JPS61226719A - Focus correcting structure - Google Patents

Abstract

PURPOSE:To obtain an inspection result with invariably high precision by moving up and down an optical system for a pattern read by an optical system driving mechanism which operates under the command of a focus control circuit and correcting the focus position of laser light for inspection on the surface of a printed board to be inspected. CONSTITUTION:The quantity delta of unevenness of the scanning surface 7 of the printed board 6 to be inspected is detected by an IVT camera 15 for pattern position detection and inputted to a focus position control circuit 6. The focus position control circuit 16 analyzes the input information on the quantity delta of unevenness to calculates the proper interval F' between the scanning surface 7 and pattern read optical system 14, thereby supplying a command for moving the pattern read optical system 14 as shown by an arrow A-A' to the optical system driving mechanism 17. The optical system driving mechanism 17 rotates a driving screw 18 according to the command and moves the pattern read optical system 14 as shown by the arrow A-A' through an elevation member 19 engaged threadably with the driving screw to maintain the proper interval F between the scanning surface 7 of the printed board 6 to be inspected and the pattern read optical system 14. Consequently, the reliability and operativity of the pattern inspection of the printed board are improved greatly.

Description

[Detailed Description of the Invention] [Summary] The focus correction structure of the present invention is applied to a printed circuit board to be inspected by hanging it on a pattern inspection device as it is without particularly correcting the irregularities (waviness, warping, etc.) on the inspection side. The pattern reading optical system moves by a distance that corrects the amount of unevenness of the printed circuit board to be inspected, thereby correcting the "focal shift."

Therefore, when inspecting a printed circuit board, there is no need for a jig to press the printed circuit board to correct "undulations" or "warps", etc., and there is no restriction on the size of the printed circuit board. The efficiency of pattern inspection can be significantly improved.

[Industrial application field]

Recent printed circuit boards are becoming increasingly larger and their patterns tend to be more complex.

Therefore, if the substrate surface has irregularities, the focal position of the pattern reading optical system will shift during pattern inspection, resulting in a so-called "out of focus" phenomenon, reducing the reliability of inspection.

In order to prevent this, conventional methods have been used to correct the distortion by pressing the periphery and key points of the board with a jig, but this method differs depending on the location and amount of distortion depending on the board. In addition, since the size of the substrate is not constant, the types of distortion correction jigs are diversified, and the preparation process becomes unnecessarily complicated.

The present invention relates to a focus correction structure configured so that inspection can be performed as is without correcting the distortion of the printed circuit board.

[Conventional technology]

FIG. 3 is a diagram showing the structure and principle of pattern inspection of a printed circuit board, in which (a) is a perspective view of the main part, and (b) is a side view of the main part.

As shown in the same figure (al), the pattern inspection structure of a printed circuit board includes a pattern scanning optical system 12 comprising a laser light source 1, a scanning mirror 3, a scanning lens 4, and a half mirror 5, and a pattern reading lens 8. Photodetector 9
It is composed of a pattern reading section 13 comprising a pattern reading section 13, and a substrate moving stage 1° on which a printed circuit board 6 to be inspected is placed and transported in the direction of arrow A.

The laser beam 2 emitted from the laser light source 1 is shown by the arrow B.
The light is reflected by the scanning mirror 3 rotating in the direction, and scans the scanning surface 7 on the printed circuit board 6 to be inspected in the direction of the arrow C via the scanning lens 4 and half mirror 5.

On the other hand, the laser beam 2 reflected by the scanning surface 7 and incident on the pattern reading lens 8 via the half mirror 5 is analyzed by the pattern reading photodetector 9 and becomes pattern inspection information of the printed board 6 to be inspected.

F indicates the focal length of the scanning lens 4.

[Problem that the invention seeks to solve]

However, in the above inspection structure, if there is a convex part on the printed circuit board side, for example as shown in FIG. Therefore, "focal shift" occurs and pattern reading accuracy decreases.

In order to avoid such a situation, the irregularities around the printed circuit board 6 to be inspected are corrected by a board pressing plate 11, but a large number of pressing plates 11 must be prepared depending on the size of the board 6, and the Even if you prepare it, the board 6
If the unevenness exists near the center of the board, no countermeasures can be taken.

The present invention improves the conventional focus correction structure, which has the above-mentioned problems, namely, that it is impossible to solve the problem depending on the location where unevenness occurs on the printed circuit board, and that the preparation process is time-consuming when the size of the printed circuit board changes. It was done for.

[Means for solving problems]

The above problem is solved by an ITV camera for detecting the board position that detects the unevenness of the printed circuit board to be inspected, and a focal position of the pattern reading optical system that is controlled in accordance with the amount of unevenness of the printed circuit board obtained through the camera. The pattern reading optical system is moved up and down by an optical system drive mechanism operated by a command from the focus control circuit, and the inspection laser beam is directed onto the surface of the printed circuit board to be inspected. This is solved by the focus correction structure of the present invention which corrects the focus position.

[Effect]

The focus correction structure of the present invention includes an ITV camera for pattern position detection that detects distortion, that is, unevenness of the printed circuit board to be inspected,
The pattern reading optical system is moved according to the amount of unevenness of the printed circuit board to be inspected obtained by the ITV camera, and the focal position of the pattern reading optical system is always aligned with the surface of the printed circuit board to be inspected. It is distinctive in that it exists.

Therefore, according to the focus correction structure of the present invention, highly accurate inspection results can always be obtained without strictly correcting the unevenness of the printed circuit board to be inspected each time.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a side view showing the configuration of a focus correction structure according to the present invention.

However, the same reference numerals indicate the same parts throughout the figures.

As shown in FIG. 1, the focus correction structure of the present invention includes a pattern reading optical system 14 disposed above and facing the printed circuit board 6 to be inspected, and a pattern reading optical system 14 disposed above the printed circuit board 6 to be inspected.
a pattern position detection ITV camera 15 disposed diagonally above the ITV camera 15; a focal position control circuit 16 disposed behind the ITV camera 15; and the pattern reading optical system 14.
The optical system drive mechanism 17 is equipped with a drive screw 18 screwed into a screw hole of an elevating member 19 attached to the optical system drive mechanism 17.

Note that the pattern reading optical system 14 has a structure that includes a pattern scanning optical system 12 and a pattern reading section 13.

The amount of unevenness δ on the scanning surface 7 of the printed board 6 to be inspected is detected by the pattern position detection ITV camera 15 and input to the focal position control circuit 16.

The focal position control circuit 16 analyzes the input information regarding the amount of unevenness δ, calculates an appropriate distance F' between the scanning surface 7 and the pattern reading optical system 14, and controls the pattern reading optical system 14. A command is given to the optical system drive mechanism 17 to move it a required distance in the direction of arrow AA'.

The optical system drive mechanism 17 drives the drive screw 1 based on the command.
8, and the elevating member 1 is screwed into the drive screw.
9 through the pattern reading optical system 14 in the direction of arrow A-A'
direction to maintain an appropriate distance F' between the scanning surface 7 of the printed circuit board 6 to be inspected and the pattern reading optical system 14.

FIG. 2 is a side view of a main part for explaining the principle of detecting unevenness of a printed circuit board.

The figure shows a case where the printed circuit board 6 to be inspected is at position A1,
This indicates that a focus correction corresponding to the distance δ is required in the case of position A2, and the unevenness amount δ of the scanning surface is the displacement amount m of the scanning surface between the scanning optical axis 01 and the ITV for substrate position detection.
Optical axis of camera 15 0. It is the value divided by the inclination angle θ.

Note that the formation period of undulations and warps that cause unevenness on the printed circuit board 6 is sufficiently larger than the inspection speed, so the control speed of the focus correction may be slow.

〔Effect of the invention〕

As explained in detail above, the focus correction structure according to the present invention is a structure that allows inspection to be performed without being affected by "waviness" or "curvature" of the printed circuit board to be inspected and the stage for moving the board, so it is different from conventional ones. It has the advantage of not requiring a pressure plate to straighten the board and not being restricted by the board size.
The reliability and workability of printed circuit board pattern inspection are significantly improved.

[Brief explanation of drawings]

Figure 1 is a side view showing the configuration of the focus correction structure according to the present invention, Figure 2 is a side view illustrating the principle of detecting irregularities on a printed circuit board, and Figure 3 is a diagram showing the structure and principle for inspecting patterns on a printed circuit board. FIG. 3A is a perspective view of the main part, and FIG. 2B is a side view of the main part. In the figure, 1 is a laser light source, 2 is a laser beam, 3 is a scanning mirror, 4 is a scanning lens, 5 is a half mirror, 16 is a printed circuit board to be inspected, 7 is a scanning surface, 8 is a pattern reading lens,
9 is a pattern reading photodetector, 10 is a substrate moving stage, 11 is a substrate pressing plate, 12 is a pattern scanning optical system,
13 is a pattern reading unit, 14 is an optical system for pattern reading, 15 is an ITV camera for pattern position detection, 16 is a focal position control circuit, 17 is an optical system drive mechanism, 18 is a drive screw, F is a focal length, and Fo is an appropriate The distance, Δ, is the change in focal length, δ is the amount of unevenness on the scanning surface, 01 is the scanning optical axis, and 0□ is the optical axis of the ITV camera for detecting the substrate position. , Book 4≦Giant, 2, S East tank ゛E structure, /) P Busy ゛Figure 1? 1/> Figure 2 of the principle of scooping out 1-pole unevenness! (Q) (b) 7-cho Noshito Foundation Stone Row n 80 Turns L History - Koji x#! Third
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Claims (1)

[Scope of Claims] A focus correction structure that is installed in a printed circuit board pattern inspection apparatus and positions the focus of a pattern reading optical system (14) on a printed circuit board (6) to be inspected, the focus correction structure comprising: the pattern reading optical system (14) disposed at a position facing the printed circuit board to be inspected (6); and the scanning surface (of the printed circuit board to be inspected) scanned by the optical system (14). a pattern position detection ITV camera (15) for detecting the unevenness of the pattern position (7); and the scanning surface (15) obtained by the ITV camera (15)
a focal position control circuit (16) that calculates an appropriate distance between the scanning surface (7) and the pattern reading optical system (14) based on the unevenness information of (7); ) A focus correction structure characterized in that an optical system drive mechanism (17) is configured to position the pattern reading optical system (14) in response to a command from the above.