Fluid handling – Processes – Cleaning – repairing – or assembling
Reexamination Certificate
1999-04-01
2001-05-29
Kaufman, Joseph A. (Department: 3754)
Fluid handling
Processes
Cleaning, repairing, or assembling
C251S129010, C251S368000, C137S859000, C216S002000
Reexamination Certificate
active
06237619
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a micro-machined fluid-flow device and to a method of manufacturing it, said device comprising a substrate possessing a flow duct and a thin layer forming a deformable membrane.
By way of example, such a device constitutes a member for controlling liquid inlet/outlet which can be used as a check valve or in a micropump.
BACKGROUND OF THE INVENTION
Valves of this type are encountered, for example but not exclusively, in micropumps for medical use which deliver a regular and controlled quantity of medication. The manufacture of micropumps is based on the technologies of micro-machining silicon and of using a piezo-electric actuator. International patent application PCT IB 95/00028 describes a self-priming micropump. In that application, as in others, it is necessary to make an inlet valve and sometimes an outlet valve so that the leakage rate is minimized or even zero. The leakage rate from a valve corresponds to the rate at which liquid flows through the valve when the membrane is in its rest position, i.e. when the valve is closed. Furthermore, since the valve operates because of the elasticity of the membrane, with this elasticity allowing the membrane to deform when fluid is injected to the inlet of the valve at sufficient pressure, it is important not to degrade the mass and surface state of the membrane when manufacturing the valve in order to obtain a membrane that presents a minimum amount of internal stress.
The object of the present invention is to provide a machined liquid inlet/outlet device having a minimum leakage rate in the closed position of the valve and in which the method of manufacture leads to a membrane having good physical and mechanical properties with little internal stress.
When the problem arises of covering a substrate with a thin metal layer, various methods can be used. The thin metal layer can be deposited on the substrate by evaporation, or by the cathode sputtering technique. Nevertheless, those methods have certain limitations.
Usually, metal layers that have been deposited have physical properties that are less good than those of the same materials in solid form. Thus, the layer is usually obtained with considerable amounts of internal stress, particularly because of the crystal structure of the deposited layer which is very sensitive to deposition conditions. Furthermore, a deposited thin layer is of a thickness that is limited to about 1 micrometer, since greater thicknesses cause the method to become too expensive because the time required to make the deposit is too long.
Another possibility consists in depositing the metal layer electrolytically, which technique does not suffer from all of the above-mentioned drawbacks. Nevertheless, it is not possible to deposit all materials, and in particular metals, by that method, and the physical and mechanical properties of the deposited layer are often insufficient.
SUMMARY OF THE INVENTION
According to the invention, these objects are achieved by the fact that the thin layer, e.g. forming a deformable membrane, is a rolled metal sheet, preferably connected to the substrate in the overlap zone by the anodic bonding technique. According to the invention, the method of manufacturing a micro-machined fluid-flow device is characterized in that it comprises the following steps:
a substrate is provided that possesses a flow duct;
a sacrificial layer is deposited on the substrate by physico-chemical means;
zones of the sacrificial layer that are to give rise to a membrane which is not attached to the substrate are conserved by photolithography and chemical etching;
a deformable thin layer constituted by a metal sheet is made by rolling;
the thin layer is placed on the substrate;
said thin layer is connected to the zones of the substrate that are not covered by the sacrificial layer by means of a physico-chemical method;
said thin layer is machined by photolithography and chemical etching after it has been fixed on the substrate; and
the sacrificial layer is again etched, thereby releasing the membrane from the substrate.
Thus, according to the invention, a rolled metal sheet is used that can be connected to a substrate and can then be machined again to make microstructures. The advantages that stem from this invention are, in particular, physical and mechanical properties of the metal after rolling that are excellent and well-controlled. Thus, the stresses present in the metal are low, with the final stress state of the membrane resulting mainly from the method of bonding the membrane to the substrate.
Another advantage of the present invention is the possibility of fixing the sheet on a cavity of the substrate, thus making it possible to make a membrane or a bridge directly without any etching step.
Another important aspect of the present invention is the use of anodic bonding for fixing the sheet on the substrate. The prior art has never disclosed the use of that technique for metal sheets.
The anodic bonding technique is known per se and consists in raising the temperature of the parts that are to be assembled together, i.e. the substrate and the membrane, to about 300° C., and in placing the stack between two electrodes that are in contact with the substrate and with the membrane while applying a negative potential of about—1000 V to the electrode which is pressed against the substrate. A leakproof weld is thus obtained at relatively low temperature between the membrane and the substrate.
By using a rolled metal sheet, it is possible for the metal sheet that is subsequently to serve as a membrane in the valve or the micropump to be of a thickness that is fixed in very accurate manner and over a range of values that is quite large.
In the present text, the term “rolled sheet” is used to mean a sheet obtained by a metal-working method in which the sheet is obtained by successive passes between rolls.
REFERENCES:
patent: 5050838 (1991-09-01), Beatty et al.
patent: 5078581 (1992-01-01), Blum et al.
patent: 5224843 (1993-07-01), Van Lintel
patent: 5259737 (1993-11-01), Kamisuki et al.
patent: 5362213 (1994-11-01), Komatsu et al.
patent: 5417235 (1995-05-01), Wise et al.
patent: 5488255 (1996-01-01), Sato et al.
patent: 5529465 (1996-06-01), Zengerle et al.
patent: 5725117 (1998-03-01), Elsberry et al.
patent: 2 354 249 (1974-11-01), None
patent: 0 412 270 A1 (1991-06-01), None
patent: 0 546 427 A1 (1993-06-01), None
patent: 0 601 516 A1 (1994-06-01), None
patent: 1418274 (1975-12-01), None
patent: WO 95/19502 (1995-07-01), None
Kohl: “Development of Microactuators Based On the Shape Memory Effect”, Supplement of Journal de Physique III, pp. 1187-1192, vol. 5, No. 12, Dec. 1995.
Rapp et al.: “Liga Micropump for Gases and Liquids”, Sensors and Actuators, pp. 57-61, vol. A40, No. 1, Jan. 1, 1994.
Maillefer Didier
Renaud Philippe
Kaufman Joseph A.
Keasel Eric
Westonbridge International Limited
Wolf Greenfield & Sacks P.C.
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