Complex radio frequency module sintering and bonding assembly process method

Abstract

The invention discloses a sintering and bonding assembly process method for a complex radio frequency module. According to the sequence of process temperatures from high to low, the process method comprises the steps of reflow soldering of a power panel surface-mounted component, sintering of a microwave substrate and a cavity, sintering of a radio frequency connector and the cavity and sintering of a low-frequency connector and the cavity. Sintering the surface-mounted power panel and the cavity; welding a surface-mounted device filter on the microwave substrate; bonding a radio frequency connector welding carrier and the filter at low stress; and bonding a bare chip. According to the scheme, complete assembly of the complex radio frequency assembly is completed within the sintering welding bonding temperature corresponding to limited process welding flux.

Description

Technical Field

[0001] The present invention relates to the technical field of complex radio frequency module assembly, and in particular to a sintering and bonding assembly process method for a complex radio frequency module. Background Art

[0002] As the functions of RF microwave components become increasingly complex, component assembly involves the sintering, welding and bonding of various substrates, substrates, RF connectors, low-frequency connectors, conventional packaging devices, ceramic devices and bare chips. There are many assembly materials, and various materials, devices and packaging forms have special requirements for assembly methods. Conventional processes cannot meet the reliable welding of various components of complex RF modules, avoid remelting, and meet the requirements of void rate and airtightness. Summary of the Invention

[0003] In response to the above technical problems, the present invention provides a sintering and bonding assembly process method for a complex radio frequency module.

[0004] The present invention is achieved by adopting the following technical solutions: A sintering and bonding assembly process for a complex radio frequency module comprises the following steps: Step S1: reflow soldering of surface mount components on the power board, sintering of the microwave substrate and the cavity, sintering of the RF connector and the cavity, and sintering of the low-frequency connector and the cavity; Step S2: sintering the surface-mounted power board and the cavity, welding the surface-mounted device filter on the microwave substrate, and welding the RF connector; Step S3: low-stress bonding between the carrier and the filter; Step S4: Bonding of bare chips.

[0005] Specifically, step S1 is performed sequentially based on the first temperature gradient, wherein the reflow soldering of the surface-mount components of the power board is performed using Sn96.5Ag3.0Cu0.5 solder paste to perform reflow soldering on various packaged surface-mount components, wherein the maximum reflow setting temperature is 235° C. to 245° C.; wherein the power board is an FR-4 multilayer board and the power board is independently soldered in the reflow oven; The first gradient temperature is set to a maximum temperature of 235°C to 245°C, and the solder temperature (melting point) used is 217°C.

[0006] Specifically, the microwave substrate and the cavity are sintered using Sn96.5Ag3.0Cu0.5 solder sheets, the microstrip substrate is a double-sided 4350B panel, and the sintered surface is gold-plated with a thickness of 0.5um; the cavity is a partially gold-plated 6061 aluminum alloy cavity, and the sintered surface is gold-plated with a thickness of 0.5um. During sintering, a sintering tool is used to flatten the microwave substrate onto the front mounting surface of the cavity; wherein, the maximum reflow setting temperature is 245°C to 255°C.

[0007] Specifically, the sintering of the RF connector and the cavity is carried out using a Sn96.5Ag3.0Cu0.5 circular solder ring. The RF connector is an SMP socket, the circular solder ring is a solder ring of preset size, and the RF connector is pressed into the RF connector mounting hole on the back of the cavity by tooling.

[0008] Specifically, the sintering of the low-frequency connector and the cavity is carried out using a Sn96.5Ag3.0Cu0.5 rectangular solder ring. The low-frequency connector is a J30J 9-core rectangular socket. The rectangular solder ring is a preset-size solder ring. The low-frequency connector is pressed into the low-frequency connector mounting hole on the back of the cavity by a tool. The sintering of the microwave substrate double-sided board 4350B, the radio frequency connector SMP socket, and the low-frequency connector J30J 9-core rectangular socket and the cavity is completed simultaneously in a vacuum reflow furnace.

[0009] Specifically, step S2 is performed sequentially based on the second gradient temperature. The surface-mounted power board and the cavity are sintered using Sn63Pb37 solder sheets. Based on the power board and cavity that have been soldered and sintered at the first gradient temperature, the power board is pressed against the sintering surface on the back of the cavity through a tool. The tool is provided with an opening that increases the temperature inside the cavity during reflow, and the pressing surface avoids the soldered components on the power board. Among them, the second gradient temperature is set to a maximum temperature of 212°C~225°C, and the solder temperature (melting point) used is 183°C.

[0010] Specifically, the soldering of the surface-mounted device filters on the microwave substrate is carried out using Sn63Pb37 solder paste. The surface-mounted filters are LC filters and FBAR filters. The filters are attached to the corresponding mounting positions of the microstrip substrate on the front of the cavity through a manual solder paste spotting process. The soldering of the surface-mounted device filters on the microwave substrate and the sintering of the power supply board and the cavity after the surface mounting are completed simultaneously in a vacuum reflow furnace.

[0011] Specifically, the RF connector is welded using Sn63Pb37 solder wire, and the RF connector and the cavity are mechanically fixed based on the sintering in step S1. After the welding of the surface-mounted device filter on the microwave substrate and the sintering of the surface-mounted power board and the cavity are completed, manual welding with solder wire is used to electrically connect the RF connector and the microwave substrate.

[0012] Specifically, in step S3, the low-stress bonding between the carrier and the filter is performed based on the third gradient temperature, using ME8456 low-stress conductive adhesive having a curing temperature of the third gradient temperature, and performing low-stress bonding between the carrier and the filter, and between the carrier and the cavity in a curing furnace; The third gradient temperature is set to 150°C.

[0013] Specifically, the step S4 is based on the fourth gradient temperature, the bare chips are bonded to the carrier using H20E conductive adhesive, wherein the bare chips are gallium arsenide chips, and the curing temperature of the conductive adhesive is the fourth gradient temperature; The fourth gradient temperature is set to 120°C.

[0014] The beneficial effects of the present invention are as follows: the present invention proposes a sintering and bonding assembly process method for a complex radio frequency module, which can complete the complete assembly of a complex radio frequency component within the sintering, welding and bonding temperature corresponding to a limited process solder, and ensure that the microwave substrate, radio frequency connector, low frequency connector, power board and packaging device are prevented from remelting during the entire assembly process, thereby meeting the requirements of the prohibited and restricted process; the sintering of the microwave substrate, radio frequency connector, low frequency connector and power board meets the requirement of a void rate of ≤20%; the sintering of the radio frequency connector and the low frequency connector meets the requirement of an airtightness of 10 -9 Pa.cm 3 / s requirements; ceramic filters meet low stress assembly requirements; bare chips meet shear force requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0016] Figure 1 This is a schematic diagram of the sintering and bonding assembly of a complex RF module in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0018] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0019] The following is combined with Figure 1 , some embodiments of the present invention are described in detail. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0020] The present invention proposes a complex radio frequency module sintering and bonding assembly process method, according to the process temperature from high to low order, such as Figure 1 As shown, the following steps are included: Step S1: reflow soldering of surface mount components on the power board, sintering of the microwave substrate and the cavity, sintering of the RF connector and the cavity, and sintering of the low-frequency connector and the cavity; Step S2: sintering the surface-mounted power board and the cavity, welding the surface-mounted device filter on the microwave substrate, and welding the RF connector; Step S3: low-stress bonding between the carrier and the filter; Step S4: Bonding of bare chips.

[0021] The following is a detailed description of the assembly process of each module based on specific parameters: For reflow soldering of surface-mount components on the power board, Sn96.5Ag3.0Cu0.5 solder paste (217°C) is used. For sintering the microwave substrate and cavity, Sn96.5Ag3.0Cu0.5 solder sheets (217°C) are used. For sintering the RF connector and cavity, Sn96.5Ag3.0Cu0.5 circular solder rings (217°C) are used. For sintering the low-frequency connector and cavity, Sn96.5Ag3.0Cu0.5 rectangular solder rings (217°C) are used.

[0022] The power supply board and cavity are sintered after surface mounting using Sn63Pb37 183°C solder sheets. The surface-mount device filters on the microwave substrate are soldered using Sn63Pb37 183°C solder paste. RF connectors are soldered using Sn63Pb37 183°C solder wire. ME8456 low-stress conductive adhesive is used for low-stress bonding between the ceramic filter and the carrier, and between the carrier and the cavity. H20E conductive adhesive is used for bonding bare chips.

[0023] In this embodiment, the reflow soldering of the surface-mount components on the power board uses Sn96.5Ag3.0Cu0.5217°C solder paste for various surface-mount components in package sizes such as 0805, 0603, CA45, and LNA. The maximum reflow temperature is set between 235°C and 245°C (the first gradient temperature). The power board is an FR-4 multilayer board. This reflow soldering of the power board is performed independently in a reflow oven and does not participate in the subsequent 217°C sintering.

[0024] The microwave substrate and cavity are sintered using Sn96.5Ag3.0Cu0.5 solder at 217°C. The microstrip substrate is a double-sided 4350B board with a 0.5µm gold plating thickness on the sintered surface. The cavity is a 6061 aluminum alloy cavity with a partially gold-plated surface and a 0.5µm gold plating thickness on the sintered surface. A specially designed sintering fixture is used to flatten the microwave substrate onto the cavity's front mounting surface. The maximum reflow temperature is set at 245°C to 255°C. The sintering of the microwave substrate and cavity is performed in a vacuum reflow oven.

[0025] The RF connector and cavity are sintered using a Sn96.5Ag3.0Cu0.5 217°C circular solder ring. The RF connector is an SMP socket, and the circular solder ring is custom-designed. The RF connector is pressed into the RF connector mounting hole on the back of the cavity using a specially designed tool. This sintering of the RF connector and cavity is performed simultaneously with the sintering of the microwave substrate and cavity in a vacuum reflow oven.

[0026] The sintering of the low-frequency connector and the cavity is performed using a Sn96.5Ag3.0Cu0.5 217°C rectangular solder ring. The low-frequency connector is a J30J 9-pin rectangular socket. The rectangular solder ring is a custom-designed, specially sized solder ring. The low-frequency connector is pressed into the low-frequency connector mounting hole on the back of the cavity using a specially designed tool. This sintering of the low-frequency connector and the cavity is completed simultaneously with the microwave substrate and RF connector SMP. That is, the microwave substrate, RF SMP, and low-frequency connector J30J are sintered simultaneously at the same temperature in a vacuum reflow oven.

[0027] In this embodiment, the surface-mounted power board and cavity are sintered using Sn63Pb37 183°C solder. The various components on the power board are soldered with Sn96.5Ag3.0Cu0.5 217°C solder paste. The lower surface is grounded over a large area with a 0.5µm gold plating thickness. The cavity is the same cavity that has been sintered at 217°C. The maximum reflow temperature is set between 212°C and 225°C (the second gradient temperature), which prevents remelting of the components already mounted on the power board. The power board is pressed against the sintered surface on the back of the cavity using a specially designed fixture. The fixture opening facilitates heating of the cavity during reflow, while also avoiding the contact surface between the components already soldered to the power board. The sintering of the power board and cavity is performed in a vacuum reflow oven.

[0028] The soldering of surface-mount device filters on microwave substrates uses Sn63Pb37 183°C solder paste. The surface-mount filters, including LC and FBAR filters, are manually applied to the corresponding mounting locations on the microstrip substrate on the front of the cavity using a solder paste dispensing process. This soldering of the surface-mount device filters on the microwave substrate is completed simultaneously with the sintering of the power supply board in a vacuum reflow oven.

[0029] The RF connectors were soldered using Sn63Pb37 183°C solder wire. The RF connectors were mechanically fixed to the cavity by sintering at a temperature gradient of 217°C. After the power board, LC filter, and FBAR filter were soldered, the RF connectors were electrically connected to the microwave substrate using manual soldering.

[0030] In this embodiment, low-stress bonding between the carrier and the filter, and between the carrier and the cavity, is achieved using ME8456 low-stress conductive adhesive. The adhesive cures at 150°C (the third gradient temperature). This adhesive prevents cracking in the ceramic filter. This low-stress bonding is performed in a vertical curing oven.

[0031] In this embodiment, H20E conductive adhesive is used to bond the bare chips to the carrier. The conductive adhesive is cured at 120°C (the fourth gradient temperature). The bare chip bonding is performed in a vertical curing furnace.

[0032] For the sake of simplicity, the aforementioned embodiments are described as a series of actions. However, those skilled in the art should be aware that this application is not limited by the order of the actions described, because according to this application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions involved are not necessarily required by this application.

[0033] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Without departing from the spirit and scope of the present invention, modifications and variations made by those skilled in the art without departing from the spirit and scope of the present invention should be within the scope of protection of the appended claims.

Claims

1. A complex radio frequency module sintering and bonding assembly process method, characterized in that: The following steps are involved: Step S1: reflow soldering of surface mount components on the power board, sintering of the microwave substrate and the cavity, sintering of the RF connector and the cavity, and sintering of the low-frequency connector and the cavity; Step S2: sintering the surface-mounted power board and the cavity, welding the surface-mounted device filter on the microwave substrate, and welding the RF connector; Step S3: low-stress bonding between the carrier and the filter; Step S4: Bonding of bare chips.

2. A complex radio frequency module sintering and bonding assembly process method according to claim 1, characterized in that: The step S1 is performed sequentially based on the first gradient temperature. The reflow soldering of the surface-mount components of the power board adopts Sn96.5Ag3.0Cu0.5 solder paste to perform reflow soldering on various packaged surface-mount components. The power board is an FR-4 multilayer board and the power board is independently soldered in the reflow oven.

3. The sintering and bonding assembly process of a complex radio frequency module according to claim 2, characterized in that: The microwave substrate and the cavity are sintered using Sn96.5Ag3.0Cu0.5 solder sheets, the microstrip substrate is a double-sided 4350B board, and the sintered surface is gold-plated with a thickness of 0.5um; The cavity is a partially gold-plated 6061 aluminum alloy cavity with a gold plating thickness of 0.5um on the sintered surface. During sintering, a sintering tool is used to flatten the microwave substrate onto the front mounting surface of the cavity.

4. A complex radio frequency module sintering and bonding assembly process according to claim 3, characterized in that: The sintering of the RF connector and the cavity is carried out using a Sn96.5Ag3.0Cu0.5 circular solder ring. The RF connector is an SMP socket. The circular solder ring is a solder ring of preset size. The RF connector is pressed into the RF connector mounting hole on the back of the cavity by tooling.

5. A complex radio frequency module sintering and bonding assembly process method according to claim 4, characterized in that: The sintering of the low-frequency connector and the cavity is carried out using a Sn96.5Ag3.0Cu0.5 rectangular solder ring. The low-frequency connector is a J30J 9-core rectangular socket. The rectangular solder ring is a solder ring of preset size. The low-frequency connector is pressed into the low-frequency connector mounting hole on the back of the cavity by a tool. The sintering of the microwave substrate double-sided board 4350B, the radio frequency connector SMP socket and the low-frequency connector J30J 9-core rectangular socket and the cavity is completed simultaneously in a vacuum reflow furnace.

6. The sintering and bonding assembly process of a complex radio frequency module according to claim 2, characterized in that: The step S2 is performed sequentially based on the second temperature gradient. The sintering of the surface-mounted power board and the cavity is performed using Sn63Pb37 solder sheets. Based on the power board and cavity that have been soldered and sintered under the first temperature gradient, the power board is pressed onto the sintering surface on the back of the cavity through a tooling. The tooling is provided with an opening that heats up the inside of the cavity during reflow, and at the same time, the pressing surface avoids the soldered components on the power board.

7. A complex radio frequency module sintering and bonding assembly process according to claim 6, characterized in that: The soldering of the surface-mount device filters on the microwave substrate is carried out using Sn63Pb37 solder paste. The surface-mount filters include LC filters and FBAR filters. The filters are attached to the corresponding mounting positions of the microstrip substrate on the front of the cavity by a manual solder paste spotting process. The soldering of the surface-mount device filters on the microwave substrate and the sintering of the power supply board and the cavity after the surface mounting are completed simultaneously in a vacuum reflow furnace.

8. The sintering and bonding assembly process of a complex radio frequency module according to claim 7, characterized in that: The RF connector is welded using Sn63Pb37 solder wire, and the RF connector and the cavity are mechanically fixed based on the sintering in step S1. After the welding of the surface-mounted device filter on the microwave substrate and the sintering of the surface-mounted power board and the cavity are completed, manual welding with solder wire is used to electrically connect the RF connector and the microwave substrate.

9. The sintering and bonding assembly process of a complex radio frequency module according to claim 6, characterized in that: The step S3 is based on the third gradient temperature. The low-stress bonding between the carrier and the filter adopts ME8456 low-stress conductive adhesive with a curing temperature of the third gradient temperature. The low-stress bonding between the carrier and the filter and between the carrier and the cavity is performed in a curing furnace.

10. The sintering and bonding assembly process of a complex radio frequency module according to claim 9, characterized in that: The step S4 is based on the fourth gradient temperature, and the bare chips are bonded to the carrier using H20E conductive adhesive, wherein the bare chips are gallium arsenide chips, and the curing temperature of the conductive adhesive is the fourth gradient temperature.

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