of miniaturization and high-density integration, this planar assembly method has a large overall size and is difficult to meet subsequent needs. The device module design based on the stacking of multi-layer ceramic substrates can be interconnected in the vertical direction, thereby reducing the device planar size. However, this also makes the overall assembly process more difficult. The traditional micro-assembly process method is difficult to meet the needs of multi-layer ceramic substrate stacking and high-density packaging. In addition, as the packaging density increases, the internal heat dissipation demand also increases, and the requirements for high heat dissipation assembly technology are higher. Moreover, due to the need for electromagnetic isolation of microwave modules, the entire device needs to complete component assembly and airtight packaging in the cavity. Therefore, how to achieve the stacking of multi-layer substrates and multi-temperature gradient welding of components in the cavity is a difficult problem at present. Summary of the invention

[0004] Purpose of the invention: In view of the above problems, the present invention proposes a microwave transceiver module assembly process method based on ceramic substrate stacking assembly, which solves the problem of high difficulty in assembling the current miniaturized, high-density integrated microwave transceiver module micro-assembly process technology in the cavity.

[0005] Technical solution: The technical solution adopted by the present invention is a microwave transceiver module assembly process method based on ceramic substrate stacking assembly, comprising the following steps:

[0006] Step S1: The bottom metal heat sink, the bottom ceramic substrate, the external pins, and the metal frame are welded with high-temperature solder to prepare a shell with both the bottom and the side frame being metal. In order to achieve high airtightness, the high-temperature solder here is mainly silver-copper eutectic solder, and the welding temperature is 850°C-950°C. In order to ensure high thermal conductivity, the bottom metal heat sink material is a molybdenum-copper alloy or diamond-copper composite material with high thermal conductivity and low expansion coefficient.

[0007] Step S2: A microwave power amplifier chip, a microstrip line, a ceramic matching circuit chip, etc. with high heat dissipation requirements are assembled on the bottom metal heat sink using high temperature resistant and high thermal conductivity solder to form the microwave transmitting part as the first bottom layer. In order to achieve high heat dissipation, the solder here should be gold tin or nano silver solder paste; at the same time, the load chip with high heat dissipation requirements of the second layer receiving part is assembled with the bottom metal heat sink through a ceramic substrate using high temperature resistant and high thermal conductivity solder. The ceramic substrate here is a high thermal conductivity aluminum nitride ceramic and is made into an L shape to reduce the area occupied by the ceramic at the bottom. The sintering temperatures of the gold tin eutectic solder and the nano silver solder paste are 300℃-320℃ and 200℃-250℃ respectively, and the welding coating of the corresponding area is nickel / gold, wherein the thickness of the nickel layer is 3-8.9μm and the thickness of the gold is 1.3-4μm.

[0008] Step S3: Assemble the second electronic component onto the upper surface of the second ceramic substrate to obtain the receiving part of the transceiver module, wherein the second electronic component includes a radio frequency chip; implant high-melting-point solder balls at the corresponding positions of the solder pads on the back of the second ceramic substrate to form a high-melting-point solder ball array, and use screen printing to apply solder paste on the high-melting-point solder ball array to obtain the assembled second ceramic substrate. Use screen printing to apply solder paste on the high-melting-point solder ball array, which is achieved by steel screen printing, and reflow soldering is performed in a vacuum reflow furnace. The high-melting-point solder ball array assembly here uses Sn96.5Ag3Cu0.5 solder balls, the reflow temperature is 220℃-250℃, and the corresponding welding coating is nickel / gold, wherein the nickel layer thickness is 3 to 8.9μm, and the gold thickness is 0.13 to 0.45μm.

[0009] Step S4: Assemble the assembled second layer of ceramic substrate onto the pads corresponding to the bottom ceramic substrate of the shell prepared in step S1, and then interconnect the substrates by reflow soldering, the reflow soldering temperature being 220°C-250°C.

[0010] Step S5: Assemble the third electronic component onto the upper surface of the third ceramic substrate to obtain the power control part of the transceiver module, wherein the third electronic component includes a power control chip and a resistor and capacitor; implant solder balls with a lower melting point than that in step (3) at the corresponding positions of the solder pads on the back of the third ceramic substrate to form a low-melting-point solder ball array, and apply solder paste on the low-melting-point solder ball array by screen printing to obtain the assembled third ceramic substrate. The low-melting-point solder ball array here is assembled using Sn63Pb37 solder balls, the reflow temperature is 190°C-210°C, and the corresponding solder coating is nickel / gold, wherein the nickel layer thickness is 3 to 8.9 μm, and the gold thickness is 0.13 to 0.45 μm.

[0011] Step S6: assembling the assembled third-layer ceramic substrate onto the upper surface of the intermediate-layer ceramic substrate of the housing, and then interconnecting the third-layer substrate with the second-layer substrate by reflow soldering.

[0012] Step S7: The metal housing cover is packaged by parallel sealing and welding to form an airtight package to obtain a high-density stacked microwave transceiver module.

[0013] The interconnection of the two substrates is achieved by printing solder paste on the solder balls on the solder ball array of the upper substrate through a special steel mesh, then flipping it to the bottom substrate and then entering the reflow oven for soldering. The solder paste is applied to the high melting point solder ball array using screen printing, and the solder paste is printed on the solder balls using a special steel mesh. Since the surface of the solder ball is curved, in order to ensure the uniformity of the printed solder paste thickness and the quality of subsequent flip welding, the opening parameters of the steel mesh need to be specially required, where the opening diameter of the steel mesh printing is D = 0.6 ~ 0.8d (where d is the solder ball diameter), and the steel mesh thickness is H = 50μm + 0.2 ~ 0.4d. The solder paste is applied to the low melting point solder ball array using screen printing, and the parameters of the steel mesh used are the same. The reflow temperature is 220℃-250℃.

[0014] In all the above steps, electronic components such as chips and circuits are interconnected with the ceramic substrate through wire bonding.

[0015] Beneficial effects: Compared with the traditional microwave transceiver module assembly process, the present invention realizes the vertical packaging interconnection of three-layer substrates through two solder ball processes with different melting points. By sintering the high-power heat dissipation chip with high heat dissipation requirements to the bottom heat sink with gold tin or nano silver solder, and placing the chip with low heat dissipation requirements on the upper substrate, while achieving heat dissipation, it also improves the packaging integration and reduces the volume of the module. The present invention uses a steel mesh to print solder paste on the solder balls of the solder ball array of the upper substrate and then assembles it with the lower substrate and then flows and solders it. Compared with the existing method of applying solder paste to the solder pad in the cavity, the operation is simpler and more efficient. Moreover, compared with the existing method of assembling layer by layer in the cavity, the present invention adopts the method of first mounting and bonding the chip on the ceramic substrate and then loading it into the shell cavity, which can reduce the use of solder gradient, reduce the difficulty of assembly, and improve the reliability of assembled devices. The present invention proposes a microwave transceiver module assembly process method based on the stacking assembly of three-layer ceramic substrates, and proposes a new solution for completing the assembly of multi-layer ceramic substrates in a deep body, which can improve the generation efficiency and reduce the assembly cost. This process method has the characteristics of high integration, simple operation, high reliability and mass production capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of a microwave transceiver module in an embodiment;

[0017] Figure 2 It is a schematic diagram of step 1 of the microwave transceiver module assembly process method based on ceramic substrate stacking assembly of the present invention;

[0018] Figure 3It is a schematic diagram of step 2 of the microwave transceiver module assembly process method based on ceramic substrate stacking assembly of the present invention;

[0019] Figure 4 It is a schematic diagram of step 3 of the microwave transceiver module assembly process method based on ceramic substrate stacking assembly of the present invention;

[0020] Figure 5 It is a schematic diagram of step 4 of the microwave transceiver module assembly process method based on ceramic substrate stacking assembly of the present invention;

[0021] Figure 6 It is a schematic diagram of step 5 of the microwave transceiver module assembly process method based on ceramic substrate stacking assembly of the present invention;

[0022] Figure 7 It is a schematic diagram of step 6 of the microwave transceiver module assembly process method based on ceramic substrate stacking assembly of the present invention;

[0023] Figure 8 It is a schematic diagram of step 7 of the assembly process method of the microwave transceiver module based on ceramic substrate stacking assembly of the present invention.

[0024] Among them: ① is the bottom metal heat sink; ② the bottom ceramic substrate; ③ the external pins; ④ the metal frame; ⑤ the power chip and the peripheral matching circuit; ⑥ the load chip; ⑦ the ceramic heat sink; ⑧ the RF chip and some passive components; ⑨ the second layer of ceramic substrate; ⑩ the high melting point solder ball; Power control chip and resistors and capacitors; The third layer of ceramic substrate; Low melting point solder balls; Cover. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0026] The microwave transceiver module assembly process method based on ceramic substrate stacking assembly of the present invention is as follows: Figure 1 The figure shows a schematic diagram of the packaging structure of the transceiver module with three layers of ceramic substrates stacked in this embodiment, and its process method mainly includes the following steps:

[0027] Step 1: See Figure 2 , silver-copper (AgCu) eutectic high-temperature solder is used to weld the metal heat sink ①, the bottom ceramic substrate ②, the external pins ③, and the metal frame ④ in a vacuum welding furnace at a welding temperature of 850℃-950℃ to obtain a deep cavity shell.

[0028] Step 2: See Figure 3, use high-temperature gold-tin (Au80Sn20) or high-thermal-conductivity nano-silver solder to sinter the bottom power chip and peripheral matching circuit ⑤ on the metal heat sink at the bottom of the deep cavity shell obtained in step 1, and interconnect with the bottom ceramic substrate ② through wire bonding; at the same time, the load chip ⑥ of the second layer receiving part with higher heat dissipation requirements is assembled with the bottom metal heat sink through the ceramic heat sink ⑦ using Au80Sn20 high-temperature solder or nano-silver solder. The sintering temperature of the above gold-tin solder is 300℃-320℃, and the sintering temperature of the nano-silver solder is 200℃-250℃.

[0029] Step 3: See Figure 4 , use low-temperature solder (Sn96.5Ag3Cu0.5) or conductive adhesive to weld the RF chip and some passive components⑧ on the second layer of ceramic substrate ⑨, and interconnect them through wire bonding. Then use a steel mesh to apply solder paste (Sn96.5Ag3Cu0.5) on the back BGA pad of the ceramic substrate ⑨, and then use a ball planting steel mesh to plant high-melting-point tin balls ⑩ (Sn96.5AgCu0.5 or Pb90Sn10 solder balls) at the corresponding pad positions, and perform reflow soldering. Finally, print solder paste on the reflowed solder balls through the steel mesh for standby use. The reflow temperature of the above Sn96.5Ag3Cu0.5 solder is 220℃-250℃. The diameter of the tin ball used is 500μm, the opening diameter of the steel mesh is 400μm, and the thickness of the steel mesh is 150μm.

[0030] Step 4: See Figure 5 , assemble the second layer substrate obtained in step three into the cavity obtained in step two, and then enter the reflow furnace for reflow soldering, the reflow soldering temperature is 220℃-250℃, and then interconnect the load chip and the substrate ⑨ through metal wire bonding.

[0031] Step 5: See Figure 6 , use conductive glue to connect the power control chip and resistors and capacitors Mounted on the third ceramic substrate Then a steel mesh is used on the ceramic substrate to interconnect them. Apply solder paste (Sn63Pb37) on the back BGA pad, and then use the ball planting steel mesh to plant low melting point solder balls on the corresponding pad positions. (Sn63Pb37), and reflow soldering is performed, and finally the solder paste is printed on the reflow solder ball through the special steel screen in the above step 3 for standby use. The reflow temperature of the above Sn63Pb37 solder is 190℃-210℃.

[0032] Step 6: See Figure 7, assemble the third layer substrate obtained in step five into the cavity obtained in step four, and then put it into a reflow furnace for reflow soldering, and the reflow soldering temperature is 190℃-210℃.

[0033] Step 7: See Figure 8 , put the shell obtained in step 6 and the metal cover The parallel sealing welding is performed by a parallel sealing welding machine to obtain a microwave transceiver module with an airtight package.

Claims

1. A microwave transceiver module assembly process method based on ceramic substrate stacking assembly, characterized in that: The following steps are involved: (1) welding the bottom metal heat sink, the bottom ceramic substrate, the external pins, and the metal surrounding frame to obtain a shell; (2) welding a first electronic component on the bottom metal heat sink to obtain a microwave transmitting part, wherein the first electronic component includes: a microwave power amplifier chip, a microstrip line and a ceramic matching circuit chip; welding a load chip of the receiving part with a higher heat dissipation requirement on the bottom metal heat sink through a ceramic substrate; (3) assembling a second electronic component onto the upper surface of the second ceramic substrate to obtain a receiving portion of the transceiver module, wherein the second electronic component includes a radio frequency chip; implanting high-melting-point solder balls at corresponding positions of solder pads on the back of the second ceramic substrate to form a high-melting-point solder ball array, and applying solder paste on the high-melting-point solder ball array by screen printing to obtain an assembled second ceramic substrate; (4) The assembled second-layer ceramic substrate is mounted on the corresponding pads of the bottom ceramic substrate of the shell by flip-flopping, and the high-melting-point solder ball array on the assembled second-layer ceramic substrate and the corresponding pads on the bottom ceramic substrate are interconnected by reflow soldering; (5) Assembling a third electronic component onto the upper surface of the third ceramic substrate to obtain a power control part of the transceiver module, wherein the third electronic component includes a power control chip and a resistor and a capacitor; implanting a solder ball with a lower melting point than that in step (3) at a corresponding position of the solder pad on the back of the third ceramic substrate to form a low-melting-point solder ball array, and applying solder paste on the low-melting-point solder ball array by screen printing to obtain an assembled third ceramic substrate; (6) The assembled third-layer ceramic substrate is flip-fitted onto the corresponding pads of the second-layer ceramic substrate, and the low-melting-point solder ball array on the assembled third-layer ceramic substrate and the corresponding pads on the second-layer ceramic substrate are interconnected by reflow soldering; (7) Encapsulating the metal shell cover to form an airtight package to obtain a microwave transceiver module.

2. The microwave transceiver module assembly process method based on ceramic substrate stacking assembly according to claim 1 is characterized in that: The bottom metal heat sink, the bottom ceramic substrate, the external pins and the metal frame adopt AgCu eutectic high temperature solder, and the welding temperature is 850℃-950℃.

3. The microwave transceiver module assembly process method based on ceramic substrate stacking assembly according to claim 1 is characterized in that: The high temperature resistant and high thermal conductivity solder used on the bottom metal heat sink is gold-tin (Au80Sn20) eutectic solder or nano silver solder paste, and the sintering temperature is 300℃-320℃ and 200℃-250℃ respectively. The corresponding welding plating is nickel / gold, wherein the nickel layer thickness is 3-8.9μm and the gold thickness is 1.3-4μm.

4. The microwave transceiver module assembly process method based on ceramic substrate stacking assembly according to claim 1 is characterized in that: The back of the second ceramic substrate is used for high melting point solder ball array assembly using Sn96.5Ag3Cu0.5 solder balls, the reflow temperature is 220℃-250℃, and the corresponding solder plating is nickel / gold, wherein the nickel layer thickness is 3-8.9μm, and the gold thickness is 0.13-0.45μm.

5. The microwave transceiver module assembly process method based on ceramic substrate stacking assembly according to claim 1 is characterized in that: The solder paste is coated on the high melting point solder ball array by screen printing, and the solder paste is printed on the solder balls by using a special steel mesh, the opening diameter of the special steel mesh is D=0.6~0.8d, where d is the solder ball diameter, and the thickness of the steel mesh is H=50μm+0.2~0.4d.

6. The microwave transceiver module assembly process method based on ceramic substrate stacking assembly according to claim 1, characterized in that: The solder paste is coated on the low melting point solder ball array by screen printing, and the solder paste is printed on the solder ball by using a special steel mesh, the opening diameter of the special steel mesh is D=0.6~0.8d, where d is the solder ball diameter, and the thickness of the steel mesh is H=50μm+0.2~0.4d.

7. The microwave transceiver module assembly process method based on ceramic substrate stacking assembly according to claim 1, characterized in that: The reflow temperature is 220°C-250°C.

8. The microwave transceiver module assembly process method based on ceramic substrate stacking assembly according to claim 1, characterized in that: The low-melting-point solder ball array implanted at the back pad position of the third-layer ceramic substrate is Sn63Pb37 solder ball, the reflow temperature is 190℃-210℃, and the corresponding solder plating is nickel / gold, wherein the nickel layer thickness is 3~8.9μm, and the gold thickness is 0.13~0.45μm.

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