A microwave transceiver module assembly process method based on ceramic substrate stacking assembly

Abstract

The application discloses a microwave transceiving module assembly process method based on ceramic substrate stacking assembly, which comprises the following steps: welding a shell; welding a first electronic element on a bottom metal heat sink and welding a load chip through a ceramic substrate; assembling a second electronic element to an upper surface of a second layer ceramic substrate; implanting a high-melting-point tin ball array on a back surface of the second layer ceramic substrate, coating soldering paste on the high-melting-point tin ball array by using silk screen printing, and obtaining an assembled second layer ceramic substrate; inversely assembling the assembled second layer ceramic substrate to a corresponding bonding pad of the bottom ceramic substrate of the shell, and realizing interconnection through reflow soldering; similarly, after assembling a third layer ceramic substrate, realizing interconnection between the third layer ceramic substrate and corresponding bonding pads of the second layer ceramic substrate through reflow soldering; and finally, packaging a metal shell cover plate. The application provides a new scheme for completing multi-layer ceramic substrate assembly in a deep body, and can improve generation efficiency and reduce assembly cost.

Description

TECHNICAL FIELD

[0001] The present application relates to a microwave transceiver module assembly process method, and particularly relates to a microwave transceiver module assembly process method based on ceramic substrate stacking assembly. BACKGROUND

[0002] The microwave transceiver module is widely used in communication systems and is an important part of the wireless transceiver system, which is mainly assembled by a transmitting part, a receiving part, a power supply control and a shell. In the current transceiver module, electronic components including power amplifier chips, radio frequency chips and power supply chips are assembled in a plane in a shell, then different parts are isolated by walls to prevent internal electromagnetic interference, and finally, the air-tight packaging is performed to realize the whole process flow.

[0003] However, with the continuous development of devices and modules towards miniaturization and high-density integration, the overall size of the plane assembly method is large and cannot meet the subsequent requirements. The device module design based on multi-layer ceramic substrate stacking can reduce the device plane size through vertical interconnection, but this also makes the overall assembly process difficulty increase sharply. The traditional micro-assembly process method cannot meet the requirements of multi-layer ceramic substrate stacking and high-density packaging. In addition, with the increase of packaging density, the internal heat dissipation requirement also increases, and the requirement for high heat dissipation assembly process is higher. Moreover, due to the requirement of electromagnetic isolation of the microwave module, the device assembly and air-tight packaging need to be completed in the cavity. Therefore, how to realize the stacking of multi-layer substrates and the multi-temperature gradient welding of components in the cavity is a difficult problem at present. SUMMARY

[0004] The present application provides a microwave transceiver module assembly process method based on ceramic substrate stacking assembly to solve the problem of high assembly difficulty of the micro-assembly process technology of the current miniaturized and high-density integrated microwave transceiver module in the cavity.

[0005] The technical scheme adopted by the present application 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 pin and the metal frame are welded by high-temperature solder to prepare a shell with metal frames on the bottom and the side. In order to achieve high air tightness, the high-temperature solder here is mainly silver-copper eutectic solder, and the welding temperature is 850-950 DEG C. In order to ensure high thermal conductivity, the bottom metal heat sink material is molybdenum-copper alloy or diamond-copper composite material with low expansion coefficient.

[0007] Step S2: Assemble the microwave power amplifier chip, microstrip line, ceramic matching circuit piece and other components which require high heat dissipation on the bottom metal heat sink to form the bottom first layer of the microwave transmitting part. In order to achieve high heat dissipation, the solder used here should be gold-tin or nano-silver solder paste. At the same time, assemble the second layer of the receiving part of the load chip which requires high heat dissipation with the bottom metal heat sink through the ceramic substrate using high-temperature-resistant and high-thermal-conductivity solder. The ceramic substrate here is high-thermal-conductivity aluminum nitride ceramic and is made into an L shape to reduce the area occupied by the ceramic on the bottom. The sintering temperatures of the gold-tin eutectic solder and the nano-silver solder paste are 300-320°C and 200-250°C respectively, and the corresponding solder plating layers are nickel / gold, in which the thickness of the nickel layer is 3-8.9 μm and the thickness of the gold layer is 1.3-4 μm.

[0008] Step S3: Assemble the second electronic component to the upper surface of the second layer of the 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 tin balls at the corresponding positions of the back pads of the second layer of the ceramic substrate to form a high-melting-point tin ball array, coat solder paste on the high-melting-point tin ball array using screen printing to obtain the assembled second layer of the ceramic substrate. Coat solder paste on the high-melting-point tin ball array using screen printing, which is realized by steel screen printing and reflow soldering in a vacuum reflow furnace. The high-melting-point tin ball array assembly here uses Sn96.5Ag3Cu0.5 solder balls, the reflow temperature is 220-250°C, and the corresponding solder plating layer is nickel / gold, in which the thickness of the nickel layer is 3-8.9 μm and the thickness of the gold layer is 0.13-0.45 μm.

[0009] Step S4: Assemble the assembled second layer of the ceramic substrate to the corresponding pads of the bottom ceramic substrate of the shell prepared in step S1, and then realize the interconnection between the substrates through reflow soldering. The temperature of the reflow soldering is 220-250°C.

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

[0011] Step S6: Assemble the assembled third layer of the ceramic substrate to the upper surface of the middle layer of the ceramic substrate of the shell, and then realize the interconnection between the third layer of the substrate and the second layer of the substrate through reflow soldering.

[0012] Step S7: The parallel sealing and welding is used to seal the metal shell cover plate to form airtight packaging, and a high-density stacked microwave transceiver module is obtained.

[0013] The interconnection of the two-layer substrate is achieved by printing solder paste on the tin ball array of the upper substrate through a special steel mesh, then inversely mounting on the lower substrate, and then reflow soldering. The solder paste is coated on the high-melting-point tin ball array using silk screen printing, and the solder paste is printed on the tin ball through a special steel mesh. Since the surface of the tin ball is arc-shaped, in order to ensure the uniformity of the thickness of the printed solder paste and the quality of the subsequent inverse mounting and soldering, the opening parameters of the steel mesh need to be specially required. The opening diameter D of the steel mesh printing is 0.6-0.8d (where d is the diameter of the solder ball), and the thickness H of the steel mesh is 50μm+0.2-0.4d. The solder paste is coated on the low-melting-point tin ball array using silk screen printing, and the steel mesh parameters are the same. The reflow soldering temperature is 220-250℃.

[0014] In all the above steps, the electronic elements 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 application realizes vertical packaging interconnection of three-layer substrates through tin ball processes with two different melting points. The high-power heat dissipation chip with high heat dissipation requirement is sintered to the bottom heat sink using gold tin or nano silver solder, and the chip with low heat dissipation requirement is placed on the upper substrate. The heat dissipation is realized while the packaging integration is improved and the volume of the module is reduced. The present application uses a steel mesh to print tin paste on the solder balls of the tin ball array of the upper substrate, and then assembles and reflow soldering with the lower substrate. Compared with the existing method of printing tin paste on the pads 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 application first performs chip mounting and bonding assembly on the ceramic substrate, and then assembles into the cavity of the shell, which can reduce the use of solder gradient, reduce the assembly difficulty, and improve the reliability of the assembled device. The present application proposes a microwave transceiver module assembly process method based on three-layer ceramic substrate stacking assembly, proposes a new scheme for completing multi-layer ceramic substrate assembly in a deep cavity, which can improve the generation efficiency and reduce the assembly cost. The process method has high integration, simple operation, high reliability, and batch production characteristics. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0018] Figure 3Step 2 schematic diagram of the microwave transceiver module assembly process method based on ceramic substrate stacking of the present application;

[0019] Figure 4 Step 3 schematic diagram of the microwave transceiver module assembly process method based on ceramic substrate stacking of the present application;

[0020] Figure 5 Step 4 schematic diagram of the microwave transceiver module assembly process method based on ceramic substrate stacking of the present application;

[0021] Figure 6 Step 5 schematic diagram of the microwave transceiver module assembly process method based on ceramic substrate stacking of the present application;

[0022] Figure 7 Step 6 schematic diagram of the microwave transceiver module assembly process method based on ceramic substrate stacking of the present application;

[0023] Figure 8 Step 7 schematic diagram of the microwave transceiver module assembly process method based on ceramic substrate stacking of the present application.

[0024] Wherein: ① is a bottom metal heat sink; ② is a bottom ceramic substrate; ③ is an external pin; ④ is a metal frame; ⑤ is a power chip and peripheral matching circuit; ⑥ is a load chip; ⑦ is a ceramic heat sink; ⑧ is a radio frequency chip and part of passive devices; ⑨ is a second layer ceramic substrate; and ⑩ is a high melting point tin ball; Power control chip and resistor capacitor; Third layer ceramic substrate; Low melting point tin ball; Cover plate. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be further described below in combination with the drawings and examples.

[0026] The microwave transceiver module assembly process method based on ceramic substrate stacking described in the present application, as shown in Figure 1 The packaging structure schematic diagram of the three-layer ceramic substrate stacked transceiver module of the present embodiment, the process method thereof mainly includes the following steps:

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

[0028] Step two: refer to Figure 3, the bottom power chip and the peripheral matching circuit 5 are sintered on the bottom metal heat sink of the deep cavity shell obtained in step one by using high-temperature gold-tin (Au80Sn20) or high-thermal-conductivity nano-silver solder, and are interconnected with the bottom ceramic substrate 2 through wire bonding; meanwhile, the second layer load chip 6 with high heat dissipation requirement is assembled with the bottom metal heat sink through the ceramic heat sink 7 by using Au80Sn20 high-temperature solder or nano-silver solder. The sintering temperature of the above gold-tin solder is 300-320°C, and the sintering temperature of the nano-silver solder is 200-250°C.

[0029] Step three: refer to Figure 4 , the radio frequency chip and part of the passive device 8 are welded on the second layer ceramic substrate 9 by using low-temperature solder (Sn96.5Ag3Cu0.5) or conductive adhesive, and are interconnected through wire bonding. Then, solder paste (Sn96.5Ag3Cu0.5) is coated on the BGA pads on the back of the ceramic substrate 9 by using a steel mesh, high-melting-point tin balls 10 (Sn96.5AgCu0.5 or Pb90Sn10 solder balls) are planted on the corresponding pad positions by using a ball planting steel mesh, and reflow soldering is performed, and finally solder paste is printed on the reflowed solder balls by using the steel mesh prepared in step three. The reflow temperature of the above Sn96.5Ag3Cu0.5 solder is 220-250°C. The diameter of the tin balls used is 500 μm, the opening diameter of the steel mesh is 400 μm, and the thickness of the steel mesh is 150 μm.

[0030] Step four: refer to Figure 5 , the second layer substrate obtained in step three is assembled into the cavity obtained in step two, and then is placed into a reflow furnace for reflow soldering. The reflow soldering temperature is 220-250°C, and then the load chip and the substrate 9 are interconnected through metal wire bonding.

[0031] Step five: refer to Figure 6 , the power control chip and the resistor and capacitor are assembled on the third layer ceramic substrate by using conductive adhesive, and are interconnected through wire bonding. Then, solder paste (Sn63Pb37) is coated on the BGA pads on the back of the ceramic substrate by using a steel mesh, low-melting-point tin balls (Sn63Pb37) are planted on the corresponding pad positions by using a ball planting steel mesh, and reflow soldering is performed, and finally solder paste is printed on the reflowed solder balls by using the steel mesh prepared in step three. The reflow temperature of the above Sn63Pb37 solder is 190-210°C.

[0032] Step six: refer to Figure 7The third layer substrate obtained in step five is assembled into the cavity obtained in step four, and then is put into a reflow furnace for reflow soldering, and the reflow soldering temperature is 190-210°C.

[0033] Step seven: see Figure 8 The shell obtained in step six and the metal cover plate are parallelly sealed by a parallel sealing machine, and a hermetically sealed microwave transceiver module is obtained. The parallel sealing machine is used for parallel sealing, and a hermetically sealed microwave transceiver module is obtained.

Claims

1. A method for assembling a microwave transceiver module based on ceramic substrate stacking, characterized in that, Includes the following steps: (1) Weld the bottom metal heat sink, bottom ceramic substrate, external pins and metal frame to obtain the housing; (2) A first electronic component is soldered onto the bottom metal heat sink to obtain a microwave emitting part. The first electronic component includes a microwave power amplifier chip, a microstrip line and a ceramic matching circuit chip. A load chip with high heat dissipation requirements for the receiving part is soldered onto the bottom metal heat sink through a ceramic substrate. (3) Assemble the second electronic component onto the upper surface of the second ceramic substrate to obtain the receiving part of the transceiver module. The second electronic component includes an RF chip. Implant high melting point solder balls at the corresponding positions of the pads on the back of the second ceramic substrate to form a high melting point solder ball array. Apply solder paste to the high melting point solder ball array using screen printing to obtain the assembled second ceramic substrate. (4) The assembled second ceramic substrate is upside down and assembled onto the corresponding pads of the bottom ceramic substrate of the housing. The high melting point solder ball array on the assembled second ceramic substrate and the corresponding pads on the bottom ceramic substrate are interconnected by reflow soldering. (5) Assemble the third electronic component onto the upper surface of the third ceramic substrate to obtain the power control part of the transceiver module. The third electronic component includes a power control chip and resistors and capacitors. Insert solder balls with a lower melting point than those in step (3) into the corresponding positions of the back pads of the third ceramic substrate to form a low melting point solder ball array. Apply solder paste to the low melting point solder ball array using screen printing to obtain the assembled third ceramic substrate. (6) The assembled third ceramic substrate is upside down and assembled onto the corresponding pads of the second ceramic substrate. The low melting point solder ball array on the assembled third ceramic substrate and the corresponding pads on the second ceramic substrate are interconnected by reflow soldering. (7) Encapsulate the metal outer casing cover to form an airtight package to obtain the microwave transceiver module.

2. The assembly process method for a microwave transceiver module based on ceramic substrate stacking according to claim 1, characterized in that: The bottom metal heat sink, bottom ceramic substrate, external leads, and metal frame are made of AgCu eutectic high-temperature solder, with a soldering temperature of 850℃-950℃.

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

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

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

6. The assembly process method for a microwave transceiver module based on ceramic substrate stacking according to claim 1, characterized in that: Applying solder paste to an array of low-melting-point solder balls using screen printing involves printing the solder paste onto the solder balls using a special stencil. The opening diameter of the special stencil is D = 0.6 to 0.8d, where d is the diameter of the solder ball, and the thickness of the stencil is H = 50 μm + 0.2 to 0.4d.

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

8. The assembly process method for a microwave transceiver module based on ceramic substrate stacking 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, with a reflow temperature of 190℃-210℃. The corresponding solder plating layer is nickel / gold, with a nickel layer thickness of 3~8.9μm and a gold layer thickness of 0.13~0.45μm.

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