EP1754249A1

EP1754249A1 - Method and device for detaching a component which is attached to a flexible film

Info

Publication number: EP1754249A1
Application number: EP04804931A
Authority: EP
Inventors: Joachim Trinks; Andreas Marte; Wolfgang Herbst
Original assignee: Alphasem AG
Current assignee: Kulicke and Soffa Die Bonding GmbH
Priority date: 2004-05-19
Filing date: 2004-12-17
Publication date: 2007-02-21
Also published as: EP2306496A3; US20070277929A1; KR20070085112A; EP2306496A2; US7981246B2; CN101019205B; WO2005117072A1; HK1111263A1; CN101019205A; KR101097500B1; CH697213A5

Abstract

The invention relates to a film (2) which comprises a component (1) to be detached therefrom. Said film is placed in the area of the component on a detaching tool (5) that is provided with at least one supporting element (6) for the film, which extends in a plane of support (11). The film is sucked against the support element (6) and partially under the plane of support by exerting negative pressure. The area of the supporting element is provided with at least one surface section (8) which extends in the plane of support when the detaching process begins, and which can be displaced, once the component (1) is grasped by a suction tool (4), plane-parallel to the plane of support while the negative pressure is maintained. The invention allows to control the detaching process of the film in a controlled movement without damaging or displacing the component.

Description

Method and device for detaching a component glued to a flexible film

The invention relates to a method for detaching a component glued to a flexible film according to the preamble of claim 1. Such methods are used in particular in the processing of semiconductor chips to remove a large number of chips from the wafer film in rapid succession and to place them on a base.

The semiconductor chips with the electronic circuits arranged thereon are previously separated from the silicon wafer referred to as a wafer by sawing. At the latest for the sawing process, the wafer is glued to the wafer film stretched in a frame, the adhesion obviously having to be sufficiently high to prevent breakouts or chip detachments during the sawing process. In contrast, when the individual chips are detached from the film, the adhesion should be as small as possible in order to avoid excessive mechanical forces acting on the chip.

Methods and devices are already known in which the detachment process is supported by needles or plungers which can be pressed against the film. According to another detachment process, the film is sucked into a support base with a plurality of depressions, so that the adhesive surface on the components is considerably reduced and the required detachment force can thereby be reduced. Examples of such methods are described in US Pat. No. 4,778,326 or US Pat. No. 6,202,292. Finally, US Pat. No. 6,561,743 has also disclosed a method of comparable generic type, in which a step is shifted laterally in the plane of the film. The film is simultaneously sucked into a lower level of the step, so that the film is continuously removed from the component as the stage is advanced.

US 2003/0075271 describes a method and device for detaching semiconductor elements, in which a detaching tool has a plurality of circumferential, concentrically arranged contact elements which can be telescopically extended, the semiconductor element being raised and the film gradually detaching.

According to JP 2001-196443, the detaching tool has a pyramid-like structured suction surface. This suction surface is surrounded by a flat contact surface.

JP 63-228638 describes a removal tool in which a plunger with a smaller area than the electronic component is pressed against the film from below. The holding device for gripping the component is designed like a fork and grasps the component in the edge area that has already been detached from the film.

Finally, JP 3-76139 describes a detachment tool for a semiconductor element in which a detachment stamp is combined with a needle, the detachment stamp being raised first and then the needle being pushed through the film.

A problem with all known methods is that they are only of limited use for processing chips with a very small thickness of, for example, 0.05 mm. There is a risk of mechanical damage when lifting the chip with needles or pestles. Even the uncontrolled suction of the film in recesses can lead to strong bending forces on the chip and thus permanent damage. When the sliding stage according to US 6 561 743, the detachment from the film takes place continuously and thus asymmetrically, which can cause a slight shift to one side. Depending on the size of the chip, there is also a need for adequate lateral clearance for the displacement, which can lead to space problems in the peripheral area of the wafer.

It is therefore an object of the invention to provide a method of the type mentioned at the outset which also makes it possible to detach components with a very small thickness without unduly stressing them. The process should also have a high degree of operational reliability and work as independently as possible from the type of film used. This object is achieved according to the invention with a method which has the features in claim 1.

The surface section, which can be shifted plane-parallel, results in very precise control of the film deformation under the influence of the negative pressure in order to reduce the adhesive surface. As a result of the movement, which is preferably perpendicular to the support plane, a complete symmetry of the detachment process can be achieved. The stroke of the plane-parallel feed or retraction movement can be set exactly. This enables the detachment process to be adapted to certain workpiece parameters, such as certain film qualities or component heights. The speed of the detachment process can also be controlled. In contrast to the known methods, the component is held in a clamping manner between the holding surface of the holding tool and the surface section or between the holding surface and the support element until it is finally lifted off in any sequence of detachment. Support of this type on both sides and preferably across the board at any time is particularly important in the case of very thin chips. For the final detachment, the surface section is withdrawn from the support plane into a detachment position while the holding tool holds the component. The surface section covers a defined stroke at an adjustable speed and moves away from the underside of the film. Under the action of vacuum, the film follows the control surface section and detaches from the underside of the component, which is only supported by the support element. The component can then be detached from the connection still held by the supporting element, for which only a small amount of force is required.

According to a somewhat modified method, the surface section can first be pushed out of the support plane simultaneously with the holding tool beyond the support plane and then put back into the support plane. During this displacement movement, the component is supported over a large area and held securely and stably between the holding tool and the surface section. When the surface section is pushed forward, the release process of the film is started gently along the edge, depending on the configuration of the surface section. For this purpose, it is advantageous if the surface section or the sum of the surface sections has a somewhat smaller area than the component. When resetting, the surface section continues its movement until it has again reached the separation position mentioned at the beginning.

Depending on the size of the component, a plurality of surface sections spaced apart from one another can be moved simultaneously in such a way that a support element is arranged at least between two surface sections. The movable surface sections are penetrated by the support element, so that as possible in each sequence well-distributed support of the component on the underside of the film is guaranteed.

In certain applications it can be advantageous to move several surface sections independently of one another.

The film is preferably supported on the support element in a punctiform and / or linear manner, depending on the size and configuration of the component.

Further advantages can be achieved if the component is supported on at least 50% of its surface at least at the beginning of the detachment process by the surface section or by the surface sections. Such a large-area support is particularly important when the component is first lifted out of the support plane, an edge detachment being intended.

In special applications, it is advantageous if the surface section is heated. In this way, heat can be transferred to the chip or to the wafer film. The temperature control is process-dependent.

The invention also relates to a device according to the preamble of claim 10. On the one hand, this device is intended to be able to carry out the aforementioned method in a simple manner. The device should also, if possible, be installed in existing processing machines, in particular in existing die bonders. This object is achieved according to the invention with a device which has the features in claim 8.

The movably mounted control element with the plane section that can be moved plane-parallel can be particularly easily with couple to the same drive system as can already be found for conventional stripping needles. The control element can be both retractable and advanced relative to the support plane. In the case of very small chips, it may be sufficient if the control surface has at least one flat surface section, next to which at least one support element is arranged in a suitable manner. However, it is advantageous to have a plurality of support elements which surround the surface section at a suitable distance from one another or from the surface section. The fact that the control surface has a plurality of flat surface sections spaced apart from one another ensures a large-area support on the underside of the film. If a support element is arranged at least between two surface sections, extensive support of the component is ensured even when the surface sections are retracted below the support plane.

Depending on the geometry of the component, the control element can have several surface sections that are firmly connected to one another. It is particularly advantageous if the .. control element is made monolithic, so that all surface sections can be machined together and thus also lie exactly in the same plane.

However, the control element can also have a plurality of surface sections which can be moved independently of one another and which can be moved laterally offset with respect to one another via a corresponding gear.

The support element can have support pyramids or support cones for the point-like support of the film or support strips for the linear support of the film.

It is also particularly advantageous if at least four surface sections are arranged next to one another in a matrix. at In this arrangement, similar to a cloverleaf, the support element can have a plurality of support pyramids or support cones, which are also arranged in a matrix-like manner around the surface sections. Alternatively, cross bars forming a cross could also be arranged between the four surface sections.

The control surface or the individual surface sections can be heated by means of a heating device in order to heat the wafer film or the individual chip. The heating device can be an electrical resistance heater or another heating element. The heating device can also have suitable control means for temperature control.

Further individual features and advantages of the invention result from the following description of exemplary embodiments and from the drawings. Show it:

FIG. 1 shows a first example of a detachment process according to the invention in three sequences,

FIG. 2 shows a second example of a detaching process according to the invention in four sequences,

FIG. 3 shows a top view of the end face of a first release tool according to the invention,

FIG. 4 shows a cross section through the plane A-A according to FIG. 3,

FIG. 5 shows a perspective illustration of the detaching tool according to FIGS. 3 and 4, FIG. 6 shows a top view of the end face of a second removal tool according to the invention,

FIG. 7 shows a cross section through the plane B-B according to FIG. 6,

FIG. 8 shows a perspective illustration of the detaching tool according to FIGS. 6 and 7,

FIG. 9 shows a cross section through a further example of a detaching tool with a plurality of independently movable surface sections, and

FIG. 10 shows a detaching process with a detaching tool according to FIG. 9 in the sequences a to k.

A first embodiment of a detaching process is shown in three sequences in FIGS. In this case, a plurality of chips 1 are glued onto a stretched wafer film 2, or the coherent wafer originally glued on was divided into individual chips by sawing. After sawing, the film is stretched in a known manner in order to facilitate the separation of the chips. The detachment tool, designated as a whole by 5, is only shown schematically here. It is arranged in a fixed position relative to the wafer film 2 in a work machine. The chip 1 is placed over the detachment tool 5 via an X-Y coordinate drive.

A holding tool 4 with a flat holding surface with a suction function can be placed on the surface 3 of the chip facing away from the film. A vacuum is applied to this surface via a vacuum channel 20, so that the chip adheres to the holding tool 4. The holding tool 4 can be lifted off while maintaining the negative pressure in the direction of the arrow a (FIG. 1c) and transports the chip to a substrate or to an intermediate station.

The detaching tool 5 has at least one support element 6, which lies in a support plane 11. The wafer film 2 lies flat on this support plane at the beginning of the detachment process. A plurality of surface sections 8a, 8b arranged at the end of a control element 10 also preferably run in the support plane 11 in the immediate vicinity of the support element 6. The surface sections or control element 10 can be retracted in the direction of arrow b (FIG. 1b).

During the entire detachment process, a vacuum is present in the area of the detachment tool 5 on the underside of the wafer film 2 (arrows v). This can attack via special vacuum channels 9 or simply through the play between the fixed and moving parts on the film. In the edge region of the surface sections 8, depressions 7 can be formed, for example, by corresponding bevels, at which the detachment process can be initiated under the action of the negative pressure.

Such a starting phase is shown in Figure la. The depressions 7 run not only in the edge region of the surface sections 8a, 8b, but also in the edge region of the chip 1. Under the action of the vacuum, they cause a locally very limited deformation of the wafer film 2 and thus its detachment from the chip 1.

In a next step according to FIG. 1b, the surface sections 8a, 8b are withdrawn relative to the support plane 11 in the direction of the arrow b. The wafer film 2 follows this movement continuously and remains only in the area of the support by the support element 6 in the support plane 11. The detachment speed can be controlled precisely by means of the movement of the surface sections. The holding tool 4 holds the chip 1 immovably in the starting position.

Only when, according to FIG. 1c, the wafer film 2 has reached its complete deformation and only rests on the support element 6, or adheres to the chip 1 in the region of this support, does the chip begin to be lifted in the direction of arrow a with the aid of the holding tool 4. After lifting off, Atmospheric pressure is restored under the wafer foil and the foil is shifted to lift off the next chip.

A somewhat modified detachment process is shown in FIGS. 2a to 2d. Figure 2a partially corresponds to the initial situation according to Figure la. However, the film 2 is stretched flat over the depressions 7, so that the detachment process does not start at this point. In addition, FIGS. 2c and 2d correspond to the situations according to FIGS. 1b and 1c in the final phase of the detachment process. To initiate the detachment process, however, a further step according to FIG. 2b is interposed. The surface sections 8a, 8b are simultaneously advanced with the holding tool 4 by a small distance in the direction of arrow a, so that the chip 1 to be detached initially projects above the support plane 11. This minimal offset gently starts the detaching process in the edge area of the chip 1. The holding tool 4 is then again lowered synchronously with the surface sections 8a, 8b until the film 2 rests on the support 6 again. The surface sections 8a, 8b continue their movement according to FIG. 2c in the direction of arrow b, whereupon the remaining detachment process takes place as in FIG. 1. In both detachment operations according to FIGS. 1 and 2, the chip 1 is first touched with the holding tool 4 before the surface sections 8a and 8b move up and down. As a result, the chip is gripped between the holding surface of the holding tool and the surface sections 8a, 8b or the support element 6 before any tensile or bending forces act on the film 2 at all. When the surface sections 8a, 8b according to FIG. 2 are raised, this clamping holder is retained.

FIGS. 3 to 5 show a detaching tool 5 as can be used for the previously described methods. The tool consists of a pot-like housing 23 with a hollow cylindrical fastening collar 12 and with a support surface 13 on which the film comes to rest in the area surrounding the chip to be removed. The entire inside of the fastening sleeve can be connected to a vacuum source. For example, a negative pressure of 200 mbar absolute can be achieved compared to atmospheric pressure. A total of four suction bores 14 are arranged on the circular support surface 13 in a uniform angular division, via which the wafer film is fixed.

An approximately square depression 21 is arranged on the support surface 13. Within this lowering four approximately triangular tappet openings 17 are provided in a cloverleaf arrangement. A support bar cross 16 runs between these tappet openings and a support pyramid 15 is arranged at the crossing point. The support pyramid and support strip cross together form the support element 6, which runs in the support plane 11.

An approximately cylindrical control element 10 is held axially movably in the center and coaxially to the fastening collar 12. On At one end of this control element, four individual plungers 18 are arranged, the configuration of which in the support plane 11 corresponds to the configuration of the plunger openings 17. The plungers 18 each have a surface section 8 at their ends and they penetrate the plunger openings 17 with play, so that the negative pressure can also act on the wafer film lying above the recess 21 along their side walls. For this purpose, a suction bore 19 can also be arranged in the center of the control element 10.

In the present exemplary embodiment, the plan area of the chip to be removed is slightly larger than that of the one-piece plunger arrangement. Support is provided via the diagonals of the chip and in the center.

In the detachment tool according to FIGS. 6 to 8, the fastening collar 12 is essentially similar to that in the previous exemplary embodiment. The suction bores 14 in the support surface 13 are also arranged identically. However, the configuration of the support surface itself and of the control element 10 is different. Here too, a square depression 21 is provided. However, the support element 6 is formed exclusively by support pyramids 15, which are arranged in a matrix-like manner in the corner area, in the middle of each side edge and in the center. A total of four approximately square tappet openings 17 are arranged in the bottom of the depression 21. Additional bores 22 can be provided in the edge region for better distribution of the negative pressure.

The control surface or the individual surface sections can be heated by means of a heating device 40, which is indicated here as an electrical heating cartridge. The control element 10 also has four plungers 18, the configuration of which corresponds approximately to that of the plunger openings.

In this exemplary embodiment, the wafer film is supported in the area of the glued-on chip exclusively in a punctiform manner. Otherwise, the function of the detachment tool is the same as in the exemplary embodiment described above.

FIG. 9 finally shows a modified embodiment of a detaching tool 25. This has a housing 26, in which several individual plungers 28 may be axially displaceably mounted in a matrix-like manner. The individual plungers are stored both in a control slide 30 and in a feed element 34. The feed element is designed like a pot, similar to the housing 26, and has an end face 35, which is slightly recessed under a housing opening 27. Openings through which the individual plungers 28 penetrate are arranged in the end face 35.

The feed element 34 is biased under the action of a helical compression spring 36 against a support 37 on the housing 26. In contrast, the control slide 30 can be lowered further in the direction of arrow b. The control slide 30 has a gradation 33 with different levels, wherein two or more individual tappets can be arranged on the same gradation level. The individual plungers each have a stop 38 at the upper end, which limits the plunger movement upwards. At the lower end, the individual plungers are each provided with a driver element 32, with all driver elements lying on the same plane in the neutral starting position shown. The individual plungers are prestressed with a helical compression spring 31 between the stops 38 and the step 33. The vacuum required for the detachment process can act on the wafer film 2 via vacuum channels 29. Additional channels, for example in the individual plungers 28, would, however, be conceivable.

In the neutral starting position shown, the control surface sections 8 of the individual tappets are all in the support plane 11. The special feature of this exemplary embodiment is that the surface sections 8 simultaneously take on the function of a support. This means that there is no support which is rigid relative to the surface sections 8 in the support plane 11.

When the control slide 30 is displaced in the direction of arrow a, it is evident that the feed element 34 is raised against the force of the helical compression spring 36 and the individual plungers or their surface sections 8 are advanced through the opening 27 beyond the support plane 11. The force of the helical compression springs 31 is sufficient to hold the stops 38 in the stop position. However, if the control slide 30 is retracted in the direction of arrow b, it is evident that the two outermost individual tappets are withdrawn first via the step 33. Then follow them in pairs from the outside inwards until the two innermost plungers are pulled back. In the case of a matrix-like arrangement of the tappets, rows of tappets are withdrawn concentrically from the outside inwards. This guided retraction movement causes a continuous detachment of the film from the outside inwards in a guided and supported movement. The detachment is completely symmetrical, so that the chip cannot be moved. 10 shows in the individual representations a) to k) a detachment sequence using the detachment tool 25 according to FIG. 9, a) shows the neutral starting position after the wafer film has been placed over the detachment tool and before the holding tool 4 detects the chip 1.

According to b), the holding tool detects the chip and the underside of the wafer film 2 is placed under vacuum.

The control slide 30 is then advanced according to c), the surface sections 8 being raised simultaneously with the holding tool 4. At the same time, the wafer film 2 is sucked somewhat under the support plane 11. The detachment process already begins along the outer edges of the chip 1.

Then, according to d), the control slide 30 is reset again, so that the chip 1 returns to the starting position. All individual tappets now initially have the function of a support for the wafer film. However, this remains in a detached position along the edges.

According to e), the control slide is pulled back further, the two outermost tappets being taken along and lowering. Under the influence of the negative pressure, the wafer film follows in a guided movement and detaches from the underside of the chip. According to f), g) and h), further retraction sequences of the tappets follow from the outside inwards, until finally only the two innermost tappets serve as supports.

Finally, according to i), the innermost plungers are also lowered below the support plane 11, so that the detachment process is ended without the holding tool 4 having to be moved. Only now, according to k), is the holding tool 4 raised and the pressure equalized, so that the elastic wafer film 2 relaxes again. The individual plungers can now be pushed back into the starting position according to a) and the wafer film can be positioned above the detaching tool in order to detach a new chip. Modifications of the detaching tool according to FIG. 9 would of course be conceivable. In particular, the plunger arrangement and the sequences of the retreat could each be adapted to the special circumstances. It would also be conceivable to provide individual rigid supports or support elements between the movable plungers, which could also be arranged in a matrix.

Claims

claims

1. A method for detaching a component (1) glued to a flexible film (2), in particular a semiconductor chip glued to a wafer film, the component on its surface (3) facing away from the film using a holding tool (4) on a flat holding surface is captured and lifted off the film, the film (2) being placed in the region of the component (1) on a detachment tool (5) such that it rests in a support plane (11) and in the support plane by at least one support element (6 ) is supported, and wherein the film is sucked by means of negative pressure both against the support element (6) and partially below the support plane (11), and wherein at least one control element (10) is provided with a control surface which is removed before the Component of the film is moved plane-parallel to the support plane (11) while maintaining the negative pressure, characterized in that the film on at least one flat surface section (8) on de r. Control surface rests and that the component is first gripped by the holding tool and held until it is lifted in each sequence of detachment either between the holding surface and the surface section or between the holding surface and the support element (6).

2. The method according to claim 1, characterized in that the surface section (8) from the support plane (11) is withdrawn into a detachment position (X) while the holding tool holds the component (1) and that the component is then held by the Support element (6) held connection with the film is detached.

3. The method according to claim 1, characterized in that the surface section (8) is first pushed out of the support plane (11) simultaneously with the holding tool (4) beyond the support plane and set back into the support plane, that the surface section (8) is then is withdrawn from the support plane into a detachment position (X) while the holding tool (4) holds the component (1) and that the component is finally detached from the connection with the film still held by the support element (6).

4. The method according to any one of claims 1 to 3, characterized in that a plurality of spaced-apart surface sections are moved simultaneously in such a way that a support element is arranged at least between two surface sections.

5. The method according to any one of claims 1 to 4, characterized in that the support of the film (2) on the support element (6) is punctiform and / or linear.

6. The method according to any one of claims 1 to 5, characterized in that the component is supported at least at the beginning of the detachment process by the surface section on at least 50% of its surface.

7. The method according to any one of claims 1 to 6, characterized in that the surface section is heated with a heating device (40).

8. The method according to any one of claims 1 to 7, characterized in that the control surface or the surface section (8) at the beginning of the detachment process runs approximately in the support plane (11).

9. The method according to any one of claims 1 to 8, characterized in that a plurality of surface sections (8a, 8b) are moved independently of one another.

10. Device for detaching a component (1) glued to a flexible film (2), in particular a semiconductor chip glued to a wafer film, with a holding tool (4) for gripping the component on its surface (3) facing away from the film and for lifting it off from the film, with a detachment tool (5) on which the film (2) can be placed in the area of the component in such a way that it rests in a support plane (11) and can be supported in the support plane by at least one support element (6), and with at least one vacuum channel (9) opening against the support plane, at least one control element (10) with a control surface being movably mounted in the detaching tool in such a way that the control surface can be displaced plane-parallel from the support plane (11), characterized in that the control surface at least has a flat surface section (8) next to which at least one support element is arranged.

11. The device according to claim 10, characterized in that the surface section (8) from the support plane (11) in a detachment position (X) is retractable at a distance from the support plane.

12. The device according to claim 10 or 11, characterized in that the surface section (8) can be pushed simultaneously with the holding tool (4) over the support plane (11).

13. Device according to one of claims 10 to 12, characterized in that the control surface (10) has a plurality of spaced-apart surface sections (8) and that at least between two surface sections (8a, 8b) a support element (6) is arranged.

14. The apparatus according to claim 13, characterized in that the surface sections (8a, 8b) are firmly connected.

15. The apparatus according to claim 13, characterized in that the surface sections are movable independently of one another.

16. Device according to one of claims 14 or 15, characterized in that at least four surface sections are arranged next to one another in a matrix

17. Device according to one of claims 10 to 16, characterized in that the support element (6) has punctiform ... and / or linear supports for the film.

18. The apparatus according to claim 17, characterized in that the support element has a plurality of support pyramids or support cones, which are arranged in a matrix around the surface section or the surface sections.

19. Device according to one of claims 10 to 18, characterized in that the control surface can be heated by means of a heating device (40).