JP3340013B2 - Defect detection method for coverlay film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting defects in a coverlay film, and more particularly to a method for detecting defects such as foreign matter, bubbles, glue chips, and gel in a polyimide coverlay film used for a printed circuit or the like. .

[0002]

2. Description of the Related Art In recent years, weight reduction of electronic products,
With the miniaturization, thinning, and enhancement of functions, demand for printed circuit boards is increasing. Among them, flexible printed circuit boards are used in a wider range, and demand is growing more and more. In recent years, the functionalities of printed circuit boards have become more sophisticated and fine patterns have been developed, and the demand for surface defects on flexible substrates has become more and more severe. In particular, foreign substances, air bubbles, pinholes, glue defects, gels, etc. Defects cause product defects, such as poor embedding, poor insulation, peel strength, and reduced folding endurance, for fine pattern printed circuit boards.
Therefore, it is necessary to detect these defects. Conventionally, this kind of inspection is performed by a visual inspection for observing with the naked eye of a human.

[0003]

However, in the visual inspection, there is an individual difference in the defect judgment criteria, and the concentration cannot be maintained, and the defect is often overlooked. It is desired to establish a method of inspecting and marking a defect position.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for detecting a defect of a cover lay film which solves such disadvantages and problems, and applies an adhesive to a polyimide film in a cover lay film manufacturing process. and Engineering, dried with a drier, before laminating the release agent, lamination
At a defect detection position within 2,000 mm before
The roll interval of the projecting part is 100 to 400 mm, and the wavelength is 0.3 to 1.1 μm from the polyimide film side of the coverlay film.
Of transmitted light and the resolution of transmitted light
C with a density of 5 bits or more per mm in the width direction
Light is received by the image element of the CD line sensor, and the voltage change caused by the amount of light is signal-processed. Identify and detect defects
The detected defect is determined by the position of the coverlay film.
This is a method for detecting a defect in a cover lay film, characterized by marking an edge portion of the cover lay film.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows a component arrangement in the defect detection method of the present invention, and FIG. 1B shows a component configuration. In FIG. 1A, reference numeral 1 denotes an adhesive-coated polyimide film (the arrow side indicates the polyimide film side, and the opposite side indicates the adhesive-coated layer side);
Is a CCD camera, 4 is a release material, 5 is a laminating roll,
Reference numeral 6 denotes an encoder, and 7 denotes a marking device. In the method for detecting a defect of a coverlay film according to the present invention, light is applied from the polyimide film side of the coverlay film 1 coated with an adhesive and dried, and transmitted light is received by an image element on a CCD line sensor, and is generated by the amount of light. The voltage change is signal-processed, and it is determined that there is a defect when the signal level is equal to or higher than a preset light-dark reference value or equal to or lower than the reference value. However, in the present invention, a transmission-type defect detection device is used. It is also possible to detect hard-to-detect defects such as foreign substances buried in the adhesive and the adhesive gel.

The resolution of the CCD line sensor in the method of the present invention is 1 mm with respect to the width direction of the coverlay film.
A density of 5 bits or more per pixel is good, and if it is less than 5 bits, sufficient resolution cannot be obtained. This gives a diameter of 0.2
It suffices if a minute defect up to about mm can be detected. FIG.
Is a detailed view of the light source 2 and the CCD camera 3 in FIG. 1A, 9 is a lens, 10 is a CCD line sensor, and 11 is a defect of the adhesive layer. As the light source 2 for applying light from the polyimide film side (arrow side) of the coverlay film 1,
Considering the sensitivity wavelength and scanning cycle of the line sensor, for example, a transmission light using a high-frequency (20 kHz or more) fluorescent lamp or a halogen lamp as a light source, a fiber light using an optical fiber using a laser or the like as a light source, and the like are preferable. Used for A condenser lens may be attached to the light source to increase the directivity of light. At this time, the wavelength of light is 0.3 ~
It is preferable to use a light source of 1.1 μm. It is appropriate to set the defect detection position of the coverlay film behind the process where surface defects of the film may occur, apply an adhesive, dry with an inline dryer, and laminate with the release material. It is better to be 2,000 mm or less, preferably 1,500 mm before the roll, so that it is possible to prevent foreign matter from entering the cover lay film and the occurrence of defects after the inspection. Roll spacing between defect detection sites is 100 to 400 mm
When the thickness is preferably 100 to 300 mm, wrinkles, fluttering and meandering of the film can be suppressed, the detecting section can be stabilized, and malfunction at the time of detecting a defect can be eliminated. The roll interval is the distance between the rolls before and after the defect detection device is sandwiched. In addition, after detecting a defect by the method described above, a labeler, an ink jetter, a laser or the like is provided at the edge of the film at the detection position, and if the marking is performed, the defect can be detected continuously in-line, and the film at the detection position can be detected. If the labeling is performed on the edge portion, the adhesive of the label will not be transferred to the copper foil.

Next, a description will be given of a component configuration used in the method for detecting a defect of a coverlay film of the present invention. This is Figure 1
As shown in (b), a CCD line sensor, a transmitted light differentiation / binarization processing circuit, a defect determination circuit, a shift register,
The picture elements, which consist of an encoder and a marking device, are arranged in a line in the width direction of the coverlay film to be inspected. The picture elements receive different amounts of transmitted light condensed by the lens, and the picture elements are generated by receiving the light. Since the voltage is output as a pixel data signal, this is differentiated through an image processing device,
A binarization process is performed. At this time, the signal S / N (Signal
/ Noise) ratio to facilitate defect determination. FIG.
FIG. 5 shows the steps of differential processing and binarization processing as an example of signal processing by this component configuration. The dark defect 13 and the light defect 14 of the video signal shown in FIG. The waveform becomes a differential waveform shown in b) and is binarized to obtain a signal of the binarized waveform shown in (c). Therefore, two signals excluding the signals at the edges at both ends are taken out as defects.
At this time, if the difference between the signal and the noise is small, noise may be picked up, which is not preferable. The defect signal is compared with a light / dark reference value (light amount of the cover lay film when there is no foreign substance) adjusted in advance by a judgment circuit, and when this exceeds the reference value or is less than the reference value, it is judged as a defect. The result is marked. If there is a pinhole, a value exceeding the reference value is detected, and if there is a foreign substance, a value lower than the reference value is detected.

In addition, since the detection signal may be disturbed at the edge of the product due to uneven coating of the adhesive and the film may meander a little, a range of 10 mm from the edge is masked and excluded from inspection. Therefore, it is sufficient to remove the signal at the edge portion and compare it with the reference value. The defect signal is compared with the light / dark reference value adjusted in advance by the determination circuit as described above, and if a signal that is higher than the light reference value and a signal that is lower than the dark reference value are measured during the scanning cycle, it is determined to be defective. And
The timing is output to the marking device with the signal from the encoder and the marking is performed. Labelers, ink jetters, lasers, and the like are exemplified as marking devices for marking defective positions of the product. The marking is preferably made at the edge of the coverlay film so as not to damage or stain the product.

This scanning cycle is calculated by the following equation. Scanning cycle (sec) = minimum defect diameter (mm) / line speed (mm / sec) Scanning cycle should be set in the range of 0.25 to 10msec. Generally, set to a value smaller than the calculated value to prevent detection omission. Good to do. The minimum defect diameter represents the minimum defect diameter that must be detected. The line speed is preferably between 50 and 400 mm / sec. There are various types of defects in the cover lay film detected by the present invention, for example, bubbles and pinholes are permeable defects, the amount of light is larger than the baseline of the cover lay ground, and exceeds the reference value on the light side Is determined to be defective. In addition, the foreign matter or the gel is a light-shielding defect, and is determined to be a defect when the amount of light is lower than the base line of the coverlay and falls below the reference value on the dark side.

The cover lay film is produced by applying an adhesive to a polyimide film, drying and laminating the polyimide film with a release material. The polyimide film may be a commercially available product, which generally has a thickness of 12.5 to 125 μm and a width of 500 to 1,016 mm, but is preferably dried in advance because it easily absorbs moisture.

Further, since the adhesive is required to have high adhesive strength and heat resistance to withstand the use of solder or the like,
Epoxy resin, NBR-phenol resin, phenol-butyral resin, epoxy-NBR resin, epoxy-polyester resin, epoxy-nylon resin,
Examples thereof include an epoxy-acrylic resin, an acrylic resin, a polyamide-epoxy-phenolic resin, a polyimide resin, and a silicone resin. The thickness of this resin layer is preferably 5 to 30 μm when dried.

Examples of the release material include a release film or a release film such as a polyethylene film, a polypropylene film, a TPX film, and a silicone film, such as a polyester film with a silicone release agent, or a film coated with a polyolefin film such as polyethylene or polypropylene. However, these may be subjected to a surface treatment such as a low-temperature plasma treatment or a corona discharge treatment in order to improve the adhesion to the polyimide film.

[0013]

EXAMPLES Next, examples of the present invention and comparative examples will be described, but these do not limit the present invention. Example 1 Kapton (trade name, manufactured by Dupont Toray Co., Ltd.), a polyimide film having a thickness of 25 μm and a width of 508 mm, was placed in a cylindrical shape with four electrodes, and the film was placed on the outer periphery of the electrodes at a distance of 40 mm outside the electrodes. Using a continuous plasma processing apparatus moved at 50 m / min, low-temperature plasma processing was performed under the conditions of a vacuum degree of 0.1 Torr, an oxygen flow rate of 1.0 L / min, an applied voltage of 2 kv, a frequency of 110 kHz, and a power of 30 kw.

Next, with the parts arrangement shown in FIG. 1A, epoxy-NB was applied to the polyimide film at a line speed of 5 m / min.
The R-based adhesive is coated with a roll coater so that the thickness after drying becomes 30 μm, and the solvent of the adhesive is dried and removed at 50 to 140 ° C. with an in-line dryer, and the adhesive is semi-cured. Before the laminating roll 500
The coverlay film was inspected for defects in mm.
The defect detector is a simple defect detector shown in Fig. 2 ・ LS-30
[Takenaka System Equipment Co., Ltd.], a high-frequency fluorescent lamp as the light source 2, and light transmitted through the film (sensitivity wavelength
(0.35 to 0.6 μm) was condensed on the image element on the CCD line sensor 10 through the lens 9 to detect a change in transmitted light.
At this time, two CCD line sensors 10 each having a 2,048-bit number of pixels were arranged in the product width direction with respect to the 520 mm width of the cover lay film 1, and the number of pixels per 1 mm was 7.9 bits, and a defect was detected at a scanning cycle of 2 msec ( However, 10
mm was masked).

In this case, the roll interval of the detecting section is 200 mm.
The film was stable without wrinkles, flutter, or meandering. Detected defects were obtained by thermocompression bonding the film to a silicone-based release material coated with a silicone-based release agent on a polyethylene film using a laminating roll (roll temperature 100 ° C, pressure 2.0 kg / cm). The edge of the film at the position was marked by a labeler. Table 1 shows the number of detected defects. Next, this coverlay product is wound 100m, and the number of defects is determined by visual inspection in the slitting process as before, and the number of missed defects is compared with the number of defects detected by the defect detection device. When the number of detection errors that detected
The results shown in Table 1 were obtained. As a result, the defect was detected without being overlooked, and there was no detection error.

Example 2 Kapton (described above) of a polyimide film having a thickness of 25 μm and a width of 508 mm was subjected to low-temperature plasma treatment by the same continuous plasma processing apparatus as in Example 1, and then an epoxy-NBR adhesive was applied at a line speed of 5 m / min. Is coated with a roll coater so that the thickness after drying becomes 30 μm, the solvent of the adhesive is dried and removed at 50 to 140 ° C. with an inline drier, and the adhesive is semi-cured. At the point of mm, the coverlay film was inspected for defects.

The defect detection device was the simple defect detection device LS-30 (described above) used in Example 1, and the number of pixels per 1 mm was 7.9 bits, and the defect was detected at a scanning period of 2 msec.
Although the roll interval of the detection section was set to 300 mm, the film was stable without wrinkles, fluttering and meandering. Detected defects, laminate the film (roll temperature 100 ℃,
A silicone-based release material (described above) was thermocompression-bonded to the product at a pressure of 2.0 kg / cm) to form a product, and the edge of the film at the position of the product defect was marked with a labeler. Table 1 shows the number of detected defects. This coverlay product was wound up 100 m and visually inspected in the slitting process as usual, and the number of missed defects and the number of detection errors were obtained. The results shown in Table 1 were obtained. As a result, the defect could be detected without being overlooked, and there was no detection error.

Example 3 Kapton (described above) of a polyimide film having a thickness of 25 μm and a width of 508 mm was subjected to low-temperature plasma treatment in the same continuous plasma processing apparatus as in Example 1, and then an epoxy-NBR adhesive was applied at a line speed of 5 m / min. Is coated with a roll coater so that the thickness after drying is 20 μm, and the solvent of the adhesive is dried and removed at 50 to 140 ° C. with an inline dryer to semi-harden the adhesive. At the point of mm, the coverlay film was inspected for defects.

This defect detection apparatus was the simple defect detection apparatus LS-30 (described above) used in the first embodiment, and the number of pixels per 1 mm was set to 5.0 bits, and defect detection was performed at a scanning cycle of 2 msec. Further, although the roll interval of the detecting section was set to 400 mm, the film was stable without wrinkles, flutter and meandering. Detected defects are obtained by laminating the film (roll temperature 100 ° C, pressure 2.0kg / cm) with a silicone-based release material (described above) and thermocompressing it into a product. Marked by.
Table 1 shows the number of detected defects. The coverlay product was visually inspected in the conventional manner in the winding step of 100 m and the slitting process, and the number of missed defects and detection errors were obtained. The results shown in Table 1 were obtained. As a result, the defect could be detected without being overlooked, and there was no detection error.

Comparative Example 1 Kapton (described above), a polyimide film having a thickness of 25 μm and a width of 508 mm, was subjected to low-temperature plasma treatment using the same continuous plasma processing apparatus as in Example 1, and then an epoxy-NBR adhesive was applied at a line speed of 5 m / min. Is coated with a roll coater so that the thickness after drying becomes 30 μm, the solvent of the adhesive is dried and removed at 50 to 140 ° C. with an inline drier, and the adhesive is semi-cured. At the point of mm, the coverlay film was inspected for defects.

The inspection device is the simple defect detection device LS-30 (described above) used in the first embodiment, and the number of pixels per 1 mm is
At 3.9 bits, defect detection was performed at a scanning cycle of 2 msec. Although the roll interval of the detection section was set to 200 mm, the film was stable without wrinkles, flutter and meandering. Detected defects laminate film (roll temperature 1
After thermocompression bonding with a silicone-based release material (described above) at 00 ° C. and a pressure of 2.0 kg / cm) to obtain a product, the edge of the film at the position of the product defect was marked with a labeler. Table 1 shows the number of detected defects. Also, this coverlay product is 100
Inspection was carried out visually in the conventional manner in the m-winding and slitting steps, and the missed defects and detection errors were determined. The results shown in Table 1 were obtained. As a result, a small defect of 0.2 mm was missed due to low resolution.

Comparative Example 2 Kapton (described above) of a polyimide film having a thickness of 25 μm and a width of 508 mm was subjected to low-temperature plasma treatment by the same continuous plasma processing apparatus as in Example 1, and then an epoxy-NBR adhesive was applied at a line speed of 5 m / min. Coat with a roll coater so that the thickness after drying becomes 30 μm, dry and remove the adhesive solvent at 50 to 140 ° C with an inline dryer, semi-harden the adhesive, and cover at 1,000 mm before the inline dryer The ray film was inspected for defects.

The inspection device is the simple defect detection device LS-30 (described above) used in the first embodiment, and the number of pixels per 1 mm is
At 7.9 bits, defect detection was performed at a scanning cycle of 2 msec. Although the roll interval of the detection section was set to 200 mm, the film was stable without wrinkles, flutter and meandering. Detected defects are obtained by thermocompression bonding the film with a silicone-based release material (described above) using a laminating roll (roll temperature 100 ° C, pressure 2.0 kg / cm) to produce a product. Marked by labeler. Table 1 shows the number of detected defects. In addition, this coverlay product was visually inspected in the conventional manner in a 100 m winding and slitting process, and missing defects and detection errors were obtained. As a result, the results shown in Table 1 below were obtained. This defect was missed because the air bubbles generated in the dryer could not be detected because the defect was detected in the above.

COMPARATIVE EXAMPLE 3 Kapton (described above) of a polyimide film having a thickness of 25 μm and a width of 508 mm was subjected to low-temperature plasma treatment using the same continuous plasma processing apparatus as in Example 1, and epoxy-NB was applied at a line speed of 5 m / min.
The R-based adhesive is coated with a roll coater so that the thickness after drying becomes 30 μm, and the solvent of the adhesive is dried and removed at 50 to 140 ° C. with an in-line dryer, and the adhesive is semi-cured. Before laminating roll 1,0
A defect inspection of the coverlay film was performed at a point of 00 mm.

The inspection device is the simple defect detection device LS-30 (described above) used in the first embodiment, and the number of pixels per 1 mm is
At 3.9 bits, defect detection was performed at a scanning cycle of 2 msec. When the roll interval of the detection unit was set to 700 mm, the film fluttered. Detected defects include laminating the film on a roll (roll temperature 100 ° C, pressure 2.0kg / cm)
After thermocompression bonding with a silicone-based release material (described above) to form a product, marking was performed on the film edge at the position of the product defect with a labeler. Table 1 shows the number of detected defects. In addition, this coverlay product was visually inspected in the conventional manner in a 100m winding and slitting process, and missing defects and detection errors were obtained. The results shown in Table 1 were obtained, but the film fluttered. As a result, 12 detection errors occurred.

Comparative Example 4 A 25 μm thick, 508 mm wide polyimide film Kapton (described above) was subjected to low-temperature plasma treatment with the same continuous plasma treatment apparatus as in Example 1, and epoxy-NB was applied at a line speed of 5 m / min.
The R-based adhesive is coated with a roll coater so that the thickness after drying becomes 30 μm, and the solvent of the adhesive is dried and removed at 50 to 140 ° C. with an in-line dryer, and the adhesive is semi-cured. Before laminating roll 1,0
A defect inspection of the coverlay film was performed at a point of 00 mm.

The inspection device is the simple defect detection device LS-30 (described above) used in the first embodiment, and the number of pixels per 1 mm is
At 7.9 bits, defect detection was performed at a scanning cycle of 2 msec. Although the roll interval of the detection unit was 300 mm, the film was stable without wrinkles, fluttering and meandering. Detected defects laminated film roll (roll temperature 1
After thermocompression bonding with a silicone release material (described above) at 00 ° C. and a pressure of 2.0 kg / cm) to obtain a product, the defect position of the product was directly marked with a labeler. Table 1 shows the number of detected defects. This coverlay product was visually inspected in the conventional way in the slitting process with 100 m winding and slitting process. The results shown in Table 1 were obtained when missing defects and detection errors were obtained. The adhesive on the label has been transferred to the copper foil.

Comparative Example 5 Kapton (described above), which is a polyimide film having a thickness of 25 μm and a width of 508 mm, was subjected to low-temperature plasma treatment in the same continuous plasma processing apparatus as in Example 1, and epoxy-NB was applied at a line speed of 5 m / min.
The R-based adhesive is coated with a roll coater so that the thickness after drying becomes 30 μm, and the solvent of the adhesive is dried and removed at 50 to 140 ° C. with an inline drier, and the adhesive is semi-cured. After thermocompression bonding with a silicone-based release material (described above) at a temperature of 100 ° C and a pressure of 2.0 kg / cm), this is rolled up as a coverlay product for 100 m, and is visually inspected as before in the slitting process. Find the number,
The slits were visually inspected again to determine missing defects and detection errors. The results shown in Table 1 were obtained. In addition, the visual inspection in the slitting process was not performed at a speed less than 1/2 that of the case where the defect detection device was used, so that there was an oversight, resulting in poor productivity.

[0029]

[Table 1]

[0030]

According to the present invention, defects such as air bubbles, foreign matter, pinholes, glue chips, and gels on a cover lay film can be automatically detected without any omission and can be marked. Inspection detection work that has been performed visually can be accurately performed based on objective numerical criteria, and labor can be saved.

[Brief description of the drawings]

FIGS. 1A and 1B show a component arrangement diagram and a component configuration diagram of a defect detection apparatus used in the present invention.

FIG. 2 is a perspective view of a defect detection device used in the present invention.

FIGS. 3A, 3B, and 3C show an example of a signal processing step of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Adhesive coating polyimide film 2 ... Light source 3 ... CCD camera 4 ... Release material 5 ... Laminating roll 6 ... Encoder 7 ... Marking device 8 ... In-line dryer 9 ... Lens 10 ... CCD line sensor 11 ... Defect of adhesive layer 12 … Edge 13… dark defect 14… bright defect

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshiji Sakaguchi 1 Towada, Kazu-gun, Kashima-gun, Ibaraki Pref. Shin-Etsu Chemical Co., Ltd. PVC Research Laboratory (56) References JP-A-7-306160 (JP) JP-A-4-264790 (JP, A) JP-A-6-235624 (JP, A) JP-A-4-359139 (JP, A) JP-A-6-242023 (JP, A) 6-147867 (JP, A) JP-A-58-173456 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/30 C08J 7/04 G01N 21/892

Claims (1)

(57) [Claims] In a coverlay film manufacturing process, an adhesive is applied to a polyimide film, dried with a drier, and laminated with a release material before lamination.
At the defect detection position within 2,000 mm before
The roll interval is 100 to 400 mm, and light with a wavelength of 0.3 to 1.1 μm is emitted from the polyimide film side of the coverlay film.
Irradiates the transmitted light with resolution in the width direction of the coverlay film
On the other hand, light is received by an image element of a CCD line sensor having a density of 5 bits or more per 1 mm, and a voltage change caused by the amount of light is signal-processed, and a signal level is equal to or higher than a preset light-dark reference value or lower than a reference value. Sometimes bubbles, foreign matter, gel, glue, etc. are identified as defects, detected and identified
The detected defect to the edge of the discrimination position of the coverlay film
A method for detecting a defect in a coverlay film, characterized by marking a part .