Packaging method for reducing ball mounting void rate of ceramic sealing circuit

Abstract

The invention relates to the technical field of ceramic circuit packaging, and particularly discloses a packaging method for reducing the ball mounting void rate of a ceramic-sealed circuit, and the method comprises the steps: providing soldering paste, and correspondingly printing the soldering paste on a metal bonding pad of a ball mounting surface of the ceramic-sealed circuit; the ceramic seal circuit printed with the soldering paste is put into a reflow oven to be directly subjected to reflow soldering, and solid alloy is formed on the metal bonding pad after the soldering paste is melted and solidified; cleaning the ceramic seal circuit after reflow soldering, preparing a soldering flux after cleaning is completed, and printing the soldering flux on the solid alloy according to the size proportion; after the soldering flux is printed, a high-lead solder ball is fixed to the solid alloy through a positioning carrier; the positioning carrier and the ceramic seal circuit fixed with the high-lead solder balls are integrally put into a reflow oven for reflow soldering, so that brazing of the high-lead solder balls and the solid alloy is completed; and the brazed ceramic sealing circuit is taken out and cleaned, so that packaging and ball mounting of the ceramic sealing circuit are completed. According to the method, the void rate of high-lead ball mounting can be effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic circuit packaging, and more specifically, to a packaging method for reducing the void rate of ceramic circuit planting balls. Background Art

[0002] The current circuit packaging method is as follows: (1) Printing solder paste: Place the circuit shell horizontally into the printing carrier, and cover the printing stencil onto the carrier according to the direction; Use a scraper to add an appropriate amount of solder paste and place it in the printed steel mesh, avoiding the mesh holes. Keep the scraper at a certain angle to the steel mesh and manually print the solder paste in one direction; After printing, take out the printed stencil vertically and take out the printed shell. (2) Placing solder balls: According to the circuit pad array, match the mesh holes of the ball planting stencil with the printed circuit pad array, pour the solder balls so that they fall into the corresponding mesh holes one by one and remove the excess solder balls; (3) Reflow soldering: Reflow soldering is to re-melt the solder paste pre-allocated to the circuit pads through hot air convection heating, so as to achieve soft soldering of the electrical and mechanical connection between the high-lead solder ball welding section and the circuit pads, and generate intermetallic compounds.

[0003] Low-lead solder is mainly composed of flux and metal particles, wherein the metal particles are generally alloy tin powder, and the flux is composed of rosin resin, activator, solvent, thixotropic agent, etc.

[0004] Reflow soldering is divided into four stages: preheating, heat preservation, reflow and cooling. During the preheating and heat preservation stages, the flux in the solder paste will volatilize due to the heat, and part of it will be separated from the solder paste, while the tin beads will be tightly gathered due to the volatilization of the flux. During the reflow stage, the remaining flux in the solder paste will evaporate quickly, and the tin beads will melt and aggregate. The volatilized gas of the residual flux and the air between the tin beads cannot escape, but remain in the molten tin, sandwiched by the pad and the solder ball and wrapped in the liquid tin. It is difficult to escape by buoyancy alone.

[0005] In addition, highly viscous residues left by the volatilization of flux, gases generated by the reaction of metal pad oxides with flux, and some gases released from the pad pores are also easily captured at the bottom of the solder ball and difficult to escape due to the tension of the molten liquid tin, forming voids after solidification. Summary of the invention

[0006] In view of the defects and shortcomings in the prior art, the present invention provides a packaging method for reducing the void rate of ceramic-sealed circuit balls, which can effectively reduce the void rate of high-lead balls.

[0007] In order to solve the above problems, the present invention provides a packaging method for reducing the void rate of ceramic package circuit implantation, comprising the following steps: Step S1: providing solder paste, and printing the solder paste onto the metal pads on the ball implantation surface of the ceramic package circuit; Step S2: placing the ceramic-sealed circuit printed with solder paste into a reflow furnace for direct reflow soldering, so that the solder paste is melted and solidified to form a solid alloy on the metal pad; Step S3: cleaning the ceramic-sealed circuit after reflow soldering, preparing soldering flux after cleaning, and printing the soldering flux onto the solid alloy according to the size ratio; Step S4: after the solder flux printing is completed, the high-lead solder ball is fixed on the solid alloy by a positioning carrier; Step S5: placing the positioning carrier and the ceramic-sealed circuit with the high-lead solder balls fixed thereon into a reflow furnace for reflow soldering to complete the brazing of the high-lead solder balls with the solid alloy; Step S6: taking out the brazed ceramic circuit and cleaning it to complete the packaging and ball implantation of the ceramic circuit.

[0008] Furthermore, the step S1 further includes: Place the ceramic-sealed circuit horizontally into the printing carrier, and cover the printing stencil on the printing carrier according to the direction; at the same time, align the opening of the printing stencil with the metal pad on the ball-planting surface of the ceramic-sealed circuit; Use a scraper to add an appropriate amount of solder paste and place it on the printing stencil. Keep a certain angle between the scraper and the printing stencil, and print the solder paste on the metal pads of the ceramic sealing circuit in one direction. After the solder paste is printed, the printed stencil is taken out vertically upwards to take out the pottery-sealed circuit after the solder paste is printed.

[0009] Furthermore, the material of the solder paste is Sn63Pb37.

[0010] Furthermore, the cleaning of the ceramic-sealed circuit after reflow soldering also includes: Select the corresponding cleaning solvent based on the solder paste. For water-washable solder paste, use water or alcohol for cleaning. The ceramic-sealed circuit after reflow soldering is cleaned with a cleaning solvent to remove the flux and impurities precipitated from the solder paste during the reflow soldering process.

[0011] Further, the method of preparing soldering flux after cleaning is completed, and printing the soldering flux onto the solid alloy in proportion to the size, further comprises: Align the opening of the printed stencil with the solid alloy on the ball implant surface of the ceramic circuit; Use a scraper to add a proper amount of flux and place it on the printing stencil. Keep a certain angle between the scraper and the printing stencil, and print the flux on the solid alloy of the ceramic circuit ball planting surface in one direction; After the flux printing is completed, the printed stencil is taken out vertically upwards to take out the pottery-sealed circuit after the flux printing is completed.

[0012] Furthermore, after the solder flux printing is completed, the high-lead solder ball is fixed on the solid alloy through a positioning carrier, and further includes: Align the opening of the positioning carrier with the solid alloy on the ball planting surface of the ceramic sealing circuit; pouring high-lead solder balls onto the positioning carrier; The positioning carrier is shaken so that the high-lead solder ball falls into the opening of the positioning carrier and is fixed on the solid alloy by the flux.

[0013] Furthermore, the method of taking out the brazed ceramic circuit and cleaning it to complete the packaging and ball planting of the ceramic circuit also includes: Select the corresponding cleaning solvent based on the solder paste. For water-washable solder paste, use water or alcohol for cleaning. The ceramic sealed circuit after brazing is cleaned by a cleaning solvent.

[0014] Furthermore, the material of the positioning carrier is graphite.

[0015] The packaging method for reducing the void rate of ceramic-sealed circuit balls provided by the present invention has the following advantages: since there are no high-lead solder balls to block the flux from reducing oxides and the volatilized gases of the solvent, and the flux and impurities precipitated after the solder paste reflow are cleaned, the void rate of high-lead balls can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0017] Figure 1 The present invention is a schematic flow chart of a packaging method for reducing the void rate of ceramic package circuit implant balls provided by the present invention.

[0018] Figure 2 A flowchart of a specific implementation of the packaging method for reducing the void rate of ceramic package circuit implants provided by the present invention.

[0019] FIG. 3A to FIG. 3D A process flow chart of printing solder paste onto metal pads provided by the present invention.

[0020] Figure 4 This is a structural diagram of a solid alloy formed after the solder paste provided by the present invention is reflowed.

[0021] FIG. 5A to FIG. 5D A process flow chart of printing soldering flux onto solid alloy provided by the present invention.

[0022] FIG. 6A to FIG. 6B A process flow chart of fixing a high-lead solder ball on a solid alloy via a positioning carrier provided by the present invention.

[0023] 7A to 7C The present invention provides a process flow chart of placing the positioning carrier and the ceramic sealing circuit as a whole into a reflow furnace for reflow soldering and then taking out the ceramic sealing circuit.

[0024] In the figure: 1- solder paste; 2- ceramic sealing circuit; 3- solid alloy; 4- flux; 5- high lead solder ball; 6- printing stencil; 7- scraper; 8- positioning carrier; 9- metal pad. DETAILED DESCRIPTION

[0025] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation method, structure, characteristics and effects of the packaging method for reducing the void rate of the ceramic package circuit ball according to the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0026] In this embodiment, a packaging method for reducing the void rate of ceramic package circuit planting is provided. Figure 1-2 As shown, the packaging method for reducing the void rate of the ceramic package circuit ball includes the following steps: Step S1: providing a solder paste 1, and printing the solder paste 1 on the metal pad 9 on the ball implantation surface of the ceramic package circuit 2; wherein the material of the solder paste 1 is tin-lead alloy particles such as Sn63Pb37.

[0027] Preferably, if FIG. 3A to FIG. 3D As shown, the step S1 further includes: Place the ceramic-sealed circuit 2 horizontally into the printing carrier, and cover the printing stencil 6 onto the printing carrier according to the direction; at the same time, align the opening of the printing stencil 6 with the metal pad 9 on the ball-planting surface of the ceramic-sealed circuit 2; like FIG. 3A to FIG. 3C As shown, a proper amount of solder paste 1 is added by a scraper 7 and placed on the printing stencil 6, a certain angle is maintained between the scraper 7 and the printing stencil 6, and the solder paste 1 is printed on the metal pad 9 of the ceramic sealing circuit 2 along one direction according to the opening ratio of the metal pad 9; wherein, as Figure 3A As shown, the solder paste 1 rolls forward under the force of the scraper 7; Figure 3B As shown, the scraper 7 generates pressure to inject the solder paste 1 into the opening of the printing screen 6; Figure 3C As shown, the scraper 7 generates shear force to scrape off the excess solder paste; like Figure 3D As shown, after the solder paste 1 is printed, the printing stencil 6 is vertically taken out upwards to take out the pottery-sealed circuit 2 after the solder paste is printed.

[0028] Step S2: Figure 4 As shown, the solder paste 1 is directly reflow-welded to the metal pad 9; wherein the ceramic-sealed circuit 2 after the solder paste printing is placed in a reflow furnace for direct reflow soldering, so that the solder paste 1 is melted and solidified to form a solid alloy 3 on the metal pad; It should be noted that the reflow temperature curve of different solder paste materials requires debugging temperature, and the specific curve refers to the TDS of the solder paste material. When measuring the reflow temperature curve in this step, only the temperature curve when the circuit is placed alone is measured.

[0029] Step S3: cleaning the ceramic sealing circuit 2 after reflow soldering, and preparing the soldering flux 4 after cleaning, and printing the soldering flux 4 on the solid alloy 3 according to the size ratio; Preferably, the cleaning of the ceramic sealing circuit 2 after reflow soldering further includes: Select the corresponding cleaning solvent based on solder paste 1, where water-washable solder paste is cleaned with water or alcohol; The ceramic-sealed circuit 2 after reflow soldering is cleaned by a cleaning solvent to remove the solder flux and impurities precipitated from the solder paste 1 during the reflow soldering process. The surface of the ceramic-sealed circuit 2 can be cleaned manually or by equipment.

[0030] Preferably, if FIG. 5A to FIG. 5D As shown, after the cleaning is completed, the soldering flux 4 is prepared, and the soldering flux 4 is printed on the solid alloy 3 according to the size ratio, and further includes: Align the opening of the printed screen 6 with the solid alloy 3 on the ball implantation surface of the ceramic sealing circuit 2; Use a scraper 7 to add an appropriate amount of flux 4 and place it on the printing screen 6. Keep a certain angle between the scraper 7 and the printing screen 6, and print the flux 4 on the solid alloy 3 on the ball planting surface of the ceramic sealing circuit 2 in one direction; Figure 5A As shown, the soldering flux 4 rolls forward under the force of the scraper 7; Figure 5B As shown, the scraper 7 generates pressure to inject the soldering flux 4 into the opening of the printing screen 6; Figure 5C As shown, the soldering flux 4 is attached to the solid alloy 3; like Figure 5D As shown, after the soldering flux 4 is printed, the printing screen 6 is taken out vertically upward to take out the pottery-sealed circuit 2 after the soldering flux 4 is printed.

[0031] Step S4: After the soldering flux 4 is printed, the high-lead solder ball 5 is fixed on the solid alloy 3 by a positioning carrier 8; wherein the material of the positioning carrier 8 is graphite.

[0032] Preferably, if FIG. 6A to FIG. 6B As shown, after the solder flux 4 is printed, the high-lead solder ball 5 is fixed on the solid alloy 3 through a positioning carrier, and further includes: like Fig. 6A As shown, align the opening of the positioning carrier 8 with the solid alloy 3 on the ball planting surface of the ceramic sealing circuit 2; pour the high-lead solder ball 5 on the positioning carrier 8; like Figure 6B As shown, the positioning carrier 8 is shaken so that the high-lead solder ball 5 falls into the opening of the positioning carrier 8 and is fixed on the solid alloy 3 through the flux 4.

[0033] Step S5: Fig. 7A As shown, the reflow curve is tested, and the positioning carrier 8 and the ceramic package circuit 2 fixed with the high-lead solder ball 5 are placed in a reflow furnace for reflow soldering. Figure 7B As shown, the brazing of the high-lead solder ball 5 and the solid alloy 3 is completed; It should be noted that the reflow temperature curve of different soldering materials requires debugging temperature, and the specific curve refers to the TDS of the material. In this step, when measuring the reflow temperature curve, the temperature curve when the circuit is placed in the positioning carrier is measured.

[0034] Step S6: Figure 7C As shown, the brazed ceramic-sealed circuit 2 is taken out and cleaned to complete the packaging and ball implantation of the ceramic-sealed circuit.

[0035] Preferably, the method of taking out the brazed ceramic-sealed circuit 2 and cleaning it to complete the packaging and ball implantation of the ceramic-sealed circuit also includes: Select a corresponding cleaning solvent based on the solder paste 1, wherein the water-washable solder paste 1 is cleaned with water or alcohol; The brazed ceramic circuit 2 is cleaned by a cleaning solvent. The surface of the ceramic circuit 2 can be cleaned manually or by an apparatus.

[0036] The packaging method for reducing the void rate of ceramic-sealed circuit balls provided by the present invention can effectively reduce the void rate of high-lead balls because there are no high-lead solder balls to block the flux from reducing oxides and the volatilized gases of the solvent, and the flux and impurities precipitated after the solder paste reflow are cleaned.

[0037] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A packaging method for reducing the void rate of ceramic circuit implantation, characterized in that: The following steps are involved: Step S1: providing solder paste (1), and printing the solder paste (1) onto the metal pad (9) on the ball implantation surface of the ceramic package circuit (2); Step S2: placing the ceramic-sealed circuit (2) printed with solder paste into a reflow furnace for direct reflow soldering, so that the solder paste (1) is melted and solidified to form a solid alloy (3) on the metal pad; Step S3: cleaning the ceramic sealing circuit (2) after reflow soldering, and preparing a soldering flux (4) after cleaning, and printing the soldering flux (4) onto the solid alloy (3) according to a size ratio; Step S4: after the solder flux (4) is printed, the high-lead solder ball (5) is fixed on the solid alloy (3) by a positioning carrier (8); Step S5: placing the positioning carrier (8) and the ceramic sealed circuit (2) with the high-lead solder ball (5) fixed thereon into a reflow furnace for reflow soldering to complete the soldering of the high-lead solder ball (5) with the solid alloy (3); Step S6: taking out the brazed ceramic-sealed circuit (2) and cleaning it to complete the packaging and ball implantation of the ceramic-sealed circuit.

2. The packaging method for reducing the void rate of ceramic circuit implants according to claim 1, characterized in that: The step S1 further includes: Place the ceramic-sealed circuit (2) horizontally into a printing carrier, and cover the printing screen (6) onto the printing carrier according to the direction; and align the opening of the printing screen (6) with the metal pad (9) on the ball-planting surface of the ceramic-sealed circuit (2); Using a scraper (7), add an appropriate amount of solder paste (1) and place it on the printing stencil (6), maintain a certain angle between the scraper (7) and the printing stencil (6), and print the solder paste (1) in one direction on the metal pad (9) of the ceramic sealing circuit (2); After the solder paste (1) is printed, the printing stencil (6) is vertically removed upwards to remove the pottery-sealed circuit (2) after the solder paste is printed.

3. The packaging method for reducing the void rate of ceramic circuit implants according to claim 1, characterized in that: The material of the solder paste (1) is Sn63Pb37.

4. The packaging method for reducing the void rate of ceramic circuit implants according to claim 1, characterized in that: The cleaning of the ceramic-sealed circuit (2) after reflow soldering also includes: Select the corresponding cleaning solvent based on the solder paste (1), where water-washable solder paste is cleaned with water or alcohol; The ceramic sealing circuit (2) after reflow soldering is cleaned by a cleaning solvent to clean off the flux and impurities precipitated from the solder paste (1) during the reflow soldering process.

5. The packaging method for reducing the void rate of ceramic circuit implants according to claim 1, characterized in that: The step of preparing a soldering flux (4) after cleaning is completed, and printing the soldering flux (4) onto the solid alloy (3) in proportion to the size of the solid alloy (3) further comprises: Aligning the opening of the printing screen (6) with the solid alloy (3) on the ball implantation surface of the ceramic sealing circuit (2); A scraper (7) is used to add an appropriate amount of solder flux (4) and place it on the printing stencil (6), with the scraper (7) and the printing stencil (6) maintaining a certain angle, and the solder flux (4) is printed in one direction on the solid alloy (3) on the ball implantation surface of the ceramic sealing circuit (2); After the soldering flux (4) is printed, the printing screen (6) is vertically removed upwards to remove the pottery-sealed circuit (2) after the soldering flux (4) is printed.

6. The packaging method for reducing the void rate of ceramic circuit implants according to claim 1, characterized in that: After the solder flux (4) is printed, the high-lead solder ball (5) is fixed on the solid alloy (3) by a positioning carrier, and further comprises: Aligning the opening of the positioning carrier (8) with the solid alloy (3) on the ball-planting surface of the ceramic-sealed circuit (2); Pouring high-lead solder balls (5) onto the positioning carrier (8); The positioning carrier (8) is shaken so that the high-lead solder ball (5) falls into the opening of the positioning carrier (8) and is fixed on the solid alloy (3) through the soldering flux (4).

7. The packaging method for reducing the void rate of ceramic circuit implants according to claim 1, characterized in that: The method of taking out the brazed ceramic-sealed circuit (2) and cleaning it to complete the packaging and ball implantation of the ceramic-sealed circuit also includes: Select a corresponding cleaning solvent based on the solder paste (1), wherein the water-washable solder paste (1) is cleaned using water or alcohol; The brazed ceramic sealing circuit (2) is cleaned by a cleaning solvent.

8. The packaging method for reducing the void rate of ceramic circuit implants according to claim 1, characterized in that: The material of the positioning carrier (8) is graphite.

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