The invention relates to a component-handling machine having a robot with a component-handling head which is provided with a vacuum pick-up nozzle and having means for creating a suction force at a nozzle opening of the pick-up nozzle for sucking a component to the nozzle opening and keeping it there.

Such component handling-machines are generally known, e. g. from US-A- 5 722 527 (PHN 15255), and used to pick up components, usually small components (SMDs), from a storage and place them on printed circuit boards. The size of the opening of the pick-up nozzle is adapted to the size of the components to be picked up. For a specific pick-up nozzle only a few components, having sizes which are close to each other, can be used. If, e. g. smaller components should be picked up, a smaller opening of the nozzle must be used. This is done by exchanging the pick-up nozzle for another nozzle with a smaller suction opening. If the nozzle is adapted to pick up of a component of a certain size and this nozzle is used to pick up a smaller component, there is a risk that such a smaller component is totally sucked into the tube or sucked askew against the edge of the nozzle opening. If, on the other hand, bigger components should be picked up, there is a risk that the suction force is too small.

It is an object of the invention to find a solution to the above-described problem, so that during operation of the component-handling machine the process of placing components can be continued while components of different sizes are used.

According to the invention, the component-handling machine is characterised in that the nozzle opening of the pick-up nozzle is provided with a gas-permeable cover against which components of different sizes can be sucked and held during operation.

Due to this gas-permeable cover, a wide range of components can be picked up and placed e. g. on a printed circuit board without the necessity to stop the machine and change the pick-up nozzle. The cover also causes an increase of the surface of the component on which the suction force is acting. The invention results in greater flexibility and better handling of the placement process. The cover represents a very simple and cheap means to solve the problem of changing the pick-up nozzle. The picked up component is always positioned flat against the cover. The suction force should, of course, be adapted to the largest component to be picked up.

It should be noted here that DE-A-41 00 023 discloses a vacuum pick-up tube for SMD components having a diaphragm nozzle with an adjustable nozzle opening which can be adapted to the size of the components. Such a construction however is much more complicated.

Preferably, a fine-meshed gauze or porous foam is used as the gas- permeable cover.

The invention also relates to a component-handling head having a pick-up nozzle for use in a component-handling machine as described above.

The invention also relates to a vacuum pick-up nozzle for use in a component-handling head of a component-handling machine as described above.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the drawings: Fig. 1 schematically shows a component-placement machine, Fig. 2 shows a pick-up nozzle according to the invention.

In the schematic drawing of Fig. 1, only the main parts of a component-placement machine are shown. The component-placement machine comprises a machine frame 1 to which a robot 2 is connected. The robot comprises a slide 3 mounted on two parallel guide beams 4 of the frame. The slide can be moved over the beams in the Y- direction. A component-placement head 5 is fastened on the slide 3 and can be moved along the slide in the X-direction. The component-placement head comprises a pick-up nozzle 6 which can be moved in the placement head in the Z-direction. The pick-up nozzle can also

rotate about the Z-axis in order to make a rotational correction during the placement of components. The machine has a transport mechanism for transporting printed circuit boards 7 through the machine. Only the conveyor belt 8 of this transport mechanism is shown. The component-placement head 5 picks up components 9 from a storage or feeder 10 and places them on the printed circuit board 7. For picking up a component, the component-placement machine is provided with means 11 which create a suction force at the nozzle opening 12 of the pick-up nozzle 6.

In Fig. 2 the lower end part of the pick-up nozzle 6 is shown. The nozzle is in the form of a metal tube. According to the invention the nozzle opening 12 is provided with a cover 13 of a gas-permeable material, such as a fine-meshed gauze or a porous foam.

The cover could be made of stiff material or flexible material stretched over the nozzle opening and fastened to the nozzle e. g. by means of a clamping bush 14 situated around the tube, or by laser welding. During operation of the machine, a component 9 can be sucked up and held against the cover 13 by means of a suction force created at the nozzle opening 12.

As the cover has a flat surface, the component always takes a flat position, i. e. perpendicular to the central axis 15 of the nozzle. Different sizes of the components 9a, 9b, 9c can be used now, as is indicated by broken lines. Often a component is held to the nozzle opening in an off-center position, as shown for component 9b. Without a cover, this component 9b would be sucked askew against the edge 16 of the nozzle opening. This would result in an improper placement of the component on the printed circuit board, if no other appropriate steps were taken. Usually, such an improperly sucked up component will be detected by visual means and then removed. Due to the cover, component 9b remains in a flat and correct position.

Without a gas-permeable cover, the surface of the component, on which the suction force is acting, is defined by the size of the opening 12 of the nozzle. By virtue of the presence of the cover, gas (air) is also sucked through the cover material between the edge 16 of the nozzle opening and the component 9, as indicated by arrows in Fig. 2. This results in an increase of the surface area on which the suction force is acting, so that the component is held in a more reliable and more stable manner.

The suction of gas (air) through the gas-permeable cover could lead to impurities being caught in the cover and hence to a reduction in suction force. If such a problem arises, a solution might be to instantaneously reverse the gas stream, i. e. blow out the impurities. This could be done just before picking up every component or e. g. before every tenth component to be picked up.

Usually pick-up nozzles have a circular suction opening. However, the

suction opening may also have a rectangular or oval shape.

Usually component-handling machines are used for placing electronic components (chips, SMDs) on printed circuit boards or other substrates. However, the invention can also be used in other kinds of component-handling machines, such as a component-taping machine. This is a machine in which components are placed in pockets of a tape which is subsequently wound on a reel. Later on the reeled tapes are used in a feeder for a component-placement machine to pick up the components and place them on a substrate. But the invention can also be used in machines for handling other components, e. g. small mechanical parts, which have to be picked up and placed in a certain position in or on a device.