Imaging device and method for a bonding apparatus

An imaging device and method of a bonding apparatus in which the imaging device includes: a high-magnification optical system having first and second high-magnification optical paths that extend to multiple imaging planes through a high-magnification lens and have different optical path lengths from the high-magnification lens to the respective imaging planes correspondingly to multiple subject imaging ranges which are at different distances from the high-magnification lens; and a low-magnification optical system having a low-magnification optical path that extends to an imaging plane through a low-magnification lens and having a field of view wider than those of the high-magnification optical paths. The imaging elements on the respective imaging planes in the high-magnification optical system are adapted to image semiconductor chips, while the imaging element on the imaging plane in the low-magnification optical system is adapted to image a lead frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application calms priority under 35 USC 119 from Japanese Patent Application No. 2007-152641, the disclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a structure of an imaging device for a bonding apparatus and to an imaging method using the imaging device for a bonding apparatus.

The assembling of semiconductor devices includes: a die bonding step of bonding semiconductor chips cut out from a wafer on a lead frame or substrate; and a wire bonding step of wire-connecting pads on the semiconductor chips bonded on the lead frame or substrate to the lead frame or leads on the substrate. The wire bonding provides wire connections between the pads and leads by pressing a bonding tool such as a capillary with a wire inserted therethrough at a first bonding point on a lead or pad, thus bonding the wire with an ultrasonic vibration, and then looping the wire from the first bonding point toward a corresponding pad or lead, and pressing and bonding the wire at a second bonding point on the corresponding pad or lead with an ultrasonic vibration. Since wire bonding is required to provide precise connections between pads and leads that have small areas, it is necessary to press the leading end of a bonding tool such as a capillary precisely on the pads and leads.

However, the bonding accuracy between a lead frame or substrate and semiconductor chips is often varied, which can result in a deterioration in bonding quality unless the positional relationship is corrected.

To address this issue, it has been practiced that before wire bonding, pads and leads are imaged using a camera, the image is then processed to read a particular pattern as a binary image, and the positions of the pads and leads are detected and corrected accordingly.

However, if the difference in level between the surfaces of semiconductor chips and leads is increased with an increase in the size of the semiconductor device and the number of pins, the pads on the surfaces of the semiconductor chips and the lead frame or the leads on the surface of the substrate can not be included concurrently within the depth-of-field of the camera, resulting in defocusing either of the images to make position detection impossible.

For this reason, there has been a proposed method of providing two cameras that are focused, respectively, on chips and leads in the same field of view, imaging the chips and leads using the respective cameras, and performing position detection based on the images (see Patent Document 1, for example).

There has also been a proposed method of providing a shutter for switching optical paths in an optical system having two optical paths with different optical path lengths that include chips and leads within their respective depth-of-fields, and switching the optical paths by the shutter to image the chips and leads using a common camera through each optical path (see Patent Document 2, for example).

There has further been a proposed method of imaging semiconductor chips and leads at mutually different heights using three cameras (refer to Patent Document 3, for example).

However, multilayer semiconductor devices in which semiconductor chips are stacked in multiple layers on a lead frame have started to be produced in the recent demand for capacity increase and space saving in semiconductor devices. Such stacking semiconductor chips in multiple layers increase the difference in level in the height direction of the semiconductor chips, requiring imaging devices available for the more increased difference in level in the height direction. In addition, the demand for space saving makes the pitch as well as the size of the pads on the semiconductor chips smaller. This requires an improved imaging accuracy to detect the positions of the pads accurately before wire bonding, requiring high-magnification imaging devices.

In contrast, the dimensional accuracy of lead frames is lower than that of semiconductor chips, and leads are often arranged in substantially varied positions. It is, therefore, necessary to image all the leads connected to the pads on the semiconductor chips to detect the positions of all the leads before wire bonding between each semiconductor chip and lead frame.

Trying to address such demands with the related arts disclosed in Patent Documents 1 to 3 requires multiple higher-magnification and small-field optical systems to be combined, where such higher-magnification optical systems would narrow the field of view imageable in each optical system. However, since the leads are provided around the semiconductor chips, the imaging area for detecting the positions of the leads becomes larger. Imaging such a large area using a small-field optical system for each semiconductor chip or each layer would take a long time to detect the positions of the leads, resulting in a problem that high-speed wire bonding cannot be achieved. On the contrary, combining multiple lower-magnification optical systems using the related arts disclosed in Patent Documents 1 to 3 would not take a long time to detect the positions of the leads, but the imaging accuracy for pads cannot be so high, resulting in a problem that the positions of pads arranged at a small pitch can not be detected accurately.

In other words, the demands for accurate imaging of semiconductor chips having a great difference in level in the height direction and the demands for reduction in time for imaging a lead frame to achieve high-speed wire bonding conflict with each other. The related arts disclosed in Patent Documents 1 to 3 cannot meet such conflicting demands.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to accurately image semiconductor chips having a great difference in level in the height direction and to reduce the time for imaging a lead frame.

According to an exemplary embodiment of the present invention, an imaging device for a bonding apparatus for imaging an imaging subject and multi-layered semiconductor chips mounted on the imaging subjects configured to include:a first optical system having a plurality of optical paths that extend to a plurality of imaging planes through a first lens and have different optical path lengths from the first lens to the respective imaging planes correspondingly to a plurality of subject imaging ranges at different distances from the first lens;a second optical system branching from the first optical system on a subject side of the first lens and having an optical path that extends to an imaging plane through a second lens with lower magnification than the first lens, the second optical system having a field of view wider than that of the first optical system;first imaging elements provided on the respective imaging planes in the first optical system to image each layer of the multi-layered semiconductor chips mounted on the imaging subject; anda second imaging element provided on the imaging plane in the second optical system to image the imaging subject.

In this imaging device of the present invention, the above-described imaging subject is one of a lead frame and a substrate.

According to another exemplary embodiment of the present invention, an imaging device for a bonding apparatus for imaging imaging subject and multi-layered semiconductor chips mounted on the imaging subject is configured to include:a first optical system having a plurality of optical paths that extend to a plurality of imaging planes through a subject side lens and a first imaging plane lens and have different optical path lengths from the subject side lens to the respective imaging planes;a second optical system branching from the first optical system between the subject side lens and the first imaging plane lens and having an optical path that extends to an imaging plane through a second imaging plane lens having a total magnification with the subject side lens which is lower than a total magnification of the subject side lens with the first imaging plane lens, the second optical system having a field of view wider than that of the first optical system;first imaging elements provided on the respective imaging planes in the first optical system to image each layer of the multi-layered semiconductor chips mounted on the imaging subject; anda second imaging element provided on the imaging plane in the second optical system to image the imaging subject.

In this imaging device of the present invention as well, the above-described imaging subject is one of a lead frame and a substrate.

In the imaging devices for a bonding apparatus according to the present invention, the first imaging elements in the first optical system are preferably configured to cooperate with each other to image each layer of the multi-layered semiconductor chips mounted on the imaging subject. The first optical system preferably has an optical path length adjustment means installed in each optical path between the first imaging plane lens and each imaging plane, and this optical path length adjustment means is provided so as to be variable in position in the direction along each optical path. The optical path length adjustment means is preferably an optical path length adjustment lens, the optical path length adjustment lens is made any one of light transmitting glass, plastic, and ceramic.

According to another exemplary embodiment of the present invention, an imaging method of imaging an imaging subject and multi-layered semiconductor chips mounted on the imaging subject using an imaging device for a bonding apparatus is configured to include the steps of:providing an imaging device for a bonding apparatus, the imaging device including:a first optical system having a plurality of optical paths that extend to a plurality of imaging planes through a first lens and have different optical path lengths from the first lens to the respective imaging planes correspondingly to a plurality of subject imaging ranges at different distances from the first lens,a second optical system branching from the first optical system on a subject side of the first lens and having an optical path that extends to an imaging plane through a second lens with a lower magnification than the first lens, the second optical system having a field of view wider than that of the first optical system,first imaging elements provided on the respective imaging planes in the first optical system, andsecond imaging element provided on the imaging plane in the second optical system;a lead image imaging step of scanning the field of view of the second optical system on the imaging subject to cause the second imaging element provided on the imaging plane in the second optical system to image the imaging subject including leads around an entire circumference of the multi-layered semiconductor chips; anda semiconductor chip imaging step of, using the first imaging elements provided on the respective imaging planes in the first optical system, imaging each layer of the multi-layered semiconductor chips at a plurality of height positions.

In this imaging method of the present invention, the above-described imaging subject is one of a lead frame and a substrate.

According to another exemplary embodiment of the present invention, an imaging method of imaging an imaging subject and multi-layered semiconductor chips mounted on the imaging subject using an imaging device for a bonding apparatus is configured to include the steps of:providing an imaging device for a bonding apparatus, the imaging device including:a first optical system having a plurality of optical paths that extend to a plurality of imaging planes through a subject side lens and a first imaging plane lens and have different optical path lengths from the first subject side lens to the respective imaging planes correspondingly to a plurality of subject imaging ranges at different distances from the subject side lens,a second optical system branching from the first optical system between the subject side lens and the first imaging plane lens and having an optical path that extends to an imaging plane through a second imaging plane lens having a total magnification with the subject side lens which is lower than a total magnification of the subject side lens with the first imaging plane lens, the second optical system having a field of view wider than that of the first optical system,first imaging elements provided on the respective imaging planes in the first optical system, anda second imaging element provided on the imaging plane in the second optical system;a lead image imaging step of scanning the field of view of the second optical system on the imaging subject to cause the second imaging element provided on the imaging plane in the second optical system to image the imaging subject including leads around an entire circumference of the multi-layered semiconductor chips; anda semiconductor chip imaging step of, using the first imaging elements provided on the respective imaging planes in the first optical system, imaging each layer of the multi-layered semiconductor chips at a plurality of height positions.

In this imaging method of the present invention as well, the above-described imaging subject is one of a lead frame and a substrate.

The present invention exhibits an advantageous effect that semiconductor chips with a great difference in level in the height direction can be imaged accurately and the time for imaging the lead frame and the substrate can be reduced.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments when the present invention is applied to a wire bonder will hereinafter be described in detail with reference to the accompanying drawings. In the following descriptions, the feed direction, width direction, and height direction of a lead frame61are defined, respectively, as X, Y, and Z directions. As shown inFIG. 1, a wire bonder10includes a Z-direction drive mechanism18installed in a bonding head11that is mounted on an X-Y table12to be movable freely in the X and Y directions. The Z-direction drive mechanism18is equipped with an ultrasonic horn13and a clamper15, and a capillary14is fixed to the leading end of the ultrasonic horn13. A wire16is inserted through the capillary14, the wire16being supplied from a spool17. In addition, an imaging device21for bonding apparatus is fixed to the bonding head11.

Guide rails81aand81bfor guiding the lead frame61with semiconductor chips63mounted thereon in a die bonding step and a bonding stage83for providing a vacuum to cause the lead frame61to stick thereto are attached to a frame (not shown in the drawing) of the wire bonder10.

The wire bonder10is adapted to detect the positions of the semiconductor chips63and the lead frame61based on images taken by the imaging device21, drive the X-Y table12so that the capillary14is positioned over each pad on the semiconductor chips63, operate the Z-direction drive mechanism18to drive the capillary14in the Z direction that is fixed to the leading end of the ultrasonic horn13, and bond the wire16, which is inserted through the capillary14, between each pad on the semiconductor chips63and each lead on the lead frame61.

After bonding between a pad on one semiconductor chip63and a lead on the lead frame61, the wire bonder10drives the X-Y table12so that the capillary14is positioned over the next pad to bond the wire16between each pad and lead, as in the case described above. Then, if all the pads on one set of semiconductor chips63have completely been connected to leads on the lead frame61by wires16, the lead frame61is carried so that the next set of semiconductor chips63are brought to the bonding position. The imaging device21images the semiconductor chips63and the lead frame61to position the capillary14for wire bonding based on the images obtained.

As shown inFIG. 2, the imaging device21includes: an introduction section22for introducing light from the subject semiconductor chips63or lead frame61therethrough; a tubular framework23incorporating optical components such as lenses and mirrors to guide light incident through the introduction section22; and cameras24,25, and26that include imaging elements attached to the tubular framework23to receive light passing through the tubular framework23.

As shown inFIG. 3, the imaging device21has a high-magnification optical system as a first optical system and a low-magnification optical system as a second optical system.

The high-magnification optical system includes: a first high-magnification optical path51extending from the subject semiconductor chips63or lead frame61to an imaging plane36through the introduction section22, a half mirror41, a high-magnification lens34, and a half mirror42; and a second high-magnification optical path52extending from the subject semiconductor chips63or lead frame61to an imaging plane37through the introduction section22, half mirror41, high-magnification lens34, reflected at the half mirror42to branch from the first high-magnification optical path51, and reflected at a mirror43. The low-magnification optical system includes: a low-magnification optical path53extending from the subject semiconductor chips63or lead frame61to an imaging plane38through the introduction section22, reflected at the half mirror41on the subject side of the high-magnification lens34to branch from the high-magnification optical system, and reflected at a mirror44to pass through a low-magnification lens35.

The imaging planes36,37, and38are provided, respectively, with imaging elements31,32, and33for converting images provided on the respective imaging planes36,37, and38into electrical signals. The imaging elements31,32, and33are each constituted by a CCD (Charge-Coupled Device) and/or a CMOS (Complementary Meta-Oxide Semiconductor) element, etc., including a great number of pixels, capable of converting and outputting images into electrical signals for each pixel. The high- and low-magnification lenses34and35each can also be a single lens or a group of lenses in which multiple lenses are combined to correct aberration.

The distance from the high-magnification lens34to the imaging plane37in the second high-magnification optical path52is greater than the distance from the high-magnification lens34to the imaging plane36in the first high-magnification optical path51. Therefore, the second high-magnification optical path52has a focus position where the distance from the high-magnification lens34to the subject semiconductor chips63is smaller than the distance from the high-magnification lens34to the subject semiconductor chips63in the first high-magnification optical path51.

The relationship between the distance between a lens and an imaging plane and the distance between the lens and an imaging subject will be described with reference toFIG. 4.

As shown inFIG. 4, for the lens L, there is a relationship 1/f+1/S=1/S′ wherein the distance from the lens L to a subject focus position A1is S, the distance from the lens L to an imaging plane B1is S′, and f is the focal distance of the lens L. Therefore, if the distance from the lens L to an imaging plane B2on the imaging plane side of the lens L is greater by dS′ than the distance S′ from the lens L to the imaging plane B1, the distance from the lens L to a focus position A2on the subject side of the lens L becomes smaller by dS than the distance S from the lens L to the focus position A1. Here, the “focus position” means a position where an imaging subject therein is imaged on an imaging plane with being focused. In other words, the lens L has a property that the greater the distance between the lens and the imaging plane on the imaging plane side of the lens L, the smaller the distance between the lens and the focus position on the subject side of the lens L. This allows the focus position of the lens L to be adjusted by adjusting the distance between the lens L and the imaging plane on the imaging plane side of the lens L.

Based on the above-described operating principle of the lens L, as seen fromFIG. 5, the second high-magnification optical path52, in which the distance from the high-magnification lens34(corresponding to the lens L) to the imaging plane37(seeFIG. 2) is greater than the distance from the high-magnification lens34to the imaging plane36, has a focus position A2where the distance from the high-magnification lens34to the subject semiconductor chips63is smaller than in the first high-magnification optical path51. In contrast, the first high-magnification optical path51, in which the distance from the high-magnification lens34to the imaging plane36(seeFIG. 2) is smaller than the distance from the high-magnification lens34to the imaging plane37, has a focus position A1where the distance from the high-magnification lens34to the subject semiconductor chips63is greater than in the second high-magnification optical path52.

It should be noted that inFIG. 5, optical systems other than the lenses34and35and the optical paths51,52, and53are omitted.

In the multilayer semiconductor device shown inFIG. 5, three layers of semiconductor chips63a,63b, and63care stacked and mounted on the lead frame61. Pads64a,64b, and64con the respective multi-layered semiconductor chips63a,63b, and63cand corresponding leads62a,62b, and62con the lead frame61are connected with each other by wires16. Since the semiconductor chips63a,63b, and63chave their respective thicknesses, the pads64a,64b, and64cthereon have their respective different levels in the Z direction, i.e., the height direction. In contrast, the leads62a,62b, and62c, which are formed on the surface of the lead frame61, have little differences in level in the Z direction, i.e., the height direction.

The first high-magnification optical path51has a focus position A1where the distance from the high-magnification lens34is greater than in the second high-magnification optical path52, while the second high-magnification optical path52has a focus position A2where the distance from the high-magnification lens34is smaller than in the first high-magnification optical path51. The distance between the focus positions A1and A2is dZ. In contrast, the high-magnification lens34has a depth-of-field D within which imaging subjects can be imaged with being focused. Thus, in the first high-magnification optical path51, imaging subjects can be imaged on the imaging plane36with being focused within the depth-of-field D centering on the focus position A1in the direction along the first high-magnification optical path51, that is, in the Z direction, i.e., the height direction. The depth-of-field D centering on the focus position A1provides a subject imaging range66in the first high-magnification optical path51, and the imaging element31for the first high-magnification optical path51can image imaging subjects within the subject imaging range66. In the second high-magnification optical path52, imaging subjects can also be imaged on the imaging plane37with being focused within the depth-of-field D centering on the focus position A2in the direction along the second high-magnification optical path52, that is, in the Z direction, i.e., the height direction. The depth-of-field D centering on the focus position A2provides a subject imaging range67in the second high-magnification optical path52, and the imaging element32for the second high-magnification optical path52can image subjects within the subject imaging range67.

Since both the first and second high-magnification optical paths51and52pass through the same high-magnification lens34, the depth-of-fields D of the respective optical paths51and52have an equal range. The distance dZ between the focus positions A1and A2depends on the difference between the distance from the high-magnification lens34to the imaging plane36and the distance from the high-magnification lens34to the imaging plane37. According to the exemplary embodiment of the present invention, dZ is set to be equal to the depth-of-field D, as shown inFIG. 5. The first and second high-magnification optical paths51and52can also have the same field of view or their respective different fields of view.

In contrast, as shown inFIG. 5, the low-magnification optical path53uses the low-magnification lens35with a magnification lower than that of the high-magnification lens34for imaging. Since lower-magnification lenses have larger depth-of-fields, the low-magnification lens35has a depth-of-field E larger than that of the high-magnification lens34, and imaging subjects can be imaged on the imaging plane38with being focused within the depth-of-field E centering on the focus position A3in the direction along the low-magnification optical path53, that is, in the Z direction, i.e., the height direction. The depth-of-field E centering on the focus position A3provides a subject imaging range68in the low-magnification optical path53. Since the depth-of-field E of the low-magnification lens35is large, the subject imaging range68in the low-magnification optical path53includes the lead frame61and the multi-layered semiconductor chips63a,63b, and63cmounted on the lead frame.

FIG. 6shows an example of a field of view71of the high-magnification optical system including the first and second high-magnification optical paths51and52and a field of view72of the low-magnification optical system including the low-magnification optical path53on the lead frame61and the semiconductor chips63. As shown inFIG. 6, since the high-magnification optical system uses the high-magnification lens34for imaging, the field of view71includes one corner of the semiconductor chips63. However, since the low-magnification optical system uses the low-magnification lens35for imaging that has a magnification lower than that of the high-magnification lens34, the field of view72is wider than the field of view71of the high-magnification optical system. AlthoughFIG. 6shows a case where the field of view72of the low-magnification optical system includes part of the semiconductor chips63and several leads62, leads62can only be included depending on the position of the field of view.

FIG. 7shows the field of view71of the high-magnification optical system in the same size as the field of view72of the low-magnification optical system, where the field of view71of the high-magnification optical system includes pads64on the semiconductor chips63and a particular pattern65imaged largely therein. As shown inFIG. 8, since the field of view72of the low-magnification optical system images a larger area than the high-magnification optical system within the same sized field of view, pads on the semiconductor chips63and leads62arranged on the lead frame61are imaged smaller than in the high-magnification optical system.

The alignment between pads64on the semiconductor chips63and leads62on the lead frame61using the above-described images taken by the imaging device21for bonding apparatus will be described below.

When the lead frame61with semiconductor chips63bonded thereon is carried to a predetermined position along the guide rails81aand81bshown inFIG. 1, the imaging device21sets the position of the field of view72of the low-magnification optical system to include several leads62on the lead frame61as shown inFIG. 8, and the imaging element33(seeFIG. 3) outputs an image including the several leads62as electrical signals for each pixel. The electrical signals for each pixel of the imaging element33is input to a control device not shown in the drawings, and the control device detects the edges L11and L12of a lead621that extend in the X direction by, for example, normalized correlation processing. Then, the distances in the Y direction between the center of the field of view72and the respective edges L11and L12detected are obtained based on the difference in the number of pixels between the pixel positions in the Y direction of the respective edges L11and L12and the pixel position of the center of the field of view72. Similarly, the control device detects the leading end portion L13of the lead621that extends in the X direction by, for example, normalized correlation processing, and then the distance between the center of the field of view72and the leading end portion L13detected are obtained based on the difference in the number of pixels between the pixel position in the X direction of the leading end portion L13and the pixel position of the center of the field of view72. The control device thus obtains the coordinate positions in the X and Y directions of the leading end of the lead621with respect to the center of the field of view72. Since the imaging device21is fixed to the bonding head11and thereby the coordinate position of the center of the field of view72in the imaging device21with respect to the wire bonder10is known, thus obtaining the X and Y coordinate positions of the leading end of the lead621with respect to the center of the field of view72allows the coordinate position of the leading end of the lead621with respect to the entire wire bonder10to be obtained. Subsequently, the control device obtains the coordinate positions in the X and Y directions of the leading end of each of the several leads62with respect to the center of the field of view72to obtain the coordinate position of the leading end of each lead62with respect to the entire wire bonder10.

After obtaining the coordinate positions in the X and Y directions of the leading end of each lead62included in the field of view72with respect to the entire wire bonder10, the imaging device21then moves to a position where the area adjacent to the field of view72in the Y direction shown inFIG. 6is included in the field of view, and the coordinate position of the leading end of each lead62imaged in the next field of view is obtained. The imaging device21repeats these operations sequentially to scan all the leads62around the semiconductor chips63and thereby obtain the coordinate positions of the leading ends of all the leads62. According to the exemplary embodiment of the present invention, since the field of view72shown inFIG. 6can include about one-third of the leads62arranged to face one side of the semiconductor chips63, only twelve different positions for each field of view are required for imaging to obtain the coordinate positions of all the leads62on the lead frame61, which requires only a significantly smaller number of captive images than in the case of scanning each lead62using the field of view71of the high-magnification optical system shown inFIG. 6to image all the leads62. The shown exemplary embodiment thereof thus has such an advantageous effect that the time for imaging the lead frame61and therefore the time for obtaining the coordinate positions of the leads62can be reduced to achieve high-speed wire bonding.

Next, the imaging device21sets the position of the field of view71of the high-magnification optical system to include the particular pattern65in the corner of the semiconductor chips63as shown inFIG. 7, and the imaging element31or32outputs an image including the particular pattern65as electrical signals for each pixel. The electrical signals for each pixel of the imaging element31or32is input to the control device not shown in the drawings, and the control device performs, for example, normalized correlation processing to obtain the distances in the X and Y directions between the center of the field of view71and the particular pattern65based on the difference in the number of pixels between the pixel position of the particular pattern65and the pixel position of the center of the field of view72. Then, the X and Y coordinate positions of the particular pattern65are obtained with respect to the center of the field of view71and therefore the wire bonder10.

Next, the imaging device21moves to a position where the opposing corner of the semiconductor chips63is included in the field of view to obtain the coordinate position of another particular pattern65in the opposing corner. Since pads64on the semiconductor chips63are manufactured to have more accurate positions than leads62on the lead frame61, obtaining the coordinate positions of the two opposing particular patterns65to locate the coordinate positions of the semiconductor chips63leads to locating the coordinate positions of the pads64. This allows the coordinate positions of the pads64on the semiconductor chips63to be obtained without detecting the position of each pad64.

When obtaining the coordinate positions of the pads64on the semiconductor chips63, the imaging element31for the first high-magnification optical path51is used if the position in the Z direction, i.e., the height direction of each pad64on the subject semiconductor chips63, is within the subject imaging range66in the first high-magnification optical path51shown inFIG. 5, while the imaging element32for the second high-magnification optical path52is used if the position in the Z direction of each pad64on the subject semiconductor chips63is within the subject imaging range67in the second high-magnification optical path52shown inFIG. 5. If the semiconductor chips63are stacked in multiple layers as shown in, for example,FIG. 5, the imaging element31for the first high-magnification optical path51is used to image the semiconductor chips63aand63band obtain the coordinate positions of the pads64aand64bin the first and second layers belonging to the subject imaging range66far from the high-magnification lens34, while the imaging element32for the second high-magnification optical path52is used to image the semiconductor chip63cand obtain the coordinate position of the pad64cin the third layer belonging to the subject imaging range67centering on the focus position A2close to the high-magnification lens34. Since the exemplary embodiment of the present invention thus includes two high-magnification optical paths51and52as well as two imaging elements31and32therefor, images within a large subject imaging range in the Z direction, i.e., the height direction, can be taken with no lens shift while using the high-magnification lens34during wire bonding in such multi-layered semiconductor chips as shown inFIG. 5with a great difference in level in the Z direction, i.e., the height direction, so that the semiconductor chips63a,63b, and63cwith a great difference in level in the height direction can be imaged accurately.

After obtaining the coordinate position of the leading end of each lead62and the coordinate position of each pad64through the foregoing operations, the wire bonder10operates the bonding head11and the Z-direction drive mechanism18shown inFIG. 1to drive the capillary14in the X, Y, and Z directions that is fixed to the leading end of the ultrasonic horn13and thereby to bond the wire16, which is inserted through the capillary14, between each pad64on the semiconductor chips63and each lead62on the lead frame61shown inFIG. 5.

Then, when all the pads64on one set of semiconductor chips63have completely been connected to leads62on the lead frame61through wires16, the lead frame61is carried so that the next set of semiconductor chips63are brought to the bonding position. The imaging device21scans images of the lead frame61again to obtain the coordinate position of each lead62and the coordinate position of each particular pattern65on the semiconductor chips63for the next wire bonding.

As seen from the above, the imaging device21according to the above-described exemplary embodiment of the present invention, which scans each lead62through the low-magnification optical system with a wide field of view to image all the leads62, requires a small number of captive images; accordingly, the time for imaging the lead frame and therefore the time for obtaining the coordinate positions of the leads62can be reduced to achieve high-speed wire bonding. In addition, since the two high-magnification optical paths51and52as well as two imaging elements31and32therefor are provided in the high-magnification optical system, images within a large subject imaging range in the height direction can be taken with no lens shift while using the high-magnification lens34during wire bonding in multi-layered semiconductor chips with a great difference in level in the height direction, so that the semiconductor chips63a,63b, and63cwith a great difference in level in the height direction can be imaged accurately.

Although in the above-described exemplary embodiment of the present invention, the high-magnification optical system includes two high-magnification optical paths, more than two high-magnification optical paths can be provided in accordance with the difference in level of the semiconductor chips63. In the exemplary embodiment of the present invention, which describes the case of imaging the lead frame61and the semiconductor chips63mounted on the lead frame61, can also be applied to the case of imaging a substrate such as a BGA (Ball Grid Array) package and semiconductor chips63mounted on a substrate.

Next will be described another exemplary embodiment of the present invention with reference toFIG. 9. Components identical with those in the exemplary embodiment thereof described with reference toFIG. 3are designated by the same reference numerals to omit descriptions thereof inFIG. 9. The imaging device21for bonding apparatus according to the exemplary embodiment thereof includes as seen fromFIG. 2: an introduction section22for introducing light from the subject semiconductor chips63or lead frame61therethrough; a tubular framework23incorporating optical components such as lenses and mirrors to guide light incident through the introduction section22; and cameras24,25, and26including imaging elements attached to the tubular framework23to receive light through the tubular framework23as shown inFIG. 2, as is the case in the above-described exemplary embodiment of the present invention.

As shown inFIG. 9, the imaging device21for bonding apparatus according to the exemplary embodiment of the present has a high-magnification optical system as a first optical system and a low-magnification optical system as a second optical system. The high-magnification optical system includes a first high-magnification optical path51extending from the subject semiconductor chips63or lead frame61to an imaging plane36through the introduction section22, a subject side lens45and a half mirror41, a first imaging plane lens46, and a half mirror42; and a second high-magnification optical path52extending from the subject semiconductor chips63or lead frame61to an imaging plane37through the introduction section22, subject side lens45and half mirror41, first imaging plane lens46, reflected at the half mirror42to branch from the first high-magnification optical path51, and reflected at a mirror43. The low-magnification optical system includes: a low-magnification optical path53extending from the subject semiconductor chips63or lead frame61to an imaging plane38through the introduction section22, subject side lens45, reflected at the half mirror41between the subject side lens45and the first imaging plane lens46to branch from the high-magnification optical system, and reflected at a mirror44to pass through a second imaging plane lens47.

The subject side lens45and the first imaging plane lens46form a high-magnification total lens, while the subject side lens45and the second imaging plane lens47form a low-magnification total lens having a lower total magnification than the high-magnification total lens formed by the subject side lens45and the first imaging plane lens46. The subject side lens45and the first and second imaging plane lenses46each can also be a single lens or a group of lenses in which multiple lenses are combined to correct aberration. Further, the imaging planes36,37, and38are provided, respectively, with imaging elements31,32, and33for converting images provided on the respective imaging planes36,37, and38into electrical signals. The imaging elements31,32, and33are each constituted by a CCD and/or a CMOS element, etc., including a great number of pixels, capable of converting and outputting images into electrical signals for each pixel.

The high-magnification optical system substantially has one high-magnification-total lens formed by the subject side lens45and the first imaging plane lens46. Accordingly, as seen fromFIG. 4, the distance S′ between the lens L and the imaging plane on the imaging plane side of the lens corresponds to the distance between the first imaging plane lens46and the imaging plane36or37. Accordingly, the second high-magnification optical path52, in which the distance from the first imaging plane lens46to the imaging plane37is greater than the distance from the first imaging plane lens46to the imaging plane36and thereby the distance from the high-magnification total lens to the imaging plane37is greater than the distance from the high-magnification total lens to the imaging plane36, has a focus position A2where the distance from the subject side of the lens45of the high-magnification total lens to the subject semiconductor chips63is smaller than in the first high-magnification optical path51. In contrast, the first high-magnification optical path51, in which the distance from the first imaging plane lens46to the imaging plane36is smaller than the distance from the first imaging plane lens46to the imaging plane37and thereby the distance from the high-magnification total lens to the imaging plane36is smaller than the distance from the high-magnification total lens to the imaging plane37, has a focus position A1where the distance from the subject side lens45of the high-magnification total lens to the subject semiconductor chips63is greater than in the second high-magnification optical path52.

The low-magnification optical system is the same as in the above-described exemplary embodiment of the present invention except that it includes the second imaging plane lens47having a lower total magnification with the subject side lens45, which is used commonly with the high-magnification optical system, than the high-magnification total lens.

The alignment method between pads64on the semiconductor chips63and leads62on the lead frame61using images taken by the imaging device21for bonding apparatus according to the exemplary embodiment of the present invention is the same as in the above-described exemplary embodiment thereof.

In addition to the same advantageous effects as in the above-described exemplary embodiment of the present invention, the exemplary embodiment thereof, in which each optical system includes a total lens formed by the subject side lens45and the first or second imaging plane lens46or47, exhibits an advantageous effect that the length of the entire optical systems can be reduced to provide a space-saving imaging device21for bonding apparatus.

In the exemplary embodiment of present invention, which describes the case of imaging the lead frame61and the semiconductor chips63mounted on the lead frame61, can be applied to the case of imaging a substrate such as a BGA package and semiconductor chips63mounted on the substrate. The substrate can also include a tape with leads printed thereon.

Still another exemplary embodiment of the present invention will be described with reference toFIG. 10. Components identical with those in the exemplary embodiments thereof described with reference toFIGS. 3 and 9are designated by the same reference numerals to omit descriptions thereof.

In the imaging device21for bonding apparatus according to the exemplary embodiment of the present invention, an auxiliary lens48for optical path adjustment is provided between the mirror43and the imaging plane37in the second high-magnification optical path52in the exemplary embodiment thereof described inFIG. 9. Adjusting the position in the direction along the second high-magnification optical path52of the auxiliary lens48allows the focus position A2of the second high-magnification optical path52and the position of the subject imaging range67to be adjusted in the direction along the second high-magnification optical path52, that is, in the Z direction, i.e., the height direction shown inFIG. 5, so that the distance dZ between the subject imaging range66in the first high-magnification optical path51and the subject imaging range67in the second high-magnification optical path52can be set so that the subject imaging ranges66and67are arranged to be overlapped with each other or to have a clearance therebetween.

Although the above-described exemplary embodiments of the present invention describe the case of applying the imaging device for bonding apparatus to the wire bonder10, the present invention can be applied to other bonding apparatuses such as die bonders, flip-chip bonders, and tape bonders.