HOLDING DEVICE FOR HOLDING PRINTED CIRCUIT BOARDS AND THE LIKE

Abstract

The invention relates to a holding device for holding substrates such as printed circuit boards, metal sheets, foils or the like, comprising a suction surface, the suction surface having a plurality of suction nozzles and the suction nozzles being subjected to a negative pressure relative to the ambient pressure by means of a device providing negative pressure for providing a holding force for one or more substrates, wherein the device providing negative pressure provides negative pressure, such that the ratio of the cumulated drop in pressure of all suction nozzles to the cumulated drop in pressure of all suction nozzles and supply lines of the suction nozzles up to the device providing negative pressure is greater than 0.25%, in particular greater than 1%, preferably greater than 25%, in particular greater than 35%, preferably greater than 40%.

Claims

1. A holding device for holding substrates such as printed circuit boards, metal sheets, foils or the like, comprising a suction surface, wherein the suction surface has a plurality of suction nozzles and wherein the suction nozzles can be subjected to a negative pressure relative to the ambient pressure by means of a device providing negative pressure for providing a holding force for one or more substrates, characterised in that, the device providing negative pressure provides a negative pressure such that the ratio of the cumulated drop in pressure of all suction nozzles and the cumulated drop in pressure of all suction nozzles and supply lines of the suction nozzles to the device providing negative pressure is greater than 0.25%, in particular greater than 1%, preferably greater than 25%, in particular greater than 35%, preferably greater than 40%.

2. The holding device according to claim 1, at least one of the suction nozzles having a suction opening such that a cross-sectional area of the suction opening is larger than the cross-sectional area of the suction nozzle.

3. The holding device according to claim 2, the ratio of the cross-sectional area of the suction openings and the cross-sectional area (101) of the suction nozzles being between 0.01 and 10,000.

4. The holding device according to claim 1, the device providing negative pressure comprising a distribution facility for distributing a suction stream to the suction nozzles.

5. The holding device according to claim 4, several suction areas of the suction plate being separately controllable by means of the distribution facility.

6. The holding device according to claim 4, the distribution facility having one or more supply lines for supplying the suction nozzles of the suction surface or of one or more suction areas, wherein for the suction surface or for each suction area the ratio of the cumulated cross-sectional area of the respective supply lines and the cumulated cross-sectional area of the suction nozzles in the suction surface or in the suction area is at least 0.3.

7. The holding device according to claim 4, the distribution facility having switching valves for controlling different suction areas.

8. The holding device according to claim 7, the device providing negative pressure having a suction pulse facility arranged fluidically between a suction facility and the distribution facility for providing a first suction pulse.

9. The holding device according to claim 8, the suction pulse facility having a negative pressure chamber.

10. The holding device according to claim 1, further including a facility measuring negative pressure and/or a flow measuring facility for measuring the flow through the supply lines is arranged for measuring and regulating a negative pressure of the suction stream.

11. The holding device according to claim 10, a negative pressure of different suction areas measurable and regulated by at least one of means of the facility measuring negative pressure and means of the flow measuring facility.

12. The holding device according to claim 1, a detection facility being arranged for detecting empty areas of the suction plate which are substrate-free.

13. The holding device according to claim 12, the detection facility comprising at least one of a group including optical and and/or acoustic detection means.

14. The holding device according to claim 3, the detection facility being connected to the distribution facility in such a way that, upon detection of empty areas, these can be switched off by means of the distribution facility.

15. The holding device according to claim 1, at least one of the suction nozzles and the suction openings are regularly arranged in a distributed way.

16. The holding device according to claim 15, in which substantially adjacent rows of suction nozzles and/or suction openings are arranged in an offset manner from one another.

17. The holding device according to claim 15, in which, in the edge area of the suction surface, the suction nozzles and/or the suction openings have a different arrangement density.

18. The holding device according to claim 5, various suction areas have various arranged and/or configured suction nozzles and/or suction openings.

19. The holding device according to claim 5, the different suction areas being configured to hold differently rigid and/or differently thick substrates.

20. A method for holding substrates such as printed circuit boards, metal sheets, foils or the like, wherein one or more substrates are held by means of a suction surface, wherein the suction surface has a plurality of suction nozzles, and wherein the suction nozzles are subjected to a negative pressure relative to the ambient pressure to provide a holding force for one or more substrates, a negative pressure is provided by means of a device providing negative pressure such that the ratio of the cumulated drop in pressure of all suction nozzles and the cumulated drop in pressure of all suction nozzles and supply lines of the suction nozzles to the device providing negative pressure is greater than 0.25%.

21. An ink-jet printing device with a holding device according to claim 1.

Description

[0037] In this context, the following applies:

[0038] FIG. 1 shows a part of a holding device with a view from above in accordance with an embodiment of the present invention;

[0039] FIG. 2 shows a part of a cross-section through the holding device in accordance with an embodiment of the present invention; and

[0040] FIG. 3 shows a detailed view of the cross-section of the embodiment in accordance with FIG. 2.

[0041] FIG. 1 shows a part of a holding device with a view from above in accordance with an embodiment of the present invention;

[0042] FIG. 1 is a holding device 1 shown with a view from above. The holding device 1 has a rectangular negative pressure suction plate 2, which has a suction surface 3 as a substrate. The negative pressure suction plate can also be circular, elliptical or of any other shape. Suction openings 4 are arranged in the suction surface 3 and are periodically or evenly distributed across the suction surface 3. A negative pressure is generated on the upper side of the negative pressure suction plate 2 to hold a substrate arranged on the negative pressure suction plate 2. FIG. 1 also shows examples of suction areas 7a, 7b, which can be separately controlled, and which serve to hold substrates in the respective area 7a, 7b. Suction areas 7a, 7b are essentially freely definable and controllable in their number as well as in their shape and position on the suction surface. For the detection of empty areas on the suction surface 3, i.e. areas on which there is no substrate, a camera 13 can be arrangedas shown herewhich is connected to a regulating facility not shown, e.g. a computer, for evaluation, for switching off unoccupied areas of the negative pressure suction plate 2 and for controlling the areas 7a, 7b occupied by substrates. The regulating facility can for example be configured to control the suction facility 9, the distribution facility 6, the suction pulse facility 10 and/or switching valves 8 described in FIG. 2.

[0043] For example, the suction openings here have a distance of 10 mm and the suction device 9 provides a negative pressure so that the ratio of cumulated drop in pressure in suction nozzles 5 covered by substrates, which together cover a proportion of the suction surface of approx. 50%, and cumulated drop in pressure of all suction nozzles 5 and supply lines 6a, 6b of the suction nozzles to the suction device 9 is 20%. Depending on this, the same holding force can be achieved by a corresponding proportional change, e.g. by arranging four times the number of suction openings and providing a ratio of cumulated drop in pressure in suction nozzles 5 uncovered by one or more substrates and cumulated drop in pressure of all suction nozzles 5 and supply lines 6a, 6b of the suction nozzles up to suction device 9 of 5% by suction device 9.

[0044] FIG. 2 shows a part of a cross-section through the holding device in accordance with an embodiment of the present invention.

[0045] In FIG. 2, the negative pressure suction plate 2 is now essentially shown in cross-section. On the right side of the suction plate 2 the suction surface 3 can be seen whereas on the left side of the suction plate 2 there is a supporting surface 14 for supporting the negative pressure suction plate 2 on a supporting structure or similar. Starting from the left side of FIG. 2, a suction device 9, e.g. a negative pressure pump, is schematically shown, which is connected to a suction pulse facility 10 with a negative pressure chamber 11. Further upstream of the suction pulse facility 10, a switching valve 8 is shown, which serves to switch on and off or to control the suction stream for certain suction nozzles 5 for range 7a. FIG. 2 shows only one switching valve 8 as an example; several switching valves can of course be arranged, for example one switching valve per suction nozzle or per supply line. It is also possible to regulate several supply lines 6a or suction nozzles 5 by means of a switching valve 8.

[0046] Upstream of the shown switching valve 8 supply lines 6a, 6b of a negative pressure distribution facility 6 are shown. These are used for the fluidic connection of the suction nozzles 5 with the suction facility 9 and are connected to the bottom side 14 of the negative pressure suction plate 2. The supply lines 6a are connected with the supply lines 6b in the negative pressure suction plate 2 and these are connected with the suction nozzles 5. The suction device 9 or the suction pulse facility 10 can each also be configured to provide a temporary compressed air blast. This enables an easy release of a held substrate by temporarily reversing the air flow direction.

[0047] For monitoring the negative pressure in the supply lines 6a, 6b a negative pressure measuring facility 12 and/or a flow measuring facility is arranged, which can be connected to the suction facility 9, the suction pulse facility 10 and/or the switching valves 8 for regulation purposes. The cross-section of the supply lines 6a, 6b is selected in such a way that it corresponds to at least twice, and in particular at least three times, the cumulated cross-sectional area of the suction nozzles 5 of the respective subarea 7a, 7b.

[0048] FIG. 3 shows a detailed view of the cross-section of the embodiment in accordance with FIG. 2.

[0049] FIG. 3 now shows in detail a suction nozzle 5 with connected supply lines 6b in the negative pressure suction plate 2. The ratio of the diameter 100 of the cross-section of the suction opening 4 and the diameter 101 of the cross-section of the suction nozzle 5 is preferably selected between 1 and 20, in particular between 2 and 12, in particular between 5 and 9, preferably between 6 and 8, the ratio of the cross-sectional areas is then between 0.01 and 10,000, preferably between 1 and 400, in particular between 4 and 144, in particular between 25 and 81, preferably between 36 and 64. The limiting cross-section of the respective suction nozzle 5 results in a negative pressure suction stream not collapsing with a partially open surface of the negative pressure suction plate 2, i.e. with areas on which there is no substrate, but remaining essentially constant, the configuration of the cross-section of the suction openings 4 serving to generate the necessary holding force after the suction procedure. In other words: If the cross-sectional area of the suction opening is suitably large, in particular larger than the cross-sectional area of the suction nozzle, the differential pressure is applied to the former. This is advantageous because the holding force for a substrate is essentially proportional to the differential pressure of the suction opening to the ambient pressure and the cross-sectional area of the suction opening.

[0050] The suction opening 4 can be part of the suction nozzle 5 or can be configured separately by connecting the suction nozzle 5 with the suction opening 4. In particular, the cross-sectional shape of the suction opening 4 and/or the suction nozzle 5 can be configured cylindrically or elliptically. The suction nozzle 5 with suction opening 4 can be manufactured by means of a bore with a drilling tip and/or with a chamfer.

[0051] The suction nozzle can thereby take the form of a small bore or opening with a length of a few millimetres. Alternatively, or additionally, the bore or opening can be replaced or supplemented by a foil, in particular a metal foil, which can be arranged between the distribution facility and the suction openings and which has one or more bores with an even smaller cross-section. A connection between the opening of the suction nozzle and the suction opening can be configured in a funnel-shaped way, i.e. the suction opening runs conically towards a suction nozzle geometry. A porous foil can also be used as an opening for the suction nozzle. Furthermore, the geometry of the suction nozzle(s) can be suitably formed, for example circularly, rectangularly, elliptically or the like.

[0052] In summary, the invention and, in particular, at least one of the embodiments can provide or enable the following advantages: [0053] More reliable holding of substrates [0054] easier definition/retention of substrates [0055] lower costs [0056] high efficiency [0057] little effort [0058] high process reliability [0059] high flexibility

[0060] The invention can be used in particular in the areas of ink jet printing, laser processing, laser structuring and also for measuring substrates by means of measuring systems, for example camera systems for defect detection on substrates, substrate transport, etc.

[0061] Although the present invention has been described using preferred embodiments, it is not limited to these, but can be modified in many ways.

REFERENCE NUMBERS LIST

[0062] 1 holding device [0063] 2 suction plate [0064] 3 suction surface [0065] 4 suction opening [0066] 5 suction nozzle [0067] 6 distribution facility [0068] 6a, 6b supply lines [0069] 7a, 7b suction areas [0070] 8 switching valve [0071] 9 suction facility [0072] 10 suction pulse facility [0073] 11 negative pressure chamber [0074] 12 negative pressure measuring device [0075] 13 detection facility [0076] 100 cross-section of the suction openings [0077] 101 cross-section of the suction nozzles