TWI762913B - Detection method - Google Patents

Abstract

A detection method is suitable for detecting a glue filling in a blind hole of a circuit board. The detection method includes a preparation step, a detection step, and a processing step. The preparation step prepares a detection device, the detection device includes an excitation light source having a first wavelength range, a light receiver, and a processing unit connected to the light receiver. In the detecting step, the filler is irradiated with the excitation light source, so that the filler is excited by the excitation light source to generate a photofluorescence light having a second wavelength range different from the first wavelength range, and the light receiver can receive the light fluoresce and generate a corresponding photoluminescence signal. In the processing step, the processing unit receives the photoluminescence signal and performs grayscale conversion to obtain a glue-filled grayscale image.

Description

Detection method

The present invention relates to a detection method, in particular to a detection method for detecting whether the glue filling in the blind hole of a circuit board is concave.

Existing electronic products have been developing towards the trend of being light, thin, short, and multi-functional. Therefore, the internal circuit boards are often stacked with multi-layer circuit structures. Generally, a blind hole (via) is opened and electroplated to connect the circuit structures between different layers. Fill the blind holes and scrape the overflowing glue, so that the top surface of the glue filling in the blind holes can be flush with the surface of the circuit board, and while scraping the overflowing glue, the top surface of the glue filling will be A layer of copper chips is arranged to facilitate the subsequent formation of an outer layer circuit on the surface of the circuit board.

Therefore, when the top surface of the filler in the blind hole is not flush with the surface of the circuit board (that is, the top surface of the filler is recessed in the blind hole), the top surface of the recess of the filler will not have the copper The chip layer makes the outer circuit formed on the circuit board easy to cause short circuit or open circuit.

Therefore, after plugging the blind hole with glue and scraping off the overflowing glue, the appearance inspection of the glue in the blind hole will be carried out through the automatic optical inspection system first to ensure that the glue filled in the blind hole is The top surface of the circuit board is flush with the surface of the circuit board and has a copper chip layer. However, other parts of the circuit board often have depressions due to collisions, or different types of protrusions and depressions caused by foreign matter generated by chemical oxidation of the sheet metal. The existing When optical inspection uses reflected light for its appearance inspection, it cannot effectively distinguish the difference between the depression on the top surface of the glue filling and the depression caused by external factors on the circuit board, so it is easy to judge the two depressions together. error.

Therefore, the purpose of the present invention is to provide a detection method.

Therefore, the detection method of the present invention is suitable for detecting a glue filling in a blind hole of a circuit board, and the detection method includes a preparation step, a detection step, and a processing step.

The preparation step prepares a detection device, the detection device includes an excitation light source having a first wavelength range, a light receiver, and a processing unit connected to the light receiver.

In the detecting step, the filler is irradiated with the excitation light source, so that the filler is excited by the excitation light source to generate a photofluorescence light having a second wavelength range different from the first wavelength range, and the light receiver can receive the light fluoresce and generate a corresponding photoluminescence signal.

In the processing step, the processing unit receives the photoluminescence signal and performs grayscale conversion to obtain a glue-filled grayscale image.

The effect of the present invention lies in that the filler is irradiated by an excitation light source, so that the filler generates photofluorescence, and after the light receiver receives the photofluorescence to generate a fluorescent image, the grayscale conversion is performed through the processing step, and the through Only the photoluminescence generated in the recess of the glue filling and the gray-scale image of the glue filling can be used to determine whether the top surface of the glue filling is recessed in the blind hole, and can also eliminate the depression of the circuit board itself.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are designated by the same reference numerals.

Referring to FIG. 1 and FIG. 2 , an embodiment of the detection method of the present invention is suitable for detecting a glue 11 in a blind hole 10 of a circuit board 1 .

Specifically, after the blind hole 10 of the circuit board 1 is filled with glue 11 , the excess glue 11 overflowing the blind hole 10 will be scraped off through a scraping action, so that the glue 11 located in the blind hole 10 will be removed. A top surface 110 of the filler 11 can be flush with a surface 12 of the circuit board 1 , and during the scraping process, the top surface 110 of the filler 11 that is flush with the circuit board 1 will be placed on the top surface 110 of the filler 11 . There is a copper chip layer left to facilitate the subsequent formation of an outer layer circuit on the surface 12 of the circuit board 1 , but when the top surface 11 of the filler 11 is not flush with the surface 12 of the circuit board 1 and there are parts When it is recessed, in the process of scraping, some recesses are located in the blind hole 10 and do not have a copper chip layer, which will cause the outer circuit formed later to easily cause short circuit or open circuit. Therefore, the detection method of the present invention is as follows: It is to detect whether the top surface 110 of the filler 11 is flush with the surface 12 of the circuit board 1 without being recessed in the blind hole 10 . It should be noted here that the circuit board 1 generally has a plurality of blind holes 10 , and this embodiment and the corresponding drawings are only for illustrating the detection of the state of the glue 11 in a single blind hole 10 as an example for illustration. , but not limited to this.

The detection method of this embodiment includes a preparation step 201 , a detection step 202 , a processing step 203 , and a determination step 204 .

First, perform the preparation step 201 to prepare a detection device 2, the detection device 2 includes an excitation light source 21 capable of emitting an excitation light E, an optical receiver 22, a processing unit 23 connected to the optical receiver 22, An emission filter 24 downstream of the light receiver 22, a dichroic mirror 25 downstream of the emission filter 24, and a dichroic mirror 25 disposed downstream of the excitation light source 21 and positioned A convex lens 26 between the excitation light source 21 and the beam splitter 25 .

After the detection device 2 is prepared, the circuit board 1 to be detected can be placed under the light receiver 22 of the detection device 2, and the circuit board 1 and the light receiver 22 are spaced apart from each other, so as to The preparation step 201 is completed.

Next, the detection step 202 is performed, the excitation light E emitted by the excitation light source 21 has a first wavelength range, and can be irradiated to the circuit board 1 through the beam splitter 25, and the excitation light E emitted by the excitation light source 21 When the filler 11 in the blind hole 10 of the circuit board 1 is irradiated, the filler 11 can be excited by the excitation light E to generate a photofluorescence having a second wavelength range different from the first wavelength range F, and receive the photofluorescence light F through the light receiver 22, and generate a corresponding photofluorescence signal.

In detail, in this embodiment, the first wavelength range of the excitation light E emitted by the excitation light source 21 is not particularly limited, and is mainly selected according to the material of the filler 11. In other words, as long as The first wavelength range can excite the filler 11 to generate photofluorescence F when the filler 11 is irradiated.

The excitation light source 21 suitable for this embodiment can be selected from a light emitting diode (LED) or a laser light source, and in this embodiment, the excitation light E has the first wavelength range of 460nm˜490nm, After being irradiated by the excitation light E with the first wavelength range (460nm~490nm), the filler 11 can generate photofluorescence F with a second wavelength range of 510nm~530nm; wherein, this embodiment is only a A single excitation light source 21 is used as an example for illustration, but it is not limited to this. Other numbers of excitation light sources can be added as needed for detection; in addition, the light receiver 22 can be selected from a camera for receiving the light Fluorescent F.

Since the selection of the first wavelength range is not particularly limited, it is mainly matched with the material of the filler 11, that is, when the material used for the filler 11 is different, the first wavelength range will also be different, and the The second wavelength range of the photoluminescence F generated by the excitation light E from the filler 11 also changes accordingly. Preferably, the first wavelength range has a first energy peak, and the second wavelength range has an energy second peak. When the first wavelength range changes and the second wavelength range changes, the relationship between the two is: The difference (ie, the degree of transfer) between the first peak of energy in the first wavelength range and the second peak of energy in the second wavelength range is between 0.01% and 30%.

In addition, it should be noted that the emission filter 24 used by the detection device 2 is disposed downstream of the light receiver 22 , and the photofluorescence F generated by the excitation of the filler 11 is mainly Before being received by the light receiver 22, the photoluminescence F that is really needed can be filtered through the emission filter 24. In FIG. 2, the excitation light source 21 is set on the side of the beam splitter 25, so that The generated excitation light E first passes through the spectroscope 25, and then irradiates on the filler 11, and changes the optical path of the excitation light E through the spectroscope 25, so that the excitation light E is vertically incident (incidence angle equal to zero). ) method to irradiate the glue 11, but not limited to this.

In addition, when the excitation light source 21 irradiates the glue 11, in order to enhance the irradiated light intensity, the convex lens 26 is arranged to focus the light of the excitation light source 21 to enhance the light intensity, so that the light receiver 22 can receive the light. image is clearer.

In this embodiment, the excitation light source 21 illuminates the scraped glue 11 . Therefore, the place where the glue is flush with the surface 12 of the circuit board 1 has a copper chip layer, so the light will not be generated. Fluorescence, that is to say, the photoluminescence signal generated by the filler 11 is generated at the recess of the filler 11 (without the copper chip layer), and the photoluminescence at the recess of the filler 11 is obtained. After receiving the signal, the processing step 203 will be performed, the fluorescent image generated by the photo-fluorescence signal is received by the processing unit 23, and the fluorescent image is subjected to gray-scale conversion to obtain a glue-filled gray-scale image (not shown in the figure). ), it should be noted here that when the filler 11 is completely flush with the surface 12 of the circuit board 1, the filler 11 and the circuit board 1 without a recess will not generate photofluorescence The obtained grayscale image is in a completely black state, so the photoluminescence signal generated in the recess of the glue 11 can be judged from the completely black place after grayscale conversion.

Specifically, in the present embodiment, the determining step 204 is to compare the gray-scale image of the glue filling with a gray-scale image (not shown) of the surface of the surface 12 of the circuit board 1 . When the grayscale difference between the glue grayscale image and the surface grayscale image is greater than 10%, it is determined that the glue filling 11 is recessed into the blind hole 10, but it is not limited to this, and it may also be a depression of the glue filling 11 (with The grayscale images of the filler 11 flush with the surface 11 (no photofluorescence) are compared with each other.

Referring to FIG. 3 and FIG. 4 , FIG. 3 and FIG. 4 are the fluorescent images received by the light receiver 22 of the detection method of this embodiment. From the fluorescent images, it can be seen that the fluorescent images of the recesses of the filler 11 Compared with the place where no fluorescence is generated, it has an ultra-high contrast and has obvious identification, and can more easily identify the depression of the glue 11 and the difference with the circuit board 1 .

For example, when comparing the difference between the flush portion of the filler 11 and the recessed portion of the filler 11, when the fluorescent image is converted into gray scales, there is an obvious difference in gray scale between the two; , when the filler 11 is flush with the surface 12 of the circuit board 1, and the top surface 11 has a copper chip layer, when the copper chip layer is irradiated by the excitation light source 21, no photofluorescence will be generated, and therefore Part of the fluorescent properties of the glue filler 11 are shielded; moreover, if the circuit board 1 collides with the depression, the excitation light source 21 will not generate photofluorescence, so that the detected image of the circuit board 1 is In a completely black state, in other words, when the entire circuit board 1 is irradiated with the excitation light source 21 of the detection method of the present invention, the depressions other than the filler 11 will not have fluorescent characteristics and will be in a relatively dark state. In order to make the fluorescent image in the recess of the glue filler 11 have high contrast, it can be more clearly identified.

It can be seen from this that when the circuit board 1 is detected using the reflected light of the existing optical detection, it is easy to detect the depressions of the circuit board 1 caused by collision or other factors together, that is, without using the fluorescent light of the present invention. When exposed to light, the concavity of the glue filler 11 is very similar to the concavity of the circuit board 1, so that all the concavities are grasped, which is likely to cause subsequent detection errors.

To sum up, in the detection method of the present invention, the filler 11 is irradiated with the excitation light E generated by the excitation light source 21 to generate the photofluorescence light F, and then the light receiver 22 receives the photofluorescence light F and generates the photofluorescence light F. The fluorescent image and the grayscale conversion are performed by the processing unit 23 to determine whether the top surface 110 of the glue 11 is recessed outside the blind hole 10, and the recess of the circuit board itself can also be excluded, so the invention can indeed be achieved. Purpose.

However, the above are only examples of the present invention, and should not limit the scope of implementation of the present invention. Any simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the patent specification are still included in the scope of the present invention. within the scope of the invention patent.

1: circuit board 10: Blind hole 11: Filling 110: top surface 12: Surface 2: Detection device 201: Preparation steps 202: Detection step 203: Processing steps 204: Judgment step 21: Excitation light source 22: Optical receiver 23: Processing unit 24: Emission filter 25: Beamsplitter 26: Convex Lens E: Excitation light F: Photofluorescence

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: 1 is a schematic flow diagram illustrating an implementation flow of the detection method of the present invention; 2 is a schematic diagram illustrating a detection device used in the detection method of the present invention; 3 is an image diagram illustrating the detection method of the present invention to detect a glue filling state in a blind hole; and FIG. 4 is an image diagram illustrating another state in which the glue filling in the blind hole is detected by the detection method of the present invention.

201: Preparation steps

202: Detection step

203: Processing steps

204: Judgment step

Claims (7)

A method for detecting glue filling in blind holes of a circuit board, which is suitable for detecting whether a glue filling in a blind hole of a circuit board is recessed into the blind hole compared with a surface of the circuit board, and the detection method comprises: a In a preparation step, a detection device is prepared, the detection device includes an excitation light source with a first wavelength range, a light receiver, and a processing unit connected with the light receiver; in a detection step, the excitation light source is used to illuminate the Filling glue, so that the filling glue is excited by the excitation light source to generate a photofluorescence having a second wavelength range different from the first wavelength range, and the light receiver can receive the photofluorescence and generate a corresponding photoluminescence A fluorescent signal, wherein the first wavelength range has a first energy peak, the second wavelength range has an energy second peak, and the difference between the energy first peak and the energy second peak is between 0.01% and 30% ; a processing step, the processing unit receives the photoluminescence signal and performs grayscale conversion to obtain a glue-filled grayscale image; and a judging step, the judging step is to combine the glue-filled grayscale image with the circuit board Compared with a surface grayscale image of the surface, when the grayscale difference between the glue filling grayscale image and the surface grayscale image is greater than 10%, it is determined that the glue filling is recessed into the blind hole. The method for detecting glue filling in blind holes of a circuit board according to claim 1, wherein the first wavelength range is between 460 nm and 490 nm, and the second wavelength range is between 510 nm and 530 nm. The detection method for blind hole filling of a circuit board according to claim 1, wherein the detection The measuring device also includes an emission filter downstream of the light receiver, and a beam splitter downstream of the emission filter. The method for detecting glue filling in blind holes of a circuit board as claimed in claim 3, wherein the excitation light source is arranged on one side of the spectroscope, so that an excitation light generated by the excitation light source is irradiated to the glue through the spectroscope, and the filling The photofluorescence generated by the glue passes through the emission filter to the light receiver. The method for detecting glue filling in blind holes of a circuit board according to claim 1, wherein the detection device further comprises a convex lens disposed downstream of the excitation light source. The method for detecting glue filling in blind holes of a circuit board according to claim 1, wherein the excitation light source can be selected from a light emitting diode or a laser light source. The method for detecting glue filling in blind holes of a circuit board according to claim 1, wherein the light receiver can be selected from a camera.

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