Device and method for detecting attachment quality of dry film

Abstract

The invention relates to the field of circuit board manufacturing, and particularly provides a dry film attachment quality detection device and method. The device is used for detecting the attaching quality of a dry film on the surface of a circuit board and comprises a surface wave generator and a surface wave receiver which are arranged on the surface of the circuit board and arranged at the two ends of the dry film, the surface wave generator generates surface waves, and the surface waves are transmitted along the contact face of the circuit board and the dry film. The surface wave receiver receives a surface wave. The method comprises the following steps that a surface wave generator and a surface wave receiver are arranged at the two ends of a to-be-detected dry film, the surface wave generator generates surface waves, the surface waves are transmitted along the contact face of a circuit board and the dry film, and the surface wave receiver receives the surface waves; the dry film is attached to the copper foil on the surface of the circuit board. The micro bubbles on the contact surface of the dry film and the metal copper can influence the propagation of the surface waves, and the surface waves are used for detecting the attachment quality of the dry film, so that the detection accuracy is relatively high.

Description

Technical Field

[0001] The present application relates to the field of circuit board manufacturing, and in particular to a device and method for detecting dry film attachment quality. Background Art

[0002] During the manufacturing process of circuit boards, a specific circuit pattern needs to be formed on the metal copper. Dry film is a material used to cover the surface of the circuit board, usually a photosensitive film. Specifically, the dry film needs to be in close contact with the metal copper. When exposed to light, the photosensitive compounds on the dry film will be activated, and a chemical reaction or photochemical reaction will occur, forming a photoresist layer in the illuminated area. The photosensitive compounds in the unexposed area remain intact and no photoresist layer is formed. Afterwards, a chemical solvent is used to remove the unexposed dry film area and retain the exposed area, thus forming the desired characteristic pattern.

[0003] Dry film is a solid covering layer on the surface of the circuit board. It is generally a photosensitive resin, which is sensitive to ultraviolet light and will solidify under the action of ultraviolet light to form a hard film, which is used to cover the surface of the circuit board. Additives such as photosensitizers, plasticizers, stabilizers, etc. are also added to the dry film to adjust the photosensitivity, mechanical properties and chemical properties of the dry film.

[0004] In the circuit board, the dry film is generally in contact with the metal copper. There is a gap or poor contact between the dry film and the metal copper, which will increase the resistance of the circuit, increase the impedance of signal transmission, cause signal attenuation and interference, and make the signal transmission in the circuit blocked or the circuit fail, affecting the performance of the circuit, affecting the stability and reliability of the circuit; it will also cause welding difficulties, unstable welding quality, and even failure to completely weld successfully. The existing dry film attachment quality detection has direct visual or microscopic inspection methods, which detects by observing uneven features such as gaps and bubbles. The detection accuracy and precision depend on the experience of the inspector and the resolution of the equipment. The detection accuracy is low and the efficiency is poor. There is also a contact resistance detection method, which detects the degree of fit between the dry film and the metal copper by measuring the contact resistance between the dry film and the metal copper. For example, a contact resistance meter is used for detection. The lower the contact resistance, the better the contact between the dry film and the metal copper. Contact resistance detection is to judge the contact quality between the dry film and the metal copper by the resistance value. For local small gaps, it is difficult to detect because the resistance change caused is extremely small. Therefore, the detection accuracy is low.

[0005] In summary, the existing dry film attachment quality detection method has low detection accuracy. Summary of the invention

[0006] The object of the present invention is to provide a dry film attachment quality detection device and method to solve the problem of low detection accuracy of the existing dry film attachment quality detection method in view of the above-mentioned deficiencies in the prior art.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A dry film attachment quality detection device is used to detect the attachment quality of the dry film on the surface of a circuit board. The device includes a surface wave generator and a surface wave receiver arranged on the surface of the circuit board. The surface wave generator and the surface wave receiver are arranged at both ends of the dry film. The surface wave generator generates surface waves, which propagate along the contact surface between the circuit board and the dry film, and the surface wave receiver receives the surface waves.

[0008] Furthermore, the surface wave generator and the surface wave receiver are in contact with the dry film; the dry film is attached to the copper foil on the surface of the circuit board.

[0009] Furthermore, a fixing block is respectively arranged at both ends of the circuit board, and the two fixing blocks are respectively arranged at the two ends of the circuit board.

[0010] Furthermore, the mass of the fixing block is greater than 3 times the mass of the circuit board.

[0011] Furthermore, a pressing block is arranged on a side of the dry film away from the circuit board.

[0012] A method for detecting the attachment quality of a dry film comprises the following steps: a surface wave generator and a surface wave receiver are arranged at both ends of a dry film to be detected, the surface wave generator generates a surface wave, the surface wave propagates along the contact surface between a circuit board and the dry film, and the surface wave receiver receives the surface wave; the dry film is attached to the copper foil on the surface of the circuit board.

[0013] Further, a surface wave generator and a surface wave receiver are in contact with the dry film.

[0014] Furthermore, a fixing block is respectively arranged at both ends of the circuit board, and the two fixing blocks are respectively arranged at the two ends of the circuit board.

[0015] Furthermore, the mass of the fixing block is greater than 3 times the mass of the circuit board.

[0016] Furthermore, a pressing block is arranged on a side of the dry film away from the circuit board.

[0017] Compared with the prior art, the present invention has the following beneficial effects: the present application utilizes surface waves to detect the adhesion quality of the dry film. The surface wave is a wave that propagates along the surface of the material. A tiny air gap will affect the propagation of the surface wave, causing the propagation of the surface wave to change, thereby changing the scattered wave entering the receiver. The transmitted wave received by the receiver can detect the adhesion quality between the dry film and the metal copper. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a dry film attachment quality detection device provided by the present invention; Figure 2A schematic diagram of a fixed block in another dry film attachment quality detection device provided by the present invention.

[0019] Icon: 1-circuit board; 2-dry film; 3-surface wave generator; 4-surface wave receiver; 5-limit block. DETAILED DESCRIPTION

[0020] In order to make the implementation process of the present invention clearer, it will be described in detail below with reference to the accompanying drawings.

[0021] The present invention provides a dry film attachment quality detection device, such as Figure 1 As shown, a dry film 2 is attached to the surface of the circuit board 1, and the dry film 2 is attached to the metal copper on the surface of the circuit board 1. A surface wave generator 3 and a surface wave receiver 4 are arranged on the surface of the circuit board 1. The surface wave generator 3 and the surface wave receiver 4 are arranged on the same side of the circuit board 1 as the dry film 2, and the surface wave generator 3 and the surface wave receiver 4 are respectively arranged at both ends of the dry film 2, preferably, contacting the two ends of the dry film 2, so that the loss of the surface wave is small and the detection result is more accurate. The surface wave generator 3 and the surface wave receiver 4 are simply fixed to ensure that they do not move during the working process. They do not need to be completely fixed to the circuit board 1, and they need to be removed after the detection. During the detection, the surface wave generator 3 generates a surface wave, and the surface wave propagates along the contact surface between the circuit board 1 and the dry film 2, and the surface wave receiver 4 receives the surface wave. Small bubbles or uneven force between the dry film 2 and the metal copper will affect the propagation of the surface wave, so that the surface wave received by the surface wave receiver 4 can accurately reflect the adhesion quality between the dry film 2 and the metal copper.

[0022] A surface wave is a wave that propagates along the surface of a medium. The surface wave in the present application may be an acoustic surface wave. The surface wave generator 3 and the surface wave receiver 4 are piezoelectric materials, such as lithium tantalate, zinc oxide, etc. The surface wave generator 3 uses the piezoelectric effect to convert electrical energy into mechanical energy. Under the action of an alternating electric field, the piezoelectric material deforms; the surface wave receiver 4 uses the piezoelectric effect to convert mechanical energy into electrical energy, that is, to convert the received vibration into an electrical signal. On the one hand, the surface wave propagates forward by utilizing the interaction between the medium and the metal. The bubbles or uneven gaps between the dry film and the metal copper will change the interaction between the medium and the metal, thereby causing different resistances during the propagation of the surface wave and different losses to the surface wave, which ultimately causes changes in the frequency and amplitude of the surface wave received by the surface wave receiver 4. On the other hand, small bubbles will scatter and reflect the propagating surface wave, causing the propagation direction of the surface wave to change, thereby changing the energy of the surface wave when it reaches the surface wave receiver 4, that is, the amplitude. Therefore, the adhesion degree between the dry film 2 and the circuit board 1 can be obtained by the waveform change, frequency change and amplitude change of the received signal; it can be judged by a single indicator or by multiple indicators together.

[0023] Furthermore, a fixed block is provided at each end of the circuit board 1, and the two fixed blocks are provided on the surface of the circuit board 1, on the same side as the dry film 2, the surface wave generator 3, and the surface wave receiver 4, and on the same straight line. The material of the fixed block can be silicon or silicon oxide. The shape is a rectangular parallelepiped, and the end face of the fixed block protrudes slightly outward, which can play a better fixing role. The mass of the fixed block is greater than 3 times the mass of the circuit board 1. The large mass can exert a large pressure on the two ends of the circuit board 1, so that the two ends of the circuit board 1 are fixed on the platform. In this way, on the one hand, the energy of the surface acoustic wave is not easy to dissipate outside the circuit board 1, so that the energy of the surface wave is localized on the circuit board 1, the interaction is more sufficient, the energy dissipation is more, and the amplitude change caused by the surface wave transmission process is greater; on the other hand, the fixed blocks at both ends exert pressure on the circuit board 1, so that the stress distribution inside the circuit board 1 changes, thereby changing the frequency of the surface wave, so that the surface frequency changes more, and the accuracy of detection is further improved.

[0024] On the basis of the above scheme, a pressing block is provided on the side of the dry film 2 away from the circuit board 1. The lower surface area of ​​the pressing block is larger than the area of ​​the dry film 2. The pressing block completely covers the dry film 2 and applies uniform and vertical pressure to the dry film 2. The pressing block is in the shape of a rectangular parallelepiped and the material of the pressing block can be silicon, silicon oxide, etc. In this way, on the one hand, the uniform stress increases the pressure at the edge of the small bubble between the dry film 2 and the circuit board 1. When the surface wave propagates through, the scattering loss generated is large, and the energy change of the passing surface wave is greater, so that the amplitude change of the received surface wave is greater, so that the detection is more accurate. On the other hand, the pressing block makes the contact between the dry film 2 and the circuit board 1 closer, the coupling effect becomes stronger, the propagation speed of the surface wave is faster, and the frequency changes more, that is, the change of the signal received by the surface wave receiver 4 is greater, further improving the detection accuracy.

[0025] The circuit board 1 and the dry film 2 are heated at a temperature of 30-60°C. The increase in temperature increases the volume of the air in the bubbles between the circuit board 1 and the dry film 2, thereby generating a greater squeezing force on the surroundings, and the dry film 2 will also undergo a greater deformation; the density and Young's modulus of the material will change more. In this way, the bubbles or air gaps have a stronger scattering effect on the surface waves, and the intensity of the transmitted surface waves changes more. Under the combined effect of the heating of the pressing block, the pressure of the air in the bubbles increases significantly, the inhomogeneity on the interface is greater, and the energy loss during the propagation of the surface waves is greater, resulting in greater changes in the amplitude and frequency, thereby further improving the accuracy of the detection.

[0026] Furthermore, a shell is provided on the detection device, that is, the upper side and the surrounding of the device are closed, and the lower side is a workbench, and the space between them is sealed. During detection, the inside of the shell is evacuated to a negative pressure, which can be 0.5-0.8 standard atmospheric pressure, so that the pressure in the small bubbles between the dry film 2 and the circuit board 1 is still one standard atmospheric pressure, while the pressure of the air on the other side of the dry film 2 is smaller, so that the volume of the small bubbles between the dry film 2 and the circuit board 1 increases, and the original smaller bubbles become larger, which has a greater impact on the propagation of surface waves, including the degree of scattering affecting the path of surface wave propagation, and energy loss affecting the amplitude of the surface wave; the amplitude and frequency of the surface wave are more varied, thereby improving the accuracy of detection. The pressure difference is used to enlarge smaller bubbles that are difficult to detect, making them easier to detect, and making the detection results more accurate.

[0027] like Figure 2 As shown, two limit blocks 5 are arranged in a direction perpendicular to the propagation direction of the surface wave. The two limit blocks 5 are arranged on both sides of the circuit board 1. The material of the limit blocks 5 can be porous ceramics, porous polymers, etc. The length of the limit blocks 5 is greater than the length of the circuit board 1, and the height of the limit blocks 5 is greater than twice the thickness of the circuit board 1. In this way, on the one hand, the limit blocks 5 play a role in limiting the position of the circuit board 1, so that the circuit board 1 will not move, maintain the stability during the detection process, and is not prone to relative errors; on the other hand, the limit blocks 5 absorb the surface waves, preventing the reflected acoustic surface waves from entering the surface wave receiver 4, thereby making the detection results inaccurate.

[0028] The present invention also provides a method for detecting the attachment quality of a dry film, the method comprising the following steps: a surface wave generator 3 and a surface wave receiver 4 are arranged at both ends of a dry film 2 to be detected, the surface wave generator 3 generates a surface wave, the surface wave propagates along the contact surface between the circuit board 1 and the dry film 2, and the surface wave receiver 4 receives the surface wave; the dry film 2 is attached to the copper foil on the surface of the circuit board 1.

[0029] The working arrangement is as follows Figure 1 As shown. The surface wave generator 3 and the surface wave receiver 4 are in contact with the dry film 2. The surface wave generator 3 and the surface wave receiver 4 are piezoelectric materials, such as lithium tantalate, zinc oxide, etc. The surface wave generator 3 uses the piezoelectric effect to convert electrical energy into mechanical energy. Under the action of the alternating electric field, the piezoelectric material deforms; the surface wave receiver 4 uses the piezoelectric effect to convert mechanical energy into electrical energy, that is, converts the received vibration into an electrical signal.

[0030] The present application uses surface acoustic waves for detection. Surface acoustic waves can propagate on the contact surface between the circuit board 1 and the dry film 2, and are very sensitive to defects on the contact surface, such as uneven distribution, small bubbles, etc., which will affect the propagation of the surface waves, causing the surface waves received by the surface wave receiver 4 to change, so that the surface wave receiver 4 detects the surface waves and can detect the attachment quality of the dry film 2.

[0031] Generally, surface waves propagate forward by utilizing the interaction between the medium and the metal. In the present application, defects such as bubbles between the dry film and the metal copper will cause resistance to the propagation of the surface wave, resulting in different resistances during the propagation of the surface wave, and different losses to the surface wave, resulting in changes in the frequency and amplitude of the surface wave received by the surface wave receiver 4; at the same time, due to the influence of scattering and reflection, small bubbles will change the direction of the surface wave propagation, thereby changing the amplitude of the surface wave when it reaches the surface wave receiver 4. The present application obtains the degree of adhesion between the dry film 2 and the circuit board 1 through the waveform changes, frequency changes, amplitude changes, etc. of the surface wave received by the surface wave receiver 4.

[0032] Fixed blocks are set at both ends of the circuit board 1 to prevent the surface acoustic wave from escaping easily, and the interaction between the bubbles and the surface wave is enhanced, so that the amplitude change caused by the surface wave transmission process is greater; at the same time, the pressure generated by the fixed block changes the stress distribution inside the circuit board 1, thereby changing the frequency of the surface wave, making the surface frequency change more, and further improving the accuracy of detection. The specific settings are the same as those in the above-mentioned device. The scheme of setting the pressing block, heating, shell, and limit block 5 is also the same as that of the above-mentioned device.

[0033] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A dry film attachment quality detection device, characterized in that: The device is used to detect the attachment quality of a dry film on the surface of a circuit board. The device comprises a surface wave generator and a surface wave receiver arranged on the surface of the circuit board. The surface wave generator and the surface wave receiver are arranged at two ends of the dry film. The surface wave generator generates surface waves, which propagate along the contact surface between the circuit board and the dry film, and the surface wave receiver receives the surface waves.

2. The dry film attachment quality detection device according to claim 1, characterized in that: The surface wave generator and the surface wave receiver are in contact with the dry film; and the dry film is attached to the copper foil on the surface of the circuit board.

3. The dry film attachment quality detection device according to claim 2, characterized in that: A fixing block is respectively arranged at two ends of the circuit board, and two fixing blocks are respectively arranged at two ends of the circuit board.

4. The dry film attachment quality detection device according to claim 3, characterized in that: The mass of the fixing block is greater than 3 times the mass of the circuit board.

5. The dry film attachment quality detection device according to claim 4, characterized in that: A pressing block is arranged on one side of the dry film away from the circuit board.

6. A method for detecting the quality of dry film attachment, characterized in that: The method comprises the following steps: a surface wave generator and a surface wave receiver are arranged at two ends of a dry film to be detected, the surface wave generator generates a surface wave, the surface wave propagates along a contact surface between a circuit board and the dry film, and the surface wave receiver receives the surface wave; the dry film is attached to a copper foil on the surface of the circuit board.

7. The method for detecting dry film attachment quality according to claim 6, characterized in that: The surface wave generator and the surface wave receiver are in contact with the dry film.

8. The method for detecting dry film attachment quality according to claim 7, characterized in that: A fixing block is respectively arranged at two ends of the circuit board, and two fixing blocks are respectively arranged at two ends of the circuit board.

9. The method for detecting dry film attachment quality according to claim 8, characterized in that: The mass of the fixing block is greater than 3 times the mass of the circuit board.

10. The method for detecting dry film attachment quality according to claim 9, characterized in that: A pressing block is arranged on one side of the dry film away from the circuit board.

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