A method for designing a sealed enclosure and a welded joint for such an enclosure

Abstract

The base substrate (10) has a functional region (20), and a cover substrate (14) in contact with the base substrate (10) covers the functional region (20). The base substrate (10) and the cover substrate (14) are directly and hermetically sealed and joined to each other via at least one laser bonding wire (2). Thereby, a method for designing a laser weld between the base substrate (10) and the cover substrate (14) of the enclosure (1) in which the functional region (20) is hermetically enclosed inside the formed enclosure (1) is proposed. In this case, with respect to the joint between the cover substrate (14) and the base substrate (10), a minimum shear force F min to be withstood by laser welding is set, and based on the force P per unit length of the laser bonding wire determined based on experience, the shortest length L min with respect to the total length of all the bonding wires (2) is determined, and the contact surface width B is the contact surface A i where the base substrate (10) and the cover substrate (14) can come into contact, and the laser bonding surface A w defined by the laser bonding wire (2) having a width w. The ratio = A i / A w is selected to be in the range of 1 to 10. Another aspect of the present invention relates to such an enclosure (1), and a sensor unit and / or a medical implant including such an enclosure (1).

Description

Technical Field

[0001] The present invention relates to an enclosure which is sealed and includes a base substrate having a functional area and a cover substrate contacting the base substrate to cover the functional area. The base substrate and the cover substrate are directly and hermetically sealed and joined to each other via at least one laser bonding wire, and the functional area is hermetically enclosed inside the formed enclosure. Further, the present invention relates to a method for designing a laser welding joint between substrates and the use of such an enclosure.

[0002] A sealed enclosure is provided, for example, to protect one or more components inside the enclosure from adverse environmental conditions. Fields of use for such sealed enclosures can be found, for example, in electronic device applications for protecting delicate electronic components, and can also be found in optical applications for encapsulating optical components. Another use exists particularly in the fields of medical implants, microfluidic chips, augmented reality, and mobile sensor devices (such as pressure sensors).

[0003] In this case, particularly in optical applications, a transparent material such as glass is desirable for the enclosure. However, even in electronic applications where wireless communication or wireless charging is desired, a glass material is advantageous compared to a common metal enclosure made of, for example, titanium. This is because the glass material does not shield the radiation used each time.

[0004] An example of such a sealed enclosure is known from European Patent Application Publication No. 3812352. The enclosure forms a housing and includes at least one base substrate and a cover substrate that encloses a functional area inside. The cover substrate and the base substrate selected, for example, from a glass material are joined to each other by forming a laser bonding wire.

[0005] A method of forming a transparent portion for protecting an optical component while using a laser method to form a laser bonding line is also known from European Patent No. 3012059.

[0006] In these known laser methods, two substrates are overlapped, and an interval or gap that may exist between the substrates is sealed by performing laser welding, whereby the joint between the two substrates is hermetically sealed.

[0007] The formed enclosure needs to meet high mechanical requirements, especially when used as an implant. The criterion for the mechanical strength of the joint between the two housing parts is the durability against shear force. The higher the stability of the joint, the more resistant the joint can be to stronger shear forces without dissociation. When joining two substrates, the shear force durability depends on the size of the contact surface where the two substrates contact each other.

[0008] Therefore, in order to ensure sufficient shear force durability, known hermetic enclosures have a relatively large wall thickness that can be several millimeters. In addition to the increase in wall thickness, it is also possible to form the parts to be joined so that they have a form fit. However, this also requires a lot of construction space and is particularly time-consuming in the case of components made of glass or the like. This makes it difficult to achieve a particularly compact configuration of the hermetic enclosure.

[0009] Therefore, it can be recognized that an object of the present invention is to provide a hermetic enclosure that has a particularly thin wall and at the same time meets mechanical requirements. Another object of the present invention is to provide a method of designing a laser weld between components of an enclosure that, starting from the set mechanical requirements, can obtain an enclosure that is particularly compact and at the same time sufficiently durable.

[0010] Disclosure of the Invention A method is proposed for designing a laser weld between a base substrate and a cover substrate of an enclosure. The enclosure to be formed has at least a base substrate with a functional area and a cover substrate. The cover substrate is in contact with the base substrate and covers the functional area. The base substrate and the cover substrate are directly connected to each other in a gas-tight seal via at least one laser joining line, so that the functional area is hermetically enclosed inside the formed enclosure. In this case, a minimum shear strength F 0 that must be withstood for the laser welding is determined for the joint between the cover substrate and the base substrate. min is preset, and the sum of the lengths of all the laser welding lines L ges However, the required minimum length L of all the laser joining lines is min In this case, the minimum shear force F min By dividing by the empirically determined force P per length of the laser weld line, L min =F min / P is defined, and in this case the contact area width B, measured in the plane of the end face of the base substrate facing the cover substrate as the shortest distance between the functional area and the outside of the enclosure, is the contact area A where the base substrate and the cover substrate can come into contact. i and a laser bonding surface A defined by a laser bonding line having a width w at the end surface of the base substrate facing the cover substrate. w The ratio formed by J=A i / A w is selected to lie in the range 1 to 10.

[0011] Preferably, a number N of closed paths of laser bond lines having a width w and a distance H between the center points of two adjacent laser bond lines of at least width w are arranged to surround the functional area, where the number N is equal to or less than the total length L of all the laser bond lines formed by multiplying the number N by the length of the contour line defining the functional area. ges is the shortest length L min It is defined as the smallest number N greater than

[0012] In the context of this application, the contact surface is the common part consisting of the facing surfaces of two substrates to be brought into contact. The matching contact surface means a partial surface of the contact surface where the mutual distance between the two substrates has become so small that it is optically no longer measurable. In particular, in the region of the matching contact surface, the distance between the surfaces of adjacent substrates is less than 250 nm. In this case, generally, the contact surface is larger than or equal to the matching contact surface.

[0013] In other words, first, two substrates are arranged in contact with each other, that is, for example, stacked one on top of the other, and at this time, gravity presses the typically first substrate located above against the second substrate. In this case, the directions of up or down are merely for illustrative purposes only. This is because, of course, the substrates can take any direction in space, and parallel arrangements do not deviate from the scope of protection. The two substrates are typically arranged to contact each other with their larger surfaces.

[0014] When both substrates are formed absolutely flat, that is, when they have no recesses, protrusions, or curvatures at all (this can only be achieved theoretically in this absolute state), it is considered that the first substrate and the second substrate are in full contact and match with each other. That is, it is considered that the two substrates contact each other at all points of the aligned surfaces. Therefore, this is generally impossible to achieve in terms of structural realizability. Rather, even if the substrates are only slightly curved, tilted, bent, or have recesses or protrusions, complete matching contact is achieved only in absolutely exceptional cases.

[0015] The functional area surrounded by the enclosure may be a cavity, particularly configured to accommodate functional elements. The cavity has a bottom surface and side walls provided by the base substrate, and a cover surface provided by the cover substrate. The thickness of the side wall corresponds to the contact surface width in this embodiment.

[0016] In another example of the enclosure, the functional region may be the functionalized region of the base substrate. Such functionalization can be performed, for example, by coating deposition and / or surface structuring.

[0017] The functional region is hermetically sealed and closed by a welding joint. In this case, hermetically sealing particularly means having a helium leak rate of less than 1·10 -8 mbar·l / s, preferably having a helium leak rate in the range of 1·10 -10 mbar·l / s to 1·10 -9 mbar·l / s, which means an enclosure located within this range.

[0018] The welding joint is implemented by introducing at least one laser bonding line or laser welding line. In this case, the welding joint is preferably implemented using an ultra-short pulse laser. The typical pulse width is located within the range of 100 fs to 100 ps. A method of implementing such a welding joint by one or more laser welding lines is known, for example, from European Patent No. 3012059.

[0019] The laser welding line has a height HL in a direction perpendicular to its bonding surface. The bonding surface is the direction in which adjacent or continuous beam points are placed. Typically, laser welding is performed from a top view, that is, the substrate stack is located on a surface such as a - table, etc., and the laser is emitted from above, passing through at least the uppermost substrate layer or multiple substrate layers to the location of the beam focus. That is, the height HL is measured in the direction of the laser beam, while the width w of the laser welding line is measured perpendicular to the direction of the laser beam.

[0020] The width w of the region changed by the laser beam varies along the depth T of the processed region, i.e., along the laser beam direction. The description regarding the width w of the laser welding line made within the framework of this application is related to the plane of the contact surface between the substrates joined by the laser welding line. In this case, in the plane having the width w defined in this way, it means the region where a material change has been caused by laser processing. Such a material change caused by laser processing results from heating exceeding the glass transition temperature T G and / or the melting temperature of the material involved, followed by subsequent re-cooling. By this laser processing, without additional bonding material being involved, both substrates are joined to each other in a material bonding manner in this processed region. In the case of an optically transparent material, the material change caused by laser processing can be detected, for example, by measuring the difference in refractive index with respect to the unprocessed material. For this purpose, a cross-section can be inspected, for example, by an optical microscope. In this case, in particular, a change in refractive index greater than 1×10 -5 can be used as a marker for the material change and, correspondingly, as a marker for specifying the width w. Micrographs of such cross-sections can be seen in FIG. 10 and will be described in more detail below.

[0021] Multiple materials can be joined to each other by the laser welding method. In this case, it is desirable that at least the substrate facing the direction of the laser source is at least partially transparent to the laser used.

[0022] The generated laser weld line or laser bond line is arranged around the functional area, whereby a closed area surrounding the functional area is formed by the laser bond surface at the contact surface corresponding to the end face of the base substrate facing the cover substrate. In this case, in a cuboid enclosure, one or more linearly extending laser bond lines can be arranged on each of the four sides defining the functional area, and in this case, the laser bond lines may overlap each other at the four corners. In this case, one or more laser bond lines may extend particularly parallel to the side walls. It is also possible to arrange one or more closed laser bond lines, for example, parallel to the contour line of the functional area.

[0023] In order to hermetically enclose the functional area, it is necessary to guide at least one laser bond line around the functional area without gaps. However, this criterion can also be met by a plurality of individually written laser bond lines, which overlap at the intersections and in this case form a single closed path surrounding the functional area. In this case, in the sense of this method, each of these closed paths corresponds to a laser bond line arranged to surround the functional area, and in this case, if such a path is exactly one, the number N = 1, and for example, if the closed path is exactly two, the number N = 2. The preset minimum shear force F min to be satisfied, in order to exceed a specific minimum length L min if a single such closed laser bond line is sufficient, the number N of laser bond lines guided to surround the functional area can be selected as N = 1. In this case, there are no laser bond lines arranged adjacent to each other in the sense of this method.

[0024] Preferably, a plurality of laser bond lines are introduced in the form of a plurality of such closed paths, and in this case, the adjacent laser bond lines extending within the area defined by each contact surface width are preferably arranged parallel to each other. In this case, laser bond lines separated from each other by the functional area are not considered adjacent.

[0025] Preferably, the distance H between the center points of two adjacent laser bonding lines having a width w is selected within the range of 1w to 5w, preferably within the range of 1.01w to 2.5w, and particularly preferably within the range of 1.05w to 2w. Thereby, except for the intersections of different laser bonding lines that may exist in some cases, the overlapping of the laser bonding lines is avoided.

[0026] Particularly, by providing at least a gap equal to the width of the laser bonding line between two adjacent laser bonding lines extending parallel to each other, it is achieved that the material of the substrate is processed only once, except for the intersections of the laser bonding lines at the four corner portions around, for example, a rectangular functional region.

[0027] On the other hand, by providing an upper limit for the gap, a particularly compact configuration of the laser bonding surface is achieved. Thereby, the contact surface width B can be selected to be particularly small, and nevertheless, sufficient space can be provided for forming the laser bonding lines.

[0028] Preferably, the contact surface width B is selected within the range of 100 μm to 1000 μm. The exact selection of the contact surface width B depends on various criteria such as the material of the base substrate, the material of the cover substrate, the dimensions of the enclosure, and / or the form of the functional region. When a cavity is provided as the functional region, the contact surface width B sets the thickness of the sidewalls of the functional region. In this case, the contact surface width is preferably selected to be at least large enough so that the mechanical stability of the sidewalls is sufficiently large.

[0029] Preferably, the contact surface width B is selected to be larger than 200 μm, particularly preferably larger than 300 μm, more preferably larger than 400 μm, and most preferably larger than 500 μm.

[0030] However, the larger the contact surface width B is selected, the larger the enclosure becomes with respect to the enclosed functional area. Correspondingly, it is preferable to select the contact surface width B to be less than 750 μm, particularly preferably less than 500 μm, and extremely particularly preferably less than 400 μm. The minimum contact surface width is limited by the width w of the laser bonding line, and thus is preferably selected to be greater than 30 μm, particularly preferably greater than 50 μm, and extremely particularly preferably greater than 100 μm.

[0031] The width w of the laser bonding line is preferably selected within the range of 20 μm to 75 μm, particularly preferably within the range of 30 μm to 60 μm. For example, a width w of 50 μm is selected. This range is optimally selected so that sufficient energy can be introduced for welding both substrates via the laser. In this case, it is particularly advantageous if the width w is substantially constant over the entire laser bonding line. Correspondingly, the width w of all laser bonding lines varies by at most 30%, particularly preferably by at most 20%, and most preferably by at most 10% over the entire length L ges of these laser bonding lines. Since the width w depends on the location of the laser focus with respect to the contact surface, it is preferable to use a laser processing method that accurately controls the distance of the laser focus from the contact surface. Suitable methods are known, for example, from European Patent No. 3012059.

[0032] To obtain an enclosure that is as compact as possible, the contact surface A i wherein the base substrate and the cover substrate can come into contact, and the laser bonding surface A w defined by at least one laser bonding line having a width w, the filling factor J = A i / A w is desirably selected to be minimized. Correspondingly, it is particularly preferable to select the filling factor J within the range of 1 to 5, and most preferably within the range of 1 to 2.

[0033] In the proposed method, the total length of the laser bonding lines to be introduced, and thus the laser bonding surface A wIt is assumed that the size of is selected such that there is a preset durability against the shear force acting on the welded joint. In this case, the concept of shear force specifically means a force that acts on both substrates perpendicular to the joint surface of the two substrates and causes displacement between the substrates without bonding between these substrates.

[0034] The inventors confirmed that the shear force durability of the welded joint increases linearly with the total length of the non-overlapping laser bonding lines. In this case, regarding the criterion of non-overlapping, for example, a small overlap at the intersection of laser bonding lines extending perpendicular to each other and arranged to surround a rectangular functional area can be ignored based on the small area of these intersections. Correspondingly, when the minimum shear force F min that the welded joint should withstand and a constant P determined based on experience with respect to the increase in force per unit length are preset, the required shortest total length of the laser bonding lines is given by the relational expression L min = F min / P and can be obtained. The total length L ges of the introduced laser bonding lines can be determined as an integer multiple of the length of the contour line around the functional area, especially in the case of laser bonding lines extending parallel around the functional area. In this case, a small increase in the actual length of the circumferentially extending laser bonding lines based on the fact that the laser bonding lines are not formed overlapping can also be ignored based on the small width of the laser bonding lines. Another short bonding line portion that may occur during the manufacture of a plurality of enclosures by wafer processing and subsequent individualization of the enclosures can also be ignored based on their short length.

[0035] The constant P is specific to the materials of the substrates to be joined and the selected width of the laser bonding lines, and can be easily determined based on experience by manufacturing a plurality of, for example, 30 samples in which a first substrate made of a cover substrate material is joined to a second substrate made of a base substrate material by laser bonding lines. In this case, in these samples, the total length L gesThey are selected identically. Next, by applying an increasing shear force to the joint between the first substrate and the second substrate, identifying the force that breaks the joint and evaluates the fracture probability distribution, the shear force durability of the sample is determined.

[0036] The minimum shear force F that the welded joint should withstand min is preferably not set higher than necessary, whereby the welded joint itself and thus the entire enclosure can be made as compact as possible. Preferably, the setting is determined based on the mechanical requirements for the enclosure. One criterion can in particular be the fact that the minimum shear force is associated with the different force durabilities of the substrates. For this purpose, preferably, a first substrate made of a cover substrate material is joined to a second substrate made of a base substrate material by means of a laser bonding line, whereby these substrates are designed with respect to the minimum shear force F min to produce a plurality of samples, and when this minimum shear force F min is applied, more than 50%, preferably more than 75%, particularly preferably more than 90%, most preferably more than 95% of the samples are not broken along the contact surface due to the fracture of the welded joint, but are broken at another location on one or more of the substrates, in particular at one edge, so that the minimum shear force F min is set.

[0037] To identify the failure rate, in the same way as for determining the empirical constant P, a plurality of, for example 30, identical samples in which two substrates are welded to each other by the introduction of a laser bonding line can be produced. In this case, the total length of the laser bonding line is selected corresponding to the test shear force F min Next, a shear force is gradually applied to the sample. The location where the sample is mechanically broken can be easily detected by optically inspecting the sample. When the welded joint is broken, the individual substrates are separated again, but there is substantially no further damage. If the number of samples that do not break along the contact surface due to the fracture of the welded joint is within the expected range, for example more than 75%, it means that the test shear force F min has been correctly selected. Otherwise, depending on the results, the test is repeated for a higher or lower test shear force.

[0038] After the design of the welded joint, the step of manufacturing the enclosure may follow. These steps may particularly include the preparation of the substrate, and optionally the cleaning of the surface of the substrate, the superposition of the substrates (at this time, optionally, the functional elements are introduced into the functional area), and the introduction of the laser bonding wires.

[0039] In manufacturing, it may be assumed that a plurality of enclosures are formed at once. For this purpose, first, a large wafer is prepared instead of the substrate that has already been cut to the final size of the enclosure, superposed in layers, and bonded to each other by laser welding. Then, the individual enclosures are individualized by cutting the formed wafer stack. In such a procedure, the introduced laser bonding wires are written along a predetermined grid pattern. In this case, it may be assumed that each functional area is surrounded by four laser bonding wires forming a rectangle.

[0040] Another aspect of the present invention is to provide a sealed enclosure. The proposed sealed enclosure includes a base substrate having a functional area and a cover substrate that contacts the base substrate and covers the functional area. The base substrate and the cover substrate are directly and hermetically sealed and bonded to each other via at least one laser bonding wire, and the functional area is hermetically enclosed inside the formed enclosure. Further, a contact surface A where the base substrate and the cover substrate can contact i and a laser bonding surface A defined by at least one laser bonding wire having a width w on the end face of the base substrate facing the cover substrate w form a ratio J = A i / A w which is located in the range of 1 to 10. In this case, on the plane of the end face of the base substrate facing the cover substrate, the contact surface width B measured as the shortest distance between the functional area and the outside of the enclosure is assumed to be located in the range of 100 μm to 1000 μm.

[0041] The proposed enclosure is particularly compact. This is because the laser bonding surface A w occupies the maximum portion of the entire contact surface A i . In the case of a hermetic enclosure obtained by laser welding of substrates, which is known from the prior art, it was assumed that most of the mechanical stability was provided by the maximum contact surface, and the laser bonding surface was substantially required to ensure the hermetic enclosure of the functional area. The contact surface A i is usually small compared to the whole, and the laser bonding surface A w was hitherto assumed to make only a small contribution to the mechanical stability, particularly the durability against shear forces, with respect to the laser bonding surface A w itself.

[0042] Furthermore, it was surprisingly confirmed that maximizing the shear force durability of the welded joint of both substrates is not advantageous. This is because, in this case, when a large mechanical force acts, the enclosure breaks without being controlled at a plurality of different locations. That is, further welding seam extension does not contribute to the improvement of the total strength of the enclosure. Furthermore, such a "redundant" welding seam requires a larger contact surface and thus increases the "installation area" of the enclosure. Correspondingly, it is preferable to preset not only the lower limit but also the upper limit with respect to the shear force durability.

[0043] For this purpose, preferably, the laser bonding surface A w defined by at least one laser bonding line is selected such that the joint between the cover substrate and the base substrate has a breaking shear force in the range of 10 N to 1000 N, preferably in the range of 50 N to 500 N, particularly preferably in the range of 100 N to 400 N.

[0044] Preferably, the total length L ges of the laser bonding lines of the enclosure is determined according to one of the plurality of design methods described herein. In this case, particularly preferably, the minimum shear force F minThis is the case where it corresponds to the breaking shear force within the range of 10 N to 1000 N.

[0045] The enclosure can be obtained using one of the described methods. Therefore, the features described within the framework of one of the plurality of methods also apply to the enclosure, and conversely, the features disclosed within the framework of the enclosure also apply to the method.

[0046] Preferably, the welded part is formed by a plurality of laser bonding lines. In this case, the laser bonding lines have a width w, and the distance H between the center points of two adjacent laser bonding lines is within the range of 1w to 5w, preferably within the range of 1.01w to 2.5w, and particularly preferably within the range of 1.05w to 1.5w.

[0047] The width w of the laser bonding line is preferably located within the range of 20 μm to 75 μm, and particularly preferably within the range of 30 μm to 60 μm. For example, the width of the laser bonding line is 50 μm. In this case, it is particularly advantageous if the width w is substantially constant over the entire length of the laser bonding line. Correspondingly, the width w of all laser bonding lines varies by at most 30%, particularly preferably by at most 20%, and most preferably by at most 10% over the entire length L ges of these laser bonding lines.

[0048] The enclosure is preferably configured to be as compact as possible. This is achieved by minimizing the portion of the contact surface that is not occupied by the laser bonding surface, and as a result, by configuring the contact surface width B to be minimized. For this purpose, preferably, at least 20% of the end face of the base substrate corresponding to the contact surface A i facing the cover substrate is covered by the laser bonding lines, and thus it is assumed that J is located within the range of 1 to 5. Particularly preferably, at least 1 / 2 of the contact surface A i is covered by the laser bonding lines, and in this case, J is located within the range of 1 to 2.

[0049] The cover substrate is preferably formed as a transparent thin-film substrate. In this case, the cover substrate has a thickness of less than 200 μm, preferably less than 170 μm, particularly preferably less than 125 μm, and preferably has a thickness of more than 10 μm, particularly preferably more than 20 μm. Thereby, also in the stacking direction of the substrates, the dimensions of the enclosure can be configured to be particularly compact.

[0050] In this case, the cover substrate may already be prepared in the form of a thin-film substrate and welded to the base substrate. Alternatively, a substrate with a larger thickness can also be thinned by material removal after bonding to the base substrate.

[0051] The cover substrate and the base substrate are in direct contact with each other at the contact surface A i such that the joint portion within the laser joint surface A w defined by at least one laser bonding wire does not contain foreign matter, and in particular does not contain a bonding material such as an adhesive, glass frit, or absorption layer. Since no foreign matter is used when closing the enclosure, for example, contamination of the functional area by the components of the adhesive is avoided.

[0052] The functional area may be formed as a cavity. Such a cavity is preferably configured to accommodate functional elements, so one or more functional elements may be accommodated within the cavity of such an enclosure. The cavity has a bottom surface and side walls provided by the base substrate, and a cover surface provided by the cover substrate. The width or thickness of the side walls corresponds to the contact surface width in this embodiment.

[0053] The base substrate may have a planar bottom substrate that forms the bottom surface of the functional region configured as a cavity, and an intermediate substrate that forms the side wall of the cavity having an end face facing the cover substrate. In this case, the bottom substrate and the intermediate substrate are preferably hermetically sealed and joined to each other via at least one laser bonding wire. In order to design this welded joint, the method described in particular in this specification can be similarly applied, and the welded joint may be configured in the same manner as the joint between the cover substrate and the base substrate described in this specification.

[0054] Alternatively or additionally thereto, the base substrate may be formed as a functional region in the form of a recess having a bottom surface and a side wall, and the recess forms a cavity together with the cover substrate as a cover surface. Such a recess can be formed, for example, by grinding or etching.

[0055] In another example of the enclosure, the functional region may be a functionalized region of the base substrate. Such functionalization can be performed, for example, by applying a coating and / or surface structuring.

[0056] The cover substrate and / or the base substrate preferably consist of glass, glass ceramic, silicon, sapphire or a combination of the above materials. As the glass material, borosilicate glass is particularly suitable.

[0057] The present invention also relates to the use of the proposed enclosure as an enclosure for a sensor unit and / or a medical implant. In these applications, the hermetic sealing of the enclosure and the achievable compact dimensions are particularly advantageous. For example, with a contact surface width of 500 μm selected, at a small wall thickness, the enclosure is only slightly larger than the functional elements housed therein.

[0058] Furthermore, correspondingly, one of the enclosures described herein includes a sensor unit and / or a medical implant. In this case, preferably, the enclosure has a cavity surrounding the functional elements of the sensor unit and / or the medical implant.

[0059] An example of the enclosure includes a bottom substrate and an intermediate substrate that together form a base substrate, as well as a cover substrate. All the substrates are made of borosilicate glass available, for example, under the name BOROFLOAT33. The bottom substrate and the intermediate substrate have a thickness of 1.1 mm, and the cover substrate has a thickness of 500 μm. The length and width of the substrates are each 5 mm. By selecting a contact surface width B of 500 μm, a cavity is provided with side walls and a cover wall having a thickness of 500 μm.

[0060] Example regarding the determination of the empirical parameter P: Samples were manufactured in which two substrates each made of float borosilicate plate glass with a length and width of 5 mm and a thickness of 1.1 mm, available under the name BOROFLOAT® 33, were stacked. To verify the assumption that the shear force is linear with respect to the total length of the laser bonding line, for the first type 1, a bonding line with a total length L of 20 mm ges was written. For the second type 2, a laser bonding line with a total length L of 40 mm ges was written, and for the third type 3, a laser bonding line with a total length L of 60 mm ges was written. In this case, the laser bonding line may in principle be introduced in any arbitrary geometry. In this example, in each case, half of the bonding line length was written along a first direction, and the other half of the bonding line length was written along a second direction perpendicular to the first direction, thereby forming a "+" shape. The overlap of the laser bonding lines at the center of this cross can be ignored based on its small area.

[0061] Thirty samples were produced from each of the three types, and the shear force that broke the joint between the two substrates was measured respectively. For this purpose, a device that can shift, that is, shear, two overlapping plates relative to each other with a predetermined force was used. Each plate has a recess, and its shape and depth correspond to the dimensions of the substrate except for small manufacturing errors. Correspondingly, the side walls of the recesses are in close contact with the side surfaces of each substrate. To determine the shear force that breaks the joint between the two substrates of one of the samples, one sample was inserted between the two plates, and the two plates were shifted relative to each other at a speed of 1.5 mm / min, and the force was measured at that time. When the joint is broken, this sample no longer resists the shift, and this is recognized through the sharp drop in the measured force. In this case, the shear force that broke the joint is the maximum force obtained during the shift or shear of the two plates.

[0062] This measurement was repeated for all the samples, and the shear force that breaks the joint between the two substrates of one sample was recorded respectively. The measurement results regarding the cumulative probability KP are shown in the double-logarithmic graph in FIG. 6.

[0063] In this case, by fitting the parameters of the distribution function p(F) regarding the cumulative failure probability at the shear force of F, the failure shear force F that breaks the corresponding sample type v can be identified. The distribution function p(F) is [Equation] given by, in which case the parameter z indicates the width of the distribution function and can also be obtained by fitting the parameters.

[0064] Regarding the 95% confidence interval, for the three sample types, the following results regarding the failure shear force F shown as a function of the total length L ges of the laser bonding line in FIG. 7 are obtained: namely v Type 1: F = 107.9(101.8...114.3) N v ​Type 2: F v = 144.1 (139.6...148.8) N Type 3: F v = 219.6 (206.6...233.6) N By fitting the affine function, it can be easily read that the sample without laser welding, that is, with a laser bond line length of 0, already has a fracture shear force of approximately 45 N, which is different from 0. This basic contribution to the shear force durability is due to the adhesion force across the optical interface surface A c and further, it can be read that the shear force durability increases by approximately 2.8 N for every 1 mm of the laser bond line.

[0065] Accordingly, for both material pairs used in sample types 1 to 3, an empirical constant P of 2.8 N / mm is obtained.

[0066] Since this is a linear relationship in this case, in order to specify the constant P based on experience, it is sufficient to perform this measurement in only one sample type for the material pair to be inspected.

[0067] It is obvious that the above-described features and further features to be described later can be used not only in the described combinations but also in other combinations or alone without departing from the scope of the present invention.

[0068] Preferred configurations and embodiments of the present invention are illustrated and will be described in more detail in the following description. In this case, the same reference numerals relate to the same, or similar, or functionally identical components or elements.

Brief Description of the Drawings

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Figure 11

[0070] FIG. 1 shows a perspective view of two substrates 3 and 4 joined by one laser bonding line 2. In this case, the first substrate 3 is placed on the second substrate 4, whereby the two substrates 3 and 4 are in direct contact with each other. The surface where the two substrates 3 and 4 contact each other is the contact surface A i which is called.

[0071] When the surfaces of both substrates 3 and 4 are smooth, the overlapping surfaces have an interspacing that can no longer be optically measured. This usually applies when the spacing is less than about 250 nm. In the case of such a small spacing, an adhesive force already occurs between the two substrates 3 and 4 during placement. This adhesive force occurs in a region called the matching contact surface A c The matching contact surface A c is smaller than the entire contact surface A i

[0072] ​ Matched contact surface A c In order to hermetically seal and join the two substrates 3 and 4 in the region of, laser welding is performed by introducing a laser bonding line 2. Along the laser bonding line 2, the material is melted by an ultrashort pulse laser and then cooled again, whereby the two substrates 3 and 4 c are extremely closely in contact with each other in the region of, the two substrates 3 and 4 will be joined to each other. The laser bonding surface A formed by laser welding w In, since the two substrates 3 and 4 are joined to each other by material bonding, the gap between the substrates 3 and 4 no longer exists. Since the width of the laser bonding line 2 is about 20 μm to 75 μm in thickness, in the case of the full-surface bonding of the substrates 3 and 4 shown as an example in FIG. 1, the matched contact surface A c or the contact surface A i Only a very small part of is additionally welded by laser processing.

[0073] Surprisingly, in the example shown in FIG. 1, compared with the entire contact surface A i and the matched contact surface A c Despite the very small area, the contribution of the joint of the two substrates 3 and 4 by the laser bonding surface A w to the shear force durability is found to be much greater than the contribution of the adhesion force in the region of the matched contact surface A c . Correspondingly, the laser bonding surface A w Can be used not only to seal the gap existing between the two substrates hermetically, but also to enhance the durability of the joint against the acting shear force.

[0074] FIG. 2 shows a plan view of one embodiment of the hermetic enclosure 1. This enclosure has a length a, a width b, and a height c (see FIG. 3). Inside the enclosure 1, a functional region 20 in the form of a hollow chamber or cavity 21 is formed, and inside the functional region 20, functional elements 22 such as sensors or transponders are hermetically sealed and enclosed.

[0075] Typical dimensions of the enclosure are a = 5 mm, b = 5 mm, c = 2.5 mm, but larger area and flatter dimensions (e.g., a = 10 mm, b = 5 mm, c = 0.9 mm), or more compact dimensions (a = 3 mm, b = 4 mm, c = 2 mm) are also possible.

[0076] To form the enclosure 1, the cover substrate 14 is placed on the base substrate 10 (see FIG. 3), and contacts the base substrate 10 at the contact surface A i and is in contact with the base substrate 10 at the contact surface A. The contact surface A i corresponds to the end face 16 of the base substrate 10 (see FIG. 3).

[0077] The cover substrate 14 is hermetically sealed and joined to the base substrate 10 via a plurality of laser bond lines 2. In this case, the laser bond lines 2 extend parallel to the side walls of the cavity 21. In the illustrated example, the cavity 21 is rectangular and accordingly has four side walls. In this example, two bond lines 2 extend parallel to each of one of the side walls of the cavity. In this case, the thickness of the side wall corresponds to the contact surface width B. In this case, only the bond lines 2 that are not separated from each other by the functional region 20 or the cavity 21 are considered to be adjacent to each other. The laser bond lines 2 form two closed rectangular paths surrounding the functional region 20 in this example.

[0078] The enclosure shown in FIG. 2 is obtained from a wafer stack in which the wafer for the base substrate 10 and the wafer for the cover substrate 14 are overlapped and joined to each other. Thereby, a wafer stack including a plurality of enclosures 1 joined to each other is obtained. In this case, the laser bond lines 2 are formed over the entire width or length of the wafer stack, respectively. By individuating the plurality of enclosures, individual enclosures 1 as shown in FIG. 2 are obtained.

[0079] FIG. 3 shows a side sectional view of the hermetic enclosure 1 shown in FIG. 2 taken along the sectional line A-A in FIG. 2.

[0080] In the cross-sectional view shown in FIG. 3, it can be seen that the base substrate 10 is composed of a bottom substrate 11 and an intermediate substrate 12 in this embodiment. The bonding between the bottom substrate 11 and the intermediate substrate 12 was carried out in the same manner as the bonding between the cover substrate 14 and the base substrate 10 or the intermediate substrate 11, that is, it was hermetically sealed via a plurality of laser bonding lines 2.

[0081] The side wall of the formed cavity 21 is formed by the intermediate substrate 12 here, and the bottom of the cavity 21 is formed by the bottom substrate 11. In the illustrated example, the functional element 22 in the cavity 21 is arranged on the bottom substrate 11.

[0082] FIG. 4 shows a cross-section of the laser bonding line 2 along the welding direction. In this case, the welding direction is the direction in which the laser beam is guided across the substrates 11, 12, 14 to be joined. In this case, since the individual pulses overlap locally multiple times, a heat accumulation above the focus (32) causes a weld seam. The cross-section of the seam is spherical and is called a weld ball 30. In this case, the weld ball 30 is formed by heating the material beyond the glass transition temperature T G or the melting temperature, and is formed by the regions of the substrates 11, 12, 14 processed by each laser pulse so that the adjacent substrates 11, 12, 14 can be joined in a material bonding manner. In this case, the scanning speed is selected in relation to the pulse repetition frequency of the ultra-short pulse laser so that a continuous laser bonding region is formed in the region of the laser bonding line 2.

[0083] In this case, the laser beam is focused so that the focus 32 is arranged at an interval T with respect to the bonding surface between each of the two substrates 11, 12, 14. Then, starting from the focus 32, a weld ball 30 having a height HL is formed by the energy transmitted from the laser pulse to each of the substrates 11, 12, 14.

[0084] FIG. 5 shows a cross-section of the laser bonding line 2 perpendicular to the welding direction. From this cross-sectional view, it can be recognized that each laser bonding line 2 has a width w with respect to the bonding surfaces between the substrates 11, 12, and 14 to be joined, that is, here, on the one hand, between the bottom substrate 11 and the intermediate substrate 12, and on the other hand, between the intermediate substrate 11 and the cover substrate 14. Since the width of the weld ball 30 varies along the height HL of the weld ball 30, correspondingly, the width w of the laser bonding line 2 can be adjusted by selecting the depth T of the focus 32 with respect to each bonding surface. The distance H between each two adjacent laser bonding lines 2, measured from center point to center point, is preferably selected so that the laser bonding lines 2 do not overlap. Correspondingly, the distance H is equal to or greater than the width w. Further, the enclosure 1 is configured to be as compact as possible, and correspondingly, the goal here is to select the contact surface width B (see FIG. 3), which corresponds to the width of the side wall of the cavity 21, to be minimized. Correspondingly, the distance between two laser bonding lines 2 is preferably selected to be at most five times the width w.

[0085] FIG. 6 shows a double logarithmic plot of the cumulative failure probability of laser welded samples for three different total lengths of laser bonding lines with respect to the shear force N applied in the shear test. The first curve 101 shows the cumulative failure probability for 30 samples having a total laser bonding line length of 20 mm, the second curve 102 shows the cumulative failure probability for 30 samples having a total laser bonding line length of 40 mm, and the third curve 103 shows the cumulative failure probability for 30 samples having a total laser bonding line length of 60 mm.

[0086] FIG. 7 shows a diagram of the characteristic breaking force of laser welded samples with respect to the total length of the laser bonding line. The fitted affine function can be used to determine the empirical constant P. The slope of the function corresponds to the constant P. The y-axis interval corresponds to the adhesion force provided by the mating contact surface A c (see FIG. 1).

[0087] FIG. 8 shows a diagram of the empirical constant P defined with respect to the bonding strength per unit length for three curves 101, 102, 103 (see FIG. 6). It is recognized that the value obtained for the constant P within the failure tolerance frame is independent of the laser bonding line length of each sample.

[0088] FIG. 9 shows a micrograph of a cross-section of two substrates 10, 14 made of borosilicate glass and bonded to each other by a laser bonding line 2. The laser bonding line 2 is clearly recognized due to the refractive index changes occurring during heating and subsequent cooling.

[0089] FIG. 10 shows three examples a, b, and c of fracture images related to the fracture of the welded joint between two substrates when the fracture shear force is exceeded. In this case, it is well recognized that both substrates are separated from each other along the weld seam or the laser bonding line with substantially no further damage.

[0090] FIG. 11 shows three examples a, b, c of fracture images when one or both substrates are fractured by the action of force without prior fracture of the welded joint. Here, it is well recognized in each case that the fracture line does not extend along the original surface of the substrate, but rather each substrate itself is fractured. In this case, a part of each substrate is peeled off.

[0091] Although the present invention has been described based on preferred embodiments, the present invention is not limited thereto and can be variously modified.

Description of Reference Numerals

[0092] A i Contact surface A c Matched contact surface A w Laser bonding surface 1 Enclosure 2 Laser bonding line 3 First substrate 4 Second substrate 10 Base substrate 11 Bottom substrate 12 Intermediate substrate 14 Cover substrate 16 End face 20 Functional area 21 Cavity 22 Functional element 30 Welded joint 32 Focus A Section line a Length of the enclosure b Width of the enclosure c Height of the enclosure B Contact surface width HL Height of the laser bonding line T Depth of the laser bonding line w Width of the laser bonding line H Spacing between two laser bonding lines 101 First curve 102 Second curve 103 Third curve KW Cumulative failure probability S Shearing force P Empirical constant F v Breaking shearing force L Laser bonding line length

Claims

1. In a method for designing a laser-welded joint between the base substrate (10) and the cover substrate (14) of an enclosure (1), In a method in which the base substrate (10) has a functional region (20), the cover substrate (14) in contact with the base substrate (10) covers the functional region (20), and the base substrate (10) and the cover substrate (14) are directly and hermetically sealed and bonded to each other via at least one laser bonding line (2), thereby hermetically sealing the functional region (20) inside the formed enclosure (1), Regarding the joint between the cover substrate (14) and the base substrate (10), the minimum shear force F that must withstand laser welding is specified. ｍｉｎ Set in advance, and The sum of the lengths of all laser junction lines (2) L ｇｅｓ The minimum required length L of all laser bonding lines (2) ｍｉｎ Select a value greater than the predetermined minimum shear force F. ｍｉｎ By dividing this by the force P per unit length of the laser junction wire, which is determined based on experience, L ｍｉｎ = F ｍｉｎ / P, L ｍｉｎ Establish and On the plane of the end face (16) of the base substrate (10) facing the cover substrate (14), the contact surface width B measured as the shortest distance between the functional region (20) and the outside of the enclosure (1) is defined as the contact surface A where the base substrate (10) and the cover substrate (14) can come into contact ｉ and the laser bonding surface A defined by the laser bonding line (2) having a width w at the end face (16) of the base substrate (10) facing the cover substrate (14) ｗ The ratio J = A ｉ / A ｗ is selected so as to be within the range of 1 to 10 A method characterized by the following features.

2. A number of closed paths N of laser junction lines (2), each having a width w and a distance H between the center points of at least two adjacent laser junction lines (2) of the width w, are arranged to surround the functional region (20), and the number N is the total length L of all laser junction lines (2) formed by multiplying the number N by the length of the contour line defining the functional region (20). ｇｅｓ The shortest length L ｍｉｎ The method according to claim 1, wherein the minimum number N is determined to be greater than or equal to the minimum number of items.

3. The method according to claim 1 or 2, wherein the distance H between the center points of two adjacent laser junction lines (2) having the width w is selected from within the range of 1w to 5w, preferably within the range of 1.01w to 2.5w, and particularly preferably within the range of 1.05w to 2w.

4. The method according to claim 1 or 2, wherein the contact surface width B is selected within the range of 100 μm to 1000 μm.

5. The method according to claim 1 or 2, wherein the width w of the laser bonding line (2) is selected within the range of 20 μm to 75 μm, preferably within the range of 30 μm to 60 μm.

6. By manufacturing a plurality of samples in which a first substrate (3) made of a cover substrate material is bonded to a second substrate (4) made of a base substrate material by a laser bonding line (2), the force P per unit length of the laser bonding line is determined empirically, and in this case, the total length L of the laser bonding line in the sample is ｇｅｓ The method according to claim 1 or 2, wherein the shear force durability of the sample is determined by selecting the same and specifying a force that increases the shear force at the joint between the first substrate (3) and the second substrate (4), thereby destroying the joint and evaluating the probability distribution of the failure.

7. A first substrate (3) made of cover substrate material is bonded to a second substrate (4) made of base substrate material by a laser bonding line (2), thereby enabling the substrates (3, 4) to withstand a minimum shear force F ｍｉｎ In the manufacture of multiple samples designed with respect to the minimum shear force F, ｍｉｎ When the minimum shear force F is applied, more than 50%, preferably more than 75%, particularly preferably more than 90%, and most preferably more than 95% of the samples will not break along the contact surface due to the failure of the welded joint, but will break at another location on one or more of the substrates (3, 4), particularly at one edge, such that the minimum shear force F is applied. ｍｉｎ The method according to claim 1 or 2 for setting up

8. A sealed enclosure (1) comprising a base substrate (10) having a functional region (20) and a cover substrate (14) that contacts the base substrate (10) and covers the functional region (20), wherein the base substrate (10) and the cover substrate (14) are directly and hermetically sealed and joined to each other via at least one laser bonding line (2), and the functional region (20) is hermetically sealed inside the formed enclosure (1), in the enclosure (1), Contact surface A where the base substrate (10) and the cover substrate (14) can come into contact. ｉ The laser bonding surface A is defined by at least one laser bonding line (2) having a width w on the surface of the interface between the base substrate (10) and the cover substrate (14). ｗ The ratio J = A is formed from the above. ｉ / A ｗ However, it is located within the range of 1 to 10. On the plane of the end face (16) of the base substrate (10) facing the cover substrate (14), the contact surface width B, measured as the shortest distance between the functional area (20) and the outside of the enclosure (1), is located within the range of 100 μm to 1000 μm. An enclosure (1) characterized by the following features.

9. The surface A defined by the at least one laser junction line (2) ｗ The enclosure (1) according to claim 8, wherein the joint between the cover substrate (14) and the base substrate (10) is selected to have a breaking shear force in the range of 10N to 1000N, preferably in the range of 50N to 500N, and particularly preferably in the range of 100N to 400N.

10. The total length L of the laser bonding wire (2) ｇｅｓ The enclosure (1) according to claim 8, which is selected by the design method described in claim 1.

11. The enclosure (1) according to claim 8 or 9, wherein two or more laser junction lines (2) are provided, the laser junction lines (2) having a width w, and the distance H between the center points of two adjacent laser junction lines (2) is selected from within the range of 1 w to 5 w, preferably from 1.01 w to 2.5 w, and particularly preferably from 1.05 w to 2 w.

12. The enclosure (1) according to claim 8 or 9, wherein the cover substrate (14) is formed as a transparent thin film substrate, and the cover substrate (14) has a thickness of less than 200 μm, preferably less than 170 μm, and particularly preferably less than 125 μm, and preferably more than 10 μm, and particularly preferably more than 20 μm.

13. The cover substrate (14) and the base substrate (10) are connected by the contact surface A ｉ The laser bonding surface A is in direct contact with the laser bonding surface A, and is thus defined by at least one laser bonding line (2). ｗ The enclosure (1) according to claim 8 or 9, wherein the internal joints do not contain foreign matter, and in particular do not contain bonding materials such as adhesives, glass frit, or absorbent layers.

14. The enclosure (1) according to claim 8 or 9, wherein the base substrate (10) has a planar bottom substrate (11) that forms the bottom surface of a functional region (20) configured as a cavity (21), and an intermediate substrate (12) that forms the side wall of the cavity (21) having an end face facing the cover substrate (14), and the bottom substrate (11) and the intermediate substrate (12) are hermetically sealed and bonded to each other via at least one laser bonding line (2), or a functional region (20) in the form of a recess having a bottom surface and a side wall is formed within the base substrate (10), and the recess together with the cover substrate (14) as a cover surface forms the cavity (21).

15. The enclosure (1) according to claim 8 or 9, wherein the cover substrate (14) and / or the base substrate (10) are made of glass, glass ceramic, silicon, sapphire, or a combination of the above materials.

16. The width w of the laser junction line (2) is within the range of 20 μm to 75 μm, preferably within the range of 30 μm to 60 μm, and / or the width w of all laser junction lines (2) is equal to the total length L of the laser junction line (2). ｇｅｓ The enclosure (1) according to claim 8 or 9, wherein the change is by a maximum of 30%, preferably by a maximum of 20%, and particularly preferably by a maximum of 10% over the specified period.

17. A sensor unit and / or medical implant comprising an enclosure (1) obtained based on the design according to claim 8 or the method according to claim 1.

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