An apparatus and method for detecting dry film adhesion quality

Abstract

This application relates to the field of circuit board manufacturing, specifically providing a device and method for detecting the adhesion quality of dry film. The device is used to detect the adhesion quality of dry film on the surface of a circuit board. The device includes a surface wave generator and a surface wave receiver disposed on the surface of the circuit board, located at both ends of the dry film. The surface wave generator generates surface waves that propagate along the contact surface between the circuit board and the dry film, and the surface wave receiver receives the surface waves. The method includes the following steps: a surface wave generator and a surface wave receiver are disposed at both ends of the dry film to be tested; the surface wave generator generates surface waves that propagate along the contact surface between the circuit board and the dry film; the surface wave receiver receives the surface waves; the dry film is adhered to copper foil on the surface of the circuit board. Tiny air bubbles on the contact surface between the dry film and the metallic copper can affect the propagation of surface waves. This invention utilizes surface waves to detect the adhesion quality of the dry film, achieving high accuracy.

Description

TECHNICAL FIELD

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

[0002] In the process of manufacturing circuit boards, it is necessary to form a specific circuit pattern 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 undergo a chemical or photochemical reaction, forming a photoresist layer in the exposed area. The photosensitive compounds in the unexposed area remain unchanged and do not form a photoresist layer. Then, using a chemical solvent to remove the unexposed dry film area, leaving the exposed area, i.e., forming the desired characteristic pattern.

[0003] Dry film is a solid covering layer covering the surface of the circuit board, usually a photosensitive resin, which has sensitivity to ultraviolet light and will solidify to form a hard film under the action of ultraviolet light, used to cover the surface of the circuit board. Additives such as photosensitizers, plasticizers, stabilizers, etc. are added to the dry film to adjust the photosensitive properties, 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, and 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 the signal transmission, cause signal attenuation and interference, and make the signal transmission in the circuit difficult or the circuit failure affect the performance of the circuit, affecting the stability and reliability of the circuit; it will also cause welding difficulty, resulting in unstable welding quality, or even complete failure of welding. The existing dry film attachment quality detection has direct visual or microscopic examination methods, which detect by observing uneven features such as gaps and bubbles, and the detection accuracy and precision depend on the experience of the detection personnel and the resolution of the equipment, with low detection accuracy and poor efficiency. There is also a contact resistance detection method, which detects the contact degree between the dry film and the metal copper by measuring the contact resistance between them, for example, using a contact resistance meter to detect, and 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, and for local small gaps, the resistance change caused by the gap is very small and difficult to be detected, so the detection accuracy is low.

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

[0006] The present application aims to solve the problem of low detection accuracy of the existing dry film attachment quality detection method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A device for detecting the adhesion quality of dry film is provided for detecting the adhesion quality of dry film on the surface of a circuit board. The device includes a surface wave generator and a surface wave receiver disposed on the surface of the circuit board. The surface wave generator and the surface wave receiver are disposed 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.

[0009] Furthermore, the surface wave generator and 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.

[0010] Furthermore, a fixing block is set at each end of the circuit board, with the two fixing blocks respectively located at both ends of the circuit board.

[0011] Furthermore, the mass of the fixing block is more than three times the mass of the circuit board.

[0012] Furthermore, a pressure block is provided on the side of the dry film away from the circuit board.

[0013] A method for detecting the quality of dry film bonding includes the following steps: setting a surface wave generator and a surface wave receiver at both ends of the dry film to be tested; the surface wave generator generates a surface wave, which propagates along the contact surface between the circuit board and the dry film; and the surface wave receiver receives the surface wave; the dry film is bonded to the copper foil on the surface of the circuit board.

[0014] Furthermore, the surface wave generator and surface wave receiver come into contact with the dry film.

[0015] Furthermore, a fixing block is set at each end of the circuit board, with the two fixing blocks respectively located at both ends of the circuit board.

[0016] Furthermore, the mass of the fixing block is more than three times the mass of the circuit board.

[0017] Furthermore, a pressure block is provided on the side of the dry film away from the circuit board.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This application utilizes surface waves to detect the adhesion quality of dry film. Surface waves are waves that propagate along the surface of a material. Tiny air gaps can affect the propagation of surface waves, causing changes in the propagation of surface waves, thereby changing the scattered waves entering the receiver. The adhesion quality between the dry film and the metallic copper can be detected by the transmitted waves received by the receiver. Attached Figure Description

[0019] Figure 1 A schematic diagram of a dry film adhesion quality detection device provided by the present invention;

[0020] Figure 2 A schematic diagram of a fixing block in another dry film adhesion quality detection device provided by the present invention.

[0021] Icons: 1-Circuit board; 2-Dry film; 3-Surface wave generator; 4-Surface wave receiver; 5-Limit block. Detailed Implementation

[0022] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0023] This invention provides a device for detecting the quality of dry film adhesion, such as... Figure 1 As shown, a dry film 2 is attached to the surface of circuit board 1, and the dry film 2 is bonded to the copper metal on the surface of circuit board 1. A surface wave generator 3 and a surface wave receiver 4 are disposed on the surface of circuit board 1, on the same side of circuit board 1 as the dry film 2, and respectively at both ends of the dry film 2. Preferably, they are in contact with both ends of the dry film 2, thus minimizing surface wave loss and improving detection accuracy. The surface wave generator 3 and the surface wave receiver 4 are simply fixed to ensure they do not move during operation; they do not need to be completely fixed to circuit board 1 and need to be removed after testing. During testing, the surface wave generator 3 generates surface waves that propagate along the contact surface between circuit board 1 and the dry film 2, and the surface wave receiver 4 receives the surface waves. Small air bubbles or uneven forces between the dry film 2 and the copper metal can affect the propagation of the surface waves. Therefore, the surface waves received by the surface wave receiver 4 can accurately reflect the adhesion quality between the dry film 2 and the copper metal.

[0024] Surface waves are waves that propagate along the surface of a medium. The surface wave in this application can be a surface acoustic wave (SAW). The surface wave generator 3 and the surface wave receiver 4 are made of piezoelectric materials, such as lithium tantalate or zinc oxide. The surface wave generator 3 utilizes 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 utilizes the piezoelectric effect to convert mechanical energy into electrical energy, that is, to convert the received vibration into an electrical signal. On one hand, surface waves propagate forward using the interaction between the medium and the metal. Air bubbles or uneven gaps between the dry film and the copper metal will change the interaction between the medium and the metal, resulting in different resistances and losses during surface wave propagation, ultimately causing changes in the frequency and amplitude of the surface wave received by the surface wave receiver 4. On the other hand, small air bubbles will scatter and reflect the propagating surface wave, changing the direction of propagation and thus altering the energy, i.e., the amplitude, of the surface wave reaching the surface wave receiver 4. Therefore, the degree of adhesion between the dry film 2 and the circuit board 1 can be obtained by observing changes in the waveform, frequency, and amplitude of the received signal; this can be determined by a single indicator or by using multiple indicators together.

[0025] Furthermore, a fixing block is set at each end of the circuit board 1. The two fixing blocks are located on the surface of the circuit board 1, on the same side as the dry film 2, surface wave generator 3, and surface wave receiver 4, and are aligned in a straight line. The fixing blocks can be made of silicon or silicon oxide. They are rectangular in shape, with the end faces of the fixing blocks slightly protruding outwards for better fixation. The mass of the fixing blocks is more than three times the mass of the circuit board 1, which allows them to apply greater pressure to both ends of the circuit board 1, thus fixing the two ends of the circuit board 1 to the platform. In this way, on the one hand, the energy of the surface acoustic wave is less likely to dissipate outside the circuit board 1, making the energy of the surface wave localized on the circuit board 1, resulting in more complete interaction, more energy dissipation, and greater amplitude changes during the transmission of the surface wave; on the other hand, the pressure exerted by the fixing blocks at both ends on the circuit board 1 causes changes in the stress distribution inside the circuit board 1, thereby changing the frequency of the surface wave and further improving the accuracy of detection.

[0026] Based on the above scheme, a pressure block is provided on the side of the dry film 2 away from the circuit board 1. The lower surface area of ​​the pressure block is larger than the area of ​​the dry film 2, and the pressure block completely covers the dry film 2, applying uniform and vertical pressure to the dry film 2. The pressure block is cuboid in shape and can be made of 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, resulting in greater scattering loss when surface waves propagate through it, and greater energy variation of the surface waves, leading to greater amplitude variation of the received surface waves and thus more accurate detection. On the other hand, the pressure block makes the contact between the dry film 2 and the circuit board 1 tighter, strengthens the coupling, and increases the propagation speed and frequency variation of the surface waves, meaning that the signal received by the surface wave receiver 4 changes more significantly, further improving detection accuracy.

[0027] The circuit board 1 and the dry film 2 are heated to a temperature of 30-60℃. The increased temperature causes the air volume in the bubbles between the circuit board 1 and the dry film 2 to increase, resulting in a greater compressive force on the surrounding area. The dry film 2 also undergoes significant deformation; the density and Young's modulus of the material change even more. Consequently, the scattering effect of the bubbles or air gaps on surface waves is stronger, and the intensity of the transmitted surface waves varies more significantly. Under the combined effect of the heating of the pressure block, the air pressure in the bubbles increases considerably, the non-uniformity at the interface is greater, and the energy loss during surface wave propagation is greater, resulting in larger changes in amplitude and frequency, thus further improving the accuracy of the detection.

[0028] Furthermore, an outer shell is installed on the detection device, that is, the upper side and surrounding area of ​​the device are sealed, with the lower side serving as the worktable, and the space between them is sealed. During detection, the inside of the outer shell is evacuated to a negative pressure, which can be 0.5-0.8 standard atmospheres. This ensures that the pressure inside the small bubble between the dry film 2 and the circuit board 1 remains at one standard atmosphere, while the air pressure on the other side of the dry film 2 is lower. This causes the small bubble between the dry film 2 and the circuit board 1 to increase in size, significantly affecting the propagation of surface waves. This includes the degree of scattering affecting the propagation path of surface waves, and energy loss affecting the amplitude of surface waves. This results in more variations in the amplitude and frequency of surface waves, improving detection accuracy. By utilizing the pressure difference to enlarge smaller, harder-to-detect bubbles, they become easier to detect, leading to more accurate detection results.

[0029] like Figure 2As shown, two limiting blocks 5 are provided in a direction perpendicular to the surface wave propagation direction. The two limiting blocks 5 are located on both sides of the circuit board 1. The material of the limiting blocks 5 can be porous ceramic, porous polymer, etc. The length of the limiting blocks 5 is greater than the length of the circuit board 1, and the height of the limiting blocks 5 is greater than twice the thickness of the circuit board 1. In this way, on the one hand, the limiting blocks 5 limit the position of the circuit board 1, preventing it from moving and maintaining stability during the detection process, thus minimizing relative errors; on the other hand, the limiting blocks 5 absorb the surface waves, preventing reflected surface acoustic waves from entering the surface wave receiver 4, thereby preventing inaccurate detection results.

[0030] The present invention also provides a method for detecting the quality of dry film adhesion, the method comprising the following steps: setting a surface wave generator 3 and a surface wave receiver 4 at both ends of the dry film 2 to be tested, the surface wave generator 3 generating surface waves, the surface waves propagating along the contact surface between the circuit board 1 and the dry film 2, and the surface wave receiver 4 receiving the surface waves; the dry film 2 is adhered to the copper foil on the surface of the circuit board 1.

[0031] Work arrangements such as Figure 1 As shown, the surface wave generator 3 and surface wave receiver 4 are in contact with the dry film 2. The surface wave generator 3 and surface wave receiver 4 are made of 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 and generates energy. 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.

[0032] This application utilizes surface acoustic waves (SAWs) for detection. SAWs can propagate on the contact surface between the circuit board 1 and the dry film 2, and are highly sensitive to defects on the contact surface, such as uneven distribution or small air bubbles. These defects affect the propagation of the surface waves, causing changes in the surface waves received by the surface wave receiver 4. Based on the surface waves detected by the surface wave receiver 4, the adhesion quality of the dry film 2 can be detected.

[0033] Generally, surface waves propagate forward using the interaction between a medium and a metal. In this application, defects such as bubbles between the dry film and the copper metal impede the propagation of the surface waves, resulting in varying resistance and losses during propagation. This leads to changes in the frequency and amplitude of the surface waves received by the surface wave receiver 4. Simultaneously, due to scattering and reflection, small bubbles alter the direction of surface wave propagation, thus changing the amplitude of the surface wave upon reaching the surface wave receiver 4. This application uses the waveform, frequency, and amplitude changes of the surface waves received by the surface wave receiver 4 to determine the adhesion degree between the dry film 2 and the circuit board 1.

[0034] Fixing blocks are placed at both ends of circuit board 1 to prevent surface acoustic waves from dissipating, thus enhancing the interaction between the bubble and the surface waves and causing greater amplitude changes during surface wave transmission. Simultaneously, the pressure generated by the fixing blocks alters the stress distribution within circuit board 1, thereby changing the frequency of the surface waves and resulting in more significant frequency changes, further improving detection accuracy. The specific setup is the same as in the aforementioned device. The arrangement of the pressure block, heating element, outer shell, and limiting block 5 is also partially the same as in the aforementioned device.

[0035] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dry film adhesion quality detection device, characterized by, The application relates to a device for detecting the attaching quality of dry film on the surface of a circuit board, which 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 on the same side of the dry film on 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, the surface waves propagate along the contact surface between the circuit board and the dry film, the air gap between the dry film and the circuit board affects the propagation of the surface waves, and the surface wave receiver receives the surface waves; a pressing block is arranged on the side of the dry film away from the circuit board, the lower surface area of the pressing block is larger than the area of the dry film, the pressing block completely covers the dry film, and the pressing block applies uniform and vertical pressure on the dry film; during detection, the circuit board and the dry film are heated; 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; one fixing block is arranged at each end of the circuit board, the two fixing blocks are arranged at the two ends of the circuit board respectively; the two fixing blocks are arranged on the surface of the circuit board, on the same side of the dry film, the surface wave generator and the surface wave receiver, and on the same straight line; an outer shell is arranged on the detection device, and the inner part of the outer shell is extracted into negative pressure during detection. The mass of the fixing block is greater than 3 times the mass of the circuit board. ​ ​ 2. The dry film adhesion quality detection device according to claim 1, wherein ​

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