Large-warpage substrate soldering flux printing method and printing device

Abstract

The invention relates to a soldering flux printing method for a large-warping substrate. The soldering flux printing method comprises the steps that 1, soldering flux is stored and fed; 2, positive pressure is generated on the scaling powder, and the scaling powder flows to the printing points and wraps the lower surfaces of the printing points; 3, the positive pressure is stopped from being applied to the scaling powder, the scaling powder stops flowing, or the negative pressure is applied to the scaling powder, and the scaling powder flows back; 4, the printing points descend, after the printing points make contact with the corresponding substrates, the printing points are pressed down on the welding pads of the substrates, and the scaling powder is printed on the surfaces of the welding pads; and 5, resetting the printing points, and feeding the soldering flux next time. A large warping substrate soldering flux printing device comprises a sub-control pressurizing mechanism, a steel mesh and a lifting mechanism. The sub-control pressurizing mechanism comprises a soldering flux container and a pressure adjusting device; and the printing salient points are provided with flow guide channels. The method has the advantages that the printing amount of the scaling powder is controlled, the scaling powder is evenly distributed on the printing salient points through the printing steel mesh flow guide structure, and the problem that the scaling powder printing distribution of a large-warping substrate is not uniform is solved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor packaging, in particular to a method and a printing device for soldering flux printing on a large warping substrate. Background Art

[0002] In the electronic manufacturing process, the warping characteristics of the substrate during the printing process may cause reduced printing accuracy, difficulty in component installation, and welding quality problems. Most of the existing technologies focus on solving the problems of accuracy and efficiency, and do not consider the problems of large warp substrates in the flux coating process. The flux can remove oxides on the surface of the substrate and reduce the surface tension of the solder. Flux coating and printing plays an important role in the subsequent welding quality of large warp substrates.

[0003] Due to the warping characteristics of large-warp substrates, when printing flux on large-warp substrates, it is easy for the center area of ​​the substrate to have less or no flux, while the surrounding areas have more flux, resulting in uneven distribution of flux on the substrate, which seriously affects the quality of subsequent welding of the substrate.

[0004] Therefore, the problem of flux printing on large warped substrates needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a method and a printing device for printing solder flux on a large warping substrate, which can solve the problem of uneven distribution of solder flux on the substrate when printing solder flux on the large warping substrate.

[0006] A first aspect of the present invention provides a method for printing solder flux on a large warped substrate, comprising the following steps:

[0007] Step 1: Storage and loading of flux;

[0008] Step 2: Generate positive pressure on the flux, the flux flows to the printed point and covers the lower surface of the printed point;

[0009] Step 3: Stop applying positive pressure to the flux to make the flux stagnate, or apply negative pressure to the flux to make the flux reflow, so as to adjust the thickness of the flux coated on the lower surface of the printed point;

[0010] Step 4: The printing point descends, and after the printing point contacts the corresponding substrate, it is pressed down on the solder pad of the substrate, and the flux is printed on the surface of the solder pad;

[0011] Step 5: The printing point rises and resets, and the next flux feeding is carried out.

[0012] In the above steps 2-4, the coverage of the flux on the solder pad is observed through optical inspection to adjust the initial positive pressure value of the flux and prepare for subsequent batch printing tests.

[0013] In the above step 4, after the printing point contacts the pad, the pressure of the printing point is monitored in real time, and when the pressure value reaches a preset value, the printing point stops descending.

[0014] Based on the above-mentioned method for printing flux on a large warping substrate, the second aspect of the present invention provides a device for printing flux on a large warping substrate, which runs the above-mentioned method for printing flux on a large warping substrate, and specifically includes a sub-controlled pressurizing mechanism, a steel mesh, and a lifting mechanism, wherein the sub-controlled pressurizing mechanism is connected to the steel mesh; the lifting mechanism is connected to the sub-controlled pressurizing mechanism;

[0015] The separate control pressurizing mechanism comprises a soldering flux container and a pressure regulating device, and the soldering flux container and the pressure regulating device are connected;

[0016] The steel mesh is provided with a plurality of printing convex points, and the printing convex points are provided with a guide channel, and the guide channel is connected with the divided control pressurizing mechanism;

[0017] The sub-control pressurizing mechanism is used for storing and loading the soldering flux in steps 1-3, and generating positive and negative pressure on the soldering flux;

[0018] The steel mesh is used for guiding the flux in step 2 and covering the lower surface of the printed dots;

[0019] The lifting mechanism is used for lifting and lowering the printing point in steps 4-5.

[0020] As a further improvement of the invention, the guide channel is provided at the center of the printed convex dot, and four guide channels are arranged in a circular array around the printed convex dot.

[0021] Preferably, the printed bumps are made of elastic material.

[0022] Furthermore, the bottom of the printed convex point is hemispherical.

[0023] Furthermore, the surface of the printed convex point is provided with textures.

[0024] As a further improvement of the invention, an optical mechanism is provided above the substrate.

[0025] As a further improvement of the invention, a pressure sensor is provided below the steel mesh.

[0026] The key point of the present invention is that the flux stored in the flux container flows in the guide channel through the positive pressure generated by the pressure regulating device, so that the flux is coated on the surface of each printed convex point; then, the pressure regulating device stops applying positive pressure, or adjusts to negative pressure, so that the flux stagnates in the guide channel, or the flux is reflowed, so as to adjust the thickness of the flux coated on the lower surface of the printed point, so that the printed points at different positions can be adaptively matched with the large warp substrate. The lifting mechanism controls the steel mesh to descend, and each printed convex point is pressed down above the corresponding solder pad, so that the surface of the printed convex point contacts and fits with the solder pad, and the flux is coated on each area of ​​the upper surface of the solder pad, so as to realize the simultaneous printing of the flux of multiple solder pads.

[0027] Compared with the prior art, the solder flux printing method and printing device of the present invention for a large warping substrate have the following advantages:

[0028] By controlling the feeding pressure and direction, the amount of flux printed can be controlled, and the printed steel mesh guide structure can make the flux evenly distributed on the printed bumps, solving the problem of uneven distribution of flux printing on large warped substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of a solder flux printing method and a printing device for a large warping substrate of the present invention;

[0030] Figure 2 It is a schematic diagram of the connection between the steel mesh and the sub-control pressurizing mechanism;

[0031] Figure 3 It is a schematic diagram of the printed bump structure;

[0032] Figure 4 This is a schematic diagram showing that the contact area between the printed bump and the pad is less than 10%;

[0033] Figure 5 This is a schematic diagram showing that the contact range between the printed bump and the pad reaches 50%;

[0034] Figure 6 This is a schematic diagram showing that the contact range between the printed bump and the pad reaches 100%;

[0035] Figure 7 is a schematic diagram of the location of the pressure sensor;

[0036] Figure 8 Schematic diagram of the optical mechanism position. DETAILED DESCRIPTION

[0037] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0038] A first aspect of the present invention provides a method for printing solder flux on a large warped substrate, comprising the following steps:

[0039] Step 1: Storage and loading of flux;

[0040] Step 2: Generate positive pressure on the flux, the flux flows to the printed point and covers the lower surface of the printed point;

[0041] Step 3: Stop applying positive pressure to the flux to make the flux stagnate, or apply negative pressure to the flux to make the flux reflow, so as to adjust the thickness of the flux coated on the lower surface of the printed point;

[0042] Step 4: The printing point descends, and after the printing point contacts the corresponding substrate, it is pressed down on the solder pad of the substrate, and the flux is printed on the surface of the solder pad;

[0043] Step 5: The printing point rises and resets, and the next flux feeding is carried out.

[0044] In the above steps 2-4, the coverage of the flux on the solder pad is observed through optical inspection to adjust the initial positive pressure value of the flux in step 2 to prepare for subsequent batch printing tests.

[0045] Before batch printing, the feeding is debugged through optical observation. When there is more flux around the pad, reduce the initial pressure value of the flux; when there is less flux in the middle, increase the initial pressure value to increase the flux on the printing point; when the printing point cannot contact the pad, increase the amount of flux, use fluid tension to make the flux contact the pad and spread evenly, and then use negative pressure to absorb excess flux.

[0046] In the above step 4, after the printing point contacts the pad, the pressure of the printing point is monitored in real time, and when the pressure value reaches a preset value, the printing point stops descending.

[0047] like Figure 1-3 As shown, based on the above-mentioned method for printing flux on a large warping substrate, the second aspect of the present invention provides a device for printing flux on a large warping substrate, which runs the above-mentioned method for printing flux on a large warping substrate, and specifically includes a sub-control pressurizing mechanism 1, a steel mesh 2, and a lifting mechanism 5, wherein the sub-control pressurizing mechanism 1 is connected to the steel mesh 2; the lifting mechanism 5 is connected to the sub-control pressurizing mechanism 1;

[0048] A sub-controlled pressurizing mechanism 1 is used for storing and loading the soldering flux in steps 1-3, and generating positive and negative pressure on the soldering flux;

[0049] Steel mesh 2, used for guiding the flux in step 2 and covering the lower surface of the printed dots;

[0050] The lifting mechanism 5 is used for lifting and lowering the printing point in step 4-5.

[0051] The present invention further introduces in detail various devices involved in a method for printing solder flux on a large warping substrate.

[0052] Separate control pressurizing mechanism 1

[0053] The separate control pressurizing mechanism 1 comprises a solder flux container 12 and a pressure regulating device 11, and the solder flux container 12 and the pressure regulating device 11 are connected;

[0054] The flux container 12 is used to store the flux to ensure continuous feeding of the flux. The pressure regulating device 11 is used to adjust the feeding pressure and direction, and control the flow rate of the flux according to the demand and preset instructions. First, a positive pressure is applied to the flux so that the flux flows from the flux container 12 to the printing point. After the preset time is reached, a negative pressure is generated on the flux, so that the flux stagnates and flows, thereby preventing the flux from overflowing at the printing point after continuous feeding.

[0055] Steel mesh 2

[0056] The steel mesh 2 is provided with a plurality of printing convex points 21, and the printing convex points 21 are provided with a guide channel 22, and the guide channel 22 is connected with the sub-control pressurizing mechanism 1;

[0057] After being pressurized by the pressure regulating device 11 , the soldering flux 4 in the soldering flux container 12 flows toward the printed bumps 21 through the capillary action of the guide channel 22 , and the soldering flux 4 is coated on the lower surface of the printed bumps 21 .

[0058] A guide channel 22 is provided at the center of the printed bump 21, and four guide channels 22 are arranged in a circular array around the printed bump 21. The five-point distribution of the guide channels 22 can accelerate the flow of flux in each printed bump 21, and allow the flux to be evenly distributed on the surface of the printed bump 21, further enhancing the subsequent printing effect on the solder pad 31 of the substrate 3.

[0059] The printed bump 21 is preferably made of elastic material, such as polydimethylsiloxane, polyurethane, etc. When the lower surface of the printed bump 21 contacts the pad 31, it is slightly deformed, so that the printed bump 21 and the pad 31 are more closely attached, and the soldering flux 4 can be more evenly coated on the surface of the pad 31.

[0060] The bottom of the printed bump 21 is hemispherical, and the hemispherical shape structure can better match the characteristics of the elastic material of the printed bump 21 to produce deformation, which can further promote the fit between the printed bump 21 and the pad 31. Figure 4 As shown, when the hemispherical printed convex dot 21 contacts the center of the substrate 3, the hemispherical printed convex dot 21 and the center of the pad 31 only touch each other. At this time, the hemispherical printed convex dot 21 and the pad 31 fit in the range of 0 to 10%. Figure 5As shown, when the hemispherical printed bump 21 descends to the inner periphery of the substrate 3, the printed bump 21 with good elasticity begins to deform while being pressed down, and at this time, the contact range between the hemispherical printed bump 21 and the pad 31 reaches 50%; Figure 6 As shown, when the hemispherical printed bump 21 descends to the periphery of the substrate 3, the lower surface of the hemispherical printed bump 21 is squeezed and deformed into a plane, which is completely fitted with the surface of the solder pad 31. The contact range between the hemispherical printed bump 21 and the solder pad 31 reaches 100%, so that the flux coated by the hemispherical printed bump 21 is evenly coated on various areas of the solder pad 31.

[0061] The surface of the printing protrusion 21 is provided with textures (not shown in the figure) to enhance the wettability and fluid tension of the surface of the printing protrusion 21 and improve the printing effect.

[0062] Optical mechanism 6

[0063] like Figure 8 As shown, an optical mechanism 6 may be provided above the substrate 3, and the optical mechanism 6 may be an existing camera and display assembly. When debugging the equipment and presetting parameters, the camera will take a picture of the coating state of the printing bumps 21 on the substrate 3, and upload the image to the display, so that the debugging personnel can detect the coating state and debug the pressure value of the pressure regulating device 11 to ensure that the feeding amount of the printing bumps 21 is within the appropriate range for printing.

[0064] Lifting mechanism 5

[0065] The lifting mechanism 5 can be an existing cylinder assembly to separately control the synchronous lifting of the pressurizing mechanism 1 and the steel mesh 2. Figure 7 As shown, a pressure sensor 32 is provided under the steel mesh 2. When the printing convex dot 21 is pressed down, the pressure value of the steel mesh 2 on the substrate 3 can be monitored in real time. The pressure sensor 32 converts the sensed force signal into an electrical signal and transmits it to the terminal. When the pressure value reaches a preset value, the terminal sends a command to the lifting mechanism 5, and the lifting mechanism 5 controls the printing convex dot 21 to stop pressing down and rise to reset.

[0066] In a method for printing flux on a large warp substrate of the present invention, the flux 4 stored in the flux container 12 flows in the guide channel 22 through the positive pressure generated by the pressure regulating device 11, so that the flux is coated on the surface of each printed bump 21; then, the pressure regulating device 11 stops applying positive pressure, or adjusts to negative pressure, so that the flux stagnates in the guide channel 22, or the flux refluxes, so as to adjust the thickness of the flux coated on the lower surface of the printed point, so that the printed points at different positions can be adaptively matched with the large warp substrate. The lifting mechanism 5 controls the steel mesh 2 to descend, and each printed bump 21 is pressed down above the corresponding pad 31, so that the surface of the printed bump 21 contacts and fits with the pad 31, and the flux is coated on each area on the upper surface of the pad 31, so that the flux of multiple pads 31 can be printed simultaneously.

[0067] The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the described embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for printing flux on a large warped substrate. It is characterized in that The steps include: Step 1: Storage and loading of flux; Step 2: Apply positive pressure to the flux, the flux flows toward the printed point and covers the lower surface of the printed point; Step 3: Stop applying positive pressure to the flux to make the flux stagnate, or apply negative pressure to the flux to make the flux reflow, so as to adjust the thickness of the flux coated on the lower surface of the printed point; Step 4: The printing point descends, and after the printing point contacts the corresponding substrate, it is pressed down on the solder pad of the substrate, and the flux is printed on the surface of the solder pad; Step 5: The printing point rises and resets, and the next flux feeding is carried out.

2. A method for printing flux on a large warped substrate as claimed in claim 1, It is characterized in that Through optical inspection, the coverage of the flux on the solder pad is observed to adjust the initial positive pressure value of the flux and prepare for subsequent batch printing tests.

3. A method for printing solder flux on a large warped substrate as claimed in claim 1, It is characterized in that After the printing point contacts the pad, the pressure of the printing point is monitored in real time. When the pressure value reaches the preset value, the printing point stops descending.

4. A solder flux printing device for a large warped substrate, It is characterized in that The above-mentioned method for printing solder flux on a large warped substrate specifically includes a separate control pressurizing mechanism, a steel mesh, and a lifting mechanism, wherein the separate control pressurizing mechanism is connected to the steel mesh; the lifting mechanism is connected to the separate control pressurizing mechanism; The separate control pressurizing mechanism comprises a soldering flux container and a pressure regulating device, and the soldering flux container and the pressure regulating device are connected; The steel mesh is provided with a plurality of printing convex points, and the printing convex points are provided with a guide channel, and the guide channel is connected with the divided control pressurizing mechanism; The sub-control pressurizing mechanism is used for storing and loading the soldering flux in steps 1-3, and generating positive and negative pressure on the soldering flux; The steel mesh is used for guiding the flux in step 2 and covering the lower surface of the printed dots; The lifting mechanism is used for lifting and lowering the printing point in steps 4-5.

5. A soldering flux printing device for a large warped substrate as claimed in claim 4, It is characterized in that The guide channel is provided at the center of the printed convex point, and four guide channels are arranged in a circular array around the printed convex point.

6. A solder flux printing device for a large warpage substrate as claimed in claim 4, It is characterized in that The printed convex points are made of elastic material.

7. A solder flux printing device for a large warpage substrate as claimed in claim 6, It is characterized in that The bottom of the printed convex point is hemispherical.

8. A soldering flux printing device for a large warped substrate as claimed in claim 6 or 7, It is characterized in that The surface of the printed convex point is provided with textures.

9. A soldering flux printing device for a large warpage substrate as claimed in claim 4, It is characterized in that An optical mechanism is arranged above the substrate.

10. A soldering flux printing device for a large warpage substrate as claimed in claim 4, It is characterized in that A pressure sensor is arranged below the steel mesh.

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