US3626492A

US3626492A - Means for fracturing a plate of material

Info

Publication number: US3626492A
Authority: US
Inventors: Kenneth Hobbs
Original assignee: US Philips Corp
Current assignee: US Philips Corp
Priority date: 1968-11-29
Filing date: 1969-11-25
Publication date: 1971-12-07
Anticipated expiration: 1988-12-07
Also published as: FR2024549A1; JPS4923952B1; DE1957569A1; NL6917697A; GB1242237A

Abstract

A roller arrangement suitable for fracturing into dice semiconductor wafers is described comprising an unpivoted working roller of 2 mm. diameter and two backing rollers of 5 mm. diameter. The working and backing rollers are of magnetic material and the working roller is held against the backing rollers using a magnet. Such a roller arrangement is satisfactory when the surface area of the dice is only 350 microns by 350 microns.

Description

United States Patent 1111 3,626,492

[72] Inventor Kenneth Hobbs [56] References Cited g' England UNlTED STATES PATENTS [21] P 8 M45 1,614,424 1/1927 Coe 100/160 ux [22] F1led Nov. 25, 1969 2,851,869 9/1958 Quoos et a1 100/160 X [45] Patented Dec. 7, 1971 3,413,915 12/1968 Goodwm et al.. 100/169 [73] Asslgnee U.S. Philips Corporation 3 526 058 2/197 l B d 225/93 X [32] Priority Nov. 29, 1968 oy [33] Great Britain Primary Examiner- Frank T. Yost [31] 56,792/68 Anorney- Frank R. Trifari [54] MEANS FOR FRACTURING A PLATE ()1? ABSTRACT: A roller arrangement suitable for fracturing into MATERIAL dice semiconductor wafers is described comprising an un- 8 Claims, 2 Drawing Figs. pivoted working roller of 2 mm. diameter and two backing rol- [52] US. Cl. 225/103, lens of 5 dlameter' The working and backing rollers are of magnetic material and the working roller is held against the 51 l Cl b gfig backing rollers using a magnet. Such a roller arrangement is li 225/2 93 satisfactory when the surface area of the dice is only 350 r r 96.5, 103; 100/160, 169; 29/413; 156/300; 53/21, by 350 l l l, 23, 123

PATENTEBnu: mm 31525492 SHEET 1 0F 3 Fig.2

INVENTOR. KENN ET H HOBBS MEANS FOR FRACTURING A PLATE F MATERIAL This invention relates to roller arrangements suitable for fracturing into pieces a scored plate of material, particularly, but not exclusively, slices of semiconductor material. The invention further relates to methods of fracturing into pieces a plate of material having substantially parallel major surfaces and a set of score lines on one major surface extending along the plate substantially parallel to one another and determining lines of fracture.

in British Pat. specification No. 925,016 there is described and claimed a method of separating into pieces a plate of brittle material having substantially parallel major surfaces and a plurality of score lines extending along the plate substantially parallel to one another and determining lines of separation, comprising the step of moving the plate in a continuous movement relative to at'least one of the two members so that contact occurs between the plate and the two members in a plane substantially at right angles to the two major surfaces of the plate and passing progressively along the plate, the relative movement and the shape and surface resilience of the two members being such that during said contact a bonding moment which moves progressively along the plate is exerted on the plate whereby separation is effected by the said bending moment along each score line in turn.

A particular embodiment describes one of the members as a rubber pad and the other as a cylindrical roller, the plate of brittle material being a germanium or silicon body having two orthogonal sets of substantially parallel diamond scribed score lines on one major surface. After fracturing along one set of score lines, the semiconductor body is reorientated through 90 and fractured along the other set of score lines so producing from the semiconductor body a plurality of semiconductor pieces, which are also called dice. It is stated, as an example, that for score lines spaced 2 mm. (2,000 microns) apart a roller diameter of about half an inch (approximately l2.5

mm.) is satisfactory.

ln present day semiconductor technology it is often necessary to fracture semiconductor slices into dice having a major surface area of 350 microns X 350 microns. For fracturing such a semiconductor slice, a roller of very small diameter is required to achieve a suitable bending moment. Even with a roller of diameter as small as 5 mm, the bending moment is such that the semiconductor slice tends to fracture along certain, but not all, of the score lines, and this often results in as many as three semiconductor dice remaining joined in one fractured semiconductor piece, and fractures occuring across a semiconductor dice damaging or destroying its electrical circuit elements.

in addition the semiconductor slice may be supported between the roller and the pad on a plastic or synthetic resin foil during fracturing. The use of a roller having a diameter of 5 mm. to fracture semiconductor slices supported on such a film can often produce drag on the film resulting in damage to the semiconductor dice.

For satisfactory fracture of such a semiconductor slice having score lines with a mutual separation of 350 microns a roller having a diameter of 2 mm. or less is preferable. It is exceedingly difficult, if not impossible, for a roller of such a diameter to be satisfactorily pivoted with journaled ends in bearings.

According to a first aspect of the invention, a roller arrangement suitable for fracturing into pieces a scored plate of material comprises first and second backing rollers, a smaller diameter working roller of magnetic material situated between said backing rollers the axes of rotation of the backing rollers and the working roller being substantially parallel and magnetic means for subjecting the working roller to a magnetic filed applied across said backing rollers to hold the working roller in rolling surface contact with said backing rollers.

It is preferable for the backing rollers to be of a magnetic material, so forming a magnetic circuit with the working roller. In this case the working roller and backing rollers may be of hardened steel, which material can give adequate support to the rollers was to reduce sagging along their length.

The working roller and backing rollers may be substantially cylindrical, the backing rollers each having substantially the same dimensions.

The magnetic means may comprise an electromagnet, if the working roller is comparatively heavy. However, if the working roller is comparatively tight it is often preferable to dispense with the electrical circuitry and for the magnetic means to comprise a permanent magnet, the magnetic axis of which is substantially perpendicular to the axes of rotation of the working roller and the backing rollers and lies substantially within a plane parallel to the said plane in which are situated the axes of rotation of the backing rollers.

in this case, the backing rollers and permanent magnet may be mounted in a brass container, the backing rollers having journaled ends mounted in bearings in supporting blocks of the container, at least that part of the peripheral surface of the working roller most remote from the plane in which are situated the axes of rotation of the backing rollers extending beyond the brass container.

In the case where the backing rollers are of a magnetic material, and the working roller and backing rollers are substantially cylindrical, the backing rollers being of substantially the same dimensions as each other, the first and second substantially cylindrical backing rollers of a magnetic material .may be situated between the working roller and third, fourth and fifth substantially cylindrical backing rollers, which third, fourth and fifth backing rollers each have substantially the same dimensions as the first and second backing rollers, the axes of rotation of the working roller and the first, second, third, fourth andfifth backing rollers being substantially parallel, the first backing roller being situated between, and held by said magnetic field in rolling surface contact with, the third and fourth backing rollers, the second backing roller being situated between, and held by said magnetic field in rolling surface contact with, the fourth and fifth backing rollers. In this case it is possible for the cross-sectional diameter of the working roller to be even smaller.

The cross-sectional diameter of the working roller may be at most 2 mm.

According to the second aspect of the invention, in a method of fracturing into pieces a plate of material having substantially parallel major surface and a plurality of score lines on one major surface extending along the plate substantially parallel to one another and determining lines of fracture, relative motion is effected between a roller arrangement ac cording to the first aspect of the invention and the opposite major surface of the plate in a direction substantially perpen dicular to the score lines, and pressure applied such that the working roller exerts on the plate a bending moment which moves progressively along the plate whereby fracture across the plate substantially perpendicular to the major surfaces is effected by said bending moment along each score line in turn.

The plate of brittle material may comprise a semiconductor slice having two substantially orthogonal sets of substantially parallel score lines on the one major surface, fracture may first be effected along one set of score lines, thereafter the plate may be reorientated through substantially and fracture may be effected along the other set of score lines.

.In this case the diameter of the working roller may be at most 2 mm. and the distance between two parallel score lines may be at most 350 microns.

The opposite major surface of the plate may be attached to a supporting film, which film during fracture of the plate is situated between the working roller and the plate, the pieces produced by fracturing the plate remaining attached to the film subsequent to the fracturing so that their position and orientation are substantially maintained. in this case the opposite major surface of the plate may be attached to the film prior to forming the score lines on the one major surface, and the elasticity of the film may be such as to permit the stretching of the film in the plane substantially parallel to the major surfaces of the plate so as to separate in that plane from contact with one another the pieces attached to the film subsequent to the fracturing of the plate. The opposite major surface of the plate may be attached to the film by an adhesive, in which case the pieces produced by fracturing may need subsequent cleaning. A preferred alternative is for the film to be of electrica!ly insulating synthetic resin, the opposite major surface of the plate being attached thereto by electrostatic attraction.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a side view of a roller arrangement according to the first aspect of the invention;

FIG. 2 is a plan view of a scored semiconductor slice attached to a portion of supporting film and suitable for fracturing into pieces using the roller arrangement shown in FIG. 1; and

FIG. 3. is a cross-sectional view of the roller arrangement shown in FIG. 1 along the line III-IIl of FIG. 1 when used to fracture a scored semiconductor slice such as is shown in FIG. 2 and;

FIG. 4 is a cross-sectional view of another roller arrangement.

The roller arrangement shown in FIGS. 1 and 3 comprises first and second

cylindrical backing rollers

1 and 2 of hardened steel having a diameter of 5 mm. A cylindrical working roller 3 of 2 mm. diameter and also of hardened steel is situated between the backing rollers 1 and on one side of the plane A B in which are situated the axes of rotation of the

backing rollers

1 and 2. The axes of rotation of the working roller 3 and the

backing rollers

1 and 2 are substantially parallel to each other.

The cylindrical permanent magnets 5 and 6 are present on the other side ofsaid plane A B and apply to the working roller 3 a magnetic field to hold the working roller 3 in rolling surface contact with the

backing rollers

1 and 2. The magnetic axis of each magnet 5 and 6 is substantially perpendicular to the axes of rotation of the working roller 3 and the

backing rollers

1 and 2, and each magnetic axis lies substantially within a plane parallel to the plane A B.

Since the

rollers

1,2 and 3 are of hardened steel, a magnetic material, they together form a magnetic circuit for the magnetic flux from the magnets 5 and 6. In this way the working roller 3 can maintain a position entirely without end bearings between the backing rollers I and 2 and also be free to rotate. Since the diameter of the working roller 3 is 2 mm., it would be exceedingly difficult, if not impossible, to pivot satisfactorily this roller with journaled ends in bearings.

The backing rollers l and 2 and the permanent magnets 5 and 6 are mounted in a brass container 19. Each

backing roller

1 and 2 has journaled

ends

7 and 8 mounted in bearings in brass supporting blocks 9 and 10 of the container 19. The blocks 9 and 10 are detachable, being screwed to the remainder of the container 19, so that the backing rollers l and 2 may be replaced or readjusted in their bearings. That part 4 of the peripheral surface of the working roller 3 most remote from said plane A B extends beyond the brass container 19, and it is this part 4, of the peripheral surface of the working roller 3 that constitutes the working surface of the working roller.

The length of each

backing roller

1 and 2, excluding the

journaled ends

7 and 8, is 55 mm., and the length of the work ing roller 3 is 60 mm. The hardened steel of these

rollers

1, 2 and 3 gives such adequate support that sagging along the length of each roller is reduced. The cylindrical permanent magnets 5 and 6 are each of cross-sectional diameter l7.6 mm. and length l 1 mm., and these are mounted in corresponding apertures in the brass container 19 with their centers spaced by 30 mm. Those parts of the peripheral surface of each

backing roller

1 and 2 nearest the magnets 5 and 6 are separated therefrom by an air gap of minimum width 1 mm., and the axis of rotation of the

backing rollers

1 and 2 are held at a distance apart of 5.5. mm. In this way, the frictional resistance between the rotating rollers is small.

The roller arrangement of FIGS. 1 and 3 may be modified by the provision of third, fourth and

fifth backing rollers

20, 21 and 22 respectively as shown in FIG. 4. Backing

rollers

20, 21 and 22 each have dimensions substantially the same as

backing rollers

1 and 2, being substantially cylindrical and having their axes of rotation parallel to the axes of rotation of

rollers

1, 2 and 3. Backing roller 1 is held in the magnetic field between

backing rollers

20 and 21 in rolling contact therewith, while backing roller 2 is held in the magnetic field between

backing rollers

21 and 22 in rolling surface contact therewith.

The roller arrangement of FIG. 1 may be used for fracturing into pieces a semiconductor slice 11 such as is shown in FIG. 2. The slice 11 has parallel major surfaces and comprises a plurality of regions 13 each containing therein a semiconductor device in the form of an integrated circuit at or adjacent one major surface of the slice 11. The slice 11 is fractured into pieces, so as to separate the regions 13 from each other and form individual semiconductor dice, in the following way.

The opposite major surface of the slice 11 is attached to a supporting film 12, the film 12 being previously charged by friction so that the slice 11 is attached thereto by electrostatic attraction.

The film 12 consists of a material commercially available under the trade name of Genotherm l00." Two sets of mutually

parallel score lines

14 and 15 are scribed on the one major surface of the slice 11 between the regions 13 using diamond scribers. The two sets of score lines 14 and I5 intersect one another at right angles and determine lines of fracture. The distance between the two adjacent lines in each plurality is approximately 350 microns.

The semiconductor slice 11 attached to the film 12 is transferred to a resilient rubber supporting layer 16 which bears on a surface of a rigid support 17. The one major surface of the slice ll rests on, and is in contact with, the layer 16. The roller arrangement of FIG. 1 is moved under suitable pressure and with a suitable velocity across the opposite major surface of the slice 11 in a direction substantially perpendicular to one set of lines 14 (see FIG. 3, where the movement of the roller arrangement is indicated by arrows 18). The film 12 is situated between the working roller 3 and the semiconductor slice 11. The relative motion, surface resilience and shape of the layer 16 and the working roller 3 and the pressure applied are such that the working roller 3 exerts on the slice 11 a bending moment which moves progressively along the slice 11. Fracturing across the slice 11 substantially perpendicular to the major surfaces is effected by said bending movement along each score line 14 in turn. The arrows associated with

rollers

1, 2 and 3 indicate their direction of rotation during fracturing of the slice along the score lines 14.

The slice 11 is then turned substantially and the roller arrangement again moved under the same pressure and with the same velocity across the opposite major surface of slice 11, but now the movement is in a direction substantially perpendicular to the other set of score lines 15. In this way fracturing is effected along each score line 15 in turn.

The semiconductor slice 11 as a result of fracturing along the two sets of

score lines

14 and 15 comprises a plurality of divided, but as yet unspaced, semiconductor pieces. Even though adjacent score lines in the slice 11 were spaced apart by only 350 microns, the majority of these pieces so formed are whole semiconductor dice 13 each containing therein a substantially undamaged semiconductor device. This is a consequence of being able to apply a suitable bending moment by employing a working roller of a diameter no greater than 2 mm. Furthermore the small diameter of the working roller 3 exerts less drag on the film 12 with which it is in direct through moving contact, hence reducing damage to patterns on the semiconductor dice 13.

The semiconductor pieces formed by fracturing the slice 11 remain attached to the foil 12 subsequent to fracturing, so that their position and orientation are maintained substantially as in the slice ll.

The elasticity of Genotherrn 100 is such as to permit the stretching of the film 12 in the plane substantially parallel to the major surfaces of the slice 11, so as to separate in that plane from contact with one another the divided but unspaced dice 13 attached to the film 12. After inspection and marking of damaged dice, approved dice 13 are subsequently removed from the film 12 by means of a pickup head or needle having a reduced pressure connection and further processed.

What we claim is:

1. A roller arrangement suitable for fracturing into pieces a scored plate of material comprising first and second backing rollers, a smaller diameter working roller of magnetic material situated between said backing rollers, the axes of rotation of the backing rollers and the working roller being substantially parallel, and magnetic means for subjecting the working roller to a magnetic field applied across said backing rollers to hold the working roller in rolling surface contact with said backing rollers.

2. A roller arrangement as claimed in claim 1, wherein the backing rollers are of a magnetic material.

3. A roller arrangement as claimed in claim 2, wherein the working roller and backing rollers are of hardened steel.

4. A roller arrangement as claimed in claim 2, wherein the working roller and backing rollers are substantially cylindrical, the backing rollers each having substantially the same dimensions.

5. A roller arrangement as claimed in claim 4 wherein the magnetic means comprise a permanent magnet, the magnetic axis of which is substantially perpendicular to the axis of rotation of the working roller and said backing rollers and lies substantially within a plane parallel to the plane in which are situated the axis of rotation of the backing rollers.

6. A roller arrangement as claimed in claim 5, wherein the backing rollers and permanent magnet are mounted in a brass container, the backing rollers having journaled ends mounted in bearings in supporting blocks of the container, at least that part of the peripheral surface of the working roller most remote from the plane in which are situated the axis of rotation of the backing rollers extending beyond the brass container.

7. A roller arrangement as claimed in claim 4 wherein the first and second substantially cylindrical backing rollers of magnetic material are situated between the working roller and third, fourth and fifth substantially cylindrical backing rollers, which third, fourth and fifth backing rollers each have substantially the same dimensions as the first and second backing rollers, the axes of rotation of the working rollers and the first, second, third, fourth and fifth backing rollers being substantially parallel, the first backing roller being situated between, and held by said magnetic field in rolling surface contact with, the third and fourth backing rollers, the second backing roller being situated between, and held by said magnetic field in rolling surface contactwith, the fourth and fifth backing rollers.

8. A roller arrangement as claimed in claim 1 wherein the diameter of the working roller is at most 2 mm.

Claims

5. A roller arrangement as claimed in claim 4, wherein the magnetic means comprise a permanent magnet, the magnetic axis of which is substantially perpendicular to the axis of rotation of the working roller and said backing rollers and lies substantially within a plane parallel to the plane in which are situated the axis of rotation of the backing rollers.

7. A roller arrangement as claimed in claim 4 wherein the first and second substantially cylindrical backing rollers of magnetic material are situated between the working roller and third, fourth and fifth substantially cylindrical backing rollers, which third, fourth and fifth backing rollers each have substantially the same dimensions as the first and second backing rollers, the axes of rotation of the working rollers and the first, second, third, fourth and fifth backing rollers being substantially parallel, the first backing roller being situated between, and held by said magnetic field in rolling surface contact with, the third and fourth backing rollers, the second backing roller being situated between, and held by said magnetic field in rolling surface contact with, the fourth and fifth backing rollers.