Method of adjusting distribution position of flux on circuit board

Abstract

To provide a method of adjusting a distribution position of flux on a circuit board.SOLUTION: A method of adjusting a distribution position of flux on a circuit board includes steps of: preparing a circuit board provided with flux covering a plurality of solder points distributed on a surface; performing optical position alignment work of sending the circuit board into a work region, imaging the circuit board by using an optical imaging lens, and outputting positional information after calculation; performing laser cleaning work of generating a laser beam by using a laser oscillator, removing excessive flux around the plurality of solder points on the basis of the positional information, and leaving only flux distributed on top surfaces of the solder points; and performing automatic optical inspection work for determining whether the circuit board is nondefective or defective. By the steps, flux having the same distribution region is formed on the top surfaces of the plurality of solder points on the circuit board, and successive soldering quality is improved. If there is remaining flux, the remaining flux can be completely removed via a reflow furnace in the subsequent step, and a step of cleaning excessive flux on the circuit board can be omitted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical field of forming flux on a circuit board, and more particularly to a method for accurately adjusting the distribution position of flux on a circuit board. [Background technology]

[0002] The principle of action of flux used in soldering is that the flux components chemically remove oxides from the metal surface at the joining surface between the objects to be soldered and the objects to be joined, and then wet and spread the solder so that it can adhere and fix to the metal interface between the objects to be soldered and the objects to be joined, thereby obtaining a strong joint.

[0003] In semiconductor manufacturing, in order to facilitate the subsequent soldering process, it is necessary to employ a technique for forming solder bumps on some circuit boards. This technique involves applying flux to multiple solder points on the circuit board in advance, placing spherical solder called solder balls on the solder points to which the flux has been applied, and then heating the solder balls in a reflow furnace to finally form protruding solder bumps on the solder points on the circuit board.

[0004] In recent years, as electronic components have become smaller in size, the wiring patterns on circuit boards have become finer, resulting in smaller and closer-spaced solder bumps. To achieve this, the flux must be distributed more precisely at each solder point when it is applied to the surface of a circuit board. However, as the spacing and size of solder points decrease, the flux tends to spread or distribute over a large area when applied to the surface of a circuit board using inkjet printing or silkscreen printing. In response to this problem, the present inventors have proposed a processing method that effectively removes excess flux during application and distributes it only within the areas of the solder points on the circuit board, facilitating the subsequent accurate formation of solder bumps. Summary of the Invention [Problem to be solved by the invention]

[0005] The main objective of the present invention is to provide a method for adjusting the distribution position of flux on a circuit board. After the flux is formed on the circuit board, optical alignment and laser cleaning operations are used to remove excess flux around the solder points on the circuit board. The laser cleaning can be used to accurately control the working area, so that the flux is ultimately distributed only to the corresponding solder points, overcoming the problems of traditional flux being easily spread and the distribution area being too large, thereby meeting the precision required for subsequent packaging operations. [Means for solving the problem]

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] The present invention is a method for adjusting the distribution position of flux on a circuit board, comprising the steps of: preparing the circuit board having flux covering a plurality of solder points distributed on its surface; carrying out an optical alignment operation in which the circuit board is sent into a work area, an optical photographing lens is used to photograph the circuit board, and position information is output after calculation; performing a laser cleaning operation in which a laser beam is generated using a laser oscillator, and excess flux around the plurality of solder points is removed based on the position information, leaving only the flux distributed on the top surfaces of the solder points; and performing an automatic optical inspection operation to determine whether the circuit board is a good product or a defective product.

[0008] In one preferred embodiment, when a circuit board is prepared, the area on the circuit board where the flux is located simultaneously covers a plurality of the solder points.

[0009] In one preferred embodiment, when preparing a circuit board, each of the solder points on the circuit board is covered with one layer of the flux, and the covered area of ​​the flux is larger than the area of ​​the solder points.

[0010] In one preferred embodiment, the flux is applied to the circuit board by an inkjet method.

[0011] In one preferred embodiment, the thickness of the flux at the solder point is 1 to 100 μm.

[0012] In one preferred embodiment, the thickness of the flux at the solder point is 2 to 50 μm.

[0013] In one preferred embodiment, the solder dots are circular in shape and have a diameter of 1 to 1000 μm.

[0014] In one preferred embodiment, the solder dots have a rectangular shape, and the length of any side of the square is 1 to 1000 μm.

[0015] In one preferred embodiment, the distance between adjacent solder dots is 20 to 100 μm.

[0016] In one preferred embodiment, the flux is formed on the circuit board by a printing method. [Effects of the Invention]

[0017] Compared with the prior art, the method used in the present invention can accurately adjust the distribution position of flux on a circuit board, and when the spacing and size of solder points are small, it can achieve the goal of distributing flux only on the top surfaces of the corresponding solder points, ultimately facilitating the processing operation of forming solder bumps on the circuit board. Furthermore, after laser cleaning using the method of the present invention, only a small amount of flux remains on the circuit board, and the remaining flux is then completely removed in a subsequent process using a reflow oven, eliminating the need to clean off excess flux on the surface of the circuit board, simplifying the production flow and reducing cleaning costs. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a flowchart of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the formation of a flux in the circuit of the present invention. [Figure 3] 10A and 10B are schematic diagrams illustrating optical alignment work performed on the circuit board of the present invention. [Figure 4] 1 is a schematic diagram showing a laser cleaning operation performed on a circuit board of the present invention; [Figure 5] 1 is a schematic diagram showing an automatic optical inspection process performed on a circuit board of the present invention; [Figure 6] FIG. 10 is a partially enlarged view showing how flux is formed on the circuit board of the present invention by an inkjet method. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following specific embodiments and drawings will clearly and fully explain the technical solutions of the present invention. It should be noted that when a component is said to be "attached or fixed" to another component, it can be understood that it is directly connected to the other component, or that there are intervening components. When a component is said to be "connected" to another component, it can be understood that it is directly connected to the other component, or that there are intervening components.

[0020] In the illustrated embodiments, directional expressions such as up, down, left, right, front, rear, etc. are relative and are used to describe the relative structure and movement of different components herein. These expressions are appropriate when the components are in the positions shown in the figures. However, if the positional description of the components changes, these expressions will likely change accordingly.

[0021] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the art of the present invention. The technical terms used in this specification are not intended to limit the present invention, but are intended to describe specific examples. The technical term "and / or" used in this specification includes any and all combinations of one or more of the associated listed items.

[0022] The present invention is a method for adjusting the distribution position of flux on a circuit board, with the ultimate goal being to accurately form a layer of flux on the top surface of each solder point on the circuit board, after which the processing work of forming solder bumps can be performed. The technique for forming these solder bumps involves placing solder balls on the solder points where flux is present, heating them in a reflow furnace, and finally forming solder bumps on the solder points on the circuit board. This is not the focus of the present invention, so it will not be described further.

[0023] As shown in FIG. 1, a flow chart of a method for adjusting the distribution position of flux on a circuit board according to the present invention includes the following steps:

[0024] Step 101: A circuit board is prepared, and a plurality of solder points are distributed on the surface of the circuit board, and flux covering the solder points is provided on the circuit board.

[0025] Step 102: Perform optical positioning, send the circuit board into the work area, photograph the circuit board using an optical photographing lens, and output the position information after calculation.

[0026] Step 103: A laser cleaning operation is performed, in which a laser beam is generated using a laser oscillator, and excess flux around the solder points is removed based on the position information, leaving only the flux distributed on the top surfaces of the solder points.

[0027] Step 104: Perform an automated optical inspection operation to determine whether the circuit board is good or bad.

[0028] Next, each step of the present invention will be described in detail with reference to FIGS.

[0029] As shown in FIG. 2, the circuit board 10 used in the present invention has multiple solder dots 11 distributed thereon. In this embodiment, the circuit board 10 is applied with surface mount technology (SMT), which uses pinless or short-lead electronic components to directly attach the electronic components to the circuit board 10. Therefore, the circuit board 10 has a large number of solder dots 11 distributed thereon depending on the corresponding electronic components. In this embodiment, the spacing between the solder dots 11 is only 20-100 μm, so the solder dots are numerous and fairly densely packed. The solder dots are circular or rectangular. If circular, the diameter is 1-1000 μm, and if rectangular, the length of one side is 1-1000 μm. In step 101, as shown in FIG. 2, in this embodiment, inkjet equipment 30 is used to inkjet-apply a layer of flux 20 to the surface of the circuit board 10. In FIG. 2, the solder dots 11 covered with flux 20 are shown in dashed lines and the uncovered solder dots 11 are shown in solid lines, but when the inkjet process is complete, the flux 20 covers all of the solder dots 11.

[0030] 3, in step 102, the present invention uses an optical photographing lens 40 to photograph the circuit board 10, adjusts the proportion of the photographed image based on the alignment lines or alignment symbols (not shown) on the circuit board 10, and obtains coordinate information within the work area of ​​the circuit board 10. At the same time as obtaining the coordinate information, a database is accessed to obtain the distribution positions of the multiple solder dots 11 on the circuit board 10, and the information is finally compiled and corrected to obtain position information, which is then used as the basis for operating the laser oscillator 50. Of course, the optical photographing lens 40 can also obtain an identification code (e.g., a QR code) while photographing the circuit board 10, and obtain each piece of data for the circuit board 10 from the identification code via a database. This data is also verified during the calculation process to confirm whether the product is the one that was just processed, thereby reducing the occurrence of processing errors.

[0031] 4, in step 103, a laser oscillator 50 used in the present invention generates a laser beam 51, which has a wavelength of 355 nm, a power of 5 watts, a pulse energy of 100 μJ, a frequency of 20 to 200 kHz, and a speed of 1 to 5,000 mm / sec. Based on the acquired position information, the laser oscillator 50 removes excess flux 20 around the solder spot 11 with the laser beam 51, leaving the flux 20 only at the solder spot 11. The solder spot 11 on the right side of the figure already has flux 20, so it is shown with a thick line. In this embodiment, the thickness of the flux 20 is 1 to 100 μm, with the optimal thickness being 2 to 50 μm.

[0032] As shown in FIG. 5, in step 104, the present invention performs quality control using automated optical inspection (AOI). Manufacturers can select an appropriate automated optical inspection device 60 (simply shown as a block in the figure) as needed to inspect the circuit board 10. The automated optical inspection device 60 is equipped with a high-speed, high-precision optical imaging detection system and uses machine vision as its standard detection technology to measure the thickness, distribution location, and distribution of flux 20 at the solder points 11. If flux 20 is present on the top surface of all solder points 11, the circuit board 10 is determined to be good. If flux 20 is absent or the distribution area of ​​flux 20 is too small at some solder points, the circuit board 10 is determined to be defective. The defective products can be collected, cleaned, and reprocessed, while the good products are collected and moved on to the next processing step.

[0033] As described above, the method for adjusting the distribution position of flux on a circuit board of the present invention utilizes optical alignment and laser cleaning to remove excess flux 20 around solder dots 11 on a circuit board 10 with a laser beam 51. Furthermore, because a single layer of flux 20 is formed on the circuit board 10 using the inkjet method, a relatively thin flux 20 can be formed. The use of a laser beam 51 effectively and reliably removes excess flux 20, and the removal area can be precisely controlled. Ultimately, the flux 20 is distributed only on the top surfaces of the solder dots 11, solving the current problem of not being able to precisely control the distribution position of the flux 20 as the size and spacing of the solder dots 11 shrinks. This facilitates the subsequent process of forming solder bumps on the solder dots 11.

[0034] In the above step 101, the present invention forms a layer of flux 20 on the surface of the circuit board 10 using an inkjet method, but the present invention is not limited to this, and a printing method can also be used to form a layer of flux 20 on the circuit board 10. In this embodiment, the flux 20 is formed on the circuit board 10 using a silk screen printing (silk printing) method on a steel plate.

[0035] Furthermore, when the inkjet method is used to form the flux 20, the inkjet method allows for precise control of the inkjet area, so as shown in FIG. 6, each distribution area 21 of the flux 20 corresponds to the area where each solder point 11 is located. Because this embodiment is applied to surface mount technology (SMT), where the solder points 11 are small in size and spaced only 20 to 100 μm apart, it is possible that the coverage area of ​​some of the flux 20 distribution areas 21 is larger than the area of ​​the solder points 11. Even in this case, the size of the flux 20 distribution areas 21 can be adjusted and modified using the method of the present invention later, so that the distribution position and shape of the flux 20 match the solder points. The advantage of spraying a small amount of flux 20 onto the corresponding solder points 11 in this embodiment is that the amount of flux 20 used can be reduced, thereby reducing production costs.

[0036] As described above, the method of the present invention can accurately form flux 20 on the circuit board 10 in a shape corresponding to the top surface of each solder point 11. Solder balls can then be placed on the solder points 11 where the flux 20 exists, and by heating in a reflow furnace, solder bumps are finally formed on the solder points 11. Furthermore, because the present invention uses a laser beam 61 to remove the flux 20, only a very small amount of flux 20 remains on the circuit board 10. When the circuit board 10 proceeds to the reflow soldering process, the very little flux 20 remaining on the circuit board 10 is completely removed by the high temperature. This eliminates the need to clean excess flux 20 from the surface of the circuit board 10, thereby simplifying the production flow and reducing cleaning costs.

[0037] The above is a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. That is, all equivalent changes and modifications within the scope of the claims of the present invention are included in the scope of the claims of the present invention. [Explanation of symbols]

[0038] Steps 101-104 10 Circuit Board 11 Solder points 20 Flux 21 Distribution area 30 Inkjet equipment 40 Optical photographic lens 50 Laser Oscillator 51 Laser Beam 60 Automatic Optical Inspection Equipment

Claims

1. A method for adjusting a distribution position of flux on a circuit board, comprising: providing the circuit board having a flux covering a plurality of solder points distributed on a surface thereof; an optical positioning step of sending the circuit board into a work area, photographing the circuit board using an optical photographing lens, and outputting position information after calculation; a step of performing a laser cleaning operation in which a laser beam is generated using a laser oscillator, and excess flux is removed from the periphery of the plurality of solder points based on the position information, leaving only the flux distributed on the top surfaces of the solder points; and performing an automated optical inspection operation to determine whether the circuit board is good or bad. A method for adjusting the distribution position of flux on a circuit board.

2. When preparing the circuit board, the region on the circuit board where the flux is located simultaneously covers a plurality of the solder points. The method for adjusting the distribution position of flux on a circuit board according to claim 1.

3. When preparing the circuit board, each of the solder points on the circuit board is covered with one layer of the flux, and the covered area of ​​the flux is larger than the area of ​​the solder points. The method for adjusting the distribution position of flux on a circuit board according to claim 1.

4. forming the flux on the circuit board by an inkjet method; The method for adjusting the distribution position of flux on a circuit board according to claim 2 or 3.

5. the thickness of the flux at the solder point is 1 to 100 μm; The method for adjusting the distribution position of flux on a circuit board according to claim 1.

6. the thickness of the flux at the solder point is 2 to 50 μm; The method for adjusting the distribution position of flux on a circuit board according to claim 5.

7. The solder dots are circular in shape and have a diameter of 1 to 1000 μm. The method for adjusting the distribution position of flux on a circuit board according to claim 1.

8. The solder dots are rectangular in shape, and the length of any side of the square is 1 to 1000 μm. The method for adjusting the distribution position of flux on a circuit board according to claim 1.

9. The spacing between adjacent solder dots is 20 to 100 μm. The method for adjusting the distribution position of flux on a circuit board according to claim 1.

10. forming the flux on the circuit board by a printing method; The method for adjusting the distribution position of flux on a circuit board according to claim 2.

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