HK1205771B - A method of producing an aperture plate for a nebulizer - Google Patents

Description

Method for manufacturing an orifice plate for a sprayer

introduction

The present invention relates to the manufacture of orifice plates for aerosol (or "nebulizer") devices. Vibrating orifice plates are used in a variety of aerosol devices and are typically supported around their edges by a vibrating support that is vibrated by a piezoelectric element. In addition, aerosol devices can have passive or electrostatic orifice plates that are operated, for example, by an acoustic signal from a speaker, causing the drug flow to filter through the orifice plate.

Orifice plates are used for aerosol delivery of liquid formulations, delivering controlled small droplet sizes suitable for pulmonary drug delivery. An ideal nebulizer is one that ensures consistent and precise particle size and an output rate that can be varied to deliver the drug to the target area as efficiently as possible. Delivery of aerosols to the deep lung (such as the bronchi and bronchiolar regions) requires a small and repeatable particle size typically within the range of 2-4 μm. Generally speaking, an output greater than 1 ml/min is required.

At present, orifice plates are manufactured by various means (including electroplating and laser drilling). From a technical and economic standpoint, electroplating is generally the most advantageous manufacturing method. US 6,235,177 (Aerogen) describes a method based on electroplating, wherein a thin sheet material is built onto a mandrel by an electrodeposition process, wherein the liquefied metal (typically palladium and nickel) in the electroplating bath is converted from a liquid form to a solid form on the thin sheet. The material is transferred to the conductive surface on the mandrel and is not transferred to the non-conductive photoresist area. The area is shielded by the non-conductive photoresist, wherein no metal accumulation is required, see Figure 1. After the electroplating process ends, the mandrel/thin sheet assembly is removed from the bath, and the thin sheet is peeled off from the mandrel for subsequent processing as an orifice plate.

However, a problem with this method is that the hole size depends on the plating time and the thickness of the resulting thin slice. The process can be difficult to control, and if not perfectly controlled, some holes may become nearly closed or blocked as shown in Figure 2 or too large as shown in Figure 3, and there may be excessive variation in the size of the holes. In addition, there are limitations on the number of holes per unit area. Furthermore, in the case of this technology, an increase in output rate generally requires an increase in particle size, which may not be desirable in general. It would be more desirable to increase output rate without increasing particle size.

The combination of hole size accuracy and the number of holes per unit area can be an important determinant of the nebulizer output rate and the resulting particle size distribution.

WO 2011/139233 (Agency for Science, Technology and Research) describes a microsieve fabricated using SU8 material by light shielding.

US4844778 (Stork Veco) describes the fabrication of membranes for separation media, and separation devices incorporating such membranes. The fabrication method comprises a two-step photolithographic procedure.

EP1199382 (Citizen Watch Co. Ltd.) describes a manufacturing method for a hole structure in which exposure to a photosensitive material is performed in multiple cycles to provide deeper holes that taper towards the top as there is exposure through the foremost hole.

The present invention is directed to providing an improved method of manufacturing an orifice plate for a sprayer in order to solve the above problems.

Summary of the Invention

According to the present invention, there is provided a method for manufacturing an orifice sheet for forming an aerosol, the method comprising:

Provide a mandrel of conductive material,

applying a mask on the mandrel in a pillar pattern,

Plating the space around the column,

removing the mask to provide a sheet of electroplating material having aerosol-forming holes, the mask post being located in the aerosol-forming holes,

wherein the masking and plating steps are followed by at least one subsequent masking and plating cycle to increase the thickness of the sheet,

wherein the at least one subsequent cycle brings the overall sheet thickness to a desired level based on criteria for removing the sheet from the mandrel, and/or a desired frequency of operation of the orifice plate, and/or physical constraints of an atomizing drive,

wherein the at least one subsequent loop provides:

spaces, at least some of which overlie the plurality of aerosol-forming apertures, and

an electroplated material that blocks some of the aerosol-forming apertures, and

Wherein the at least one subsequent cycle is performed according to a desired flow rate through the orifice plate.

In some embodiments, all masks for all cycles may be removed together, however in other embodiments, the masks for one cycle may be removed before a subsequent masking and plating cycle, and if so, the subsequent plating is more likely to at least partially fill some of the underlying holes.

In one embodiment, the depth of the pillars ranges from 5 μm to 40 μm and preferably from 15 μm to 25 μm.In some embodiments, the width dimension of the pillars in the plane of the mandrel ranges from 1 μm to 10 μm, preferably from 2 μm to 6 μm.

In one embodiment, the electroplating is continued until the plated material is substantially flush with the tops of the posts.

In one embodiment, there is substantially no overlap between the electroplated material and the mask material. In one embodiment, the at least one subsequent cycle achieves an overall sheet thickness exceeding 50 μm and preferably greater than 58 μm. In one embodiment, the degree of sealing in the or each subsequent cycle is selected based on the desired mechanical properties of the aperture plate.

In one embodiment, the first masking and electroplating are performed so that the aerosol-forming holes taper in a funnel shape.

In one embodiment, the subsequent masking and electroplating are performed so that the overlying space tapers in a funnel shape.

In one embodiment, the electroplating metal comprises Ni and/or Pd. In one embodiment, the Ni and/or Pd are present at the surface in concentrations selected based on their anti-corrosion properties. In one embodiment, the proportion of Pd is between 85% and 93% by weight and is preferably approximately 89%, with the remainder being essentially Ni. In one embodiment, the electroplating material comprises Ag and/or Cu at the surface in concentrations selected based on their antibacterial properties.

In one embodiment, described method comprises further processing described thin slice to provide the other step of being ready to be installed in the orifice plate of the device that forms aerosol.In one embodiment, described thin slice is formed into the orifice plate of non-planar shape.In one embodiment, described thin slice is formed into the shape of the configuration that has selected according to the atomizing spray angle that wants.In one embodiment, described thin slice is formed into the shape of the part with operation cam shape and the flange that is used to engage driver.In one embodiment, described thin slice is annealed before forming.

In another aspect, the present invention provides an orifice plate sheet comprising a metal body whenever formed by a method as defined above in any embodiment.

In another aspect, the present invention provides an orifice plate, whenever formed by a method as defined above in any embodiment.

In another aspect, the present invention provides an apertured sheet comprising a bottom layer of photolithographically plated metal having aerosol-forming through-holes and at least one top layer of photolithographically plated metal having spaces overlying a plurality of aerosol-forming through-holes, wherein the size and number of each macrohole in the aerosol-forming holes are related to a desired aerosol flow rate.

In one embodiment, said top layer closes some of said holes in said bottom layer.

In one embodiment, the metal is the same for all layers.

In one embodiment, the electroplated metal comprises Ni and/or Pd. In one embodiment, the Ni and/or Pd are present at the surface in a concentration selected based on anti-corrosion properties.

In one embodiment, the proportion of Pd is in the range of 85 wt% to 93 wt% and is preferably about 89%, the remainder being essentially Ni. In one embodiment, the electroplated metal comprises Ag and/or Cu at the surface in concentrations selected for antibacterial properties.

In another aspect, the present invention provides an orifice plate comprising a sheet as defined above in any embodiment.

In another aspect, the present invention provides an aerosol-forming device comprising an orifice plate as defined above in any embodiment, and a driver engaging the plate to vibrate it at a desired frequency in order to form an aerosol.

In another aspect, the present invention provides an aerosol-forming device comprising an orifice plate as defined above in any embodiment, a support for said orifice plate for passive orifice plate use, and a horn arranged to force a liquid wave through said orifice plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings, in which:

1 to 3 are cross-sectional views outlining the prior art method as described above;

Figures 4(a) and 4(b) are cross-sectional views showing the masking and plating steps of the first stage of the method, and Figure 5 is a partial plan view of a wafer used in this stage;

6( a ) and 6 ( b ) are cross-sectional views showing the second masking and plating stages, and FIG. 7 is a plan view;

FIG8 is a cross-sectional view after resist removal;

FIG9 shows the sheet after being punched to form the final orifice plate shape;

FIG10 is a graph of particle size versus flow rate to illustrate the operation of an orifice plate;

Figures 11(a), 11(b) and 12 are views corresponding to Figures 4(a), 4(b) and 5 of the second embodiment, in which the holes are gradually reduced in size; and

13(a) and 13(b) are views corresponding to FIGs. 6(a) and 6(b) and for the second embodiment, and FIG. 14 is a plan view in the region of a large upper hole after removing the photoresist mask.

DETAILED DESCRIPTION

Referring to Figure 4 (a), a mandrel 20 coats a photoresist 21 with a pattern of vertical columns having the dimensions of the holes or pores of the orifice plate to be manufactured. The column height is preferably in the range of 5 μm to 40 μm, more preferably 5 μm to 30 μm, and most preferably 15 μm to 25 μm in height. The diameter is preferably in the range of 1 μm to 10 μm, and most preferably about 2 μm to 6 μm in diameter. This mask pattern provides holes that define the size of the aerosol particles. When compared to the prior art, the number per unit area is much greater; a twenty-fold increase is possible, thus having up to 2,500 holes per square millimeter.

4( b ) and 5 , metal 22 is electrodeposited into the space around pillars 21 .

As shown in FIG6 (a), a second photoresist mask 25 of much larger (wider and taller) pillars is further applied, surrounding the area of many first pillars 21. The diameter of the holes in the second electroplated layer is between 20 μm and 400 μm, and more preferably between 40 μm and 150 μm. To ensure a higher flow rate, this diameter is made at the upper end of the range, and to ensure a lower flow rate, it is made at the lower end of the range to close more of the smaller openings in the first layer.

6 (b) and 7, the space around the photoresist 25 is plated to provide a sheet body 26 on the mandrel 20. When the photoresists 21 and 25 are cleaned with a resist remover and rinsed away, the plated materials 22 and 26 are in the form of an aperture plate blank or mask 30, as shown in FIG8, with a large top hole 32 and a small bottom hole 33. In this embodiment, all of the resists 21 and 25 are removed together, however, it is envisioned that the resist 21 can be removed before subsequent masking and plating cycles. In this case, subsequent plating is more likely to at least partially fill in some of the aerosol-forming holes.

As shown in FIG. 9 , the sheet 30 is punched into a disk and formed into a convex shape to provide the final product, the orifice plate 40 .

At this stage, the cambering diameter can be selected to provide the desired spray angle and/or to set the optimum natural frequency of the drive controller.The cambered shape provides a funneling effect, and the specific shape of the cambering plate affects the spray characteristics.

In an alternative embodiment, the orifice plate is not convex but rather remains flat, suitable for use in devices such as passive plate nebulizers. In this type of nebulizer, a sonotrode or horn is placed in contact with the drug on the plate. A piezoelectric element causes rapid motion of the transducer horn, which forces a wave of drug against the orifice plate, causing the drug flow to filter through the plate and exit the side in the form of an aerosol.

Most of the benefits of orifice plate fabrication of the present invention apply to vibrating or passive devices.

In more detail, the mandrel 20 is coated with a photoresist 21 having a column height and width equal to the target hole size. This coating and subsequent ultraviolet (UV) development keep the photoresist columns 21 upright on the mandrel 20. These columns have the desired diameter and are as high as their rigidity can support. Since the column diameter is only less than 10 μm and preferably less than 6 μm, it is possible to obtain more columns and resulting holes per unit area than in the prior art. It is expected that up to twenty times more holes may be possible compared to prior art electroplating methods. This creates the possibility of a significant increase in the open area ratio and the resulting sprayer output.

The mandrel 20 in which the selectively developed photoresist is in the form of upright columns 21 is then placed in an electroplating bath and, through an electrodeposition process, a metallic palladium nickel (PdNi) containing liquid form is typically then provided to the surface. When the column height is reached, the electroplating activity is stopped. Excessive electroplating is not allowed because electroplating is stopped just when the column height of the photoresist is reached. The electroplating solution is selected to suit the desired orifice plate size and operating parameters, such as vibration frequency. The Pd ratio can be in the range of about 85% to 93% by weight, and in one embodiment, is about 89% by weight, with the remainder being essentially Ni. The electroplated structure preferably has a fine random isotropic granular microstructure with a particle size of, for example, 0.2 μm to 2.0 μm. Those skilled in the art of electrodeposition will understand how the plating conditions for the two plating stages can be selected to suit the circumstances, and the entire contents of the following documents are incorporated herein by reference: US4628165, US6235117, US2007023547, US2001013554, WO2009/042187, and Lu S.Y., Li J.F., Zhou Y.H., "Grain refinement in the solidification of undercooled Ni-Pd alloys". Journal of Crystal Growth 309 (2007) 103-111, September 14, 2007. In general, most plating solutions comprising palladium and nickel will work, or nickel alone or even phosphorus with nickel (14:86) or platinum. Possibly a non-palladium flake could be plated in PdNi on the surface (0.5 to 5.0 μm thick, preferably 1.0 to 3.0 μm thick) to impart greater corrosion resistance. This would also reduce the hole size when smaller openings are desired.

When removed from the plating bath, the sheet thickness is typically 5-40 μm, depending on the column height. Peeling the sheet off at this point will produce a sheet that is extremely thin compared to the standard 60 μm thickness of the prior art. A sheet of this thickness would lack rigidity, be extremely difficult to process, and would require complex and expensive changes to the mechanical fabrication of the atomizer core to achieve a natural frequency equivalent to the current state of the art so that existing electronically controlled drives, which are in some cases integrated into ventilation equipment, would be usable. The use of different drive controllers would be a significant economic barrier to market acceptance due to the costs involved.

This problem is overcome by providing the plating mandrel to the second photoresist deposition process. In one embodiment, the photoresist thickness is made to reach a depth that is equal to the depth required for the overall thin sheet thickness to reach about 60 μm (similar to the thickness of the prior art thin sheet). For many applications, the second mask height is preferably within the range of 40-50 μm. It is then developed to allow larger columns to stand upright on the plating surface. Its diameter is typically between 40-100 μm but can be larger or smaller. The extra height from the second plating helps to move out from the mandrel, but importantly, it also achieves a specific thickness equivalent to the thickness of the prior art orifice plate to allow the final product orifice plate 40 to be electrically driven by an existing controller on the market. This has produced a natural frequency that is matched to achieve the appropriate vibration of the aerosol. Generally speaking, the second plating stage provides a thickness that is more suitable for sprayer applications for rigidity, flexibility and bending strength. Another aspect is that it closes some smaller holes, thereby achieving improved control of flow rate. Therefore, the second shielding and plating stage can be used to "adjust" the final product orifice plate according to the desired flow rate. At the same time, small batches can be changed quickly between each other, making a wide variety of differently tuned boards possible.

The flakes are then carefully peeled from the substrate without resorting to any subsequent processes such as etching or laser cutting. This ease of peeling has the advantage of not imparting additional mechanical stress to the already fragile flakes. The flakes are then washed and rinsed in a photoresist remover before undergoing metrological inspection.

In the aperture plate blank or mask 30, the depth of the holes 33 is equal to the first electroplated layer and the final sheet thickness will be equal to the sum of the two electroplated layers, see Figures 8 and 9. It is then ready for annealing, stamping and embossing to form the vibrating plate 40 shown in Figure 9.

For some applications, additional steps may be useful to improve the film properties. For example, the film may have an electroformed Ni substrate material that is over-plated with a corrosion-resistant material such as copper, silver, palladium, platinum, and/or a PdNi alloy. Copper and silver advantageously have antibacterial properties.

It will be appreciated that the present invention provides an aperture plate having a first layer of electroformed metal having a plurality of aerosol-forming through-holes that define the size of the ejected droplets, and a second top layer of similar or different electroformed material having larger diameter holes or spaces above the aerosol-forming holes and whose electroplated material closes some of the first layer holes.

In various embodiments, the second layer has a plurality of holes or spaces whose diameters are selected to expose a predetermined number of the first layer holes that form droplet sizes, which determines the number of holes that can function and therefore defines the amount of liquid atomized per unit time.

The size and number of holes in the two layers can be varied independently to achieve a desired range of droplet sizes and flow rate distributions, which is not possible with prior art electroplating definition techniques.

It will also be appreciated that the present invention offers the possibility of a much greater number of holes per unit area when compared to the prior art. For example, a twenty-fold increase is possible, thus having up to 2500 holes per square millimeter.

Furthermore, in various embodiments, the second layer at least completely or partially fills some of the aerosol-forming pores in the first layer, thereby forming a mechanical anchor for the two layers to help achieve the longevity requirements.

The following is a table of examples of different hole configurations for a 5 mm diameter aperture plate ("AP"):

Large hole diameter (mm) 0.10 0.08 0.06 0.04 Number of large holes/AP 815 1085 1464 2179 Small holes/large holes 12 7 4 1 Small hole/AP 9780 7595 5856 2179

Advantageous aspects of the present invention include:

(i) A larger number of holes per unit area is possible.

(ii) Smaller and more precise hole sizes in diameter are possible.

(iii) A thickness similar to existing commercially available sheets, which alleviates the onerous need to redesign the nebulizer to match the proper frequency of existing controllers to activate the aerosol generator.

(iv) Only two plating layers or plating steps are required.

(v) The flakes are still easy to carefully peel off the mandrel substrate.

(vi) It is possible to use existing electronic controllers to drive the orifice plates because the natural frequencies are matched and similar orifice thicknesses are already achieved.

(vii) Smaller and more controllable particle sizes (2-4 μm) are possible.

(viii) Higher flow rates may be achieved (0.5 to 2.5 ml/min, more typically 0.75-1.5 ml/min).

(ix) It is possible to obtain flow rate and particle size that are more independent of each other when compared to the prior art as described. (Typically in the prior art, increasing flow rate usually requires increasing particle size, and vice versa). These advantages are illustrated in the graph of Figure 10.

With reference to Figures 11 to 14, in a second embodiment, processing is almost the same as in the above embodiment. However, in this case, both sets of photoresist columns are tapered so that the resulting holes are tapered to achieve improved aerosol liquid flow. There is a mandrel 50, a first mask column 51, and an electroplated object 52 in the middle. The second mask comprises a tapered column 55, and the space in the middle is electroplated with metal 56. It is necessary to be very careful for the electroplating step to ensure that there is sufficient electroplating under the mask overhang. Figure 14 shows a plan view after removing the photoresist in this case. It will be seen that there are several small holes 61 for each large top hole 65 in the PdNi body 56/52. The top hole 65 has the effect of a funnel down to the small hole 61, which itself is funnel-shaped.

The present invention is not limited to the described embodiments, but can be varied in configuration and detail. For example, it is envisioned that if the thin slice can be removed from the mandrel, a second shielding and plating cycle may not be needed, either because the required thin slice depth is obtained in the first stage or because an improved thin slice removal technology is available. In addition, a third layer can be applied to provide greater mechanical rigidity to the orifice plate. In addition, in the above-described embodiments, each layer has the same metal. However, it is envisioned that it may be different, and even the metal in each layer forming the hole may include sublayers of different metals. For example, the composition at one or both surfaces may be different to obtain greater corrosion resistance and/or certain hydrophilicity or hydrophobicity properties. In addition, for the surface layer of the top 1 to 5 μm or 1 to 3 μm, there may be another plating step.

Claims (25)

1. A method for manufacturing an orifice plate (40) for forming an aerosol, the method comprising: A mandrel (20) provided with conductive material, A mask is coated on the mandrel in a column (21) pattern, the depth of which is in the range of 5 μm to 40 μm, and the width dimension in the plane of the mandrel is in the range of 1 μm to 10 μm. The space surrounding the pillar is electroplated (22) with a metal comprising Ni and/or Pd, wherein the electroplating continues until the electroplated material is substantially flush with the top of the pillar and substantially does not overlap with the masking material. Remove the mask to provide a sheet of electroplated material with pores for forming an aerosol, the mask pillars being located within the pores for forming the aerosol. The masking and electroplating steps are followed by at least one subsequent cycle of masking (25) and electroplating (26) to provide a sheet with a desired thickness, each subsequent electroplating comprising Ni and/or Pd. The at least one subsequent cycle brings the overall orifice plate sheet (30) thickness to the desired level according to the criteria for removing the sheet from the mandrel, the thickness being in the range of 45 μm to 90 μm, and/or the desired operating frequency of the orifice plate, and/or the physical constraints of the atomizing driver. The at least one subsequent loop provided after mask removal includes: Space (32), at least some of which cover a plurality of pores (33) forming an aerosol, and having a pore size between 20 μm and 400 μm, and Electroplating material (31), which seals some of the pores (33) that form the aerosol, The at least one subsequent cycle is performed according to the desired flow rate through the orifice plate, wherein a certain number of spaces with diameters are selected in the orifice plate such that a predetermined number of orifices for forming the aerosol are exposed. The method includes further processing of the sheet to provide an orifice plate (40) ready for installation into an aerosol-forming device, wherein the orifice plate sheet (30) is formed as a non-planar orifice plate (40) having a convex portion and a flange for engaging a actuator. 2. The method according to claim 1, wherein the depth of the column (21) is in the range of 15 μm to 25 μm. 3. The method according to claim 1 or 2, wherein the width dimension of the column (21) in the plane of the mandrel is in the range of 2 μm to 6 μm. 4. The method according to claim 1 or 2, wherein the at least one subsequent cycle causes the overall sheet thickness to reach a value exceeding 50 μm. 5. The method according to claim 1 or 2, wherein the degree of closure in the or each subsequent cycle is performed according to the desired mechanical properties of the orifice plate. 6. The method according to claim 1 or 2, wherein the masking and electroplating steps are performed to form atomized pores (51) that gradually narrow in a funnel shape. 7. The method according to claim 1 or 2, wherein at least one subsequent cycle of the shielding (25) and electroplating (26) is performed so that the overlay space (55) gradually decreases in a funnel shape. 8. The method of claim 1, wherein the Ni and/or Pd are present at the surface in a concentration selected according to the corrosion resistance properties. 9. The method according to claim 1 or 2, wherein the proportion of Pd is in the range of 85% to 93% by weight, and the remainder is substantially Ni. 10. The method of claim 9, wherein the proportion of Pd is 89%. 11. The method according to claim 1 or 2, wherein the electroplating material at the surface comprises Ag and/or Cu at a concentration selected according to its antibacterial properties. 12. The method of claim 1, wherein the sheet is formed in a shape having a configuration selected according to the desired atomization spray angle. 13. The method of claim 1, wherein the sheet is annealed prior to its formation. 14. A perforated sheet comprising a metallic body formed at any time according to the method of any one of claims 1 to 13. 15. An orifice plate which is formed whenever by the method according to any one of claims 1 to 13. 16. An apparatus for forming an aerosol, comprising an orifice plate according to claim 15, and a driver that engages the plate to vibrate at a desired frequency to form an aerosol. 17. An apparatus for forming an aerosol, comprising an orifice plate according to claim 15, a support for the orifice plate for use as a passive plate, and a horn arranged to force liquid waves through the orifice plate to form droplets. 18. An orifice plate (40) comprising a bottom layer of photolithographically plated metal having holes (33) for forming aerosols and a top layer of photolithographically plated metal having spaces (32), wherein the spaces cover a plurality of holes (33) for forming aerosols and have apertures between 20 μm and 400 μm, and wherein the top layer closes some of the holes (33) for forming aerosols in the bottom layer, the plated metal comprising Ni and/or Pd, the depth of the holes being in the range of 5 μm to 40 μm, the width of the holes being in the range of 1 μm to 10 μm, and the thickness of the orifice plate (40) being in the range of 45 μm to 90 μm, wherein the plate is formed having a portion having an operating convex shape and a flange shape for engaging a actuator. 19. The orifice plate (40) according to claim 18, wherein the width dimension of the orifice forming the aerosol is in the range of 2 μm to 6 μm. 20. The perforated plate (40) according to claim 18 or 19, wherein the metal in all layers is the same. 21. The perforated plate (40) according to claim 18 or 19, wherein the Ni and/or Pd are present at the surface in a concentration selected according to the corrosion resistance properties. 22. The perforated plate (40) according to claim 21, wherein the proportion of Pd is in the range of 85% to 93% by weight, and the remainder is substantially Ni. 23. The perforated plate (40) according to claim 18 or 19, wherein the electroplated metal at the surface comprises Ag and/or Cu at a concentration selected according to its antibacterial properties. 24. An apparatus for forming an aerosol, comprising an orifice plate (40) according to any one of claims 18 to 23, and a driver that engages the orifice plate (40) to cause it to vibrate at a desired frequency in order to form an aerosol. 25. An apparatus for forming an aerosol, comprising an orifice plate (40) according to any one of claims 18 to 23, a support for the orifice plate (40) for use as a passive orifice plate, and a horn arranged to force a liquid wave through the orifice plate.