JP3370419B2 - Positioning method for mounting electronic components on circuit boards - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning method for mounting electronic components on a circuit board, and more particularly to a semiconductor having solder bumps, solder balls, etc. formed on a mounting surface of a board on which a semiconductor chip is mounted. The present invention relates to a mounting device and a positioning method for mounting an electronic component such as a semiconductor chip having similar bumps and balls formed on a mounting surface on a circuit board such as a printed wiring board.

[0002]

2. Description of the Related Art In recent years, with downsizing and higher performance of electronic equipment, surface mounting of components such as semiconductor mounting devices having electronic components such as semiconductor chips (bare chips) onto a printed wiring board (motherboard) has progressed. I'm out.

As a surface mount component of this type, a semiconductor package using a so-called lead frame is dominated, as represented by a QFP (Quad Flat Package). However, with the high integration of ICs, the number of terminals increases and ICs connected to inner leads
As the chip connection pitch becomes narrower, a lead frame formed by etching or the like has a problem in that it is difficult to increase the number of pins and the pitch, and it is difficult to handle. Therefore, a BGA (ball grid array) in which bumps are formed on the back surface of a printed wiring board on which an IC chip is mounted and hemispherical solder bumps are formed on the bumps is used as a semiconductor package suitable for miniaturization by increasing the number of pins. Attention has been paid.

To surface-mount this BGA on a printed wiring board, the BGA is generally mounted on a mounting pad on the printed wiring board coated with solder or solder and flux.
The bumps are aligned and temporarily fixed with an adhesive or the like, and then heated in a reflow furnace to be soldered. Therefore, when performing reflow soldering, BG
Accurate alignment between the bump A and the mounting pad on the printed wiring board is required.

Conventionally, in a semiconductor package mounting device such as a BGA, a bump and a mounting pad are observed and aligned using a camera. That is, BG
The bumps are observed from the lower side of A with the first camera, and the mounting pads are observed from the upper side of the printed wiring board with the second camera to calculate each coordinate value. Then, for example, after the BGA adsorbed by the bonding head is moved onto the printed wiring board, the displacement amount in the XY-θ direction is corrected based on each coordinate value obtained by the image processing of the computer and the position is corrected. I'm trying to implement after matching.

There is also a semiconductor package in which a semiconductor chip is surface-mounted on a mounting substrate.
For example, in a so-called MCM (multi-chip module) in which a plurality of bare chips are mounted on a printed wiring board, a plurality of bare chips are directly mounted on the printed wiring board by flip chip bonding. That is, flip chip bonding is a method of electrically connecting a solder bump formed on one surface of a bare chip to a mounting pad formed on a printed wiring board or a solder bump formed on the pad by soldering or the like. is there.

For this flip-chip bonding, for example, a method described in Japanese Patent Laid-Open No. 4-206534 has been proposed. In this method, the first and second cameras are provided, the offset distance between the center points of the two is determined, and the absolute position coordinates of the pattern (pad) and bump are read to determine the amount of deviation between the two coordinates.
Then, the bonding head sucking the semiconductor chip is moved by the sum of the offset distance and the shift amount, and is aligned with the pad on the substrate for mounting.

[0008]

However, the above-mentioned B
The GA mounting method and flip chip bonding have the following problems.

In the conventional image recognition method, the first and second cameras are provided at different positions. Therefore, when aligning the pads and bumps based on the image data of the pads observed by each camera, the distance between the center points (optical axes) of the first and second cameras is set to 0, The amount of displacement between each coordinate with the bump must be corrected. Therefore, if an error occurs when the distance between the center points of the first and second cameras is set to 0, the error must be taken into consideration when correcting the deviation amount between the coordinates of the pad and the bump. In addition to the difficulty in correcting the amount of deviation, there is a problem in that the accuracy of alignment is improved. In addition, a calculation program for correcting the deviation amount must be created in consideration of the case where an error occurs, and it takes time to create the program and design the calculation processing circuit, and the device itself is complicated and expensive. There is a problem that it becomes a cost.

The present invention has been made to solve the above problems, and an object thereof is to position a semiconductor chip having bumps formed on a mounting surface or an electronic component such as a semiconductor mounting device on a circuit board. It is an object of the present invention to provide a positioning method for mounting an electronic component on a circuit board, which can easily correct the amount of displacement between the bump and the pad at the time of matching.

[0011]

In order to solve the above problems, the invention according to claim 1 corresponds to a plurality of bumps formed on a mounting surface of an electronic component and the bumps formed on a circuit board. After observing any one of the mounting pad with the first camera and moving any one of the electronic component and the circuit board observed next from the observation position, the optical axis of the first camera The second camera is arranged so that the optical axes of the second camera are optically coincident with each other, and then one of the bump and the mounting pad not observed by the first camera is attached to the second camera. Observe with a camera, the first
And based on the image data observed by the second camera, the computer calculates the coordinate values of the bump and the mounting pad in correspondence with each other, and based on the calculation result, either one of the electronic component and the circuit board is calculated. It was moved to correct the amount of displacement between the bump and the mounting pad.

According to a second aspect of the present invention, when the second camera is arranged, an index is provided on the optical axis of the first camera, and the index is observed by the second camera while the first camera is used.
And the optical axes of the second camera are optically matched.

[0013]

[0014]

According to the first aspect of the present invention, one of the plurality of bumps formed on the mounting surface of the electronic component and the mounting pad corresponding to the bumps formed on the circuit board is the first camera. To be observed. After one of the observed electronic component and the circuit board is moved from the observation position, the second optical axis of the second camera is optically aligned with the optical axis of the first camera. Cameras are placed. Next, either one of the bump and the mounting pad, which was not observed by the first camera, was observed by the second camera, and the bump and the mounting pad for computer were measured by the computer based on the image data observed by the first and second cameras. Each coordinate value of the pad is calculated corresponding to each other. Then, based on the calculation result, either one of the electronic component and the circuit board moves,
The displacement amount between the bump and the mounting pad is corrected, and the alignment between the electronic component and the circuit board is completed.

Therefore, since the error between the optical axis of the first camera and the optical axis of the second camera becomes 0, both light beams are corrected when the deviation amount between the coordinates of the bump and the mounting pad is corrected. It is not necessary to consider the error between axes. As a result, it becomes easy to correct the deviation amount.

According to the second aspect of the invention, while the index provided on the optical axis of the first camera is observed by the second camera, the optical axes of the first and second cameras are optically The second camera is arranged so as to match. Therefore, even if the second camera is repeatedly arranged on the first camera, the optical axes of the two cameras surely coincide with each other.

[0017]

[0018]

【Example】

(Embodiment 1) Hereinafter, Embodiment 1 embodying the present invention as a positioning method for mounting a BGA (ball grid array) on a printed wiring board will be described with reference to FIGS. First, the configurations of the BGA and the printed wiring board will be briefly described.

As shown in FIG. 1, BG as an electronic component
Hemispherical bumps 2 made of a plurality of solders on the bottom surface of A1.
Are arranged in two rows so as to surround a square area. As shown in FIG. 5, mounting pads (hereinafter, simply referred to as pads) 4 of the BGA 1 are arranged on the surface of a printed wiring board 3 as an electronic circuit board in the same manner as the bumps 2. A solder film (not shown) is previously formed on the pad 4. Note that the solder film may not be formed as long as sufficient bonding strength with the pad 4 can be obtained only by the bump 2.

Next, a method of aligning the BGA 1 will be described. The BGA 1 adsorbed by the adsorption nozzle 5 provided on the bonding head (not shown) is lowered and placed at an observation position close to the first camera 6 arranged upward to observe the bump 2 (FIG. 1). . At this time, the center of the suction nozzle 5 and the center of the BGA 1 do not have to coincide with each other. Further, in order to make it easy to observe the BGA 1 with the first camera 6, the illumination device 7 illuminates from diagonally below the BGA 1.

Subsequently, a computer inputs image data of the bumps 2 observed by the first camera 6, reads each coordinate position and binarizes the data, and a part of a plurality of these (on this monitor 8) is displayed on the monitor 8. In this case, 10 bumps 2 are displayed (FIG. 2). Then, the computer performs the blanking process of the bumps 2 displayed on the monitor 8 to display again a still image of the bumps 2 having a circular outline on the monitor 8 (FIG. 3).

Next, in the state of being sucked by the suction nozzle 5, B
After moving the GA 1 to the standby position above, the second camera 9 arranged downward above the first camera 6 is moved from the side (FIG. 4). At this time, based on the mark 11 as an index provided on the optical axis A1 of the lens 10 of the first camera 6 observed by the second camera 9, both cameras 6,
The second camera 9 is aligned with the first camera 6 so that the optical axes A1 and A2 of 9 are optically coincident with each other. The second camera 9 is provided with an automatic focus adjustment mechanism 12, and the mechanism 12 adjusts the focus on the mark 11 of the first camera 6.

Next, after lowering the first camera 6, the printed wiring board 3 placed on the board mounting base 13 is moved below the second camera 9 to move the pad 4 for mounting the BGA 1. Are observed (FIG. 5). At this time, the focus of the second camera 9 is adjusted by the automatic focus adjustment mechanism 12 so as to match the pad 4.

Subsequently, the computer inputs image data of the pad 4 observed by the second camera 9 to calculate each coordinate position, and the bump 2 displayed on the monitor 8 is displayed.
Image and a plurality of parts corresponding to the bump 2 (in this case,
Ten (10) raw images of the pads 4 are combined and displayed (FIG. 6). At this time, the illumination device 14 illuminates the pad 4 obliquely from above so that the second camera 9 can easily observe the pad 4.

Next, the X, Y and θ stages (not shown) mounted on the board mounting base 13 are operated by a computer to move the printed wiring board 3 to XY-θ.
The pad 4 is aligned with the bump 2 by moving in the direction. This alignment is performed by the computer correcting the displacement amount between the coordinate value of the bump 2 and the coordinate value of the pad 4 to be zero. Further, the state of alignment is visually confirmed by the movement of the pad 4 displayed on the monitor 8 and the overlapping and matching of the outline of the bump 2 (FIG. 7). In this way, the alignment of the BGA1 is completed, and then the BGA1 is mounted as follows.

After moving the second camera 9 to the original position, the BGA 1 waiting at the standby position is lowered together with the suction nozzle 5 so that the bump 2 and the pad 4 come into contact with each other. Temporarily fix it on top. At this time, BG
An adhesive is used to temporarily fix A1. Then, after the suction of the BGA 1 by the suction nozzle 5 is released, the printed wiring board 3 is put into a reflow furnace (not shown) and heated to melt the solder on the surfaces of the bumps 2 and the pads 4, thereby causing the bumps 2 and pads 4 And (FIG. 8). In this way, the bump 2 and the pad 4 are aligned and the BGA 1 is aligned.
The mounting on the printed wiring board 3 is completed.

As described above, in the first embodiment, the second
When the second camera 9 is moved onto the first camera 6, after the optical axes A1 and A2 of the two are optically aligned, the bump 2
The shift amount between the coordinate values of the pad 4 and the pad 4 is corrected. Therefore, since the error between the optical axis A1 of the first camera 6 and the optical axis A2 of the second camera 9 becomes 0, when the deviation amount between the coordinates of the pad 4 and the bump 2 is corrected, Axis A1
, It is not necessary to consider the error between A2. As a result, not only is it easy to correct the amount of deviation, but it is also useful for improving the alignment accuracy.

In addition, when the calculation program for correcting the deviation amount is created, it is not necessary to consider the above error, the time for creating the program and the design time of the calculation processing circuit is shortened, and the apparatus itself. Is simple and low cost.

Further, the optical axis A of the lens 10 of the first camera 6
The mark 11 is provided on the optical axis 1 and the automatic focus adjusting mechanism 12 provided on the second camera 9 adjusts so that the mark 11 is in focus.
A2 can be surely matched.

Further, by displaying a part of the bump 2 and the pad 4 on the monitor 8 so as to correct the deviation amount, it is possible to visually confirm the alignment condition of the BGA 1 to the printed wiring board 3. You can Moreover, the bump 2 is displayed in a circular outline by the blanking process,
Since the amount of deviation from the pad 4 is corrected, the bump 2 and the pad 4 can be easily distinguished.

(Second Embodiment) Next, a second embodiment will be described. In this embodiment, the arrangement of the second camera 9 is different from that in the first embodiment.

As shown in FIG. 9, the second camera 9 has a first
The optical axis A1 of the camera 6 and the optical axis A2 of the second camera 9 are fixed at a position orthogonal to each other. As shown in FIG. 10, with the BGA 1 placed in the standby position, a total reflection mirror 21 is placed so that the mirror surface hits the intersection of the optical axes A 1 and A 2 of the first and second cameras 6 and 9. It is supposed to be done. This mirror 21 has a flatness of 0.05 to
It is about 0.1 μm, and it moves in a direction orthogonal to the plane formed by the optical axes A1 and A2 while maintaining an inclination angle θ of 45 ° with respect to the horizontal plane.

Next, a method of aligning the BGA 1 will be described. In the state shown in FIG. 9, the BGA 1 sucked by the suction nozzle 5 is lowered, the bumps 2 are observed by the first camera 6, and the image data of the observed bumps 2 is subjected to the hollowing-out process as in the first embodiment. Go and display on the monitor 8 with a circular outline.

Next, after moving the BGA 1 to the upper standby position, the mirror 21 is moved from the side so that the mirror surface hits the intersection of the optical axes A1 and A2 of the first and second cameras 6 and 9. To arrange. At this time, the mirror 21 has an inclination angle θ.
Is 45 °, the optical axis A1 and the optical axis A2 apparently coincide with each other.

Next, below the mirror 21, the substrate mounting table 13 is provided.
The printed wiring board 3 placed on the top is moved, and the image of the pad 4 reflected by the mirror surface of the mirror 21 is observed by the second camera 9 (FIG. 10). At this time, the second camera 9 observes the pad 4 that is plane-symmetric with the actual pad 4.
Further, the second camera 9 is arranged in advance so that the mirror surface of the mirror 21 is in focus, and the automatic focusing mechanism 12 is not provided.

Then, the computer inputs the image data of the pad 4 observed by the second camera 9 to calculate each coordinate position in consideration of the pad 4 having plane symmetry, and the bumps are displayed on the monitor 8. 2 and the corresponding raw image of the pad 4 are combined and displayed.

Next, similarly to the first embodiment, the printed wiring board 3 is moved in the XY-θ direction to align the pad 4 with the bump 2. In this way, the alignment of the BGA 1 is completed.

As described above, in the second embodiment, the second
Of the camera 9 of the first camera 6 and the optical axis A1 of the first camera 6
It was fixed at a position where and were orthogonal to each other, and the mirror 21 was movably arranged so that the mirror surface hits the intersection of both optical axes A1 and A2.
Therefore, unlike the first embodiment, it is not necessary to move the second camera 9 to match the optical axis A1 of the first camera 6. Further, the mirror 21 is moved in the direction orthogonal to the plane formed by the optical axes A1 and A2 while maintaining the inclination angle θ of 45 ° with respect to the horizontal plane, whereby the second camera 9 is The pad 4 can be observed on the same optical axis as the first camera 6, and the amount of deviation between the bump 2 and the pad 4 can be easily corrected.

(Third Embodiment) Next, a third embodiment will be described. This embodiment is different from the above-mentioned embodiments in that the positioning is performed by one camera and the method of positioning a bare chip as an electronic component in flip chip bonding is embodied.

As shown in FIG. 11, the optical axis A of the camera 31 is used.
A mirror 32 having two mirror surfaces 32a and 32b is arranged in the direction of 3. The mirror 32 has mirror surfaces 32a, 3
2b is provided so as to face the lens of the camera 31 and have an inclination angle θ of 45 ° in the vertical direction with the optical axis A3 as a boundary. The mirror 32 and the camera 31 are supported by the same support member (not shown), and the substrate mounting table 1
It is designed to move in parallel with 3. The camera 31 is separated from the mirror surfaces 32a and 32b by an observable distance.

Next, a bare chip alignment method will be described. Bare chip 3 sucked by suction nozzle 33
4 is moved down, and the printed wiring board 3 mounted on the board mounting base 13 is moved so that the pad 4 is located below the bare chip 34. Then mirror 3 from the side
2 and the camera 31 are moved to arrange the mirror 32 so that the mirror surface 32a faces below the bare chip 34 and the mirror surface 32b faces above the pad 4 (FIG. 11).

Next, the image of the bump 2 reflected by the mirror surface 32a and the image of the pad 4 reflected by the mirror surface 32b are observed by the camera 31. At this time, since the mirror surfaces 32a and 32b each have an inclination angle θ of 45 ° with the optical axis A3 of the camera 31 as a boundary, the images of the bumps 2 and the pads 4 can be reliably observed by the camera 31.

Next, the image data of the observed bumps 2 is subjected to the hollowing-out process as in the first and second embodiments, and is displayed on the monitor 8 as a circular outline as shown in FIG. , The bump 2 and the corresponding raw image of the pad 4 are combined and displayed. At this time, the image of the pad 4 observed by the camera 31 is displayed on the monitor 8 while being inverted to the bump 2 side with the boundary between the mirror surfaces 32a and 32b as the center.

Next, similarly to the first and second embodiments, the printed wiring board 3 is moved in the XY-θ direction to align the pad 4 with the bump 2. In this way, the alignment of the bare chip 34 is completed.

As described above, in the third embodiment, the mirror 32 having the two mirror surfaces 32a and 32b is used, and the bump 2 and the pad 4 are observed by the single camera 31. There is no need to consider the error. Therefore, the shift amount between the bump 2 and the pad 4 can be easily corrected with a simple configuration in which the camera 31 and the mirror 32 are combined. Further, the number of cameras can be reduced, and the cost can be reduced.

The present invention can be embodied as follows. (1) In the first and second embodiments, first the first camera 6
After observing the bump 2 with, the second camera 9 was used to observe the pad 4, but after observing the pad 4 on the contrary,
The bumps 2 may be observed.

In this case, in the first embodiment, the first camera 6 is arranged so as to be movable in the horizontal direction, and the second camera 9 is arranged so as to be movable up and down. Then, after observing the pad 4 with the second camera 9, the camera 9 is moved to the upper standby position, the first camera 6 is moved from the side to the lower side of the second camera 9, and The optical axes A1 and A2 may be optically matched with each other. Further, in the second embodiment, the first camera 6 is fixed in the horizontal direction, and the second camera 9 is arranged so as to be vertically movable. Then, after observing the pad 4 with the second camera 9, the camera 9 is moved to the standby position above and the BGA 1 is moved from the side to be placed on the pad 4, and the BGA 1 and the printed wiring board 3 are also arranged. The mirror 21 whose mirror surface faces obliquely upward by 45 ° may be disposed between and so that the bump 2 is observed by the first camera 6.

(2) The number of bumps 2 and pads 4 displayed on the monitor 8 may be arbitrarily changed. In this case, it is preferable to match the numbers of both because it is easy to visually confirm the alignment condition.

(3) In each of the above embodiments, the board mounting base 13
Not shown X stage, Y stage and θ
Although the printed wiring board 3 is moved in the X-Y- [theta] direction by operating the stage with a computer, a person may operate each stage to align the position while looking at the monitor.

(4) In the above embodiment, the automatic focusing mechanism 12 is provided in the second camera 9 so that the optical axis A of the first camera 6 can be obtained.
Although it is optically matched with 1, it may be arranged in advance so that the focus of the second camera 9 is aligned with the mark 11 of the first camera 6 without providing the automatic focusing mechanism 12.

(5) The solder bumps formed on the electronic component such as the BGA 1 may be replaced by the names of solder balls, protruding electrodes, solder terminals and the like. Alternatively, solder bumps may be formed on the mounting pads 4 of the printed wiring board 3 to mount the BGA 1 or the like.

The optical axis in the present invention is defined as follows. Optical axis: A straight line passing through the center of an optical system lens equipped in a camera that uses a solid-state imaging device such as a CCD (charge coupled device) as a photographing means.

Technical ideas other than those described in the claims which can be understood from the above-described embodiments will be described below along with their effects. In the alignment method of claim 1, while displaying the coordinate values of the pads and the mounting pads calculated by a computer to monitor and to correct the deviation amount between the pad and the mounting pad. By doing so, the alignment condition can be visually confirmed.

[0054]

As described in detail above, according to the invention described in claim 1, when aligning a semiconductor chip having bumps formed on a mounting surface or an electronic component such as a semiconductor mounting device with a circuit board. In addition, the amount of displacement between the bump and the mounting pad can be easily corrected.

According to the invention described in claim 2, in addition to the above effect, even if the second camera is repeatedly arranged on the first camera, the optical axes of both can be surely matched .

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a state in which a bump is observed by a first camera according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing image data of bumps displayed on a monitor.

FIG. 3 is a schematic diagram showing image data of bumps subjected to hollowing processing.

FIG. 4 is a schematic perspective view showing a state where the optical axis of the second camera is aligned with the optical axis of the first camera.

FIG. 5 is a schematic perspective view showing a state of observing a mounting pad with a second camera.

FIG. 6 is a schematic diagram showing a state in which image data of bumps and mounting pads are combined on a monitor.

FIG. 7 is a schematic view showing a state in which bumps and mounting pads are aligned.

FIG. 8 is a schematic side view showing a state in which the BGA is mounted on a printed wiring board.

FIG. 9 is a schematic perspective view showing a state in which bumps are observed by a first camera in the second embodiment.

FIG. 10 is a schematic perspective view showing a state in which a mounting pad is observed by a second camera via a mirror.

FIG. 11 is a perspective view showing a state in which a mirror is arranged between a bare chip and a printed wiring board 3 in Example 3, and a bump and a mounting pad are observed by a camera through the mirror.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... BGA as an electronic component, 2 ... Bump, 3 ... Printed wiring board as a circuit board, 4 ... Mounting pad, 6 ... 1st camera, 9 ... 2nd camera, 11 ... Mark as an index, 21 ... Mirror, 31 ... Camera, 32a, 32b ...
Mirror surface, 34 ... Bare chips as electronic parts, A1 to A3
…optical axis.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-60-39851 (JP, A) JP-A-2-28343 (JP, A) JP-A 58-137222 (JP, A) JP-A 59- 72145 (JP, A) JP-A-4-65844 (JP, A) JP-A-4-206534 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/60 H01L 21 / 52 H04N 5/225

Claims (2)

(57) [Claims] 1. A first camera observes one of a plurality of bumps formed on a mounting surface of an electronic component and a mounting pad corresponding to the bump formed on a circuit board,
After moving one of the observed electronic component and circuit board from the observation position, the optical axis of the second camera is optically aligned with the optical axis of the second camera. An image obtained by arranging a second camera, and then observing with the second camera one of the bump and the mounting pad, which was not observed with the first camera, with the first and second cameras. Based on the data, the computer calculates the coordinate values of the bump and the mounting pad in correspondence with each other, and moves either the electronic component or the circuit board based on the calculation result to move the bump and the mounting pad. A positioning method for mounting an electronic component on a circuit board that corrects the amount of deviation from 2. When arranging the second camera, an index is provided on the optical axis of the first camera, and the optical axes of the first and second cameras are observed while observing the index by the second camera. The method for aligning the electronic components according to claim 1, wherein the electronic components are optically matched with each other.