Self-alignment assembly method for microwave hybrid integrated circuit chip

Abstract

The invention discloses a self-alignment assembly method for a microwave hybrid integrated circuit chip, and the method comprises the steps: arranging a bonding pad at a chip assembly position of a substrate, presetting welding flux on the bonding pad, carrying out the hydrophobic treatment of the periphery of the bonding pad, carrying out the plasma treatment of the bonding pad through plasma treatment equipment, and enabling the bonding pad to have a hydrophilic characteristic; putting the pretreated substrate into a chip mounting device, carrying out liquid dispensing on a bonding pad by using a dispensing machine, and forming liquid drops limited in the bonding pad due to the hydrophilic characteristic of the bonding pad and the hydrophobic characteristic around the bonding pad; the chip is picked up to the position above the bonding pad, the chip is lowered to make contact with the liquid drops, the chip is aligned with the bonding pad under the action of the surface tension of the liquid drops, and then the liquid drops are evaporated through heating; and performing reflow soldering on the substrate assembled with the chip, and performing cooling treatment after soldering to obtain the microwave hybrid integrated circuit in which the chip and the bonding pad are accurately aligned. According to the invention, the chip mounting of the hybrid circuit can be completed by adopting a chip mounter with general precision, the equipment requirement is reduced, and the chip mounting efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the field of microwave hybrid integrated circuit manufacturing, and particularly relates to a self-aligning assembly method for microwave hybrid integrated circuit chips. Background Art

[0002] With the continuous improvement of the functions and integration levels of microwave hybrid integrated circuits, the alignment accuracy requirements for bare circuit chips are getting higher and higher. Generally, the alignment accuracy is required to be within a few micrometers to more than ten micrometers. Low-precision chip mounters cannot achieve such precise chip placement. When using precision chip mounters for multi-chip pasting, generally only about 1000 chips can be pasted per hour per device, and the efficiency is reduced by 3-5 times compared with general-precision chip mounters. It can be seen that using precision chip mounters has low working efficiency and the equipment procurement cost is higher than that of general-precision chip mounters. Summary of the Invention

[0003] The purpose of the present invention is to provide a self-aligning assembly method for microwave hybrid integrated circuit chips, which can use a general-precision chip mounter to complete chip assembly work with high efficiency and high precision.

[0004] To achieve the above purpose, one aspect of the present invention provides a self-aligning assembly method for microwave hybrid integrated circuit chips, including:

[0005] Step S1: Set solder pads at the chip assembly positions on the circuit substrate, pre-place solder on the solder pads, use a film to shield and protect the solder pads, perform hydrophobic treatment on the periphery of the solder pads, remove the film covering the solder pads after the hydrophobic treatment, use a mask plate to block the hydrophobic parts, and use a plasma treatment device to perform plasma treatment on the solder pads to make the solder pads have hydrophilic properties;

[0006] Step S2: Remove the mask plate, place the substrate into the chip mounter, and use a dispensing machine to perform liquid dot coating on the solder pads. Due to the hydrophilic properties of the solder pads and the hydrophobic properties around the solder pads, droplets restricted within the solder pads are formed;

[0007] Step S3: Pick up the chip above the solder pad, lower the chip to make the chip contact the droplet. The chip is aligned with the solder pad under the action of the surface tension of the droplet, and then the droplet is evaporated by heating;

[0008] Step S4: Perform reflow soldering on the substrate with the assembled chip, and perform a cooling treatment after soldering to obtain a microwave hybrid integrated circuit with precise alignment between the chip and the solder pad.

[0009] Preferably, in step S1, using a film to shield the solder pads includes: integrally pasting a polyimide tape film on the substrate, using an ultraviolet laser engraving device to engrave the edge of the solder pad to ensure that the polyimide tape film is engraved through but the substrate is not damaged, removing the polyimide tape film around the solder pad, and retaining the tape film at the solder pad to complete the shielding and protection of the solder pad with the film.

[0010] Preferably, in step S1, the hydrophobic treatment of the surrounding position of the pad includes: spraying the surface of the surrounding position of the pad with a hydrophobic material, and then putting it into an oven for drying after spraying.

[0011] Preferably, in step S1, the plasma treatment of the pad by using a plasma treatment device includes: putting the substrate shielded by a mask plate into the plasma treatment device, evacuating the device, introducing argon gas to perform plasma treatment on the pad, and introducing nitrogen gas to break the vacuum after the treatment is completed, and then taking out the substrate.

[0012] Preferably, in step S2, the liquid dot coating of the pad by using a dispensing machine includes: putting liquid into the syringe of the dispensing machine, setting negative pressure on the syringe to keep the liquid from overflowing, moving the dispensing needle head above the pad, and releasing the negative pressure and using positive pressure to perform liquid dot coating on the pad.

[0013] Preferably, the width of the pad is between 0.5 mm and 4 mm. In step S2, for pads with a width of less than 2 mm, the liquid droplet dot coating method directly above is adopted, and for pads with a width greater than 2 mm, the liquid droplet dot coating method in an array line is adopted.

[0014] Preferably, in step S3, image recognition is performed on the chip to be assembled to determine the position and orientation of the chip, and a vacuum chuck is used to pick up the recognized chip in a vacuum, pick up the chip above the pad to be assembled, slowly lower it, stop when the chip touches the liquid droplet and release the vacuum, and flush nitrogen gas to the vacuum chuck to separate the chip.

[0015] Preferably, the liquid contains a soldering flux, and step S4 further includes: cleaning the soldered substrate by using a vapor phase cleaning agent.

[0016] Preferably, the solder is AuSn20 solder or SnAg3Cu0.5 solder, the hydrophobic material is fluorosilane or nano-silica, and the liquid is deionized water.

[0017] According to the microwave hybrid integrated circuit chip self-alignment assembly method in the above aspect of the present invention, through substrate surface treatment and droplet self-alignment, the hybrid circuit chip mounting can be completed by using a general-precision mounter, which reduces the equipment requirements and improves the mounting efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts:

[0019] Figure 1 It is a flowchart of the self - alignment assembly method for a microwave hybrid integrated circuit chip according to an embodiment of the present invention;

[0020] Figure 2 It is a schematic diagram of a substrate to be assembled according to an embodiment of the present invention;

[0021] Figure 3 It is a schematic diagram of the substrate pretreatment according to an embodiment of the present invention;

[0022] Figure 4 It is a schematic diagram of the droplet dispensing method according to an embodiment of the present invention;

[0023] Figure 5 It is a schematic diagram of the droplet dispensing effect according to an embodiment of the present invention;

[0024] Figure 6 It is a schematic diagram of the process of aligning the chip with the droplet according to an embodiment of the present invention;

[0025] Figure 7 It is a schematic diagram of the chip completing accurate alignment according to an embodiment of the present invention. Detailed implementation manners

[0026] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] The embodiments of the present invention provide a self - alignment assembly method for a microwave hybrid integrated circuit chip, Figure 1 It is a flowchart of the self - alignment assembly method for a microwave hybrid integrated circuit chip according to an embodiment of the present invention. As Figure 1 shown, the method of the embodiment of the present invention includes steps S1 - S5.

[0028] In step S1, chip mounting pads are set at the chip assembly positions on the microwave hybrid integrated circuit substrate, and solder is pre - placed on the chip mounting pads. The solder is, for example, AuSn20 solder or SnAg3Cu0.5 solder. The pads are shielded using a film. After shielding, hydrophobic materials such as fluorosilane or nano - silica are used to perform hydrophobic treatment on the periphery of the pads by spraying or other methods; after the hydrophobic treatment is completed, the mask is removed. To improve the hydrophilicity of the pads, a mask plate is used to shield the hydrophobic parts, and the substrate is placed in a plasma treatment device. After evacuating the vacuum, argon gas is used to perform plasma treatment on the pads at the mounting positions. After breaking the vacuum, the substrate is taken out, and the substrate pretreatment is completed. At the same time, to ensure that the chip can be welded to the substrate position, a gold film layer should be pre - fabricated on the back of the chip.

[0029] In step S2, remove the mask plate, place the pre-treated substrate into the chip mounter, and place the chips into the material tray. Put deionized water or a liquid containing an active flux into the syringe of the dispenser. To ensure that the liquid does not flow out of the syringe, a certain negative pressure is set for the syringe to keep the liquid from overflowing. The diameter of the dispensing needle is determined according to the amount of liquid to be dispensed. The dispenser moves the dispensing needle above the pad, releases the negative pressure, and uses positive pressure to perform liquid dispensing on the pad. Since the pad has been plasma-treated and has hydrophilic properties, a hydrophobic coating is applied around the pad, and the liquid droplet is accurately confined within the chip mounting pad.

[0030] In step S3, perform image recognition on the chips to be pasted in the material tray to determine the chip position and orientation. Use a vacuum chuck to pick up the recognized chips in the material tray, pick up the chips above the pads to be assembled, slowly lower them, stop after contacting the liquid droplet and release the vacuum, and flush nitrogen into the vacuum chuck and use positive pressure to ensure that the nozzle and the chip can be separated smoothly.

[0031] At this time, due to the low precision of the chip mounter, there may be alignment deviations such as offset and rotation. However, due to the action of the surface tension of the liquid droplet, the chip will be aligned with the pad according to the shapes of the chip and the pad. After alignment, heat the substrate to evaporate the liquid, and obtain accurate alignment between the chip and the pad.

[0032] In step S4, place the hybrid integrated circuit substrate assembled with chips into a vacuum reflow soldering furnace for reflow soldering, and perform cooling treatment after soldering. For the liquid droplet containing flux, place the soldered circuit into a vapor phase cleaning agent for cleaning, and finally obtain a hybrid integrated circuit with accurate alignment between the chip and the pad.

[0033] Through the above process, the self-alignment of chip assembly is realized by using the action of the liquid surface tension, and the assembly accuracy can reach within 10 microns, thereby improving the chip assembly efficiency and reducing the equipment cost.

[0034] The following further details the self-alignment assembly method of the microwave hybrid integrated circuit chip according to the embodiments of the present invention through a specific example.

[0035] In step S1, as Figure 2 shown, prepare a circuit substrate 2 to be assembled. The substrate 2 can be an organic dielectric board or a ceramic substrate. Chip mounting pads 1 are provided on the surface of the substrate 2. The width of the pads 1 is between 0.5 mm and 4 mm, and a solder of AuSn20 or SnAg3Cu0.5 with a thickness of 30 to 50 microns is pre-placed at the positions of the pads 1.

[0036] To ensure that pad 1 is not contaminated, a film covering is applied to pad 1 for shielding protection. The entire substrate 2 is adhered with a polyimide tape film, with the film thickness ranging from 0.01 mm to 0.05 mm. An ultraviolet laser engraving device is used to engrave the edge of pad 1. The laser power is set from 0.5 w to 5 w according to the material thickness and size, ensuring that the polyimide tape film is engraved through without damaging the substrate. The polyimide tape film around pad 1 is removed, and the tape film at pad 1 is retained, thus completing the film covering shielding protection of pad 1.

[0037] Hydrophobic treatment is performed on the surrounding area of pad 1. A hydrophobic material such as fluorosilane or nano-silica is used for surface spraying. After spraying, it is placed in an oven at 80 degrees for 2 hours for drying. After drying, the pad film covering is removed.

[0038] As Figure 3 shown, a mask plate 3 is used to cover the hydrophobic area of the substrate. To ensure that the hydrophobic area is not activated, the covered area should extend into the pad, for example, by 0.05 mm. The mask plate 3 is in close contact with the substrate 2 to expose pad 1.

[0039] Pad 1 is treated with argon plasma to improve its hydrophilicity. The substrate 2 covered by the mask plate 3 is placed in a plasma treatment device. The device evacuates the vacuum to below 10 Pa, introduces argon gas with a purity of 99.999%, the argon gas flow rate is from 50 sccm to 200 sccm, the plasma frequency is 13.56 MHz, the treatment power is from 100 w to 800 w, and the treatment time is from 1 min to 10 min. After the treatment is completed, nitrogen gas is introduced to break the vacuum, and then the substrate 2 is taken out. The substrate is placed in a dispensing device for operation within 2 hours.

[0040] In step S2, the mask plate 3 is removed, and the substrate 2 is placed in an automatic chip mounter. Deionized water or a liquid containing an active soldering flux is placed in the dispensing machine syringe. The syringe is set with a negative pressure of 0.01 MPa - 0.03 Mpa to prevent the liquid from overflowing from the syringe. The inner diameter of the dispensing needle head is selected according to the situation from 0.2 mm to 1.5 mm.

[0041] The dispensing needle head is moved above pad 1, and a pressure of 0.02 MPa - 0.15 MPa is applied to the syringe for liquid coating. For pads with a width of less than 2 mm, the direct upward droplet dispensing method can be used. As Figure 4 shown in the left figure, due to the hydrophilic characteristics of the pad, the liquid quickly fills the entire pad, and the droplet thickness is from 0.05 mm to 1 mm. For pads with a width greater than 2 mm, the array line droplet dispensing method can be used. As Figure 4 shown in the right figure, to ensure that the liquid quickly and evenly covers the pad. The formed liquid droplet 7 is as Figure 5 shown.

[0042] In step S3, image recognition is performed on the chips to be pasted in the material tray to determine the chip positions and orientations. A vacuum chuck is used to pick up the recognized chips in the material tray, and the chips are picked up to a position about 0.1 mm - 1.2 mm above the pads to be assembled. Then, the chips are slowly lowered. After contacting the droplets, the vacuum is stopped and released. Nitrogen is flushed through the vacuum chuck for 0.05 s - 0.5 s, and the chips are separated from the nozzles. Due to the low alignment accuracy of the mounter, there may be an alignment deviation between chip 8 and the pads. At this time, the tension of droplet 7 can align chip 8 back to the pad position, as Figure 6 shown. If there are multiple chip mounting positions, the above operations of dispensing and chip placement are repeated.

[0043] In step S4, the substrate with the chips placed is heated in situ in the equipment. The heating temperature is 60°C - 80°C, and the time is 5 min - 20 min. After heating, the droplets are completely evaporated to obtain accurately aligned chips 8, as Figure 7 shown.

[0044] The aligned substrate is placed in a vacuum reflow soldering furnace. The peak temperature of SnAg3Cu0.5 solder is set at 240°C - 260°C, the peak temperature of AuSn20 solder is set at 280°C - 350°C, the soldering reflow time is 30 s - 60 s, and the soldering vacuum is 10 mbar - 300 mbar to complete the soldering of the chips and the substrate.

[0045] For circuit boards with flux in the droplets, the reflow-soldered substrate is cleaned by vapor phase cleaning. The cleaning agent can be n-propyl bromide or a dual-solvent cleaning agent of hydrocarbon and hydrofluoroether. After soaking in the cleaning solution for 1 min - 10 min, rinsing for 3 min - 10 min, and steam cleaning for 2 min - 10 min, the assembled microwave hybrid integrated circuit is taken out after condensation and drying.

[0046] In summary, the method of the embodiment of the present invention performs hydrophobic solder mask treatment around the pads, performs plasma treatment on the pads to improve the hydrophilicity of the pads, dispenses droplets on the pads, picks up and moves the chips by vacuum adsorption, the chips are self-aligned on the liquid surface, and the precise positioning of the chips is completed after the liquid evaporates. The preset solder is melted by heating with a reflow soldering furnace to complete the soldering of the chips, thereby realizing self-alignment assembly of the chips. Compared with the traditional process method that has high requirements for high-precision mounter equipment and low efficiency, the present invention can complete the mounting of hybrid circuit chips with high efficiency using general-precision mounter equipment.

[0047] Only some exemplary embodiments of the present invention have been described by way of illustration above. Undoubtedly, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A microwave hybrid integrated circuit chip self-alignment assembly method, characterized in that: include: Step S1: setting a pad at the chip assembly position of the circuit substrate, pre-placing solder on the pad, using a film to shield and protect the pad, performing a hydrophobic treatment around the pad, removing the pad film after the hydrophobic treatment, using a mask plate to cover the hydrophobic part, and using a plasma treatment device to perform plasma treatment on the pad to make the pad hydrophilic; Step S2: remove the mask plate, put the substrate into the patch equipment, and use the dispensing machine to apply liquid to the pad. Due to the hydrophilicity of the pad and the hydrophobicity around the pad, droplets confined to the pad are formed; Step S3: Pick up the chip above the pad, lower the chip so that it contacts the droplet, align the chip with the pad under the action of the surface tension of the droplet, and then evaporate the droplet by heating; Step S4: reflow soldering is performed on the substrate on which the chip is assembled, and cooling treatment is performed after soldering to obtain a microwave hybrid integrated circuit with precise alignment between the chip and the pad.

2. The method according to claim 1, characterized in that In step S1, using a coating to mask the pad includes: sticking a polyimide tape film to the entire substrate, using ultraviolet laser engraving equipment to engrave the edge of the pad to ensure that the polyimide tape film is engraved through but does not damage the substrate, removing the polyimide tape film around the pad, retaining the tape film at the pad, and completing the coating masking protection of the pad.

3. The method according to claim 1 or 2, characterized in that In step S1, performing hydrophobic treatment on the surrounding area of ​​the pad includes: spraying the surface of the surrounding area of ​​the pad with a hydrophobic material, and then placing the surface of the surrounding area of ​​the pad in an oven for drying.

4. The method according to claim 1 or 2, characterized in that: In step S1, plasma treatment of the pad using plasma treatment equipment includes: placing the substrate shielded by a mask plate into the plasma treatment equipment, evacuating the equipment, introducing argon gas to perform plasma treatment on the pad, and after the treatment is completed, introducing nitrogen gas to break the vacuum and then taking out the substrate.

5. The method according to claim 1 or 2, characterized in that: In step S2, using a glue dispenser to apply liquid to the pad includes: putting liquid into the needle tube of the glue dispenser, setting negative pressure on the needle tube to prevent the liquid from overflowing, moving the glue dispenser needle to the top of the pad, releasing the negative pressure and applying positive pressure to apply liquid to the pad.

6. The method according to claim 1 or 2, characterized in that: The width of the pad is between 0.5 mm and 4 mm. In step S2, for pads with a width of less than 2 mm, a direct upper dot coating method is used, and for pads with a width greater than 2 mm, an array line dot coating method is used.

7. The method according to claim 1 or 2, characterized in that: In step S3, the chip to be assembled is image-recognized to determine the position and orientation of the chip, and the identified chip is vacuum-picked using a vacuum head. The chip is picked up above the pad to be assembled and slowly lowered. The chip stops and the vacuum is released after it contacts the droplet, and nitrogen is flushed into the vacuum head to separate the chip.

8. The method according to claim 1 or 2, characterized in that: The liquid contains soldering flux, and step S4 further includes: cleaning the soldered substrate with a vapor phase cleaning agent.

9. The method according to claim 1 or 2, characterized in that: The solder is AuSn20 solder or SnAg3Cu0.5 solder, the hydrophobic material is fluorinated silane or nano silicon dioxide, and the liquid is deionized water.

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