WO1997018697A1 - A method and a system of imaging an electronic component in a component mounting device - Google Patents

Abstract

A component mount machine for mounting electronic circuit elements (101) has movable mirrors (809, 810) for recording the accurate position of a component (101) and the coplanarity of leads (101') thereof. The mirrors are always located symmetrically in the same angle to the bottom surface of the component (101) and are moved horizontally to positions underneath the component for reflecting pictures of the component to cameras (801, 802). The two mirrors produce in first, proximate positions (114) a composite picture of the bottom of the component (101). In second, distant positions a picture is obtained, for a suitable vertical position of the component, of rows of connecting leads (101') of the component, the image plane then forming a small angle to the bottom surface of the component. In the second position a background illumination is obtained from light sources (805, 806) suitably arranged beneath the cameras (801, 802) and the light rays are then deflected by additional mirrors (803, 804) located near the cameras. Cameras having a stripshaped recording field with only a single or a few pixel elements in a horizontal movement direction of the component can be used in an alternative embodiment for taking pictures 'in the fly', producing a series of pictures to be analysed for position data.

Description

A method and a system of imaging an electronic component in a component mounting device .

FIELD OF THE INVENTION

The present invention relates to automatic assembly machines and in particular to imaging devices used in such machines for obtaining information on the actual position of a δcomponent to be mounted.

BACKGROUND OF THE INVENTION

This invention is a development of an optical centenng and electronic test device disclosed in the International Patent Apphcation published under No. WO 96/09743, which is incorporated by reference herein. io Assembly machines for surface mounted devices often use optical centenng. Such machines pick up components from component feeders and place them on a circuit board.

The position of the component in the feeder at the time of the actual pick-up operation is not known with enough precision to permit an accurate placement of the component on the circuit board The component may for example be picked up from a waffle pack or an embossed i5tape. The cavity in such a tape is larger than the component, thus permitting the component to be located anywhere within a certain area. The uncertainty of the component position within the cavity is larger than the position tolerance permitted on the board. Therefore a centenng operation is necessary to reduce the uncertainty of the component position on the pick-up nozzle after the ptck-up operation. Two methods are used. In a first method the

2ocomponent is moved by mechanical means to a position that is well centered around the axis of rotation of the pick-up nozzle, see e.g. the International Patent Apphcation published under

No. WO 86/03367. In a second method, the actual position of the component on the nozzle is maintained, but the position is measured by means of laser rays, image processing or other optical means. This method does not actually centre the component, but is anyway named

25"contactless centenng". A placement of components using data of their position relative to a pick-up nozzle obtained from image processing is normally named "optical centering".

For electronic components having many connection pins or leads, the leads should preferably be inspected before mounting in order to ensure that leads are not bent away from the intended direction. A camera looking vertically upwards from the bottom side of the 3ocomponent can identify and measure deviations of the relative position of leads in the horizontal plane. Such deviations can, if they are large enough, cause the component leads to be placed too far away from the respective pads on the circuit board which are designed to connect to them when the component is mounted on the board

Such components should also be tested for directional deviations in the vertical plane 3δSuch deviations may leave one or more leads placed so far above the pad that it/they will not be connected to the respective pad/s in the following soldering process

Another requirement of pick and place machines for high quality production environments is a capability to verify the electric values of the passive components. This is preferably done by means of test electrodes that contact electrically connect to a component

4owhιle it rests on the pick-up nozzle. This will however add more mechanical details that must

CONFIRMATION COPY move in the space at and below the nozzle, thus requiring a higher lifting movement of the nozzle and/or complex mechanics.

Today, optical centering is mainly done by two methods. In one method, the pick-up head passes over a stationary camera with a speed that is low enough to permit a distinct srecording of the image. In another method, a camera or cameras are placed on the pick-up head.

Methods and devices for reproduction of components in assembly machines are e.g. disclosed in International patent applications WO 96/10325, WO 96/12395 and WO 96/12396. io SUMMARY OF THE INVENTION

It is an object of the present invention to provide an optical coplanarity test device that can be attached to a mount head in a component assembly machine and that permits a coplanarity test of components of widely varying sizes.

It is another object of the present invention to provide an optical coplanarity test device i5that can be attached to the mount head and that permits the same basic coplanarity test method both for systems using cameras located on/rigidly attached to the pick-up head and cameras located/rigidly attached at a stationary frame of the machine.

It is another object of the present invention to provide an optical coplanarity test device that can be attached to the mount head and is compatible with an efficien : mechanism for the 2oconnection of passive components to an electric data verifier.

It is another object of the present invention to provide an optical coplanarity test device that is easily integrated using the same camera and lenses as used for optical centering.

It is another object of the present invention to provide an optical centering device that can give a high resolution without having to use expensive high pixel count image cameras 25(like 1024x 1024 pixel cameras) and instead permits use standard cameras of lower cost or linear array cameras.

The invention offers a solution to problems mentioned above by providing an optical system that has one or several optical centering cameras on the mounting head or in the frame of the mount machine combined with two movable mirrors that can move from a passive soposition far from the pick-up nozzle path to an active position, where the two mirrors changes the field of view of the image capturing system from an optical centering phase where the image capture plane is basically identical with the seating plane of the leads of the component being tested to a coplanarity test phase with the image capturing plane approximately peφendicular to the seating plane of the component. The mechanism moving the mirrors can 35also move electronic component verifying electrodes.

The objects mentioned above and others are achieved with methods and devices described below for imaging an electronic component and its electrical connecting leads or pins in a component mounting device. A surface area is provided for emitting light, in particular a light diffusing area emitting lights in many directions. Moving means such as for providing the conventional z-movement then move the component in a vertical direction to a position where the light emitted from the surface hits a bottom surface of the component, where this light should hit the bottom surface in a direction forming a small angle to the bottom surface, such as e.g. with the interval of 3 - 15°. The connecting leads or pins of 5the component can then be seen in a picture of the surface area, if looking directly at the surface area in substantially the same but inverse direction. Camera means and possible optical elements are provided for taking a picture of the surface area in substantially this direction, i.e. in a direction substantially parallel to or preferably forming a small angle to the flat bottom surface of the component, e.g. the small angle being in the interval of 3 - 15°. ιoThe camera means are focused so that in the picture the connecting leads or pins in a row are seen sharply or distinctly, i.e. the optical system for the reproduction in the camera has a focal plane or focal line passing substantially through the connecting leads or pins, particular through the outermost portions thereof. Such a focal plane or the plane of the sharply depicted portions of the component in the image is then substantially perpendicular to the ι sbottom surface of the component or preferably forms a small angle to a line perpendicular to the bottom surface, the angle being comprised in the interval mentioned above.

The surface area of the light emitting means is preferably flat and can be located substantially perpendicularly to the bottom surface of a gπpped component or so that it forms a small angle to a line perpendicular to the bottom surface.

20 A component mounting device conventionally compnses means for image reproduction and image processing and analysis for determining the position of a component to be mounted that has been gnpped by pick-up head. The image processing means can analyze such pictures for determining the position of the component leads in a depicted row for finding whether they all are coplanar, that is are located in the same plane.

25 The pick-up head generally can move in at least one hoπzontal direction by moving a wagon or slide, on which the pick-up head is mounted. The head can gnp and move a component at least in a vertical direction. Thus a gπpped component can be moved honzontally or generally in a direction substantially parallel to a bottom surface thereof. Several pictures of the bottom surface of the component can be captured when it moves by

3ocamera means. The camera means can be designed to have a stπpshaped aperture or to have a stπpshaped recording or picture field, so that each picture captured by the camera has a small extension in the movement direction of the component and a long extension in a direction peφendicular thereto. The camera means can be the digital type, e g. comprising an array of CCD-element. The digital pictures will then have only one or only a few pixel elements in

35the movement direction and a large number of pixel elements in the direction peφendicular thereto. The CCD-array can thus comprise a single line or only a few lines, e.g. 3 - 5 lines, of light-sensitive elements. Thus each picture captured by such camera means will depict only a narrow stπp of the component and/or of its electπcal connecting leads or pins, when the component moves past the area depicted by the camera means Mirror means can be provided which are movable, e.g. by having mirrors attached to movable slides or wagons, that move symmetπcally for approaching each other and travelling away from each other in a hoπzontal direction or generally substantially in parallel to the bottom surface of a gπpped component. For suitable positions of the slides and thus the

5mιrrors in relation to the component light from the component or desired portions thereof can be deflected to hit the entrance opening and the optical systems of the camera means for different imaging cases. In a first position the picture of the component can be taken to shaφly depict component portions located in a plane essentially coinciding with a bottom surface of the component for determining the overall position of the component, in particular ιothe rotation thereof in a hoπzontal plane. In a second position the picture can be taken to shaφly depict, as has already been descnbed, component portions located in a plane substantially peφendicular to the bottom surface of the component or, preferably, forms a small angle to a line peφendicular to the bottom surface, the component portions thus being the leads of a row. i5 Also other, second mirrors can be used which are not moved. The)' can be located to have a reflecting surface substantially parallel to a light entrance opening of the camera means, i.e. to plane for instance passing through an entrance lens of the cameras. Such a second mirror can for a suitable location of all the optical elements reflect the light rays to form an image only when captuπng an image in the second position of the at least one first

2omιrror.

In one arrangement, suitable when the camera means are stationary, e.g. πgidly attached to a frame of the component assembly machine, the first position of the movable mirror can be chosen, so that light rays forming the captured image pass directly to an entrance opening of the camera means and thus are not deflected by any mirror means. Then,

25in the second position of this mirror light rays from portions of the component will be deflected only once by a mirror, i.e. this movable mirror. BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be descnbed by way of example with reference to the accompanying figures:

30 - Figure la is a side view of the optical paths when a component is viewed in a plane parallel to its seating plane by two centenng cameras by means of a high speed mirror pair,

- Figure lb is another view of the optical paths for one of the two cameras,

- Figure 2a is a sectional view of the camera and mirrors of Figures la and lb together with mechanical devices required for movement of mirrors and illumination devices in the

36i mage capture position,

- Figure 2b is a top view corresponding to that of Figure 2a also showing mechanical dnvmg means,

- Figure 3a is a top view similar to that of Figure 2b but when the component moves vertically, - Figure 3b is a sectional view similar to that of Figure 2a but corresponding to the opened position of Figure 3a,

- Figure 4a is a sectional view of the mirror carrying wagons having additional mechanical means for electrodes in a position permitting the connection of the picked up

5Component to an electronic veπfier,

- Figure 4b is a sectional view similar to that of Figure 4a of the same component dunng the optical centenng phase,

- Figure 4c is a sectional view similar to the views of Figures 4a and 4b of the same component dunng vertical movement, io - Figure 5 is a schematic side view of an optical centenng device where the two mirrors in the active positions act as one single flat mirror,

- Figure 6 is a schematic side view illustrating the optical paths for a system similar to that of Figure la but having larger focal distances,

- Figure 7 is a perspective view of a component mount machine system suited to utilise i5the devices shown in the other figures,

- Figure 8 is a schematic side view of an optical centering device having added illumination and mirrors to permit a test of coplananty while performing coplananty test of a large component,

- Figure 9 is a schematic side view of an optical centenng device having added 2oillumιnatιon and mirrors to permit test of coplananty while performing coplananty test of a small component,

- Figure 10 is a schematic side view of an optical centenng and coplananty test device using a linear array camera ngidly attached to machine frame and moveable mirrors performing optical centenng of a large component,

25 - Figure 1 1 is a schematic side view similar to that of Figure 10 showing the device performing a coplananty test of a large component,

- Figure 12 a schematic side view similar to that of Figure 10 showing the device performing a coplananty test of a small component,

- Figure 13 a schematic side view similar to that of Figure 10 showing the device 3operformιng an electnc test of a small component,

- Figure 14 is a view from above of an array of light sensitive element of a camera used in the embodiment of Figures 10 - 12

DETAILED DESCRIPTION

Figures la and lb are side views of the optically relevant part of a mount head of a 35Component mount machine, see the descnption of Figure 7 hereinafter A component 101 is kept in its position as illustrated by a pick-up shaft and an associated nozzle, see Figure 3b Light from mainly the bottom side of the component is reflected by two obliquely positioned mirrors 1 13, 1 14 to hit cameras which are shown schematically at 102 and 103 and have light entrance openings as illustrated compnsing suitable optics, if needed The cameras should preferably offer a large field of view and a high resolution The resolution required is some 1000 x 1000 pixels With presently available cameras such large resolutions are costly, and therefore, using present camera technology, a set of two 1/3 inch CCD-cameras can be used One such camera could have a field of view of for example 40 5x54 mm By placing

5two such cameras side by side, they could cover an area of 54 x 81 mm'- In the embodiment shown, the utilized field of view is basically square, thus permitting a complete view of components up to some 54 x54 mm' in one exposure The total field of view is shown in Figure lb as dimension 104 by dimension 105. The field of the two cameras overlap so that both cameras cover the section shown at 106 in Figure lb The area seen from camera 102 locovers the area from 107 to 108, the other camera 103 covenng the span from points 109 - 110 to points 1 1 1 - 1 12.

Commonly available camera chips transfer data starting at the top hoπzontal line By a suitable onentation of the CCD camera chips, the image information could thus be accessed starting with the two lines in the centre of the combined field of view The camera 103 iδshould for example be so onented that the data corresponding to the line 109 - 110 is transmitted first and the data corresponding to line 1 1 1 - 112 is transmitted last Thereby the time required to wait for obtaining data regarding small components in the centre of the image can be substantially reduced.

In the embodiment shown the overlapping range 106 is small, e g less than 5 % of the

2ototal area of a camera chip With the aspect ratio of presently common camera chips, this means that the last part of the image surface of the camera chip will not be used

The mirrors 1 13 and 1 14 are basically flat mirrors and are located, in the closed position as illustrated in Figures la and lb, in a symmetrical fashion in an angle to the generally flat bottom surface of the component, and in an angle alsc to the movement

25dιrectιon of the component, the Z-direction which is substantially pe'φendicular to the component bottom surface. The angle to the bottom surface is as illustrated about 30° but can generally take any angle of the range 15 - 45 ° or even larger angles, considenng suitable mounting places of the cameras 102, 103 and the illumination directions, lor avoiding light to be emitted directly into the camera entrance openings

30 The mirrors 1 13 and 1 14 have a rectangular shape As can be seen from the optical paths as illustrated in Figure lb, the mirrors could be made smaller by eliminating the mirror outside a line from reflection area 1 15 of the rays from point 1 1 1 to the mirror corner that reflects the rays from point 109

Figures 2a to 3b are views showing parts required for moving the mirrors 1 13 and 1 14

35and for illuminating the component 101. The Figures 2a and 2b are two views of the device in the image captunng position and the Figures 3a and 3b are views of tie device in a fully open position suitable for lifting or loweπng large components

In Figure 2a the component 101 , the cameras 102 and 103 and the mirrors 1 13 and 1 14 are shown in the same position as shown in Figures la and lb The oblique mirror 1 13 is carried by a wagon 201 that runs along two parallel linear bearing shafts 202 and 203 using ball slides 204 and 205. A motor indicated by the dashed line 206 can move the wagon 201 through two steel bands 207 and 208 which at first ends are secured to an arm 209 that is integrated with the wagon 201. The two bands run around a spulley 210 secured to the shaft of the motor and the other ends of the bands are secured to an arm 211 that is an integral part of a wagon 212 that carπes the other mirror 114. The thickness of the steel bands 207 and 208 is highly exaggerated in the figure; if drawn in a correct scale they would be invisible in the figure.

The second wagon 212 uses ball slides 214 and 215 to run along the same linear ιobeanng shafts 202 and 203 as is used by wagon 201.

The illumination is arranged by LEDs 213 arranged along the exteπor edges of the flat, rectangular mirrors 1 13 and 1 14, of course not at the edges where the mirrors connect to each other.

Any lateral movement of the mirrors 1 13 and 114 wiil cause an almost equally large lδvirtual movement of an image captured by the optical centenng camera, thus causing an almost equally large error in a calculated position or in the shape of the component, when the picture data from the camera is used for calculating the position of the component 101. The basic design of the mechanism of Figure 2b can however easily be made so that the position of the mirrors when closed together as shown in Figure 2b is very stiffly and definitely 2odefined The task for the servo motor 206 controlling the movement of the two mirror carrying wagons 201 and 212 is in this position very simple: it should only apply a torque directed to press the two wagons together.

The embodiment as descnbed has therefore a very low sensitivity to servo displacement due to large hoπzontal accelerations and thus, it can be secured to the pick-up head, see 25Fιgure 7, of the mount machine without having the movements of the head interfeπng with the operation of the image acquisition system. The mirror position servo is basically pressing against a mechanical stop. The accelerations of the head affect the two hoπzontal axes, not the vertical one, and the vertical Z-axis is therefore basically unaffected. Small vertical movements of the Z-axis will only marginally affect the data obtained from the camera 3oimage. Vertical movements cause a virtual size scale error in the image taken by the cameras 102 and 103 or 503, see Figure 5 descnbed hereinafter; the data concerning the honzontal centre position of the component 101 on the nozzle 102, see Figure 3b, and its angular position will be only marginally affected by a small vertical movement of the Z-axis

From Figure 2a it also obvious that the device can operate satisfactorily with a very 35hmιted vertical lifting movement, that is the extension of the mirror system in vertical direction is small, this being achieved pπmaπly by the split mirror configuration and also by the preferred angle of about 30° of the mirrors.

The views of Figures 3a and 3b show the two mirror carrying wagons 201 and 212 in their fully opened position. The component 101 is shown at the end of a movement down to the circuit board 301. The component is retained by a vacuum nozzle 302 that is moved vertically along an axis 303 and that can be rotated around the same axis 303.

Figure 4a is a side view of the mirror wagons like 201 and 212 of Figures 2a - 3b The wagons shown have mechanical devices for electrodes. These electrodes permit the δconnection of an electronic venfier to a component.

In the normal component assembly sequence, the component is first picked up by moving the mirror-electrode units 407 and 408 when they are located apart from each other, as shown in Figure 4c so that the Z-shaft and its nozzle 402 can go down to reach a level where the components are available in the feeders, compare Figure 7. The rotation of the ιonozzle 402 around the axis 409 can be controlled by a motor. The beanngs, motors etc. used to vertically move and turn the nozzle 402 along and around the vertical axis 409 are not shown

To permit a check of the electrical value of the component 401 , the component 401 is first picked up. It is then lifted to the position shown in Figure 4a. Dunng the lift operation it i5is, if required, rotated so that its electπcal connection surfaces face the electrodes 403 and 404. These are then closed together so that the electrodes 403 and 404 can establish contact to the connection surfaces of the component 401 (This will in addition cause a mechanical centering of the component 401 in one dimension relative to the nozzle 402.)

The component 401, for example an 0805 resistor, is thereby connected to an electronic 2otest device, not shown, that can compare the expected value of the component to the real value as measured.

The electrodes are assembled on a small vertical platform 405. The electncal connections to the electrodes are made through a connector 406. This permits an easy exchange of the electrodes. By using different vertical positions different electrode sets can be

After the electronic test has been successfully performed, the mirror-wagons 407 and 408 are moved apart so that the Z-shaft can go up to reach the level shown in Figure 4b. The mirror-wagons 407 and 408 are then moved together to create the optical path shown in Figures la - lb and 4b. 30 The captured image permits the position of the components 401 position on the nozzle 402 to be calculated and a correct placement on the circuit board to be performed using control pπnciples for optical centering which are already well known

Figure 5 is a schematic side view illustrating an optical centenng device where the two mirrors act as one single flat mirror in the active positions thereof. This will give a larger 35vertιcal extension of the mirror system than that of the embodiment described above having mirrors which are located with their reflective surfaces in a substantial angle to each other.

In Figure 5 only the components are shown that determine the optical paths The mirror pair 501 and 502 are movable in the left-πght direction, for example using mirror and electrode carrying wagon pairs like 201 and 212 of Figures 1 - 4 The mechanical devices for moving the mirrors 501 and 502 can generally be designed as has been described herein for the first embodiment

The camera 503 is placed behind a double prism 504 acting as a semitransparent mirror or beam splitter. The mirror permits light from a source 505 to illuminate the component 5506 The use of two halfmirrors 501 and 502 that act as one common mirror can of course be used together with other illumination arrangements.

Figure 6 is a schematic side view of the optical paths for a system similar to that of Figures la, lb but having larger focal distances

Items in Figure 6 denoted by numbers in the 100-senes are similar to those of Figure io la Since the focal distance is larger, there is more space between the camera lenses 102 and 103 and the component 101 and mirror pair 1 13 - 1 14 Presently common camera chips having a resolution of 752x582 pixels, if used in the embodiment of Figures la - 3b and 6, will permit a 752x752 pixel resolution for a square field of view indicated by the distance 107 - 111 in Figure 6. The square field of view will however not utilize the whole camera chip; a i5rectangular field of view from points 601 to 602 can be obtained if the mirrors 1 13 and 114 are enlarged to include the optical paths indicated by 603 and 604

The two embodiments shown permits an accurate optical centering of large components using presently available camera chips.

Presently emerging camera chips having a square field of view of 1024 x 1024 pixel 20W1II, if used in the embodiment of Figure 5, permit a 1024 x 1024 pixel resolution for a square field of view.

In the cases where the resolutions of the cameras 102 103 or 503 are too low, a chassis mounted camera, not shown, could be used. As components requiring such very high resolution are low-frequent, this camera can have a small field of view and handle larger 25Components by taking several images in the pπor art manner

In Figure 7 a component assembly or pick-and-place machine is illustrated in a perspective view showing the general configuration of such a machine. The wagon 701 is movable along the honzontal bar 703 to different locations, such as above magazine sites 705 intended to hold component feeders, which are movable in a honzontal direction sopeφendicular to the guide bar 703 and above a printed circuit board 707 retained on a slide, also movable in the same direction as the magazine sites 705. The wagon 701 carπes a pickup unit 709, at the lower side of which a vacuum nozzle such as 302, 402 is located which can be moved vertically and rotated about a vertical axis The nozzle can pass through a frame 71 1 carrying the optical devices for an optical centenng of a component hold by the sδnozzle, for instance the obliquely positioned mirrors of Figures 2a - 4c

Figure 8 shows an optical centenng device similar to that of Figures la - 4c and 6 but having additional illumination and mirrors to permit a test of coplananty while performing a coplananty test of a large component and in particular of its electncal connection leads.

The mirror shown in dashed lines at 1 14 has the same position as the mirror 1 14 of Figure la, and the optical path from the line 109 - 1 10 also drawn in similar dashed lines has been added to the figure to show that the operations of optical centering can performed with the device illustrated in Figure 8 as well as with that of Figure la.

In Figure 8 the component 101 is in a somewhat lower position than in Figure la and

5the two mirror wagons (201, 212 in Figures 2b, 2c) are in an intermediate position. The only part shown of the mirror wagons are the mirrors 809 and 810; they correspond to the mirrors 1 13 and 1 14 respectively of Figures la - 4c.

The optical imaging systems of the cameras 102 and 103 of Figures la - lb are illustrated by lenses shown at 801 and 802. The camera housings have been enlarged to loaccommodate each one a mirror 803, 804 and a background illumination device 805, 806. The illumination devices 805, 806 can each comprise a diffusor plate or diffusor element 807 and light sources 808 such as LEDs.

By selecting the positions of the mirrors 809 - 810 and the vertical position of the component 101 in relation to the illumination devices 805, 806 and lhe camera optical i5systems 801 , 802 the focal distance of the camera optical systems 801 and 802 can be kept constant thus permitting fixed focus optical systems In Figure 8, only the illumination device 805 is shown to be switched on. Assuming that the illumination from other sources is low, this will cause the leads of the component 101 to be seen by the opposite camera system 802 as dark shadows against the bπght background produced by light coming from the

2oιllumιnatιon device 805.

In the device shown, the illumination devices 805, 806 are arranged to have their front surfaces substantially vertical, located below the camera lenses 801 , 802. In any case, they should give a background illumination as viewed in a nearly honzontal direction, the light rays therefrom to the connector leads having a small angle to a hoπzontal plane, e.g. in the

25magnιtude of order of 3 - 15° . The front surfaces of the illumination devices 805, 806 could thus be tilted correspondingly, a small angle in relation to a vertical line. The fixed mirrors 803, 804 are arranged to receive the background illumination from the il lumination devices 805, 806 directly at this angle, so that they are located in a hoπzontal plane placed a small distance above the illumination devices. These mirrors 803, 804 can then De arranged a little

3oabove the camera lenses 801 , 802 and be parallel therewith, e.g. positioned a little also in front of the inlet openings of the lenses in a honzontal direction. When the test for coplananty of the component leads is made, the bottom side of the component 101 will then be located in a hoπzontal plane passing through or very close to the fixed mirrors 801 , 801 in the camera housings.

35 In order to collect data on the coplananty of the whole componenl 101 , i.e. that the outermost portions of the component pms or leads 101 ' have their bottom surfaces located in substantially the same plane, several registrations must be done. First the optical centenng image is taken and analyzed. If required, the component 101 is then rotated about a vertical axis to make the long sides or edges of the component parallel with the mirrors 803 and 804 The two parallel lines of leads which then are accessible are registered using the cameras 801 and 802. The component 101 is then rotated 90° and the two remaining lead rows are registered

Figure 9 shows the device of Figure 8 performing a coplananty test of a small δcomponent 901, illustrating the fixed focus operation of the optical arrangement. A suitable focus plane of the camera optical system for depicting the leads can thus obtained for components having different sizes by positioning the movable mirrors 809, 810 appropπately.

Figures 10 and 11 show a portion of a mount head or wagon 701 in different positions relative to a stationary linear array camera 1007 πgidly attached to a frame of a component lomount machine The camera 1007 is arranged to have its optical axis directed essentially vertically in order to receive light rays coming from points above the camera. The camera 1007 basically gives only a single line or only a few parallel lines of pixels, see also the plan view of the camera in Figure 14, to get an image, the wagon 701 is moved in the hoπzontal direction while the camera 1007 takes the line images The illustrated device permits an iδoptical centenng, a test for coplananty and an electπc test.

Figure 10 shows the device using the camera 1007 for performing an optical centenng of a large component 101. Some background illumination is assumed to provide diffuse light directed downwards towards the inlet opening of the camera 1007 The wagon 701 is shown in a position where a pixel line like the line 1 1 1 - 1 12 of Figures la - lb can be registered.

2oUsιng a 1024 pixel line and an active area of 60 mm, each pixel covers an area of 58x58 μm^ and the pixel line a surface of 58x60,000 μπv. If the pixels can be read a 50 MHz rate, the time required to read a line is 20.4 μs The permitted speed of the wagon 701 is therefore limited to 58 μm in 20.4 μs or 2.84 m/s, which is above the maximum speed of most pick and place systems. Obviously, the wagon 701 can be run at slower speeds If the background

25illumιnatιon (no illumination means are shown in the figure) is fired during some 2 μs as soon as the wagon 701 has moved 58 μs and a pixel line is read after each illumination, a correct image will be obtained. The image plane is parallel to the seating plane of the leads of the component 101.

On the wagon 701 there are two mirror and electrical test connector wagons 1001 and

3ol002. They can mechanically be similar to the wagons 201 and 212 of Figures 2a and 2b. They carry electπcal test devices that can be similar to those described with reference to Figures 4a - 4c, see e g. the electrodes 403 also shown in Figure 10 Furthermore, the two wagons 1001 and 1002 carry oblique mirrors 1003 and 1004 located beneath the electπcal test devices and having their pπmary reflective surfaces turned downwards On the mount head

35701 two background illumination devices 1005 and 1006 similar to those illustrated at 805 and 806 of Figure 8 are shown but somewhat tilted in relation to a vertical line or plane

Figure 11 shows the device of Figure 10 performing a coplananty test of a large component 101 The two wagons 1001 1002 have been moved in the horizontal direction to suitable locations and the component 101 has been lowered to a position a little above a hoπzontal plane through the illumination devices and possibly rotated so that the leads thereof will be in the focusing line of the fixed focus camera 1007 The image plane is almost peφendicular to the seating plane of the leads of the component 101

Figure 12 shows the device of Figure 10 performing a coplanar ty test of a small βcomponent 901. The two wagons 1001 - 1002 have been moved in the hoπzontal direction to suitable positions closer to each other and the component 901 has been lowered to a suitable level and possibly rotated so that the leads thereof will be in the focusing line of the fixed focus camera 1007

To completely handle a component 101 , the mount head or wagon 701 has to move ιoover the fixed camera 1007 three times. First the optical centenng image is taken, see Figure 10. If required, the component is then slightly rotated to make the long sides of the component parallel with the mirrors 803 and 804 The two accessible paiallel lines of leads are registered using cameras 801 and 802 The component is then rotated 90° and the two remaining lead rows are registered. To permit the rotation of the component like 101 , the two iβwagons 1001 and 1002 have to be opened and then returned again to the correct distance for focusing

Figure 13 shows the device of Figure 10 while connecting the leads of a small passive component to an electnc parameter test system in basically the same manner as descnbed with reference to Figures 4a - 4c

20 Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted here that vaπous changes and modifications will be apparent to those skilled in the art The illumination of the components to be studied can for example be made in several ways already used in the industry for optical centenng puφoses The illumination can aim at the component leads and the bnght

25background devices like 805 can then be replaced by dark surfaces The embodiment using cameras mounted to the machine frame are shown for basically linear cameras, coplananty of components can as well be tested using wagon movable mirrors and a area coveπng camera. The mirrors 1003 and 1004 have been shown as flat mirrors, they can with some advantage be made as cylindncal mirrors, thus obtaining a higher resolution in the vertical direction soTherefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as included therein

Claims

1 A method of imaging electπcal connecting leads or pins of an electronic component in a component mounting device, characterized by the steps of

- emitting light from a surface area,

5 - moving the component to a position where the emitted light hits a bottom surface of the component in a direction forming a small angle to the surface and the connecting leads or pins thereof are seen in a picture of the surface area,

- taking a picture of the surface area, in particular as seen in a direction substantially parallel to or preferably in a direction forming a small angle to the bottom surface of the locomponent, in which picture the connecting leads or pins are also seen, and/or so that the plane of the shaφly depicted portions of the component in the image is substantially peφendicular to the bottom surface of the component or preferably forms a small angle to a line peφendicular to the bottom surface

2 A method of imaging an electronic component in a component mounting device for a issubsequent analysis of the position thereof, characterized by the steps of moving the component in a direction substantially parallel to a bottom surface thereof, taking a multitude of pictures of the bottom surface of the component when it moves, each picture having a small extension in the movement direction and a long extension in a direction peφendicular thereto, preferably by taking digital pictures, the pictures having only 2oone or only a few pixel elements in the movement direction and a large number of pixel elements in the direction peφendicular thereto, so that each picture depicts only a narrow stnp of the component and/or of electncal connecting leads or pins attached thereto.

3 A method of imaging a component in a component mounting device compnsing the steps of

25 - moving the component and mirror means in relation to each to first positions,

- taking pictures of the component as reflected by the mirror means, characterized in that the mirror means are moved to a first position and then to a second position, so that light from the component is deflected in different ways, and that pictures are taken of the component in these two positions, the positions being chosen so that

3oin the first position the picture of the component is taken to shaφly depict component portions located in a plane essentially coinciding with a bottom surface of the component, and in the second position the picture is taken to shaφly depict component portions located in a plane substantially perpendicular to the bottom surface of the component or, preferably, forms a small angle to a line peφendicular to the bottom surface.

35 4 A component assembly system compnsing image acquisition means for generating images of electπcal connecting leads or pins of an electronic component, the leads or pins being intended to have outermost or bottom surfaces substantially parallel to each other and preferably to a bottom surface of the component, characterized in that the image acquisition means compnses: means for emitting light from a surface area,

- means for moving the component to a position in relation to the light emitting means, where emitted light will hit the bottom surface of the component in a direction forming a small angle to the bottom surface and where the connecting leads or pns thereof are seen

5when looking at the surface area in said direction,

- camera means for captunng a picture of the surface area as seen in essentially said direction, in particular as seen in a direction substantially parallel to or preferably in a direction forming a small angle to the bottom surface, in which picture the connecting leads or pins are also seen, and/or so that the plane of the shaφly depicted portions of the locomponent in the picture is substantially peφendicular to the bottom surface of the component or preferably forms a small angle to a line peφendicular to the bottom surface.

5 A system according to claim 4, characterized in that the surfac e area of the light emitting means is located substantially peφendicularly to the bottom surface ot the component or forms a small angle to a line peφendicular to the bottom surface 15 6 A component assembly system comprising image acquisition means for generating images of a component for a subsequent analysis of the position thereof , characterized in that the image acquisition means compnses means for moving the component in a direction substantially parallel to a bottom surface thereof, 20 means for captunng images of the bottom surface of the component dunng the movement thereof, the captunng means having a stπpshaped aperture or picture field, so that an image captured has a small extension in the movement direction of the component and a large extension in a direction peφendicular thereto, preferably the capturing means being digital, so that the images captured have only one or only a few pixel elements in the 25inovement direction of the component and a large number of pixel elements in the direction peφendicular thereto, so that each image depicts only a narrow strip of the component and/or of electncai connecting leads or pins attached thereto

7 A component assembly system compnsing image acquisition means for generating images of a component, the image acquisition means comprising so - illuminating means for issuing light towards the component,

- mirror means for reflecting light from the component to form a picture thereof,

- means for moving the mirror means and the component in relation to each other,

- camera means for capturing a picture of the component as reflected the mirror means,

35 characterized in that the mirror means comprise at least one first mirror, the moving means being arranged to move the at least one first mirror in relation to ne component from a first position to a second position, the camera means being so located that in the first position the camera means are capable of capturing an image of the co mponent where the image plane essentially coincides with a bottom surface of the component and that in the second position the camera means are capable ot capturing an image ot the component where the image plane is substantially peφendicular to the bottom surface of the component or forms a small angle to a line peφendicular to the bottom surface

8 A system according to claim 7, characterized in that in the second position the 5image plane is also located at the ends of a row of connection leads or pins of the component

9 A system according to claim 7, characterized by a second mirror, that is located to have a reflecting surface substantially parallel to a light entrance opening of the camera means, this second mirror reflecting light rays forming the image only when captunng an image in the second position of the at least one first mirror. io 10 A system according to claim 7, characterized in that the moving means are arranged to move the at least one first mirror in a direction substantially parallel to a bottom surface of the component.

1 1. A system according to claim 7, characterized in that the moving means are arranged to move the component in a direction substantially peφendicular to a bottom surface i5θf the component

12 A system according to claim 7, characterized in that in the first position of the at least one first mirror light rays forming the captured image pass directly to an entrance opening of the camera means and thus are not deflected by any mirror means

13. A system according to claim 7, characterized in that in the second position of the 2oat least one first mirror light rays from portions of the component are deflected only once by a mirror.