MEMS microphone

Abstract

A MEMS microphone according to an embodiment of the present invention comprises: a first substrate; a second substrate laminated on the first substrate; a solder-resist layer disposed on the top surface of the second substrate and bottom surface of the first substrate; a housing disposed on the second substrate and having a receiving space; a MEMS structure disposed in the receiving space on the second substrate; and a signal processing element disposed in the receiving space on the second substrate, distanced from the MEMS structure.

Description

MEMS Microphone

[0001] The present invention relates to a MEMS microphone, and more specifically, to a MEMS microphone in which a PSR process is applied to a substrate unit to simplify the process and improve performance.

[0002] Typically, audio devices use electrodes to vibrate a diaphragm to generate sound. Recent technological advancements have led to significant advancements in the audio device field. These devices are increasingly used in diverse applications, including portable terminals and hearing aids. As the devices they are used in become slimmer, the devices themselves are also becoming smaller.

[0003] Additionally, microphones utilizing MEMS (Micro Electro Mechanical Systems), a semiconductor technology, have recently been developed and used. MEMS is a technology that enables the manufacturing of tiny mechanical components on the surface of silicon wafers. These MEMS microphones can be categorized into electrostatic and piezoelectric types, including the common condenser type.

[0004] Recently, electronic devices such as mobile communication terminals, tablet PCs, and MP3 players are becoming increasingly miniaturized. Consequently, the components of these devices are also becoming smaller. Therefore, Micro Electro Mechanical System (MEMS) technology is needed to overcome the physical limitations of these components.

[0005] The technical problem to be solved by the present invention is to provide a MEMS microphone in which the process is simplified and performance is improved by applying a PSR process to a substrate.

[0006] In order to solve the above technical problem, a MEMS microphone according to an embodiment of the present invention may include a first substrate; a second substrate laminated on the first substrate; a solder resist layer disposed on an upper surface of the second substrate and a lower surface of the first substrate; a housing disposed on an upper surface of the second substrate and having an accommodation space formed therein; a MEMS structure disposed within the accommodation space on an upper surface of the second substrate; and a signal processing element disposed within the accommodation space on an upper surface of the second substrate and spaced apart from the MEMS structure.

[0007] In addition, the solder resist layer includes a first solder resist layer disposed on the upper surface of the second substrate; and a second solder resist layer disposed on the lower surface of the first substrate, and the MEMS structure and the signal processing element may be disposed on the upper surface of the first solder resist layer.

[0008] In addition, the first solder resist layer may have a plurality of connecting lines formed on the upper surface to allow at least one of the housing, the MEMS structure, and the signal processing element to be installed.

[0009] In addition, the above-mentioned plurality of connecting lines can be formed by half-etching and plating.

[0010] Additionally, the second substrate may include a first cavity exposing the first pad of the first substrate upward, and the first solder resist layer may include a second cavity having a shape corresponding to the cavity.

[0011] In addition, the first substrate bottom surface may have one or more second pads and one or more second connection circuits connecting the second pads arranged thereon, and the second solder resist layer may cover the second connection circuits without covering the second pads.

[0012] Additionally, the solder resist layer can be formed by a photo solder resist (PSR) process.

[0013] Additionally, the solder resist layer can be formed by an exposure process and a development process.

[0014] Additionally, the solder resist layer may include polyimide.

[0015] In addition, the second substrate may further include a bonding sheet having a shape corresponding to the lower surface thereof and bonding the first substrate and the second substrate.

[0016] In addition, the plurality of connecting lines may include at least one of a first connecting line on which solder for joining the MEMS structure is applied, a second connecting line providing a guide for mounting the MEMS structure, a third connecting line providing a guide for mounting the signal processing means, and a fourth connecting line providing a guide for mounting the housing.

[0017] The MEMS microphone according to embodiments of the present invention has the following effects.

[0018] Compared to the conventional substrate unit manufacturing process, the entire process is simplified, not only reducing the process cost and process time, but also significantly reducing the risk of short circuits because a solder resist layer is formed on both the upper and lower surfaces of the substrate unit, and since the solder resist layer is arranged through a PSR process rather than an adhesion or thermal compression process, it has the effect of easily forming various circuits as well as sound holes or cavities formed in the substrate unit.

[0019] Additionally, since there is no separate manual or laser cutting process, tolerances are reduced compared to conventional processes, which not only increases product reliability, but also simplifies the process by eliminating the need for a separate plating process to improve adhesion.

[0020] In particular, not only can a solder resist layer be formed on the lower surface of the substrate unit, i.e., the lower surface of the first substrate, but it is also designed to be placed not at the position of the second pad formed on the lower surface of the first substrate but at the position of the second connection circuit, thereby reducing the short risk and improving the degree of freedom in circuit design.

[0021] In addition, by forming multiple connection lines on the first solder resist layer through plating, the combination of the MEMS structure, signal processing element, and housing is performed more stably, and the sensitivity change of the MEMS microphone is reduced, thereby enabling stable product use.

[0022] FIG. 1 is a side view illustrating the structure of a MEMS microphone according to an embodiment of the present invention.

[0023] Fig. 2 is a top view showing the structure of a MEMS microphone according to an embodiment of the present invention.

[0024] FIG. 3 is a drawing showing the upper and lower surfaces of a substrate of a MEMS microphone according to an embodiment of the present invention.

[0025] FIG. 4 is a drawing illustrating a substrate manufacturing process of a MEMS microphone according to an embodiment of the present invention.

[0026] FIG. 5 is a drawing showing the state of joining the MEMS structure of a MEMS microphone according to an embodiment of the present invention and a conventional MEMS microphone.

[0027] Figure 6 is a drawing illustrating the substrate manufacturing process of a conventional MEMS microphone.

[0028] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0029] However, the technical idea of ​​the present invention is not limited to some of the embodiments described, but can be implemented in various different forms, and within the scope of the technical idea of ​​the present invention, one or more of the components between the embodiments can be selectively combined or substituted for use.

[0030] In addition, terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that can be generally understood by a person of ordinary skill in the technical field to which the present invention belongs, unless explicitly and specifically defined and described, and terms that are commonly used, such as terms defined in a dictionary, may be interpreted in consideration of the contextual meaning of the relevant technology.

[0031] Additionally, the terms used in the embodiments of the present invention are intended to describe the embodiments and are not intended to limit the present invention.

[0032] In this specification, the singular may also include the plural unless specifically stated otherwise in the phrase, and when it is described as “A and / or at least one (or more) of B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0033] Additionally, in describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and are not intended to limit the nature, order, or sequence of the components.

[0034] And, when a component is described as being 'connected', 'coupled', or 'connected' to another component, it may include not only cases where the component is 'connected', 'coupled', or 'connected' directly to the other component, but also cases where the component is 'connected', 'coupled', or 'connected' by another component between the component and the other component.

[0035] Additionally, when described as being formed or arranged "above" or "below" each component, "above" or "below" includes not only cases where the two components are in direct contact with each other, but also cases where one or more other components are formed or arranged between the two components. Furthermore, when expressed as "above" or "below," the meaning may include not only the upward direction but also the downward direction based on one component.

[0036] Variations according to the present embodiment may include some components of each embodiment and some components of other embodiments. That is, a variation may include one embodiment among various embodiments, but may omit some components and include some components of the corresponding other embodiment. Or, the opposite may be true. The features, structures, effects, etc. described in the embodiments are included in at least one embodiment and are not necessarily limited to just one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment may be combined or modified in other embodiments by a person having ordinary skill in the art to which the embodiments pertain. Therefore, the contents related to such combinations and modifications should be construed as being included within the scope of the embodiments.

[0037] FIG. 1 is a side view showing the structure of a MEMS microphone according to an embodiment of the present invention, FIG. 2 is a top view showing the structure of a MEMS microphone according to an embodiment of the present invention, FIG. 3 is a view showing the upper and lower surfaces of a substrate of a MEMS microphone according to an embodiment of the present invention, FIG. 4 is a view showing a substrate manufacturing process of a MEMS microphone according to an embodiment of the present invention, FIG. 5 is a view showing a state of joining a MEMS structure of a MEMS microphone according to an embodiment of the present invention and a conventional MEMS microphone, and FIG. 6 is a view showing a substrate manufacturing process of a conventional MEMS microphone.

[0038] Referring to FIGS. 1 to 6, a MEMS microphone according to one embodiment of the present invention may include a first substrate (100), a second substrate (200), a MEMS structure (300), a housing (400), a signal processing element (500), a capacitor (600), a solder resist layer (700), and a bonding sheet (800).

[0039] The first substrate (100) is placed at the bottom of the MEMS microphone and is a substrate on which a circuit can be formed in a plate shape. The first substrate (100) is a flexible substrate and may be a COF (Chip on Film) substrate or a flexible printed circuit board (FPCB). A COF (Chip on Film) substrate is a substrate formed by forming a circuit or mounting a chip or other element on a base film, and is a thin substrate compared to other substrates because it has a film shape. By using a COF substrate as the substrate of the MEMS microphone, the thickness can be reduced compared to when using a conventional rigid substrate.

[0040] The first substrate (100) is a COF substrate and may include a 2-metal COF substrate. The 2-metal COF may be formed in a structure in which metal layers are laminated on the upper and lower surfaces of the base film so that circuits can be formed on both sides of the base film or devices can be mounted.

[0041] The first substrate (100) may include a via hole. In this case, the first substrate (100) may connect circuits or elements formed on both sides through a metal layer (e.g., a via) formed in the via hole. Here, the via hole may be a micro via hole and may be configured with a size of 25 um or less. Compared to a single-sided COF, the degree of integration can be increased, the degree of freedom during packaging is improved, and a fine pitch is possible by arranging circuits or elements on both sides. When only a rigid substrate is used, the basic thickness is thick during design, making it difficult to apply a fine pitch, but when a COF substrate is used, it is significantly thinner than the substrate, making it possible to apply a fine pitch, so the size of the MEMS microphone package can be reduced by more than 50%.

[0042] A flexible printed circuit board (FPCB) is a flexible circuit board. It is also flexible and thinner than standard PCBs, allowing for a reduction in the thickness of the MEMS microphone substrate. Other types of flexible substrates may also be included.

[0043] The first substrate (100) may include an acoustic hole (10). The cross-sectional area of ​​the acoustic hole may be circular, but is not limited thereto. A MEMS structure (300) may be arranged on the upper portion of the acoustic hole (10) formed in the first substrate (100).

[0044] A first substrate (100) may be electrically connected to a signal processing element (500) and a capacitor (600). A metal layer may be formed on the first substrate (100) to be electrically connected to the signal processing element (500) and the capacitor (600). Here, the metal layer may include a plurality of pads (110), a plurality of connection circuits (120a, 120b), and a plurality of vias. The pads (110) may vertically overlap with the vias and contact them, or may contact an external substrate or element. The connection circuits (120a, 120b) may connect pads arranged on the same layer or on the upper or lower surface. The vias may be formed in via holes penetrating a base film or an insulating layer. Hereinafter, to help understanding the description, the pads formed on the first substrate (100) are referred to as pads (110).

[0045] Pads (110) and connection circuits (120a, 120b) of the same or different shapes may be formed on the upper and lower surfaces of the first substrate (100). A plurality of pads (110) and connection circuits (120a, 120b) may be formed on the upper and lower surfaces of the first substrate (100). The pads (110) may include a first pad (110a) disposed on the upper surface of the first substrate (100) and a second pad (110b) disposed on the lower surface of the first substrate (100). In this case, the first pad (110a) is a pad to which a signal processing element (500) and a capacitor (600) can be electrically connected, and the second pad (110b) is a pad to which an external element can be electrically connected.

[0046] In this case, a plurality of first pads (110a) formed on the upper surface of the first substrate (100) can be electrically connected to a plurality of second pads (110b) formed on the lower surface of the first substrate (100). The first pads (110a) can be electrically connected to the second pads (110b) through vias. In addition, the plurality of first pads (110a) can be arranged at the same position as the plurality of second pads (110b) or can be arranged at different positions. That is, there is no limitation on the arrangement as long as the first pads (110a) are electrically connected to the second pads (110b).

[0047] A connection circuit (120a, 120b) may be arranged on the upper and lower surfaces of the first substrate (100). The connection circuit (120a, 120b) may be a pattern circuit for electrically connecting the first pad (110a) and the second pad (110b). The connection circuit (120a, 120b) may include a first connection circuit (120a) arranged on the upper surface of the first substrate (100) and extending from the first pad (110a) to an arbitrary position, and a second connection circuit (120b) arranged on the lower surface of the first substrate (100) and extending from the second pad (110b) to an arbitrary position. The connection circuit (120a, 120b) may have a pattern shape designed to allow the first pad (110a) and the second pad (110b) to be arranged at different positions. In this case, the signal processing element (500) and the capacitor (600) can be electrically connected to the first substrate (100) through the pad (110), and the signal processing element (500) and the capacitor (600) can be electrically connected to the second pad (110b) through the first pad (110a). In addition, the first pad (110a) to which the connection circuit (120a, 120b) is extended may not have a via hole formed therein as needed, and in this case, a via hole may be formed in the connection circuit (120a, 120b).

[0048] A solder resist layer (700) may be disposed on the lower surface of the first substrate (100). A second solder resist layer (720) may be applied and disposed on the lower surface of the first substrate (100). The second solder resist layer (720) may be disposed on the surface of the lower surface of the first substrate (100) excluding the area where the second pad (110b) is disposed. In this case, the second connection circuit (120b) may also be covered by the second solder resist layer (720). This has the effect of preventing a short circuit due to electrical connection between different second pads (110b).

[0049] The second substrate (200) is laminated so that the first substrate (100) is placed on top, and has a plate shape. The second substrate (200) may be a rigid substrate to supplement the rigidity of the first substrate (100), and may include, for example, one or more of a metal plate, SUS, and a reinforcing plate. SUS is a type of steel in which chromium is mixed with iron to enhance corrosion resistance, and refers to a high-strength substrate. In addition to the above-described configuration, the second substrate (200) may use various reinforcing plates made of metal, and there is no limitation on the material thereof as long as it can be combined with the housing (400) to maintain the shield. The second substrate (200) supplements the rigidity of the first substrate (100), so that the flexible first substrate (100) can maintain its shape.

[0050] The second substrate (200) may include one or more cavities (210). The second substrate (200) is disposed on top of the first substrate (100), and the first substrate (100) may be exposed to the upper portion of the second substrate (200) through the cavities (210) of the second substrate (200). The first substrate (100) may be exposed to the upper portion of the second substrate (200) by having a pad (110) disposed in the space where the cavities (210) of the second substrate (200) are formed. When the second substrate (200) is laminated on the first substrate (100), since the upper surface of the first substrate (100) is placed on the lower surface of the second substrate (200), the first pad (110a) formed on the upper surface of the first substrate (100) can be exposed to the upper portion of the second substrate (200) through the cavity (210) of the second substrate (200). The first pad (110a) of the first substrate (100) can be electrically connected to the signal processing element (500) and the capacitor (600) through the cavity (210) formed in the second substrate (200).

[0051] The second substrate (200) may include an acoustic hole. The cross-sectional area of ​​the acoustic hole may be circular, but is not limited thereto, and may have a size corresponding to the acoustic hole formed in the first substrate (100). The acoustic hole formed in the second substrate (200) may be in communication with the acoustic hole formed in the first substrate (100) to form one acoustic hole (10), and a MEMS structure (300) may be arranged on the acoustic hole (10).

[0052] A solder resist layer (700) may be disposed on the upper surface of the second substrate (200). A first solder resist layer (710) may be applied and disposed on the upper surface of the second substrate (200). The first solder resist layer (710) may be disposed on the surface of the upper surface of the second substrate (200) excluding the cavity (210). In this case, the first pad (110a) and the first connection circuit (120a) that vertically overlap the cavity (210) may be exposed to the outside without being covered by the first solder resist layer (710). Through this, the electrical connection between the first pad (110a) and the MEMS structure (300), signal processing element (500), and capacitor (600) disposed on the second substrate (200) may be stably established.

[0053] In addition, the first solder resist layer (710) on the upper surface of the second substrate (200) may additionally include an etching area. The etching area of ​​the first solder resist layer (710) is formed to penetrate the first solder resist layer (710), and thus, an area of ​​the second substrate (200) that vertically overlaps with the etching area may be exposed. In addition, by performing plating on the etching area of ​​the first solder resist layer (710), a plurality of connection lines (910) may be formed on the upper surface of the second substrate (200). Accordingly, since the plurality of connection lines (910) do not vertically overlap with the first solder resist layer (710), solder application is possible on the upper surface, and fixation or bonding of each component, such as the MEMS structure (300) and the signal processing element (500), is possible.

[0054] A housing (400), a MEMS structure (300), a signal processing element (500), and a capacitor (600) may be placed on the second substrate (200). The capacitor (600) may be selectively placed on the second substrate (200) as needed.

[0055] The solder resist layer (700) may be formed to cover the upper surface of the second substrate (200) and the lower surface of the first substrate (100), and may be formed to surround the substrate unit to which the first substrate (100) and the second substrate (200) are bonded. The solder resist layer (700) may include a photosensitive solder resist (PSR: Photo Solder Resist), and the photosensitive solder resist may include polyimide. The solder resist layer (700) may include a photosensitive polyimide (PSPI: Photoseneitive Polyimide). However, the present disclosure is not limited thereto, and the solder resist layer (700) may include a resin. For example, the solder resist layer (700) may include a resin, a curing agent, a photoinitiator, a pigment, a solvent, a filler, an additive, an acrylic monomer, etc., and may further include glass fiber or GCP (Glass Core Primer) depending on the embodiment. That is, there is no limitation on the material of the solder resist layer (700) as long as an insulating material capable of performing insulation is used.

[0056] The solder resist layer (700) may be disposed on the upper surface of the second substrate (200) and the lower surface of the first substrate (100). The solder resist layer (700) may have a shape corresponding to the lower surface of the first substrate (100) and the upper surface of the second substrate (200), and a circuit of a desired shape may be formed as needed. The solder resist layer (700) may include a first solder resist layer (710) disposed on the upper surface of the second substrate (200) and a second solder resist layer (720) disposed on the lower surface of the first substrate (100).

[0057] The first solder resist layer (710) may be placed on the upper surface of the second substrate (200). In this case, the substrate of the MEMS microphone may be laminated in the following order from top to bottom: the first solder resist layer (710), the second substrate (200), the bonding sheet (800), the first substrate (100), and the second solder resist layer (720).

[0058] The first solder resist layer (710) is disposed on the upper surface of the second substrate (200) and may have a shape corresponding to the shape of the second substrate (200). In detail, the first solder resist layer (710) may be disposed on the second substrate (200) so that a hole corresponding to the cavity (210) of the second substrate (200) is formed, and may include a plurality of connection lines (910: 911, 912, 913, 914911912913914) on which a preset circuit is formed.

[0059] A MEMS structure (300), a housing (400), and a signal processing element (500) can be connected to a plurality of connection lines (911, 912, 913, 914). Here, the plurality of connection lines (911, 912, 913, 914) can be arranged with a circuit formed in an etched area of ​​the first solder resist layer (710). For example, etching can be performed in a circuit shape designed on the first solder resist layer (710), and plating can be performed on the etched area to create a plurality of connection lines (911, 912, 913, 914). A plurality of connection lines (911, 912, 913, 914) are a means by which electrical connection and solder bonding between the components and the second substrate (200) can be performed, and solder can be applied to the plurality of connection lines (911, 912, 913, 914) to connect the MEMS structure (300), the housing (400), and the signal processing element (500).

[0060] A plurality of connecting lines (911, 912, 913, 914) may include a first connecting line (911) on which solder is applied to join the MEMS structure (300), a second connecting line (912) on which a guide is provided for the MEMS structure (300) to be installed, a third connecting line (913) that provides a guide for the signal processing means (500) to be installed, and a fourth connecting line (914) that provides a guide for the housing (400) to be installed. The second connecting line (912) is an area on which the MEMS structure (300) is installed, and the first connecting line (911) is an area on which an adhesive material (e.g., silicone or epoxy) is applied in a die bonding process of the MEMS structure (300) while the MEMS structure (300) is installed.

[0061] A plurality of connection lines (911, 912, 913, 914) can be formed by forming a circuit in the process of placing a solder resist layer (700) and applying plating to the generated circuit portion. In this case, the plurality of connection lines (911, 912, 913, 914) are plating areas and therefore have no resistance to solder, while the remaining upper surface portion of the second substrate (200) is maintained in a state where the solder resist layer (700) is placed and thus has resistance to solder. This has the effect of making it easy to secure airtightness in the subsequent packaging process by allowing solder to spread only in the portion of the plurality of connection lines (220).

[0062] One or more components of a MEMS structure (300), a signal processing element (500), and a capacitor (600) may be arranged on the upper surface of the first solder resist layer (710). When the first solder resist layer (710) is formed on the upper surface of the second substrate (200), one or more components of a MEMS structure (300), a signal processing element (500), and a capacitor (600) may be in contact with a plurality of connection lines (911, 912, 913, 914) on the upper surface of the first solder resist layer (710). During the process of laminating the MEMS structure (300), the signal processing element (500), and the capacitor (600) on the second substrate (200), a thermal curing process or a reflow process is performed. During the process, heat is generated in the second substrate (200), and since the thermal conductivity of the second substrate (200) is high, the MEMS structure (300) receives heat from the second substrate (200), and its shape is deformed or damaged, which causes a problem of generating noise. Accordingly, the signal-to-noise ratio (SNR), power supply rejection (PSR) related to power noise suppression, and power supply rejection ratio (PSRR) characteristics are changed, and in some cases, the acoustic signal sensing of the MEMS microphone may operate abnormally or noise may be generated. Since the MEMS structure (300), signal processing element (500), and capacitor (600) are connected to the second substrate (200) through the first solder resist layer (710), there is an effect of reducing the influence of heat generated from the second substrate (200) being transferred to the MEMS structure (300) and signal processing element (500).

[0063] The first solder resist layer (710) may include one or more cavities. The cavities formed in the first solder resist layer (710) may be arranged at positions corresponding to the cavities (210) formed in the second substrate (200), and the cavities (210) of the second substrate (200) and the cavities of the first solder resist layer (710) may be in communication with each other. The first pad (110a) and the first connection circuit (110b) of the first substrate (100) may be exposed to the upper portion of the second substrate (200) through the spaces communicated by the first solder resist layer (710) and each of the cavities of the second substrate (200). The first substrate (100) can be electrically connected to a signal processing element (500) and a capacitor (600) placed on the second substrate (200) through a cavity formed in the second substrate (200) and the first solder resist layer (710).

[0064] The second solder resist layer (720) may be placed on the lower surface of the first substrate (100). In this case, the substrate of the MEMS microphone may be laminated in the following order from top to bottom: the first solder resist layer (710), the second substrate (200), the bonding sheet (800), the first substrate (100), and the second solder resist layer (720).

[0065] When the second solder resist layer (720) is disposed on the lower surface of the first substrate (100), the second solder resist layer (720) may be disposed in an area excluding the area where the second pad (110b) disposed on the lower surface of the first substrate (100) is disposed. For example, the second solder resist layer (720) may be disposed to cover the lower surface of the first substrate and the second connection circuit (120b) disposed on the lower surface. Through this, the risk of a short circuit that may occur when the second connection circuit (120b) comes into contact with the second pad (110b) or a pad for connection to an external electronic device may be reduced, and since the solder resist is formed on the second connection circuit (120b), there is an effect of increasing the degree of freedom in circuit design, such as the arrangement of pads.

[0066] The solder resist layer (700) may include an acoustic hole. The first solder resist layer (710) and the second solder resist layer (720) may include an acoustic hole. The cross-sectional area of ​​the acoustic hole may be circular, but is not limited thereto. The acoustic hole formed in the solder resist layer (700) may be formed to have a size corresponding to the acoustic holes formed in the first substrate (100) and the second substrate (200), and may be connected to the acoustic holes formed in the first substrate (100) and the second substrate (200) to form one acoustic hole.

[0067] The housing (400) is a means for being placed on the upper portion of the second substrate (200) and forming an accommodation space therein. The housing (400) may be formed in a cover shape with an open lower surface, and the lower surface of the housing (400) may be coupled to the upper surface of the second substrate (200) to form an accommodation space. Depending on the size (Back Volume) of the accommodation space formed inside the housing (400), the signal-to-noise ratio (SNR), power supply rejection (PSR) related to power noise suppression, and power supply rejection ratio (PSRR) characteristics may be improved, thereby determining the noise state.

[0068] The housing (400) may be composed of nickel silver or SUS. Nickel silver is a material containing 15-30% zinc and 10-20% nickel in copper, and solder joints are possible without plating in the raw material state. When plating is applied to the seating area of ​​the housing (400), solder joint adhesion can be improved. Ni+Au plating can be applied. Both electroless and electrolytic plating processes can be applied. Although SUS contains nickel, solder joint adhesion may be reduced if plating is not performed. Therefore, plating can be applied. Unlike nickel silver, when electroless plating is applied, plating adhesion on the SUS surface may be reduced, so plating can be performed using an electrolytic plating process.

[0069] The housing (400) can be connected to the second substrate (200) by soldering and being seated on the fourth connection line (914) among the plurality of connection lines formed in the area where the first solder resist layer (710) is etched. An electrically stable connection can be performed by joining the housing (400) through the fourth connection line (914).

[0070] The MEMS structure (300) may be placed within a receiving space formed by the housing (400). The MEMS structure (300) may include a body (310), a back plate (330), and a vibration plate (320). The MEMS structure (300) may be placed on the upper portion of the second substrate (200), and the lower portion of the MEMS structure (300) may be placed at a position adjacent to the sound hole (10).

[0071] The MEMS structure (300) can be connected to the second substrate (200) by having its lower surface rest on a second connection line (912) among a plurality of connection lines formed in an area where the first solder resist layer (710) is etched, and an adhesive material is applied to the first connection line (911) so that the lower surface of the MEMS structure (300) is solder-bonded to the first solder resist layer (710) by the adhesive material. An electrically stable connection can be performed by having the MEMS structure (300) be coupled through the first connection line (911) and the second connection line (912).

[0072] The body (310) is a means that can form a partition wall by surrounding the sound hole formed in the second substrate (200). The body (310) can be electrically connected to the first substrate (100) via a signal processing element (500). In addition, an sound hole (360) that is in communication with the sound hole can be formed in the body (310).

[0073] The body (310) may be formed with an acoustic hole (360). When the body (310) is coupled to the second substrate (200), the acoustic hole (10) formed in the first substrate (100) and the second substrate (200) and the acoustic hole (360) of the body (310) may be arranged to communicate with each other, and thus, sound from the outside may be designed to be introduced through the acoustic hole (360).

[0074] The body (310) can be directly connected to the second substrate (200). The body (310) can be stably solder-bonded by the adhesive material applied to the first connection line (911) while the lower surface thereof is secured to the second connection line (912). In this case, the adhesive material applied to the first connection line (911) is in a plating state in which the first connection line (911) is etched and plated in the first solder resist layer (710), so that the solder does not diffuse outside the first connection line (911), and thus the body (310) and the second substrate (200) can be stably bonded.

[0075] Referring to FIG. 5, the results of comparing the structures of connecting the MEMS structure (300) on the second substrate (200) can be confirmed. The left side is a top view and a side cross-sectional view of the joint structure of the conventional MEMS structure (300) and the second substrate (200), and the right side is a top view and a side cross-sectional view of the joint structure of the MEMS structure (300) and the second substrate (200) according to an embodiment of the present invention. In contrast to the conventional joint structure in which the silicon arrangement between the MEMS structure (300) and the second substrate (200) is disordered and the balance of the bonding portion is poor, in the joint structure according to the embodiment of the present invention, it can be confirmed that the silicon arrangement between the MEMS structure (300) and the second substrate (200) is formed in a balanced manner on both sides centered on the bottom of the MEMS structure (300). In fact, as a result of measuring the change in sensitivity of the microphone due to this, it was confirmed that in the case of the conventional coupling structure, a deviation of 0.2 to 0.7 dBFS occurred, and the sensitivity difference varied by 2.3 to 8.4%, but in the case of the coupling structure of the present invention, it was confirmed that a deviation within 0.1 dBFS occurred, and the sensitivity difference varied within 1.15%. This is because in the coupling structure of the present invention, even if solder is applied to the first connection line (911), it does not spread to the external area of ​​the first connection line (911), and stable fixation of the MEMS structure (300) is possible through the second connection line (912).

[0076] The back plate (330) and the vibration plate (320) may be placed in the sound hole (360) formed in the body. The vibration plate (320) may vibrate due to the sound pressure when sound is introduced from the outside through the sound hole (360), and the back plate (330) may sense the sound signal by measuring the capacitance according to the vibration of the vibration plate (320). In the drawing, the back plate (330) is depicted as being positioned above the vibration plate, but the vibration plate (320) may also be positioned above the back plate (330).

[0077] Although not shown, one or more body pads for electrical connection may be formed on the upper surface of the body (310). The body pads may be electrically connected to the back plate (330) and the vibration plate (320), and may be electrically connected to a signal processing element (500) to be described later via wires or the like. The body pads serve as a means for electrical connection, and their shapes and materials are known in the art, and thus a description thereof will be omitted.

[0078] The signal processing element (500) is electrically connected to the MEMS structure (300) and can process an electric signal sensed by the MEMS structure (300). The MEMS structure (300) and the signal processing element (500) can be electrically connected via a body pad. For example, the MEMS structure (300) and the signal processing element (500) can be connected by wires via wire bonding. In another example, the MEMS structure (300) and the signal processing element (500) can be electrically connected while being mounted on a second substrate (200) in a flip-chip form. When the MEMS structure (300) and the signal processing element (500) are wire bonded, a signal pad can be arranged on the signal processing element (500) to be connected to the body pad of the MEMS structure (300) via wire bonding.

[0079] The signal processing element (500) can be electrically connected to the first substrate (100). The signal processing element (500) can be electrically connected to the first pad (110a) of the first substrate (100) through the cavity (210) formed in the second substrate (200). For example, the signal processing element (500) and the first substrate (100) can be connected by wires through wire bonding. As another example, the first substrate (100) and the signal processing element (500) can be electrically connected while being mounted on the first substrate (100) in a flip-chip form. When the first substrate (100) and the signal processing element (500) are wire bonded, the first pad (110a) of the first substrate (100) and the signal pad of the signal processing element (500) can be connected through wire bonding. The signal processed in the signal processing element (500) is transmitted to the first pad (110a) and connection circuit (120a, 120b) formed on the upper surface of the first substrate (100), and can be transmitted to the outside that requires the signal through the second pad (110b) formed on the lower surface of the first substrate (100).

[0080] The signal processing element (500) can amplify a signal sensed by the MEMS structure (300). Here, the signal processing element (500) may include an application-specific integrated circuit (ASIC), but is not limited thereto. The signal processing element (500) may be formed as a single module and may be formed in a chip form. The signal processing element may include an ASIC and an En-cap that coats the ASIC.

[0081] The signal processing element (500) may be placed on the second substrate (200). The signal processing element (500) may be placed on the second substrate (200) spaced apart from the MEMS structure (300). The signal processing element (500) may be placed spaced apart from the MEMS structure (300) in an accommodation space formed inside the housing (400) and may receive a signal from the MEMS structure (300). Since signal transmission between the MEMS structure (300) and the signal processing element (500) occurs in the accommodation space formed by the housing (400), external interference is reduced, thereby reducing noise.

[0082] The signal processing element (500) can be connected to the second substrate (200) by being soldered and secured to the third connection line (913) among the plurality of connection lines formed on the upper portion of the first solder resist layer (700). An electrically stable connection can be performed by connecting the signal processing element (500) through the third connection line (913).

[0083] A capacitor (600) may be selectively placed on the second substrate (200) as needed. When the capacitor (600) is placed, the PSRR performance, which is RF-related noise, may be improved, and the PSR performance, which is power-related noise, may be improved. That is, noise-related performances such as SNR, PSRR, and PSR may be improved through the capacitor (600). The capacitor (600) may be electrically connected to the signal processing element (500). As a result, the capacitor (600) may remove noise during the signal processing process in the signal processing element (500).

[0084] The capacitor (600) may be placed on the second substrate (200) and electrically connected to the signal processing element (500) and the first substrate (100). The capacitor (600) may be electrically connected to the signal processing element (500) and the first substrate (100) via a wire. When the capacitor (600) is connected to the first substrate (100) via a wire, it may be connected to the first pad (110a) or the connection circuit (120a, 120b) formed on the first substrate (100) exposed through the cavity of the second substrate (200) via the wire.

[0085] However, the capacitor (600) may be electrically connected to the first substrate (100) by being mounted on the second substrate (200) or the signal processing element (500) in a flip-chip form as well as by bonding through wires. In the case of a MEMS microphone, since miniaturization is essential, there are many cases where the capacitor (600) is not placed in the circuit design due to insufficient space for placement. In this case, a problem occurs in which the performance of SNR, PSR, and PSRR is degraded due to power noise or RF noise. In the case of power noise filtering for improving SNR and PSR performance, the frequency of the noise is at the level of 0.1uF to 10uF, whereas in the case of RF noise filtering for improving SNR and PSRR performance, the frequency of the noise is at the level of 10pF to 500pF, so they have different frequency bands. When a plurality of capacitors (600) are arranged, the filtering noise frequency of each capacitor (600) can be determined differently, and accordingly, there is an effect of improving all performances of SNR, PSR, and PSRR.

[0086] Although not shown, when the capacitor (600) is placed on the second substrate (200), the plurality of connection lines (220) of the second substrate (200) may further include a fifth connection line for the capacitor (600) to be mounted, if necessary. Accordingly, the capacitor (600) may be mounted on the fifth connection line and joined by solder.

[0087] Below, a process for manufacturing a substrate of a MEMS microphone according to one embodiment of the present invention is described.

[0088] Referring to FIG. 4, a MEMS microphone according to one embodiment of the present invention can be manufactured according to steps A to F.

[0089] First, step A is a step of preparing a first substrate (100), a second substrate (200), and a bonding sheet (800). In step A, the first substrate (100) can be prepared in a roll form because it is a flexible substrate, and the bonding sheet (800) can also be prepared in a roll form. In addition, the second substrate (200) can exist in a state in which a plurality of second substrate (200) units are arranged in a panel form, and the second substrate (200) can be prepared in a state in which sound holes and cavities (210) are formed through etching.

[0090] Step B is a step of attaching a bonding sheet (800) to the upper surface of the prepared first substrate (100). In detail, a first substrate (100) unit having a circular hole and a pad (110) and a connection circuit (120) formed through processing can be arranged and prepared in a roll-shaped first substrate (100) array, and a bonding sheet (800) unit having a circular hole and a cavity formed through processing can be arranged and prepared in a roll-shaped bonding sheet (800). In this state, the bonding sheet (800) unit can be attached to the first substrate (100) by stacking the bonding sheet (800) units so that the lower surface thereof is arranged on the upper surface of the first substrate (100) unit.

[0091] Step C is a step of forming a substrate unit of a MEMS microphone by stacking a first substrate (100) and a second substrate (200). In detail, a bonding sheet (800) is attached to the upper surface of the first substrate (100), and by applying a set temperature and a set pressure for a set time through a thermocompression process, the lower surface of the second substrate (200) is bonded to the upper surface of the bonding sheet (800), thereby forming a substrate unit in which the first substrate (100), the bonding sheet (800), and the second substrate (200) are sequentially stacked from the lower side.

[0092] Step D is a step of disposing a solder resist layer (700) on the upper and lower surfaces of the substrate unit. The solder resist layer (700) can be formed through a photo solder resist (PSR) process. In this case, a polishing process for surface modification and improved adhesion can be performed on the upper surface of the substrate unit, that is, the upper surface of the second substrate (200). Thereafter, for the PSR process, an invariant ink is coated on the upper and lower surfaces of the substrate unit, that is, the lower surface of the first substrate and the upper surface of the second substrate, and an exposure process is performed to photo-cure the ink. After that, a circuit can be formed through a drying process, a printing process, and a developing process. Through this, the second solder resist layer (720), the first substrate (100), the bonding sheet (800), the second substrate (200), and the first solder resist layer (710) can be sequentially laminated from the lower side.

[0093] This is the step where a plating process is performed on the substrate unit in step E. Plating can be performed by electrolytic plating or electroless plating, and the reliability of wire bonding or the wettability of solder can be improved by controlling the plating thickness.

[0094] In step F, the manufactured substrate units can be arranged so that they can be packaged, and then the arranged substrate units can be packaged to manufacture a MEMS microphone.

[0095] Referring to Fig. 6, conventionally, steps a to f below were followed to manufacture a substrate unit of a MEMS microphone. In step a, a second substrate unit was prepared, an acoustic hole and a cavity were formed, and plating was performed on the upper surface. In step b, a coverlay film was attached to the second substrate unit, and in step c, the coverlay film was attached to the second substrate unit through a thermocompression process. Thereafter, in step d, laser cutting was performed according to the shape of the acoustic hole and cavity formed in the second substrate unit to form a cavity in the coverlay, and in step e, a process of manually removing the cut coverlay was performed, and then in step f, a bonding sheet was attached between the first substrate and the second substrate to manufacture a substrate unit through a thermocompression process.

[0096] The conventional process required a manual process for attaching and removing the coverlay film, a separate plating process for adhering the coverlay film to the second substrate, more than two heat-compression processes, and a laser cutting process, which resulted in a large tolerance and the inability to attach a separate coverlay film to the bottom of the first substrate.

[0097] However, according to the MEMS microphone according to the embodiment of the present invention, not only is the entire process simplified compared to the conventional process, but also the solder resist layer is formed on both the upper and lower surfaces of the substrate unit, so that the risk of short circuit is significantly reduced, and since the solder resist layer is arranged by the PSR process rather than the attachment or thermal compression process, it is possible to easily form various circuits as well as sound holes or cavities formed in the substrate unit.

[0098] Additionally, since there is no separate manual or laser cutting process, tolerances are reduced compared to conventional processes, which not only increases product reliability, but also simplifies the process by eliminating the need for a separate plating process to improve adhesion.

[0099] In particular, not only can a solder resist layer be formed on the lower surface of the substrate unit, i.e., the lower surface of the first substrate, but it is also designed to be placed not at the position of the second pad formed on the lower surface of the first substrate but at the position of the second connection circuit, thereby reducing the short risk and improving the degree of freedom in circuit design.

[0100] In addition, by forming multiple connection lines on the first solder resist layer through plating, the combination of the MEMS structure, signal processing element, and housing is performed more stably, and the sensitivity change of the MEMS microphone is reduced, thereby enabling stable product use.

[0101] Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from the essential characteristics of the above-described description. Therefore, the disclosed methods should be considered illustrative rather than restrictive. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. First substrate; A second substrate laminated on the first substrate; A solder resist layer disposed on the upper surface of the second substrate and the lower surface of the first substrate; A housing disposed on the upper part of the second substrate and having a receiving space formed therein; A MEMS structure disposed within the receiving space on the upper portion of the second substrate; and A MEMS microphone including a signal processing element disposed within the receiving space on the upper portion of the second substrate and spaced apart from the MEMS structure.

2. In paragraph 1, The above solder resist layer is, A first solder resist layer disposed on the upper surface of the second substrate; and A second solder resist layer is disposed on the lower surface of the first substrate, A MEMS microphone in which the above MEMS structure and the signal processing element are arranged on the upper surface of the first solder resist layer.

3. In paragraph 2, A MEMS microphone having a plurality of connecting lines formed on the upper surface of the first solder resist layer for mounting at least one of the housing, the MEMS structure, and the signal processing element.

4. In paragraph 3, The above-mentioned plurality of connecting lines are MEMS microphones arranged in the etching area of ​​the first solder resist layer.

5. In paragraph 3, The above multiple connecting lines are, A first connecting line to which solder is applied to join the above MEMS structure, and A MEMS microphone comprising at least one of the second connecting lines providing a guide for the MEMS structure to be settled.

6. In paragraph 5, The above multiple connecting lines are, A third connecting line that provides a guide for the above signal processing means to be installed, and A MEMS microphone further comprising at least one of a fourth connecting line providing a guide for the housing to be seated.

7. In paragraph 2, The second substrate includes a first cavity exposing the first pad of the first substrate upward, A MEMS microphone, wherein the first solder resist layer includes a second cavity having a shape corresponding to the cavity.

8. In paragraph 2, The first substrate has one or more second pads and one or more second connection circuits connecting the second pads arranged on the lower surface thereof, A MEMS microphone in which the second solder resist layer does not cover the second pad but covers the second connection circuit.

9. In paragraph 1, The above solder resist layer is a MEMS microphone containing polyimide.

10. In paragraph 1, A MEMS microphone further comprising a bonding sheet having a shape corresponding to the lower surface of the second substrate and bonding the first substrate and the second substrate.

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