KR20050095223A - Apparatus and method for inspecting via hole of printed circuit board - Google Patents

Abstract

The present invention relates to a via hole inspection apparatus and method for a printed circuit board which can accurately determine whether a printed circuit board is defective by detecting an insulating resin residue remaining in a via hole of a printed circuit board using an optical method.

An apparatus for inspecting a via hole of a printed circuit board according to the present invention includes light emitting means for irradiating a light beam onto the via hole according to data about a coordinate of a via hole of a printed circuit board; Detecting means for detecting a light ray emitted from the via hole to determine whether an insulating resin remains; And control means for transmitting data on the coordinates of the via hole of the printed circuit board to the light emitting means, and determining whether the via hole is defective according to the data on the presence or absence of the insulating resin transmitted from the detection means. It is characterized by.

The via hole inspection method of a printed circuit board according to the present invention comprises the steps of: (A) aligning the position of the printed circuit board, and irradiating light rays on the via hole of the printed circuit board; (B) determining the presence or absence of insulating resin by detecting light rays emitted from the via hole; And (C) determining whether the printed circuit board is defective according to the presence or absence of the insulating resin.

Description

Apparatus and method for inspecting via hole of printed circuit board}

The present invention relates to an apparatus and a method for inspecting a via hole of a printed circuit board, and more particularly, by detecting an insulating resin residue remaining in a via hole of a printed circuit board using an optical method, thereby accurately determining whether the printed circuit board is defective. The present invention relates to a via hole inspection apparatus and method for a printed circuit board.

As the trend of light and shortening of electronic products has recently accelerated, only the necessary circuit layers are connected by connecting the necessary circuit layers rather than the plated through hole processing method implemented in a multi-layer printed circuit board. There is an increasing production of printed circuit boards that employ a build-up method that implements bonding.

The printed circuit board using the build-up method applies sequential lamination without mass lamination of the multilayer printed circuit board, and processes the insulating layer with a laser to form a junction between circuit layers. By forming a via hole diameter of 0.15 mm or less, which could not be realized in a mechanical drill in a substrate, it is possible to implement a ball pad of a fine ball grid array (BGA), increase wiring density through interlayer connection, and thin and thin end of an electronic product. Contributes to digestion and improved performance.

The via hole of 0.15 mm or less is called a micro via hole, and is implemented by burning an insulating resin of a substrate such as Resin Coated Copper (RCC) using a carbon dioxide laser. In this carbon dioxide laser, a light source that emits light is generated from carbon dioxide, and the wavelength is a hot ray in the infrared region.

As described above, since the via hole is formed by burning the insulating resin of the substrate with a carbon dioxide laser of an infrared light source, an insulating resin residue remains on the capture pad of the via hole after laser processing. In order to remove the residual insulating resin residue after the laser processing, a desmear process is usually performed prior to the copper plating process of the via hole.

The desmear process chemically removes the insulating resin residue remaining on the capture pad after mechanical drilling or laser processing, and is classified into a dry desmear process and a wet desmear process.

The dry desmear process removes residues of insulating resin through plasma method, but it has very good quality, but because it is not batch production method, productivity is very low and initial equipment cost is very expensive, so it is a special purpose. Other than that, it is not applied.

The wet desmear process removes insulating resin residues using potassium permanganate (KMnO ₄ ), which is adopted by many printed circuit board manufacturers due to its ease of use, relatively good quality and low equipment costs.

However, as shown in FIG. 1, when copper plating is performed without completely removing the insulating resin residue of the via hole in the desmear process, an open phenomenon between circuit layers (circled in FIG. 1) occurs. There was this.

Therefore, in order to guarantee the perfect quality after the desmear process, the desmeared via holes are selectively inspected after laser processing, but the number of via holes in the printed circuit board is tens of thousands, which does not provide perfect quality assurance. there was.

2 is a schematic diagram showing the configuration of a via hole inspection apparatus for a printed circuit board using a conventional optical microscope.

As shown in FIG. 2, the via hole inspection apparatus 20 of the conventional printed circuit board includes an optical microscope 21 for inspecting the via hole 11 of the printed circuit board 10 subjected to carbon dioxide laser processing and performing a desmear process. It was examined using.

However, since the number of via holes 11 of the printed circuit board 10 reaches tens of thousands, and the size of the via holes 11 is very small, the inspector inspects all the via holes 11 of the printed circuit board 10. It is impossible, and the reliability of the inspection is very low, there is a problem that can not be guaranteed perfect quality.

In addition, since the inspector inspects the via hole 11 of the printed circuit board 10 with the optical microscope 21, a lot of manpower and time are required, and there is a problem that a difference in inspection standards occurs depending on the inspector.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a via hole inspection apparatus and method for a printed circuit board capable of detecting residues of insulating resin remaining in all via holes of a printed circuit board.

Another technical problem of the present invention is to provide a bar hole inspection apparatus of a printed circuit board of an AOI (Automatic Optical Inspection) apparatus using an optical method and an inspection method thereof.

In order to solve the above technical problem, a via hole inspection apparatus of a printed circuit board according to the present invention comprises a light emitting means for irradiating a light beam on the via hole according to the data on the coordinates of the via hole of the printed circuit board; Detecting means for detecting a light ray emitted from the via hole to determine whether an insulating resin remains; And control means for transmitting data on the coordinates of the via hole of the printed circuit board to the light emitting means, and determining whether the via hole is defective according to the data on the presence or absence of the insulating resin transmitted from the detection means. It is characterized by.

Preferably, the light emitting means of the via hole inspection apparatus for a printed circuit board according to the present invention is an ultraviolet light source including a deuterium lamp and a mercury lamp.

The detection means of the via-hole inspection apparatus of the printed circuit board according to the present invention, the photoelectric multiplier tube for detecting the light rays emitted from the via hole, and amplifies the magnitude of the signal for the light beam; And a photodetector connected to the photomultiplier and determining the presence or absence of an insulating resin based on a signal for the light beam amplified and transmitted from the photomultiplier.

The via hole inspection apparatus of the printed circuit board according to the present invention further comprises condensing means for condensing the light rays emitted from the light emitting means to the via holes of the printed circuit board and condensing the light rays emitted from the via holes to the detection means. It features.

The light collecting means of the via hole inspection apparatus of the printed circuit board according to the present invention comprises: an objective lens for condensing light rays emitted from the light emitting means to the via hole of the printed circuit board; And a reflecting mirror reflecting light rays emitted from the via holes and condensing them on the detection means.

The reflective mirror of the via hole inspection apparatus of the printed circuit board according to the present invention includes a predetermined opening for condensing the light rays emitted from the light emitting means to the via hole of the printed circuit board through the objective lens, and toward the detection means. It is preferable that it is formed in a predetermined concave shape.

The light collecting means of the via hole inspection apparatus of the printed circuit board according to the present invention comprises: an objective lens for condensing light rays emitted from the light emitting means to the via hole of the printed circuit board; And a light receiving lens for condensing the light rays emitted from the via holes to the detection means.

In order to solve the above technical problem, a method of inspecting a via hole of a printed circuit board according to the present invention includes: (A) aligning a position of a printed circuit board and irradiating light rays onto the via hole of the printed circuit board; (B) determining the presence or absence of insulating resin by detecting light rays emitted from the via hole; And (C) determining whether the printed circuit board is defective according to the presence or absence of the insulating resin.

The step of irradiating a light beam on the via hole of the printed circuit board in the step (A) of the method for inspecting the via hole of the printed circuit board according to the present invention is performed according to the data of the coordinates of the via hole of the printed circuit board. It is preferable to irradiate light rays on the via holes.

Hereinafter, an apparatus and a method for inspecting a via hole of a printed circuit board according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a schematic diagram showing the configuration of the via hole inspection apparatus of the printed circuit board according to an embodiment of the present invention, Figure 4 is an energy state showing the principle that light is emitted in accordance with the energy state of the chromophore in the insulating resin of the printed circuit board 5 is a cross-sectional view and a plan view of a via hole of a printed circuit board.

As shown in FIG. 3, the via hole inspection apparatus 200 according to the present invention includes a light emitting unit 210, a light collecting unit 220, a detection unit 230, and a control unit 240.

The light emitting means 210 is an ultraviolet light source such as a deuterium lamp or a mercury lamp, and is a printed circuit transmitted from the control means 240 to detect the residue of the insulating resin remaining in the via hole 110 of the printed circuit board 100. It serves to irradiate light rays based on data on the coordinates of the via hole 110 of the substrate 100.

The light collecting means 220 includes an objective lens 221 and a reflecting mirror 222, condenses the light emitted from the light emitting means 210 to the via hole 110 of the printed circuit board 100, and prints the printed circuit board ( The light beam emitted from the insulating resin remaining in the via hole 110 of the 100 is focused on the detection means 230.

The objective lens 221 condenses the light emitted from the light emitting means 210 to the via hole 110 of the printed circuit board 100 through a predetermined opening 222a of the reflective mirror 222.

The reflective mirror 222 collects light rays emitted from the insulating resin remaining in the via hole 110 of the printed circuit board 100 by the detection means 230. The reflective mirror 222 is formed in a predetermined concave shape in the direction of the detection means 230 so that a large amount of light rays are collected by the detection means 230, and the light emitted from the light emitting means 210 is printed through the objective lens. A predetermined opening 222a is formed to condense in the via hole 110 of the circuit board 100.

The detection means 230 includes a photo-multiplier tube 231 and a photodetector 232, and detects light rays emitted from the insulating resin remaining in the via hole 110 of the printed circuit board 100. It plays a role of judging whether residue of insulation resin remains.

The photomultiplier tube 231 is required when the chromophore is removed due to oxidation of the insulating resin in the via hole 110 during carbon dioxide laser processing, and the light emission signal is weak, and remains in the via hole 110 of the printed circuit board 100. It detects the light rays emitted from the insulating resin, and amplifies the magnitude of the signal for the light beams and transmits them to the photodetector 232.

The photodetector 232 detects the light rays emitted from the insulating resin remaining in the via hole 110 of the printed circuit board 100 and determines the presence or absence of residues of the insulating resin. In this case, after being amplified through the photomultiplier tube 231, it is possible to determine whether the insulation resin residue remains.

The control means 240 is connected to the light emitting means 210 and the detecting means 230, and transmits data about the coordinates of the via hole 110 formed on the printed circuit board 100 to the light emitting means 210 for inspection. Can be irradiated only to the via holes 110 that need to be applied, and each of the via holes 110 formed on the printed circuit board 100 according to the data on the residual resin residues determined by the detection means 230 It is used to judge the defect.

On the other hand, the insulation resin of the printed circuit board 100 is a BT resin, a high Tg multifunctional epoxy (polypropylene oxide), polyimide (polyimide) and the like glass transition temperature is used. Common to these various insulating resins is the inclusion of chromophores that absorb and emit ultraviolet light, such as the benzene ring, which has conjugated double bonds.

Referring to FIG. 4, photons of the energy E ₀ = hν ₀ emitted from the light emitting means 210 (where h is Planck's constant and ν ₀ is the frequency of photons emitted from the light emitting means 210) are the residues of the insulating resin residue. The electrons of the chromophore are transferred from the ground state to the first excited state. Since the energy state of the electrons transitioned to the first excited state is an unstable state, the electrons of the chromophore are transferred to the original ground state and energy E _0. Emits a photon of = hν ₀ . Since the photons transitioned from the first excited state to the ground state have the same energy as the photons emitted from the light emitting unit 210, the photons overlap each other during data analysis, and thus it is difficult to determine whether the insulating resin residue remains.

However, when electrons transferred to the first excited state are transferred to the second excited state of the chromophore by various factors and then to the ground state, the energy E ₁ = hν ₁ (where ν ₁ is an insulating resin chromophore). Emit photons of the photon's frequency). Since the photons transitioned from the second excited state to the ground state have inherent energy according to the insulating resin, and have different energy from photons emitted from the light emitting means 210, they are generated as signals separated from each other during data analysis. Therefore, it is possible to easily determine whether the insulation resin residue remains.

Photons of the energy E ₁ emitted from the insulating resin of the via hole 110 are amplified in the photomultiplier 231 and then transmitted to the photodetector 232. According to the magnitude of the signal of the photons of the transmitted energy E ₁ , the photodetector 232 determines whether residual insulating resin residues remain, transmits the data to the control means 240, and the control means 240 transmits the It may be determined whether the via hole 110 of the printed circuit board 100 is defective based on the data on the presence or absence of the insulation resin.

Meanwhile, as shown in FIG. 5, the CO 2 laser processed via hole 110 is processed to have a wider taper in the upper layer of the printed circuit board 100 and a narrower taper in the capture pad 112. . When the top surface of the printed circuit board 100 having the via holes 110 is processed, the sidewalls 111 of the tapered via holes 110 are exposed, so that the light emitted from the light emitting unit 210 interacts with the insulating resin layer. Therefore, an error may occur in the signal for the light beam detected by the detection means 230. However, the via hole inspection apparatus 200 of the printed circuit board according to the present invention adjusts the light emitting means 210 and the light collecting means 220 to irradiate only the exposed capture pad 112 of the via hole 110, thereby preventing such an error. You can prevent it.

6 is a flowchart illustrating a method of inspecting a via hole of a printed circuit board according to an exemplary embodiment of the present invention.

As shown in FIG. 6, the control means 240 of the via hole inspection apparatus 200 of the printed circuit board receives the coordinates of the via hole 110 of the printed circuit board 100 processed by the carbon dioxide laser (S110). Only via holes 110 to be inspected may be inspected based on the coordinates of the via holes 110.

On the other hand, the via hole inspection apparatus 200 of the printed circuit board and the printed circuit board 100 on which the via holes 110 are formed are aligned (S120).

Based on the coordinates of the via hole 110 transmitted from the control means 240, the light emitting means 210 irradiates a light beam onto the via hole 110 of the printed circuit board 100 (S130). In this case, the light rays emitted from the light emitting means 210 are collected in the via hole 110 by the light collecting means 220.

The detection means 230 detects the light rays emitted from the via hole 110 of the printed circuit board 100 (S140), and analyzes the detected light rays (for example, comparing them with data of good quality products) of the insulating resin. It is determined whether there is a residual (S150).

When the insulating resin remains, the control means 240 transmits the printed circuit board 100 to a reprocessing process such as a carbon dioxide laser process or a desmear process if the degree of defect is minor, and to a waste disposal process if the degree of defect is severe. It transmits (S160).

On the other hand, if the insulating resin does not remain, the control means 240 transmits the printed circuit board 100 in a subsequent process such as copper plating (S170).

7 is a schematic view showing the configuration of a via hole inspection apparatus 300 of a printed circuit board according to another embodiment of the present invention, and includes a light emitting unit 310, a light collecting unit 320, a detection unit 330, and a control unit 340. ).

When the via hole inspection apparatus 300 of the printed circuit board of FIG. 7 is compared with the via hole inspection apparatus 200 of the printed circuit board of FIG. 3, the inspection apparatus of FIG. 7 includes the objective lens 321 and the light collecting means 320. 3, the inspection apparatus of FIG. 3 differs in that the light collecting means 220 is composed of the objective lens 221 and the reflecting mirror 222.

The via hole inspection apparatus 300 of the printed circuit board of FIG. 7 includes a position of the light receiving lens 322 that condenses the light emitted from the residue of the insulating resin of the via hole 110 to the detection means 330, and thus the detection means ( 330 has the advantage of being able to freely adjust the position.

Although the present invention has been described above, this is only one embodiment, and it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the technical spirit of the present invention. However, it will be apparent from the following claims that they fall within the scope of the invention.

As described above, an apparatus and method for inspecting a via hole of a printed circuit board according to the present invention is an AOI (Automatic Optical Inspection) apparatus capable of detecting residues of insulating resin remaining in a via hole of a printed circuit board using an optical method, and an inspection thereof. Provide a method.

Therefore, the via hole inspection apparatus and method of the printed circuit board according to the present invention can objectively determine whether the printed circuit board is defective, thereby improving the reliability of the product.

In addition, the via hole inspection apparatus and method of the printed circuit board according to the present invention can inspect all the via holes of the printed circuit board, and also has the effect of reducing the manpower and time required to inspect the via holes.

1 is a micrograph showing a cross section of a via hole in which an open phenomenon occurs between circuit layers of a printed circuit board.

Figure 2 is a schematic diagram showing the configuration of a via hole inspection apparatus for a printed circuit board using a conventional optical microscope.

Figure 3 is a schematic diagram showing the configuration of a via hole inspection apparatus of a printed circuit board according to an embodiment of the present invention.

Figure 4 is a schematic diagram of the energy state showing the principle that light is emitted in accordance with the energy state of the chromophore in the insulating resin of the printed circuit board.

5 is a cross-sectional view and a plan view of a via hole of a printed circuit board.

6 is a flowchart illustrating a method of inspecting a via hole of a printed circuit board according to an exemplary embodiment of the present invention.

7 is a schematic view showing the configuration of a via-hole inspection apparatus of a printed circuit board according to another embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

100: printed circuit board 110: via hole

111: sidewall of the via hole 112: capture pad

200, 300: Via hole inspection device of the printed circuit board

210, 310: light emitting means 220, 320: light collecting means

221, 321: objective lens 222: reflective mirror

222a: opening 230 of reflective mirror 230, detection means

231, 331: photomultiplier tube 232, 332: photodetector

240, 340: control means 322: light receiving lens

Claims (9)

Light emitting means for irradiating light rays onto the via holes according to data on the coordinates of the via holes of the printed circuit board; Detecting means for detecting a light ray emitted from the via hole to determine whether an insulating resin remains; And And control means for transmitting data on the coordinates of the via hole of the printed circuit board to the light emitting means, and determining whether the via hole is defective according to the data on the presence or absence of the insulating resin transmitted from the detection means. A via hole inspection apparatus for a printed circuit board. The method of claim 1, The light emitting means is a via hole inspection apparatus for a printed circuit board, characterized in that the ultraviolet light source including a deuterium lamp and a mercury lamp. The method of claim 1, wherein the detection means, An photomultiplier tube for detecting light rays emitted from the via holes and amplifying the magnitude of the signal with respect to the light rays; And A photodetector connected to the photomultiplier and including a photo detector to determine whether an insulating resin remains on the basis of a signal for the light beam amplified and transmitted by the photomultiplier; . The method of claim 1, And a light collecting means for condensing the light rays emitted from the light emitting means to the via holes of the printed circuit board and condensing the light rays emitted from the via holes to the detection means. The method of claim 4, wherein the light collecting means, An objective lens for condensing the light rays emitted from the light emitting means to the via holes of the printed circuit board; And And a reflecting mirror reflecting light rays emitted from the via holes and condensing them on the detecting means. The method of claim 5, The reflective mirror includes a predetermined opening for condensing light rays emitted from the light emitting means into the via hole of the printed circuit board through the objective lens, and is formed in a predetermined concave shape in the direction of the detection means. Via hole inspection device on the circuit board. The method of claim 4, wherein the light collecting means, An objective lens for condensing the light rays emitted from the light emitting means to the via holes of the printed circuit board; And And a light receiving lens for condensing the light rays emitted from the via hole to the detection means. (A) aligning the position of the printed circuit board, and irradiating light rays onto the via holes of the printed circuit board; (B) determining the presence or absence of insulating resin by detecting light rays emitted from the via hole; And (C) a method of inspecting a via hole of a printed circuit board, the method comprising determining whether the printed circuit board is defective according to the presence or absence of the insulating resin. The method of claim 8, The irradiating light beam on the via hole of the printed circuit board in the step (A) is characterized in that for irradiating the light beam on the via hole of the printed circuit board according to the data about the coordinates of the via hole of the printed circuit board How to inspect the via holes on the circuit board.