JP3346177B2 - Inspection method of conductive ball mounting condition - 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 inspecting a mounted state of a conductive ball.

[0002]

2. Description of the Related Art Small-diameter conductive balls (for example, solder balls, gold balls, or resin balls whose surfaces are coated with a conductive metal) are used to form bumps and the like of semiconductor chips. A plurality of such conductive balls are mounted at predetermined positions on the substrate, and after mounting, it is necessary to inspect the mounting state for any errors in mounting.

[0003]

However, since the use of the conductive ball has begun to be used, a method for performing such an inspection has not been established yet. Regarding this point,
As described in JP-A-81449, there is also an attempt to irradiate light obliquely to a bump to perform an inspection using a shadow formed behind the bump.

However, in practice, a large number of conductive balls (or bumps) are present on a substrate at a very narrow pitch, and are obstructed by adjacent conductive balls even when light is obliquely applied. Shadows are hardly formed,
This attempt is not realistic.

Accordingly, an object of the present invention is to provide a method for inspecting the mounted state of a conductive ball which can practically inspect the mounted state of the conductive ball with a simple mechanism.

[0006]

According to the method of inspecting a mounted state of a conductive ball of the present invention, an optical axis of a camera is directed from above vertically to a substrate, and light is obliquely applied to the substrate from above.
An image including a bright point reflected from the conductive ball and incident on the camera and located at a position shifted by a certain distance from the conductive ball is an intersection of a predetermined horizontal line and a predetermined vertical line or an image thereof.
Inspection is to be performed based on whether or not it is within an allowable range .

[0007]

According to a first aspect of the present invention, there is provided a method for inspecting a mounted state of a conductive ball, wherein an optical axis of a camera is directed from above vertically to a substrate, and light is applied from one direction obliquely upward to the substrate. Inspection is performed based on an image including a bright point reflected from the sexual ball and incident on the camera. Therefore, only a part of one conductive ball can be regarded as a bright point corresponding to one conductive ball on a one-to-one basis, and since this bright point is on the conductive ball, the conductive ball is placed on the substrate. Even if a large number exist at a narrow pitch, observation is not hindered by adjacent conductive balls. In addition, since the bright spot accurately indicates the position of each conductive ball, the mounted state can be correctly inspected.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of an inspection apparatus according to one embodiment of the present invention. In FIG. 1, 1 and 2 represent X
This is a conveyor that is provided in parallel in the direction and transports and positions the substrate 3. P1, P
As shown by 2, P3,..., Pn, a plurality of mounting areas are provided, and each mounting area P1, P2,.
Is mounted with a plurality of conductive balls having the same arrangement. In this embodiment, it is assumed that conductive balls are mounted in a 3 × 3 matrix in each of the mounting areas P1, P2,.

Reference numerals 4 and 5 denote frames arranged on both sides of the substrate 3 along the X direction. Guide rails 6 and 7 which are long in the X direction are fixed on the frames 4 and 5, respectively. I have. The moving blocks 8 and 9 are slidably engaged with the guide rails 6 and 7, respectively.

A beam 10 which is long in the Y direction is provided above the moving blocks 7 and 8. 11 is
A feed screw supported on a beam 10 and 12 is a feed screw 11
Is a feed nut screwed into the feed screw 11, and a camera 14 is fixed to a tip of an arm 13 a extending in a cantilever manner from the feed nut 13. The optical axis of the camera 14 is set so as to face vertically downward.

As described above, the moving blocks 8 and 9 are rigidly connected by the beam 10, and the feed nut 17 provided on the moving block 8 is screwed with the feed screw 18 extending in the X direction. Are rotated by an X motor 19. Therefore, the X motor 19 and the Y motor 1
2 to drive each mounting area P of the substrate 3.
1, P2,..., And the camera 14 can observe the mounting area below the camera 14 from right above at a right angle.

The moving blocks 8 and 9 include the substrate 3
A first light source unit 15 and a second light source unit 16 are provided to face each other. As shown in FIG. 2, these light source units 15 and 16 irradiate light from obliquely upward toward the mounting areas P1, P2 and P3, and have light levels of off (off) and weak. It is possible to switch between three strong levels.

[0013] The image output from the camera 14 is input to a determination unit 21 for making a quality determination, which will be described later. The result of the determination of each mounting area by the determination unit 21 is input to the control unit 22 that controls the whole. 23 is a light source control unit for controlling the light level of the light source unit, and 24 is an illumination switching unit for switching to either the first light source unit 15 or the second light source unit 16.

Next, the operation of the inspection apparatus will be described with reference to FIG. In this description, the mounting areas P1, P
2, P3 will be described.

First, an inspection of the mounting area P3 is performed. At this time, as shown in FIG.
The second light source unit 16 close to 3 is selected, and the light level of the second light source unit 16 is set to be low. At this time, the first light source unit 1
5 is turned off, and observation using only the light from the second light source unit 16 is performed. Then, at this time, the camera 14
3 and an image in the mounting area P <b> 3 immediately below the image is acquired.

Next, an inspection of the mounting area P2 is performed. At this time, as shown in FIG. 3B, the camera 14 is mounted on the mounting area P2.
Directly above. Then, the second light source unit 16 is selected, and the light level becomes strong. This is different from the case of FIG.
This is to ensure sufficient brightness because the mounting area P2 is far from the second light source unit 16.

Next, the mounting area P1 is inspected. At this time, as shown in FIG. 3C, the first light source unit 15 is selected, and the second light source unit 16 is turned off. The light level of the first light source unit 15 is weak as in FIG.

As described above, by changing the light level of the light source unit according to the distance from the light source unit to be turned on to the mounting area to be inspected, the conductive balls 20 in each mounting area are changed.
Can be uniformly illuminated, and the inspection quality can be easily maintained.

Next, the quality judgment based on the obtained image will be described with reference to FIG. In the present embodiment, as described above, the conductive balls 20 are to be mounted in a 3 × 3 matrix in each mounting area. Then, as shown in FIG. 4A, when light is irradiated from one direction (arrow N) obliquely upward, the conductive ball 20 has a spherical shape. A small bright spot can be observed at a position eccentric to the light side.

The bright points S1 to S9 are located inside the outline of the conductive ball 20 (see the broken line, which outline is observed dark and does not appear clearly on the image). That is, no matter how many conductive balls 20 are mounted at a narrow pitch, the bright spots do not become opaque with the bright spots of the adjacent conductive balls 20, and the conductive balls 2
It can be clearly observed in a state of one-to-one correspondence with 0.

Since the conductive balls 20 have the same shape, these bright spots are located at positions shifted from the center of the conductive balls 20 by a certain distance. That is, since the relative positional relationship between these bright points S1 to S9 coincides with the actual relative positional relationship of the conductive balls 20, these bright points S1 to S9 are determined as shown in FIG. When it is located at the intersection of the horizontal lines L1 to L3 and the predetermined vertical lines M1 to M3 (or within an allowable range therefrom), it can be determined that each conductive ball 20 is at the correct mounting position. Therefore, if an image as shown in FIG.
1 judges that the mounting area is in a good condition.

On the other hand, as shown in FIG. 4 (b), the bright spots having a non-negligible shift S4
Is observed, or when a bright spot is missing (S5) as shown in FIG. 4C, it indicates that the conductive ball 20 is displaced or missing. Accordingly, the determination unit 21 determines that the mounting area is in a poor state.

[0023]

According to the method for inspecting the mounted state of the conductive ball of the present invention, the camera is formed by directing the optical axis of the camera from above vertically to the substrate, irradiating light from obliquely above the substrate, and reflecting from the conductive ball. Since the inspection is performed based on an image including a bright point incident on the device, even if a large number of conductive balls exist at a narrow pitch, the inspection of the mounted state can be performed easily and accurately.

[Brief description of the drawings]

FIG. 1 is a plan view of an inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of an inspection apparatus according to an embodiment of the present invention.

FIG. 3A is a diagram illustrating an operation of an inspection apparatus according to an embodiment of the present invention. FIG. 3B is a diagram illustrating an operation of the inspection apparatus according to an embodiment of the present invention. Illustration of the operation of the device

FIG. 4A is an explanatory diagram of a pass / fail judgment according to an embodiment of the present invention. FIG. 4B is an explanatory diagram of a pass / fail judgment according to an embodiment of the present invention. Illustration

[Explanation of symbols]

 3 board 14 camera 20 conductive ball

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01B 11/00 H01L 21/66 G06T 7/00 G06T 1/00

Claims (3)

(57) [Claims] 1. A method for inspecting a mounted state of a conductive ball for inspecting a state in which a plurality of spherical conductive balls are arranged in a matrix on a substrate, comprising: Along with
Illuminated from one direction obliquely upward with respect to the substrate, is reflected from the conductive balls are incident on the camera, the image including a bright spot of the same shape in the center of the conductive balls to a certain distance displaced position Intersection of specified horizontal line and specified vertical line
Alternatively, a method for inspecting a mounted state of a conductive ball, wherein the inspection is performed based on whether or not it is within an allowable range therefrom . A plurality of spherical conductive balls on a substrate;
A conductive box for inspecting the state of mounting
A method for inspecting a mounted state of a tool, wherein an optical axis of a camera is directed from above vertically to the substrate,
Light is applied to the substrate obliquely from above in one direction,
Reflected from the conductive ball and incident on the camera, the conductive ball
Of the same shape at a position offset from the center of the
The inspection is performed based on an image including a point, and the inspection is performed for each mounting area provided at a plurality of locations on the substrate, the light is emitted from a light source unit closer to the mounting area to be inspected, in accordance with the distance until said mounting area for inspection from the light source unit for lighting, by changing the level of light of the light source unit, the conductive you characterized in that illuminate the conductive ball of said mounting area evenly Ball mounting condition inspection method. 3. The mounting state of the conductive ball according to claim 2, wherein said light source unit comprises a first light source unit and a second light source unit provided on a moving block provided on both sides of the substrate. Inspection methods.