JP2802845B2 - Face plate foreign matter inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting foreign substances adhering to a face plate, and more particularly to a printed board base material on which a wiring pattern is not formed as a face plate to be inspected and a mask plate for the same. The present invention relates to a method of aligning a face plate with a foreign object detection optical system and a method of removing noise.

[0002]

2. Description of the Related Art A multilayer printed circuit board used for a large-sized computer is made of a resin base of copper foil, and a wiring pattern is projected and copied from a mask plate to the copper foil to produce printed circuit boards of each layer. Many of these are laminated to form a multilayer. 5A and 5B illustrate a manufacturing process of a printed circuit board. In FIG. 5A, reference numeral 1 denotes a substrate on which a wiring pattern is not formed, and a cross section of the substrate is formed by depositing a copper foil 1b on the surface of a resin base 1a. For this purpose, a resist material 1c is applied.
To further protect this, a Mylar thin film 1d is spread. (b) shows a mask plate 2, in which a photosensitive layer 2b of emulsion silver chloride (hereinafter simply referred to as an emulsion layer) 2b is applied to the surface of a glass plate 2a, and projection exposure is separately performed on the photosensitive layer. Thus, a wiring pattern 2c is formed. In this case, the thickness of the emulsion layer 2b does not change due to the light exposure, and the emulsion layer 2b is flat as before the printing. In (c), when the substrate 1 is brought into close contact with the mask plate 2 and irradiation light is irradiated from the mask plate side, the wiring pattern 2c
The portion of the resist material 1c corresponding to the above is exposed to light and developed and etched to transfer the wiring pattern to the copper foil 1b. The mylar thin film 1d and the resist agent 1c are both transparent, and the surface of the copper foil 1b has the property of irregularly reflecting light on a so-called satin rough surface.

If foreign matter adheres to the base material 1 or the mask plate 2, the wiring pattern transferred to the copper foil becomes defective, and the base material 1 is bent as shown in FIG. As a result, a gap is generated between the two, and the exposed wiring pattern is blurred, which is also defective. Further, when foreign matter adheres to the mask plate 2 or foreign matter adhered to the base material is transferred to the mask plate, all the wiring patterns transferred therefrom become defective, which is the worst. In this case, the higher the height of the foreign matter, the more easily the defocusing and the transfer of the foreign matter occur. Therefore, a foreign matter detection optical system in view of the height is required. On the other hand, a foreign matter detection optical system in terms of height has been devised by the inventor of the present invention, "No. 2-62849, Foreign matter detection optical system" and "No. A system noise elimination method has been applied for a patent.

The outline of the foreign matter detecting optical system 4 according to the above patent application will be described with reference to FIG. In (a), a substrate 1 or a mask plate 2 (hereinafter referred to as a face plate 1 or 2) is mounted on a mounting table of an XY moving mechanism (not shown), and its height is set to a reference height position. The laser beam L _T irradiated at low angles theta ₀ by projector 41 of the foreign material detecting optical system 4 with respect to this,
Scan by moving in the X direction. R ₀ indicates a reference irradiation position corresponding to the reference height position of the face plate. When foreign material p is adhered to the face plate 1 or 2, foreign material p as shown in (b) to generate scattered light S _P, it is received is condensed by the condenser lens 42 to the foreign object detector 43. Intensity of foreign matters scattered light S _P V varies with position in the X direction of the foreign matter p with respect to the irradiation angle θ of the laser beam L _T, as shown by the curve of (b), rises at the position of (a) (ii) falls at (reference irradiation position R _0), the scattering range is X _L. Intensity V and scattering range X _L of the scattered light S _P is greater the higher the height of the foreign object p. Foreign object detector 43
When storing light intensity of the scattered light S _P by the light receiving element 431,
Accumulation is proportional to V × X _L, the foreign matter p and its height is detected by the detection signal indicating this. Note that the reference irradiation position R ₀ in (b) is a point (or line) where the optical axis C of the light receiving system intersects the face plate, and even on the opposite side of the laser beam irradiation C, the laser beam regular reflection light L _R In the same manner as described above, the scattered light _SP is generated, and the accumulated amount of the received light amount is doubled by both. Next, an outline of the noise removal method according to the above patent application will be described with reference to FIG. (a), the laser beam L _T is independently reference irradiation position of the presence of foreign matter p R ₀
Irradiation is always performed. Since the surface of the face plate 1 or 2 is smooth but somewhat irregularly reflected, the irradiation position R ₀
Surface scattered light S _s is received in the foreign object detector 43 around the optical axis C, a fairly large noise which is accumulated in the. In contrast, surface scattered light S _s are removed by providing a light shielding plate 44 on the optical axis as shown in (b).

[0005]

The foreign matter detecting optical system 4 according to the above patent application still has some problems. This will be described with reference to FIG. The first problem is that in FIG. 8 (a), the laser beam L _T is correctly irradiated to the reference irradiation position R ₀ when the face plate 1 or 2 is in the height position of the reference. However, the height position of the surface plate is changed for some reason, for example, when lowered to the dotted line position, the irradiation position due to the low angle illumination is moved to the right of the R _1, the light receiving position on the foreign object detector 43 Is the foreign matter scattered light _SP and the surface scattered light S
Both _s move to the left as shown by the dotted line. Due to this movement, the foreign matter scattered light _SP is partially cut by the light shielding plate 44 to reduce the amount of accumulated light, while the surface scattered light S _s is reduced by the light shielding plate 44.
Out of the light-shielding range, the noise removal effect is lost, and the both deteriorate the foreign-matter detection performance. On the other hand, a means for detecting the height position of the face plate and returning it to the reference position is required.
Next, the second problem is that in FIG. 8 (b), the even in the manufacturing stage of the inspection apparatus is configured so that the laser beam L _T correctly irradiate the reference irradiation position R _0, Ya transportation such as factory due to aging caused by operational, the irradiation angle theta ₀ of the laser beam L _T may become the angle theta ₁ is changed in the direction of the dotted line. The irradiation position in the same manner as described above for moves to R ₁
The same problem as (a) occurs. On the other hand, there is a need for a simple calibration method that can be used as needed at the site of the shipped user and sets the irradiation position to R ₀ with the changed angle θ ₁ . Next, the third problem is that the surface plate to be inspected is used as the substrate 1 of the printed circuit board. In FIG. 8C, the laser beam L _T applied to the reference irradiation position R ₀ of the substrate 1 is shown in FIG. Is a transparent Mylar thin film 1d and resist 1c
And the surface scattered light S _sc due to the rough surface of the copper foil 1b.
Occurs. In this case, the irradiation position of the laser beam moves to the position of R ₃ due to the thickness δt of the Mylar thin film and the resist agent, so that the surface scattered light S _sc is out of the light shielding range of the light shielding plate 44 and is transmitted to the foreign matter detector 43. Inputting becomes noise. On the other hand, it is necessary to provide an effective light shielding plate. An object of the present invention is to solve the above-described problems and to provide a highly reliable face plate foreign matter inspection apparatus.

[0006]

SUMMARY OF THE INVENTION The present invention is a face plate foreign matter inspection apparatus which solves the above-mentioned problems. With respect to the first problem, the specular reflection light of the laser beam by the face plate is received by the face plate with respect to the foreign object detection optical system, and the light receiving position is changed, whereby the reference height position with respect to the reference height position is changed. A height position detection unit for detecting the amount of change in the height position of the face plate is added. A vertical movement control unit is provided which raises / lowers both the foreign object detection optical system and the height detection unit according to the detection signal of the height position detection unit, and positions the face plate at the reference height position. With respect to the second problem, a calibration plate having a rough reference surface corresponding to the reference height position is fixed to the mounting table, and a calibration optical system is added to the foreign object detection optical system. The calibration optical system is provided on the light receiving optical axis of the foreign object detection optical system,
Irradiation that is composed of a half mirror that divides the scattered light of the laser beam applied to the reference surface of the calibration plate, and an irradiation position detector that receives the divided scattered light, and is moved by a change in the irradiation angle of the laser beam. The position is detected by an irradiation position detector, and the vertical position of the calibration optical system is moved up and down together with the foreign object detection optical system and the height position detection unit by the control of the vertical movement control unit based on the detection signal. And the height reference point of the height position detector is calibrated for this state. As for the third problem, the substrate of the printed circuit board is used as the face plate to be inspected, and the laser beam irradiated at a low angle to the substrate shields the surface scattered light by the copper foil surface. The light shielding plate is provided immediately before or at a position conjugate with the foreign matter detector of the foreign matter detection optical system.

[0007]

The operation of the face plate foreign matter inspection apparatus having the above-described configuration will be described for each problem. Regarding the first problem, the specularly reflected light of the laser beam from the face plate is received by the height position detector, and the change in the light receiving position detects the amount of change in the height position of the face plate with respect to the reference height position. . The vertical movement mechanism is controlled by the detection signal to raise / lower both the foreign object detection optical system and the height position detection unit, whereby the face plate is aligned with the reference height position, and the laser beam is moved with respect to the reference irradiation position. Irradiated correctly. Normally, an illumination light source and a detector for the illumination light source are separately used for detecting the height change amount of the face plate. However, in the present invention, since the inspection laser beam is shared, there is an advantage that the configuration can be simplified. .
Regarding the second problem, the laser beam applied to the reference surface of the calibration plate is scattered, and the scattered light is split by the half mirror and received by the irradiation position detector. The amount of movement of the irradiation position moved by the change of the irradiation angle is detected by the irradiation position detector, and the foreign matter detection optical system and the height position detector and the calibration optical system are controlled by the vertical movement control unit based on the detection signal. By raising / lowering both, the irradiation position is returned to the reference irradiation position, and the height reference point of the height position detector is calibrated for this state. With the calibrated height reference point as a reference, the face plate to be inspected is aligned with the reference height position, and the laser beam is correctly irradiated on the reference irradiation position. Since the calibration is performed while the irradiation angle theta ₁ which change is easy to work, but can be performed at any time at the user site. As for the third problem, the laser beam irradiated at a low angle to the substrate of the printed circuit board is transmitted through the transparent Mylar thin film and the resist agent and is irregularly reflected by the rough surface of the copper foil. In this case, because of the thickness of the Mylar thin film and the thickness of the resist agent, the irradiation position on the surface of the copper foil moves from the reference irradiation position, so that noise is removed by the light shielding plate having a light shielding range corresponding to the moved irradiation position. .

[0008]

FIG. 1 is a block diagram showing an embodiment according to the first and second aspects of the present invention, and FIGS.
FIG. 4 shows an embodiment of the present invention.

In FIG. 1 (a), a foreign matter detecting device moves the mounting table 5 and the mounting table 5 in the X or Y direction, and a foreign substance detecting optical system 4 which is substantially the same as the one shown in FIG. 6 (a) in principle. And an XY moving mechanism (not shown).
An up / down movement control unit 6 including a 61 and a Z movement mechanism 62 is provided. Note that the same elements as those in FIG. First, a configuration for the first problem of the height with respect to the foreign matter detection optical system 4, consisting of a laser beam focusing lens 71 and the height position detector 72 that receives the specularly reflected light L _R of L _T A position detector 7 is added. In order to solve the second problem, a calibration plate 8 such as a ground glass having a rough surface is mounted on the mounting table 5.
, And its surface is used as a reference surface corresponding to the reference height position of the face plate. The optical path of the foreign object detecting optical system 4, receiving scattered light of the laser beam L _T irradiated to the reference plane, adding a calibration optical system 9 in which the half mirror 91 made of the irradiation position detector 92. The height position detector 72 and the irradiation position detector 92 use a line sensor and are connected to the position control circuit 61, respectively. In the following, the foreign matter detecting optical system 4, the height position detecting unit 7, and the calibration optical system 9 are collectively referred to as an optical system 10, and the optical system 10 is moved up / down by a Z moving mechanism 62 controlled by a position control circuit 61. I do. By the way, the light condensing path of the foreign substance detection optical system 4 here is different in the X and Y directions. FIG.
(b) In the X direction shown in FIG.
After being condensed on the light shielding plate 44 at 42, the light is condensed again on the foreign substance detector 43 by the cylindrical lens 45. In the Y direction shown in FIG. 1C, scattered light generated on the surfaces of the face plates 1 and 2 is condensed on the foreign substance detector 43 by the condenser lens 42 and the cylindrical lens 46.

The operation of the height position detector 7 will be described with reference to FIGS. 2 (a) and 2 (b). For some reason, the face plate 1 or 2 is moved to the reference height position as shown by a dotted line or a dashed line in FIG. more .delta.z ₁ rises, or when .delta.z ₂ descends, the laser beam L _T irradiation position of moves to R ₁ or R ₂ from the reference irradiation position R _0, each of the specularly reflected light L _R1, L _R2 is an imaging lens 71 The light receiving element r ₁ or r of the height position detector 72
_An image is formed on the image ₂ and a deviation occurs from the height reference point r ₀ .
A detection signal indicating this shift amount, that is, a height change amount, is sent from the height position detector 72 to the position control circuit 61, and the Z movement mechanism 62 operates to raise or lower the optical system 10 according to the control signal. , The regular reflection light L _R1 or L _R2 is imaged at the height reference point r ₀ . Thus, the faceplate is aligned with the reference height position, the laser beam L _T is a reference irradiation position R ₀
Irradiated correctly. In this case, since the depth of focus of the detection optical system 4 is somewhat deep, no defocusing occurs. Further, since the reflection point (such as R ₀ ) and the imaging point (such as r ₀ ) have an image forming relationship with respect to the imaging lens 71, the surface of the reflection point is indicated by a dotted line in FIG. As shown in the figure, one feature of this method is that the image formation point does not move at all and the above-mentioned shift amount is accurately detected even if the image is inclined at an angle δθ with respect to the horizontal.

Next, the operation of the calibration plate 8 and the calibration optical system 9 will be described with reference to FIGS. 3 (a) and 3 (b). (a), the inspection apparatus is set at the manufacturing stage so that the laser beam L _T correctly irradiates the reference irradiation position R _0. On the other hand, when the irradiation angle θ ₀ changes to an angle θ ₁ (θ ₀ > θ _{1 in the} figure) due to a temporal change due to transportation or operation at the time of shipping or the like, the irradiation position moves to R ₁ . In response, calibration is performed by the calibration optical system 9. The calibration plate 8 is moved to the optical system 1 by the XY moving mechanism.
0 moves to the position beneath the optical axis of the detection optical system 4 is irradiated with the laser beam L _T to the reference plane. The surface scattered light S _{s at the} irradiation position R ₁ is reflected by the focusing lens
And the light receiving element q of the irradiation position detector 92 through the half mirror 91
Imaged on ₁ . Imaging point q ₀ with respect to the reference irradiation position R ₀
Is measured in advance, the shift amount of q ₁ with respect to q ₀ , that is, the shift amount of the irradiation position is detected, and a detection signal is input to the vertical movement control unit 6 to lower the optical system 10 by δz _{3 in the same} manner as described above. When the imaging point to match the q ₀ and the laser beam L _T correctly irradiates the reference irradiation position R ₀ as shown in (b). On the other hand, the reflection angle of the regular reflection light L _R is also θ ₁ ,
The imaging points of the height position detector 72 are height reference points r ₀ to r ₀ ′.
Go to This r ₀ 'is calibrated to a new height reference point. In the inspection of the face plate 1 or 2 by aligning the height position of the surface plate as a calibrated height reference point relative to the r ₀ 'has, the laser beam L _T is correctly irradiated with respect to the reference irradiation position R ₀ You. In the above, the irradiation angle is calibrated work because remains altered theta ₁ is easy, can be done at any time at the user site.

Next, in the embodiment of FIG. 4, as shown in FIG. 4A, the surface scattered light S _s at the irradiation position R ₀ is generated around the optical axis C in the mask plate 2, the light shielding plate 440 provided to remove the surface scattered light S _s. on the other hand,
As (b), when the printed board is a laser beam L _T is irradiated to the base material 1, the copper foil as the one
b surface scattered light S _sc by the surface of the is scattered in the irradiation position R _3, which is condensed by the condenser lens 42 as shown by a dotted line. In this case, the irradiation position R ₃ is on the right side with respect to the optical axis C, and the imaging point of the scattered light S _sc transmitted through the condenser lens 42 moves to the left side. Optical axis C
Is shielded from the left side to remove noise. However, the half foreign substances scattered light S _P also is cut by the light shielding plate 441 is unavoidable.

[0013]

As described above, in the face plate foreign matter inspection apparatus according to the present invention, the problem of the movement of the irradiation position of the laser beam due to the change in the height of the face plate to be inspected is solved.
A simple and efficient height position detection unit that uses the inspection laser beam shared by the foreign object detection optical system is added. The problem of the movement of the irradiation position due to is solved by adding a simple calibration optical system that can be used at any time at the user's site, and furthermore, the surface scattering light by the copper foil of the base material of the printed circuit board is The solution is to provide an effective light-shielding plate, so that the laser beam is correctly irradiated to the reference irradiation position of the face plate and the noise is effectively removed, and it is applied to both the base material of the printed circuit board and the mask plate. There is an excellent effect that foreign substances are inspected with high reliability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment according to claims 1 and 2;

FIG. 2 is an operation explanatory view of the height position detector of FIG. 1;

FIG. 3 is an explanatory diagram of an operation of the calibration optical system of FIG. 1;

FIG. 4 is a configuration diagram of an embodiment according to claim 3;

FIGS. 5A and 5B are explanatory views of a printed circuit board, wherein FIGS. 5A and 5B are external views and cross-sectional views of a substrate and a mask plate of the printed circuit board, and FIG.
FIG. 4 is an explanatory view of projection exposure of a mask plate to a base material, and FIG. 4 (d) is an explanatory view of occurrence of a defect in a wiring pattern due to adhered foreign matter.

FIG. 6 is an explanatory diagram of a foreign object detection optical system according to a patent application.

FIG. 7 is an explanatory diagram of a noise removing method according to a patent application.

8A and 8B are diagrams for explaining a problem to be addressed by the present invention, in which FIG. 8A is a diagram for explaining the movement of the irradiation position of the laser beam due to a change in the height position of the face plate, and FIG. FIG. 4 (c) is an explanatory view of the movement of the irradiation position due to the change of the scattered light, and FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Printed circuit board base material (face plate), 1a ... resin film, 1b ... copper foil, 1c ... resist agent, 1d ... mylar thin film, 2 ... mask plate (face plate), 2a ... glass plate, 2b ... emulsion layer 2c ... Wiring pattern 3 ... Foreign matter 4 ... Foreign matter detection optical system 41 ... Projector, 42 ... Condenser lens, 43 ... Foreign matter detector, 44,440,441 ... Light shielding plate, 45 ... Cylindrical lens, 46 ... Cylindrical lens, 5 ... Mounting table, 6 ... Vertical movement control unit, 61: position control circuit, 62: Z movement mechanism, 7: height position detection unit, 71:
Imaging lens, 72 Height detector 8 Calibration plate 9 Calibration optics 91 Half mirror 92
Irradiation position detector, 10 ... optical system.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Mitsuyoshi Koizumi 2-6-2 Otemachi, Chiyoda-ku, Tokyo Hitachi Electronics Engineering Co., Ltd. (56) References JP-A-5-45297 (JP, A) JP JP-A-2-167452 (JP, A) JP-A-2-38951 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 21/88 G01B 11/24 H05K 3/00

Claims (3)

(57) [Claims] A surface plate to be inspected is mounted on a mounting table as a reference height position, and a laser beam is irradiated at a low angle with respect to a reference irradiation position of the surface plate, and is provided in a direction perpendicular to the surface plate. A foreign matter detector that receives foreign matter scattered light from foreign matter attached to the face plate by a foreign matter detector and has a foreign matter detection optical system for detecting the foreign matter. Receiving a specularly reflected light of the beam, and adding a height position detecting unit for detecting a change amount of the height position of the face plate with respect to the reference height position by changing the light receiving position; A vertical movement control unit that relatively raises / lowers both the foreign object detection optical system and the height detection unit and the face plate according to a detection signal, and positions the face plate at the reference height position. Features,
Face plate foreign matter inspection device. 2. A calibration plate having a rough reference surface corresponding to a reference height position of the face plate is fixed to the mounting table, and the foreign matter detection optical system is A half mirror that is provided on a light receiving optical axis and divides the scattered light of the laser beam applied to the reference plane, and an irradiation position detector that receives the divided scattered light; The irradiation position moved by the change of the angle is detected by the irradiation position detector, and the control of the vertical movement control unit based on the detection signal of the irradiation position detector allows both the foreign object detection optical system and the height position detection unit to be detected. And a calibration optic for relatively raising / lowering the face plate, returning the moved irradiation position to the reference irradiation position, and calibrating a height reference point of the height position detector with respect to the returned state. Characterized by the addition of a system The face plate foreign matter inspection device according to claim 1, wherein 3. A printed circuit board base material in which a transparent resist agent and a mylar thin film are sequentially laminated on a copper foil-covered resin base as the face plate to be inspected,
A light-shielding plate for blocking the surface scattered light of the surface of the copper foil of the laser beam irradiated at the low angle with respect to the base material is provided immediately before the foreign matter detector of the detection optical system. The face plate foreign matter inspection device according to claim 1 or 2, wherein: