GB2087348A - Apparatus for transferring electronic elements to a substrate - Google Patents

Abstract

In an apparatus for transferring electronic elements to a substrate, for example, a printed-circuit board, and positioning them thereon, each element is held by a hollow suction pin (11). For centring each element on the end of the respective pin, each pin is surrounded by an alignment gripper (9) comprising resilient fingers (13) which are cooperable with a centring opening (31) in a centring device (21), the fingers and/or the centring opening having conical walls such that by moving the pin and gripper into the opening the fingers are brought into engagement with the wall of the opening and are deflected thereby to grip the electronic element held by the pin and centre it on the pin. <IMAGE>

Description

SPECIFICATION Transport holder for transferring at least one electrical or electronic part to a substrate The invention relates to a transport holder for transferring at least one electrical or electronic part to a substrate, comprising at least one vacuum opening for holding the part.

Transport holders forming the subject of the present invention are known per se and form part of devices for the correct positioning of electrical and/or electronic parts having a prismatic shape and very small dimensions in the order of magnitude of a few millimeters, without connection wires; such parts are also referred to as parts of the "chip"-type. These parts are supplied packed in tubular magazines or in a strip-shaped carrier. The transport holder lifts one or more parts, usually by means of vacuum, transports the parts to a substrate and positions the parts on the substrate.

A drawback of a device of the kind set forth which is known from U.K. Specification 20 25 910 consists in that the parts are not centred with respect to the centre line of the vacuum opening, so that the parts are present on the transport holder with a rather large positional inaccuracy and will also be positioned on the printed circuit board with rather large tolerances as regards their position.

In order to mitigate this drawback it has already been proposed to align the parts by means of a calibration plate which is slidable in a direction transversely of the centre line of the parts. A drawback of this device consists in its lack of flexibility, notably if several parts have to be aligned simultaneously; for each combination of parts a separate calibration plate is required.

The invention has for its object to provide a transport holder which has a comparatively simple construction and which enables reliable and reproducible alignment of parts, individually or simultaneously, so that their centre line occupies an accurately defined position with respect to the transport holder.

To this end, the transport holder in accordance with the invention comprises a transport block with at least one product holder which cooperates with a centring block which comprises at least one centring opening, said product holder consisting mainly of an alignment gripper and a vacuum pin whose centre lines coincide, said alignment gripper comprising a number of clamping fingers which are resilient in the radial direction and having in its rest position a continuously changing cross-section at the area of the clamping fingers.

This transport holder enables lifting of parts by means of the vacuum pin and alignment thereof by a relative movement of product holder and centring block and by a resulting radial deformation of the clamping fingers so that the centre of line of the parts coincides with the centre line of the vacuum pin; because the parts are thus accurately aligned with respect to the transport holder, their ultimate position on the printed circuit board is also accurately defined.

A further preferred embodiment of the transport holder is characterized in that the product holder is slidably journalled in the centring opening of the centring block which forms part of the transport holder, the cros.3- section of the alignment gripper gradually increasing towards its free end. These steps result in a compact construction in which the centring block undergoes all movements of the transport holder; the alignment gripper may have a square rectangular or round cross- section.

The alignment gripper of a further preferred embodiment has, at least at the area of the clamping fingers, a cylindrical outer circumference and a conical end, the centring opening in the centring block also being conical. In this embodiment, the centring block is arranged to be separate from the transport holder but accurately positioned with respect thereto. Thanks to these steps, the transport holder itself may have a simpler construction.

Even though the alignment gripper and the centring opening could have a square or rectangular cross-section, the construction will be substantially simplified by the cylindrical and conical construction of the alignment gripper and the centring opening. This embodiment offers a very compact construction, notably in the radial direction.

Because the alignment gripper of a further embodiment comprises two parallel clamping fingers on two opposite sides, the risk of jamming of the part in the alignment gripper is substantially eliminated, the part first being aligned in one direction and subsequently in the direction perpendicular thereto.

The lifting, alignment and positioning of the parts can be realized in a simple and troublefree manner in that the vacuum pin is slidable with respect to the alignment gripper. The vacuum pin can each time be placed in the optimum position for the lifting, alignment and positioning of a part.

The transport holder in accordance with the invention can be used for transferring a single part. The advantages of the invention will be most significant when a number of parts are simultaneously transferred. To this end, the transport holder in accordance with the invention comprises a transport plate which comprises a matrix of openings in which product holders are arranged in a pattern according to anumber of parts have to be positioned on a substrate, the centring block being constructed as a centring plate with a matrix of centring openings which corresponds to the matrix of the openings in the transport plate, all product holders having the same external dimensions.

Because all product holders have the same external dimensions, the use of a standard transport plate and a standard centring plate suffices. Even though the product holders are product-dependent as regards their internal dimensions, that is to say dependent on the length, width and thickness of the parts so that different product holders are required for different parts, a standard transport plate can simply be provided with various product holders in the desirable pattern thanks to the standard external dimensions. Thus, only the mechanical parts which are product-bound need to be exchanged. Because the product holders are preferably mounted for example, with a slide fit, with friction or by means of a snap connection, the product holders can be quickly fitted and-removed.

In a preferred embodiment, the centring openings are provided in centring bushes which are slidably journalled in the centring plate, so that a number of parts can be simultaneously aligned by means of the standard centring plate, in spite of different thickness dimensions.

The invention will be described in detail hereinafter with reference to the drawing.

Therein: Figure 1 is a diagrammatic sectional view of a transport holder in accordance with the invention; Figure 2 shows the transport holder of Fig.

1 in a different position; Figures 3, 4 and 5 show an embodiment of the alignment gripper; Figures 6 and 7 show a further embodiment of the transport holder.

The Figs. 1 and 2 show a transport holder 1 with a transport plate 3 which comprises a matrix of openings 5 in which product holders 7 are arranged in a pattern in which a number of parts C have to be positioned on a substrate for instance a printed circuit board (not shown). The product holders 7 consist mainly of an alignment gripper 9 and a vacuum pin 11, the centre lines of which coincide with the centre line A-A of the product holder 7.

The vacuum pin is slidably journalled in the alignment gripper.

The product holders 7 have a mainly cylindrical outer circumference with a conical end portion 13. The product holders 7 can be positioned in the axial direction and the circumferential direction with respect to the transport plate 3 by means of a flange 15 and a reference cam 17. All product holders have identical external dimensions.

The reference numeral 21 denotes a centring plate which is supported by a supporting plate 23, a plate 25 of an elastically deformable material, for example, rubber being arranged between the centring plate and the supporting plate. The centring plate 21 comprises a matrix of openings 27 which corresponds to the matrix of openings 5 in the transport plate 3. A centring bush 29 is slidably journalled in each opening 27 and rests on the plate 25. Each centring bush comprises a conical centring opening 31. Fig.

1 shows the transport holder 1 with a part C lifted and retained by-the vacuum pin 11 above the centring plate 21.

Fig. 2 shows the transport holder during the alignment of the part C in order to achieve that the centre line of the part coincides with the centre line A-A of the product holder. To this end, the alignment gripper 9 comprises clamping fingers 33 which are resilient in the radial direction and which are pressed radially towards the centre line A-A by cooperation between the conical end 13 of the alignment gripper and the inner wall of the conical centring plate 31, said fingers then contacting the part C which is thus aligned and slides over the end of the vacuum pin. After removal of the transport plate 3 from the centring plate 21, the effect of the clamping fingers 33 is cancelled, the centred part being retained in the centred position by the vacuum pin.

Figs 3, 4 and 5 show a special embodiment of the alignment gripper at an increased scale, Fig. 3 being a bottom view of the alignment gripper, Fig. 4 a longitudinal sectional view taken along the line IV-IV in Fig. 3, and Fig.

5 a longitudinal sectional view taken along the line V-V in Fig. 3. The alignment gripper 9, being shown without vacuum pin for the sake of clarity, comprises single clamping fingers 35 which are pair-wise oppositely situated, and also double clamping fingers 37 and 39 which are also oppositely situated.

The distance X between the two inner clamping fingers 37 is smaller than the distance Y between the clamping fingers 35. Consequently, during the alignment of a part first the clamping fingers 37 contact the part which is prealigned in one direction. Subsequently, the clamping fingers 35 contact the part which is then aligned in a direction perpendicular to the first direction; this is possible in that only a small frictional force is exerted on the part by the clamping fingers 37. Ultimately, the clamping fingers 39 contact the clamping fingers 37, the clamping fingers 35 then also being pressed harder against the part, so that the part is gradually positioned in the centred position, the reliability and accuracy of the centring operation thus being enhanced.

The clamping fingers 35 and 37 bound a chamber 41, the dimensions of which are slightly larger than the dimensions of the part to be accommodated.

Thanks to the elastic plate 25 shown in the Figs. 1 and 2, the separate product holders can perform different strokes during the centr ing operation; if a part has already been centred and retained by the clamping fingers in an alignment gripper, and other parts have not yet been completely aligned, the alignment gripper can be displaced, together with the associated centring bush, over a small distance thanks to the elastic plate 25; during this additional displacement, all other parts of other dimensions and tolerances are finally centred.

The Figs. 6 and 7 show a further embodiment of the transport holder in the lifting position and the centring position, respectively. In this embodiment, a centring plate 51 forms part of the transport holder 1. The centring openings 53 are not conical but cylindrical. The cross-section of the alignment grippers 55 at the area of the clamping fingers 57 gradually increases towards the end.

The centring plate 51 is slidable with respect to the transport plate 3 and the product holder 7.

Fig. 6 shows the transport holder 1 positioned over a magazine holder 59 with magazines 61; each magazine contains a stack of parts C. Pins 63 press the stacks of parts in the alignment grippers 55 and against the vacuum pins 11, each of which lifts and retains a part. By displacement of the centring plate 51 from the lifting position shown in Fig. 6 to the centring position shown in Fig.

7, the clamping fingers 57 are radially bent towards the centre line A-A in the described manner, the parts thus being centred. Obviously, the centring plate 51 must undergo all displacements of the transport holder. Fig. 7 also shows that the transport holder 1 is shifted in the transverse direction with respect to the magazine holder 59. It is thus achieved that the uppermost part is clearly separated from the parts situated therebelow, so that it is impossible to lift two parts simultaneously from the same stack; otherwise, problems would arise.

The product holders are product-bound and can be coded in known manner, for example, on the basis of colour, by means of strip code, and in other ways.

Claims (8)

1. A transport holder for transferring at least one electrical or electronic part to a substrate, comprising at least one vacuum opening for holding the part, characterized in that the transport holder comprises a transport block with at least one product holder which cooperates with a centring block which comprises at least one centring opening, said product holder consisting mainly of an alignment gripper and a vacuum pin whose centre lines coincide, said alignment gripper comprising a number of clamping fingers which are resilient in the radial direction and having in its rest position a continuously changing cross-section at the area of the clamping fingers.

2. A transport holder as claimed in Claim 1, characterized in that the product holder is slidably journalled in the centring opening of the centring block which forms part of the transport holder, the cross-section of the alignment gripper gradually increasing towards its free end.

3. A transport holder as claimed in Claim 1, characterized in that the alignment gripper has at least at the area of the clamping fingers, a cylindrical outer circumference, and a conical end, the centring opening in the centring block also being conical.

4. A transport holder as claimed in Claim 1, 2 or 3, characterized in that the alignment gripper comprises two parallel clamping fingers on two opposite sides.

5. A transport holder as claimed in any of the preceding Claims, characterized in that the vacuum pin is slidable with respect to the alignment gripper.

6. A transport holder as claimed in any of the preceding Claims, characterized by a transport plate which comprises a matrix of openings in which product holders are arranged in a pattern according to which a number of parts have to be positioned on a substrate, the centring block being constructed as a centring plate with a matrix of centring openings which corresponds to the matrix of the openings in the transport plate, all product holders having the same external dimensions.

7. A transport holder as claimed in Claim 6, characterized in that the centring openings are provided in centring bushes which are slidably journalled in the centring plate.

8. A transport holder substantially as herein described with reference to Figs. 1 to 5 or Figs. 6 and 7 of the accompanying drawings.