Dispensing Nozzle for a Coater

Abstract

A dispensing nozzle for applying a coating to a substrate has a valve seat, a valve element adapted for being displaced between a closed position in which it interacts with the valve seat so as to close a connection between a coating material inlet and a coating material outlet of the dispensing nozzle, and an open position in which this connection is open. Further, a retraction element adapted for being displaced between a forward position and a rearward position is provided, the retraction element being in fluid communication with a dispensing channel of the dispensing nozzle downstream of the valve element.

Claims

1. A dispensing nozzle for applying a coating to a substrate, having a valve seat, a valve element adapted for being displaced between a closed position in which it interacts with the valve seat so as to close a connection between a coating material inlet and a coating material outlet of the dispensing nozzle, and an open position in which this connection is open, and further having a retraction element adapted for being displaced between a forward position and a rearward position, the retraction element being in fluid communication with a dispensing channel of the dispensing nozzle downstream of the valve element, with the retraction element being a diaphragm which on one side is exposed to the dispensing channel.

2. The dispensing nozzle of claim 1 wherein the retraction element is arranged laterally of the dispensing channel, in particular in a nozzle body of the dispensing nozzle.

3. The dispensing nozzle of claim 1 wherein the retraction element is arranged in the valve element and is in fluid connection with the dispensing channel.

4. The dispensing nozzle of claim 1 wherein the valve element is a sleeve, the diaphragm being clamped to the valve element.

5. The dispensing nozzle of claim 1 wherein a sealing element is provided which seals between the valve element and the nozzle body of the dispensing nozzle.

6. The dispensing nozzle of claim 5 wherein the valve element is a sleeve, the diaphragm being clamped to the valve element and wherein the sealing element is screwed into the valve element and clamps the diaphragm therein.

7. The dispensing nozzle of claim 1 wherein the retraction element is a piston which on one side is exposed to the dispensing channel.

8. The dispensing nozzle of claim 1 wherein a retraction control chamber is provided which is operatively connected to the retraction element.

9. The dispensing nozzle of claim 8 wherein a retraction control piston is provided which is exposed to the pressure in the retraction control chamber.

10. The dispensing nozzle of claim 9 wherein an adjustable retraction abutment is provided for adjusting the maximum stroke of the retraction control piston.

11. The dispensing nozzle of claim 9 wherein a sealing element is provided which seals between the valve element and the nozzle body of the dispensing nozzle, wherein the valve element is a sleeve, the diaphragm being clamped to the valve element, and wherein the sealing element is screwed into the valve element and clamps the diaphragm therein, the sealing element being guided on the retraction control piston.

12. The dispensing nozzle of claim 11 wherein the retraction control piston is screwed onto a protrusion of the diaphragm.

13. The dispensing nozzle of claim 1 wherein a dispensing control chamber is provided which is operatively connected to the valve element.

14. The dispensing nozzle of claim 13 wherein an adjustable dispensing abutment is provided for adjusting the maximum stroke of the valve element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will now be described with reference to the enclosed drawings. In the drawings,

[0026] FIG. 1 shows a schematic cross section of the dispensing nozzle,

[0027] FIG. 2 shows a cross section of the core elements of the dispensing nozzle of FIG. 1,

[0028] FIG. 3 shows the valve element used in the dispensing nozzle in a cross-section,

[0029] FIG. 4 shows the valve element of FIG. 3 in a perspective view,

[0030] FIG. 5 shows the diaphragm used in the dispensing nozzle in a cross section,

[0031] FIG. 6 shows the diaphragm of FIG. 5 in a perspective view,

[0032] FIG. 7 shows the sealing element used in the dispensing nozzle in a cross section,

[0033] FIG. 8 shows the adjustable retraction abutment used in the dispensing nozzle in a cross section,

[0034] FIG. 9 shows the adjustable retraction abutment of FIG. 8 in a perspective view.

[0035] FIG. 10 shows at an enlarged scale a portion of the dispensing nozzle in a condition when coating material is being dispensed,

[0036] FIG. 11 shows the dispensing nozzle of FIG. 10 in a condition in which the dispensing has been shut off,

[0037] FIG. 12 shows the dispensing nozzle of FIG. 10 in a condition in which some of the coating material has been sucked back.

DETAILED DESCRIPTION OF THE INVENTION

[0038] A dispensing nozzle 1 for applying a coating material onto a substrate will now be explained with reference to FIGS. 1 to 9. The dispensing nozzle 1 is in particular suitable for machinery used for the production of semiconductor chips and MEMS.

[0039] Dispensing nozzle 1 has a nozzle body 10 provided with a coating material inlet 2 and a coating material outlet 3. Coating material inlet 2 is connected via a tube or other suitable component to a supply of coating material. Coating material outlet 3 can be in the form of a nozzle or other configuration adapted for applying a particular coating material onto a substrate.

[0040] In the interior of nozzle body 10, a chamber 12 is provided between the coating material inlet 2 and the coating material outlet 3. Within chamber 12, a valve element 14 is arranged which can cooperate with an annular valve seat 16 which is formed so as to circumscribe a dispensing channel 18 acting as the coating material outlet 3.

[0041] The side of the valve seat 16 or the direction towards the valve seat 16 will in the following be referred to as forward while the opposite side or direction will be referred to as rearward.

[0042] Valve element 14 can be displaced between a closed position and an open position. In the closed position, valve element 14 contacts valve seat 16 with its forward annular end. As valve element 14 is sealed with respect to nozzle body 10 (which will be explained in detail below), a connection between coating material inlet 2 and coating material outlet 3 of dispensing nozzle 1 is closed in this position of valve element 14. In the open position, valve element 14 is spaced (in a controllable manner) from valve seat 16 so that the flow connection between coating material inlet 2 and coating material outlet 3 is open. The amount of coating material dispensed with dispensing nozzle 1 through dispensing channel 18 then depends from the pressure with which the coating material is supplied, the viscosity of the coating material, and the stroke of the valve element 14 with which it was lifted from valve seat 16.

[0043] Valve element 14 is a hollow sleeve (please see in particular FIGS. 3 and 4) which has a tapering and rounded end face forward end face 20 adapted for contacting valve seat 16.

[0044] In its interior, valve element 14 has an abutment 22 for a diaphragm 24 (please see in particular FIGS. 5 and 6) arranged in the forward portion of valve element 14. Rearward of abutment 22 (when viewed from end face 20), valve element 14 has an internal thread 26.

[0045] Diaphragm 24 has a dish-like forward membrane 28 and a cylindrical protrusion 30 which is connected to the center of membrane 28. A thread 32 is formed on the outer surface of protrusion 30.

[0046] Diaphragm 24 is formed from polytetrafluoroethylene (PTFE) or perfluoroalcoxy (PFA). However, other materials can be used as well.

[0047] Here, membrane 28 and protrusion 30 are formed in one piece. It is however also possible to form protrusion 30 as a separate piece which is then connected to membrane 28.

[0048] Diaphragm 24 is mounted in the interior of valve element 14 by clamping the outer circumference of membrane 28 against abutment 22 formed in sleeve-like valve element 14. For doing so, a sealing element 34 (please see FIG. 7) is used.

[0049] Sealing element 34 is a hollow, generally sleeve-like body with a guiding sleeve 36 at its forward end and a sealing bellows 38 at its rearward end.

[0050] Guiding sleeve 36 has an inwardly tapering end face 40 which forms a support surface for membrane 28 of diaphragm 24. On its outer surface, an outer thread 37 is formed.

[0051] At its rearward end, guiding sleeve 36 has a control projection 42 which is provided with an outer thread 44.

[0052] Guiding sleeve 36 and control projection 42 here form a continuous cylindrical guiding surface 46.

[0053] Sealing bellows 38 is provided with an annular connecting reinforcement 48 used for clamping it to nozzle body 10.

[0054] Sealing element 34 can be formed from the same materials as diaphragm 24, in particular PTFE. However, other materials can be used as well.

[0055] By screwing guiding sleeve 36 with its thread 37 into thread 26 of valve element 14, the outer circumference of membrane 28 is clamped against abutment 22. Protrusion 30 projects into the interior space of valve element 14.

[0056] Annular connecting reinforcement 48 of sealing bellows 38 is clamped between two portions of nozzle body 10 is a tight manner, thereby sealing chamber 12 so that valve element 14 is arranged in chamber 12 between coating material inlet 2 and valve seat 16. Diaphragm 24 seals between chamber 12 and the interior of valve element 14.

[0057] The displacement of valve element 14 is controlled with a dispensing control piston 50 which is arranged in a dispensing control chamber 52 formed in nozzle body 10.

[0058] Dispensing control piston 50 has a connecting projection 51 which has at is forward end an internal thread threaded onto outer thread 44 formed on control projection 42 of sealing element 34. Accordingly, any axial displacement of dispensing control piston 50 is transferred via sealing element 34 onto valve element 14. As dispensing control piston 50 is guided in nozzle body 10, it provides a guiding effect for valve element 14.

[0059] Displacement of dispensing control piston 50 within dispensing control chamber 52 can be controlled by varying the pressure in chamber 52. To this end, a pressure connection 54 is provided (please see FIG. 1). A spring 56 is arranged in dispensing control chamber 52 on the side of dispensing control piston 50 which is opposite the side where pressure connection 54 is arranged.

[0060] For controlling the maximum displacement of dispensing control piston 50 in the direction of lifting valve element 14 from valve seat 16 (in a rearward direction), an adjustable dispensing abutment 58 is provided. Dispensing abutment 58 is formed from a screw which extends into dispensing control chamber 52. By screwing dispensing abutment 58 more or less into dispensing control chamber 52, the maximum stroke of dispensing control piston 50 can be adjusted.

[0061] As can be seen in FIG. 2, dispensing abutment 58 can be formed hollow so as to interact with a protrusion formed on dispensing control piston 50 for achieving a guiding function.

[0062] In a known manner, a seal 60 can be used for sealing the piston 50 against dispensing control chamber 52 and nozzle body 10.

[0063] Dispensing control piston 50 is formed hollow so that a retraction control chamber 62 is formed therein. Within retraction control chamber 62, a retraction control piston 64 is arranged. It is provided with a projection 66 which has a cavity with an internal thread 68 at its forward end. Thread 68 is threaded onto thread 32 of diaphragm 24.

[0064] With retraction control piston 62, membrane 28 of diaphragm 24 can be displaced between a forward and a rearward position. As membrane 28 serves as one of the boundaries of the determined volume of the dispensing channel 18 when valve element 14 is in the closed position, retracting membrane 28 results in an increase of the volume of dispensing channel 18 whereby a small volume of coating material is being retracted into dispensing channel 18 when membrane 28 is being retracted. Because of the retracting effect which membrane 28 of diaphragm 24 exerts on the coating material, diaphragm 24 is referred to as being a retraction element.

[0065] The displacement of retraction control piston 64 within retraction control chamber 62 is controlled by varying the pressure in retraction control chamber 62. To this end, a pressure connection 69 is provided (please see FIGS. 1 and 2). A spring 70 is arranged in retraction control chamber 62 on the side of retraction control piston 64 which is opposite the side where pressure connection 69 is arranged.

[0066] Pressure connection 69 can be formed in a retraction abutment 72 which is here embodied as a hollow adjustment screw which engages with an outer thread 74 into an internal thread 76 formed in a rear portion of dispensing control piston 50. Accordingly, retraction abutment 72 moves together with dispensing control piston 50 when valve element 14 is being displaced.

[0067] Retraction control piston 64 can be displaces rearwardly (away from valve seat 16) until it abuts at retraction abutment 72. The corresponding stroke can be adjusted by screwing retraction abutment 72 more or less into the rear portion of dispensing control piston 50.

[0068] For dispensing coating material, valve element 14 is brought into an open condition by increasing the pressure in dispensing control chamber 52 to the extent that the force of spring 56 is overcome and dispensing control piston 50 is being moved in the rearward direction. Accordingly, dispensing control piston 50 lifts, via sealing element 34, valve element 14 from valve seat 16. In this condition which is shown in FIG. 10, coating material supplied via coating material inlet 2 flows through chamber 12 and exits through dispensing channel 18.

[0069] When coating material is being dispensed, diaphragm 24 is in the forward position. This is done by suitably controlling the pressure in retraction control chamber 62.

[0070] When the flow of coating material is to be stopped, the pressure in dispensing control chamber 52 is decreased so that dispensing control piston 50 is moved, by the effect of spring 56 and possibly by the pressure level applied to dispensing control chamber 52, in the forward direction until valve element 14 abuts at valve seat 16. Then, the flow of coating material is stopped. This condition is shown in FIG. 11.

[0071] For preventing that coating material drops from the forward end of dispensing nozzle 1, a small amount of coating material is being sucked back into dispensing channel 18. This is accomplished by moving retraction element 24 from the forward position into the rearward position shown in FIG. 12. As valve element 14 contacts valve seat 16, the displacement of retraction element 24 (more specifically: of membrane 28) has an effect only on the coating material which is downstream of valve seat 16. Accordingly, the volume sucked back into the forward end of valve element 14 results in a small meniscus being formed at the out end of dispensing channel 18, and no coating material can drop from dispensing nozzle 1 onto the substrate to be coated.