MEMS microphone

Abstract

An MEMS microphone according to an embodiment of the present invention comprises: a first substrate; a second substrate stacked on the first substrate; a solder resist layer disposed on at least one of the upper surface and lower surface of the second substrate; an MEMS structure disposed on the second substrate; and a capacitor disposed on the second substrate to be spaced apart from the MEMS structure.

Description

MEMS Microphone

[0001] The present invention relates to a MEMS microphone, and more specifically, to a MEMS microphone capable of process simplification and a flip-chip structure.

[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 capable of process simplification and a flip-chip structure.

[0006] In order to solve the above technical problem, a MEMS microphone according to one embodiment of the present invention may include a first substrate; a second substrate laminated on the first substrate; a solder resist layer disposed on at least one of an upper surface or a lower surface of the second substrate; a MEMS structure disposed on the second substrate; and a capacitor disposed on the second substrate and spaced apart from the MEMS structure.

[0007] Additionally, the second substrate may include a first cavity exposing the first main pad of the first substrate upward, and the solder resist layer may include a second cavity having a shape corresponding to the cavity.

[0008] In addition, the solder resist layer may include 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 second substrate.

[0009] Additionally, the solder resist layer may include polyimide.

[0010] Additionally, the polyimide may include a photosensitive polyimide.

[0011] Additionally, the solder resist layer may include a photosensitive coverlay film.

[0012] In addition, the photosensitive coverlay film may be disposed on at least one of the upper and lower surfaces of the second substrate and attached to the second substrate through an exposure process and an etching process.

[0013] In addition, a MEMS microphone according to another embodiment of the present invention includes a first substrate; a second substrate laminated on the first substrate; a solder resist layer disposed on at least one of an upper surface or a lower surface of the second substrate; a MEMS structure disposed on the second substrate; and a capacitor disposed on the second substrate and spaced apart from the MEMS structure, wherein the second substrate may include a base substrate and at least one independent piece disposed spaced apart from the base substrate by a space.

[0014] In addition, the MEMS microphone includes at least one first coupling hole at a position that overlaps the upper surface of the piece in the vertical direction.

[0015] Additionally, the first solder resist layer can cover the separation space to support the arrangement of the base substrate and the piece.

[0016] Additionally, the second solder resist layer may overlap the lower surface of the piece in a vertical direction and include one or more second bonding holes having a larger size than the first bonding hole.

[0017] In addition, a bonding sheet having a shape corresponding to the upper surface of the first substrate and bonding the first substrate and the second solder resist layer may be further included.

[0018] The MEMS microphone according to embodiments of the present invention has the following effects.

[0019] According to one embodiment of the present invention, a coverlay film is attached to a second substrate laminated on an existing first substrate through a thermocompression process, and then a manual process of performing a laser cutting process to form a cavity and removing residue, and an etching process performed by placing a dry film to form a pattern of the second substrate are required, but these processes are omitted, and in the process of performing the etching process for forming a circuit pattern of the second substrate, the dry film is replaced with a photosensitive coverlay film, and etching and solder resist placement are performed simultaneously, so that the thermocompression process and the manual process for manufacturing the second substrate can be omitted, thereby simplifying the process and reducing the process cost. In addition, since the manual process is omitted, the tolerance according to circuit formation is reduced, and thus the defect rate such as short circuits is reduced.

[0020] In addition, when the heat-compression process of such a coverlay film is involved, a separate plating process is performed to improve the adhesion between the second substrate and the coverlay film, but the etching process improves the adhesion between the second substrate and the solder resist layer, so there is a process improvement effect.

[0021] In addition, by forming a solder resist layer on the upper surface of the second substrate, the stress caused by heat generated in the second substrate during the packaging process of the MEMS microphone is prevented from being transferred to the device, thereby reducing the thermal stress received by the device and reducing the defect rate. Specifically, the effect is to prevent the heat generated in each thermal curing or high-temperature reflow process for placing the MEMS structure, signal processing device, and housing on the second substrate during the packaging process from being transferred to each device.

[0022] In addition, since the risk of a short circuit between the first main pad and connection circuit formed on the upper surface of the first substrate and the lower surface of the second substrate is eliminated by forming a solder resist layer on the lower surface of the second substrate, the degree of freedom in circuit design of the first main pad and connection circuit on the upper surface of the first substrate increases. As the degree of freedom in circuit design increases, the circuit of the first substrate can be simplified, eliminating the need to form a separate resist layer on the lower surface of the first substrate. This not only simplifies the process but also prevents solder contamination when mounted on an external substrate.

[0023] According to another embodiment of the present invention, by forming a pattern on a second substrate using a conventional process and then disposing a solder resist layer on the upper and lower surfaces of the second substrate through a separate process, one or more pieces forming a separate circuit inside the second substrate can be formed. In this case, a flip-chip structure is possible by mounting a device on each piece, and since separate wire bonding is eliminated, not only is the wire cost significantly reduced, but also since each piece functions as a separate circuit, there is no need to form a separate pattern or circuit. In addition, since wire bonding is eliminated and the device is mounted directly on the second substrate, the circuit length is reduced, which has the effect of reducing the influence of impedance and parasitic capacitance.

[0024] Figures 1 to 3 are drawings illustrating the structure of a MEMS microphone according to one embodiment of the present invention.

[0025] FIG. 4 is a drawing illustrating a substrate stacking structure of a MEMS microphone according to one embodiment of the present invention.

[0026] FIG. 5 is a drawing showing the upper and lower surface structures of the first substrate of a MEMS microphone according to one embodiment of the present invention.

[0027] FIG. 6 and FIG. 7 are drawings for explaining the process structure of a MEMS microphone according to one embodiment of the present invention.

[0028] FIG. 8 and FIG. 9 are drawings showing the structure of a MEMS microphone according to another embodiment of the present invention.

[0029] Fig. 10 is a drawing for explaining the process structure of a MEMS microphone according to another embodiment of the present invention.

[0030] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] FIGS. 1 to 3 are drawings illustrating the structure of a MEMS microphone according to one embodiment of the present invention, FIG. 4 is a drawing illustrating the substrate stacking structure of a MEMS microphone according to one embodiment of the present invention, and FIG. 5 is a drawing illustrating the upper and lower surfaces of the first substrate of a MEMS microphone according to one embodiment of the present invention.

[0040] Referring to FIGS. 1 to 5, a MEMS microphone according to one embodiment of the present invention may include a first substrate (100), a second substrate (200), a solder resist layer (700), a MEMS structure (300), a signal processing element (500), a capacitor (600), and a housing (400).

[0041] 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.

[0042] 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.

[0043] The first substrate (100) may include a via hole (120). 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 (120). Here, the via hole (120) 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%.

[0044] 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.

[0045] The first substrate (100) may include an acoustic hole. The cross-sectional area of ​​the acoustic hole may be circular, but is not limited thereto. A MEMS structure (300) may be arranged above the acoustic hole formed in the first substrate (100).

[0046] A first substrate (100) may be electrically connected to a signal processing element and a capacitor. 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 (111a), and a plurality of vias. The pads may vertically overlap with the vias and contact them, or may contact an external substrate or element. The connection circuits (111a) may connect between pads arranged on the same layer. The vias may be formed in via holes (120) that penetrate 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 main pads (110).

[0047] Main pads (110) and connection circuits (111a) having the same or different shapes may be formed on the upper surface (100a) and the lower surface (100b) of the first substrate (100). A plurality of main pads (110) and connection circuits (111a) may be formed on the upper surface (100a) and the lower surface (100b) of the first substrate (100). The main pads (110) may include a first main pad (110a) disposed on the upper surface of the first substrate (100) and a second main pad (110b) disposed on the lower surface of the first substrate (100). In this case, the first main pad (110a) is a pad to which a signal processing element (500) and a capacitor (600) can be electrically connected, and the second main pad (110b) is a pad to which an external element can be electrically connected.

[0048] In this case, a plurality of first main pads (110a) formed on the upper surface (100a) of the first substrate (100) can be electrically connected to a plurality of second main pads (110b) formed on the lower surface (100b) of the first substrate (100). The first main pads (110a) can be electrically connected to the second main pads (110b) through vias. In addition, the plurality of first main pads (110a) can be arranged at the same position as the plurality of second main pads (110b) or can be arranged at different positions. That is, there is no limitation on the arrangement as long as the first main pads (110a) are electrically connected to the second main pads (110b).

[0049] A connection circuit (111a) may be arranged on the upper surface of the first substrate (100). The connection circuit (111a) may be a pattern circuit for electrically connecting the first main pad (110a) and the second main pad (110b). The connection circuit (111a) may extend from the first main pad (110a) to an arbitrary position and may be electrically connected to the second main pad (110b) through a via. The connection circuit (111a) may have a pattern shape designed to allow the first main pad (110a) and the second main 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 main pad (110), and the signal processing element (500) and the capacitor (600) can be electrically connected to the second main pad (110b) through the first main pad (110a). In addition, the first main pad (110a) to which the connection circuit (111a) is extended may not have a via hole (120) formed therein as needed, and in this case, a via hole (120) may be formed in the connection circuit (111a).

[0050] 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 ridge substrate to supplement the rigidity of the second substrate (200), and may include, for example, one or more of a metal plate, a SUS, and a reinforcing plate. SUS is a type of steel that mixes chromium 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.

[0051] The second substrate (200) may include one or more cavities (210). The second substrate (200) is disposed on the upper portion of the first substrate (100), and the first substrate (100) may be exposed to the upper portion of the second substrate (200) through the cavity (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 main pad (110) disposed in the space where the cavity (210) of the second substrate (200) is formed. In this case, since the upper surface (100a) of the first substrate (100) is disposed on the lower surface of the second substrate (200), the first main pad (110a) formed on the upper surface (100a) of the first substrate (100) may be exposed to the upper portion of the second substrate (200) through the cavity (210) of the second substrate (200). The first main 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).

[0052] 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).

[0053] 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.

[0054] The housing (400) is a means that is placed on the upper part of the second substrate (200) and forms 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 bonded to the upper surface of the second substrate (200) to form the accommodation space. In detail, the housing (400) may be bonded to the lower surface of the housing (400) on the upper part of the second substrate (200), so that the housing and the second substrate (200) may be bonded. Depending on the size (Back Volume) of the accommodation space formed inside the housing (400), the signal-to-noise ratio (SNR), the power supply rejection (PSR) related to power noise suppression, and the power supply rejection ratio (PSRR) may be improved, thereby determining the noise state. A detailed description thereof will be given later.

[0055] 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 can be made 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.

[0056] 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).

[0057] 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) through a signal processing element (500). In addition, an sound hole (360) communicating with the sound hole can be formed in the body (310). The body (310) can be directly connected to the second substrate (200), but if necessary, the body (310) can be directly connected to the first substrate (100) through the cavity (210) of the second substrate (200), and there is no limitation thereto.

[0058] 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).

[0059] 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).

[0060] 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.

[0061] 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.

[0062] 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 main 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 main 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 main pad (110a) and connection circuit (111a) formed on the upper surface of the first substrate (100), and can be transmitted to the outside that requires the signal through the second main pad (110b) formed on the lower surface of the first substrate (100).

[0063] 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.

[0064] 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.

[0065] 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).

[0066] 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 main pad (110a) or the connection circuit (111a) formed on the first substrate (100) exposed through the cavity of the second substrate (200) via the wire.

[0067] 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.

[0068] The solder resist layer (700) may be formed in a form in which it is laminated on the upper and lower surfaces of the second substrate (200) to surround the second substrate (200). The solder resist layer (700) may include polyimide. The solder resist layer (700) may include photosensitive polyimide (PSPI). 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, and the like, and may further include glass fiber or GCP (Glass Core Primer) according to an embodiment. That is, the solder resist layer (700) is not limited in its material as long as an insulating material capable of performing insulation is used.

[0069] The solder resist layer (700) may include a photo-imageable cover lay film (PIC). The photo-imageable cover lay film may include a liquid photo-imageable polyimide film. Since the solder resist layer (700) is laminated in the form of a cover lay film, the manufacturing process is simplified and the process cost is reduced.

[0070] The solder resist layer (700) may be disposed on the upper surface of the second substrate (200) or the upper and lower surfaces of the second substrate (200). The solder resist layer (700) may be laminated only on the upper surface of the second substrate (200), or may be laminated on both the upper and lower surfaces of the second substrate (200). The solder resist layer (700) may have a plate shape in order to be laminated on the second substrate (200) and may be disposed to have a shape corresponding to the shape of the second substrate (200). 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 second substrate (200). In this case, the second solder resist layer (720) may be selectively laminated.

[0071] 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 order of the first solder resist layer (710), the second substrate (200), and the first substrate (100) from the upper side to the lower side.

[0072] At least one of a MEMS structure (300), a signal processing element (500), and a capacitor (600) may be disposed on the first solder resist layer (710). When the first solder resist layer (710) is disposed on the second substrate (200), at least one of the MEMS structure (300), the signal processing element (500), and the capacitor (600) may be disposed on the upper surface of the first solder resist layer (710). In this case, the MEMS structure (300), the signal processing element (500), and the capacitor (600) may be connected to the second substrate (200) through a mounting hole formed in the first solder resist layer (710) or an unformed area of ​​the first solder resist layer (710). During the process of laminating a MEMS structure (300), a signal processing element (500), and a capacitor (600) on a 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), causing its shape to be deformed or damaged, resulting in the generation of noise. As a result, the SNR, PSR, and PSRR may be reduced, or the acoustic signal sensing of the MEMS microphone may operate abnormally. 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).

[0073] In addition, the solder resist layer (700) may be disposed on the upper and lower surfaces of the second substrate (200), respectively. In this case, the substrate of the MEMS microphone may be laminated in the following order from the upper side to the lower side: the first solder resist layer (710), the second substrate (200), the second solder resist layer (720), and the first substrate (100). In this case, a bonding sheet (800) for adhesion may be disposed between the second solder resist layer (720) and the second substrate (100).

[0074] The first solder resist layer (710) may be disposed on the upper surface of the second substrate (200). A description of the structural effect of the first solder resist layer (710) is omitted as described above.

[0075] When the second solder resist layer (720) is placed on the lower surface of the second substrate (200), the risk of a short circuit due to contact between the first main pad (110a) and the connection circuit (111a) formed on the upper surface of the first substrate (100) by the second solder resist layer (720) and the lower surface of the second substrate (200) can be reduced. In the past, in order to avoid such risks, pads were placed on the upper surface of the first substrate (100) and pads and connection circuits (111a) were placed on the lower surface of the first substrate (100), thereby preventing short circuits between the upper surface of the first substrate (100) and the lower surface of the second substrate (200), but there was a problem that the degree of freedom in circuit design was very low. However, in the MEMS microphone according to one embodiment of the present invention, since the second solder resist layer (720) is placed on the lower surface of the second substrate (200), the risk of short circuits is reduced, so the design of pads and connection circuits (111a) on the upper surface of the first substrate (100) can be freely performed, thereby providing the effect of high degree of freedom in circuit design. In addition, since the arrangement of the connection circuit (111a) on the lower surface of the first substrate (100) is eliminated or reduced, not only is the risk of a short circuit due to solder contamination reduced when the MEMS microphone is externally mounted without forming a separate solder resist on the lower surface of the first substrate (100), but the process of forming the solder resist on the lower surface of the first substrate (100) is omitted, thereby simplifying the process procedure and reducing the process cost.

[0076] The solder resist layer (700) may include one or more cavities. The first solder resist layer (710) and the second solder resist layer (720) may include one or more cavities. The cavities formed in the solder resist layer (700) 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 solder resist layer (700) may be in communication with each other. The first substrate (100) may be exposed to the upper portion of the second substrate (200) through the spaces communicated by the cavities of the first solder resist layer (710), the second substrate (200), and the second solder resist layer (720). 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 solder resist layer (700).

[0077] 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.

[0078] A MEMS microphone according to one embodiment of the present invention may further include a bonding sheet (800) for bonding the upper surface of the first substrate (100) and the lower surface of the solder resist layer (700) when the solder resist layer (700) is disposed on the lower surface of the second substrate (200). The bonding sheet (800) may bond the lower surface of the second solder resist layer (720) disposed on the lower surface of the second substrate (200) and the upper surface of the first substrate (100). The bonding sheet (800) may have a shape corresponding to the shape of the second solder resist layer (720).

[0079] Hereinafter, a process for manufacturing a substrate of a MEMS microphone according to an embodiment of the present invention will be described. Referring to FIG. 6, a MEMS microphone according to an embodiment of the present invention can be manufactured according to steps A to C. First, step A may include a step (A-1) of preparing a first substrate (100), a step (A-2) of preparing a bonding sheet (800), and a step (A-3) of preparing a second substrate (200) and disposing a solder resist layer (700). After step A, step B may include a step (B-1) of performing a thermocompression process to adhere a bonding sheet (800) to the upper surface of the first substrate (100), and a step (B-2) of performing a thermocompression process to adhere the second substrate (200) and the solder resist layer (700) manufactured in step A-3 to the upper surface of the substrate manufactured in step B-1, i.e., the upper surface of the bonding sheet (800). After this, in step C, plating is performed on the substrate manufactured through step B-2, thereby finally manufacturing a MEMS microphone substrate. After this, a step of packaging the MEMS microphone substrate can be performed.

[0080] Below, step A-3 of placing a solder resist layer (700) on a second substrate (200) is described in detail. Fig. 7 is a process of placing a solder resist layer (700) on a second substrate (200) of a MEMS microphone according to one embodiment of the present invention.

[0081] First, a solder resist layer (700) including a photosensitive coverlay film can be attached to the upper and lower surfaces of a second substrate (200) by roll lamination (a). A masking process can be performed to form a desired pattern or cavity (210) on the upper and lower surfaces of the second substrate (200) to which the photosensitive coverlay film is attached (b). Afterwards, a pattern can be formed by removing the solder resist layer (700) at the mask placement position through an exposure process (c). If an etching process is performed in that state, the second substrate (200) in an area where the solder resist layer (700) is not present can be etched by an etchant. If the solder resist layer (700) is arranged in a direction that overlaps the upper and lower surfaces of the second substrate (200), etching is not performed. If the solder resist layer (700) is arranged only on one side without overlapping the upper and lower surfaces of the second substrate (200), half-etching is performed on the area where it is not arranged. If the solder resist layer (700) is not arranged in the upper and lower surfaces of the second substrate (200), full-etching can be performed on the area where it is not arranged. By the above process, a solder resist layer (700) having a shape corresponding to the upper and lower surfaces of the second substrate (200) can be formed.

[0082] FIG. 8 and FIG. 9 are drawings illustrating the structure of a MEMS microphone according to another embodiment of the present invention.

[0083] Referring to FIGS. 8 and 9, a MEMS microphone according to another embodiment of the present invention may include a first substrate (100), a second substrate (200), a solder resist layer (700), a MEMS structure (300), a signal processing element (500), a capacitor (600), and a housing (400). Duplicate descriptions of common components with respect to the MEMS microphone of the aforementioned embodiment are omitted, and only different components are described below.

[0084] The first substrate (100) may include a first main pad (110a) and a connection circuit (111a) on the upper surface of the first substrate (100), and a second main pad (110b) may be formed on the lower surface. In this case, the first main pad (110a) and the connection circuit (111a) may be positioned on the lower surface of the second substrate (200) without being exposed because a separate cavity is not created in the second substrate (200) to be described later. The first main pad (110a) and the connection circuit (111a) may be electrically connected to the second substrate (200).

[0085] The second substrate (200) may be laminated to be placed on the first substrate (100) and may include a base substrate having a plate shape and one or more pieces (220) placed so as to be spaced apart from the base substrate. Here, the base substrate is defined as a substrate in an area of ​​the second substrate (200) excluding the piece (220), and the piece (220) may be placed in the form of an independent substrate that is spaced apart from the base substrate or another piece (220) in the second substrate (200). The shape of the second substrate (200) may be maintained by fixing the piece (220) between the base substrate or the piece (220) by a solder resist layer (700). Here, the spaced apart between the base substrate or the piece (220) and the piece (220) is defined as a spaced apart space.

[0086] The piece (220) may be formed according to a set pattern. In this case, the arrangement of the first main pad (110a) and the connection circuit (111a) formed on the upper surface of the first substrate (100) may be determined according to the arrangement pattern of the piece (220). A MEMS structure (300), a signal processing element (500), and a capacitor (600) may be mounted on the piece (220) and connected in a flip-chip form. In this case, the MEMS structure (300), the signal processing element (500), and the capacitor (600) may be mounted on separate pieces (220) and electrically connected to the first substrate (100) in an independent form. That is, as the pieces (220) are arranged separately, each piece (220) may be implemented as an independent circuit.

[0087] 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 second substrate (200). Only the differences in the material or structure of the solder resist layer (700) will be described.

[0088] The first solder resist layer (710) may have one or more first coupling holes (711) arranged therein. The first solder resist layer (710) may have one or more first coupling holes (711) arranged at positions corresponding to positions where pieces (220) of the second substrate (200) are arranged. Accordingly, the first coupling hole (711) may be arranged at a position overlapping the piece (220) in the vertical direction. The size of the first coupling hole (711) may be smaller than the size of the piece (220) at the position where it overlaps in the vertical direction. Accordingly, the first solder resist layer (710) may be formed to cover the separation space, and may support the base substrate and the piece (220) or between the pieces (220) to maintain the shape of the second substrate (200). The MEMS structure (300), signal processing element (500), and capacitor (600) can be mounted on the second substrate (200) through the first coupling hole (711).

[0089] The second solder resist layer (720) may have one or more second coupling holes (721) arranged therein. The second solder resist layer (720) may have one or more second coupling holes (721) arranged at positions corresponding to the positions of the pieces (220) of the second substrate (200). Accordingly, the second coupling holes (721) may be arranged at positions that overlap the pieces (220) in the vertical direction, so that the first coupling holes (711), the pieces (220), and the second coupling holes (721) may be arranged to be stacked in that order. The size of the second coupling holes (721) may be smaller than the size of the pieces (220) at the positions where they overlap in the vertical direction. Accordingly, the second solder resist layer (720) is formed to cover the separation space, and can serve to maintain the shape of the second substrate (200) by supporting the base substrate and the piece (220) or between the pieces (220). In addition, the second coupling hole (721) can have a size larger than the size of the first coupling hole (711). The piece (220) of the second substrate (200) and the first main pad (110a) formed on the upper surface of the first substrate (100) can be brought into contact with each other and electrically connected by the second coupling hole (721).

[0090] The bonding sheet (800) can be disposed between the second solder resist layer (720) and the first substrate (100) to adhere the second solder resist layer (720) to the first substrate (100). The bonding sheet (800) can be formed to have the same pattern arrangement (810) as the pattern arrangement of the first main pad (110a) and the connection circuit (111a) formed on the upper surface of the first substrate (100).

[0091] Below, a process for manufacturing a substrate of a MEMS microphone according to another embodiment of the present invention is described. Except for step A-3, the remaining steps in steps A through C of the MEMS microphone process according to one embodiment of the present invention are identical, and therefore only that step will be described.

[0092] Referring to Fig. 10, first, a dry film can be attached to the upper and lower surfaces of a second substrate (200) by roll lamination (a). A masking process can be performed to form a desired pattern or cavity on the upper and lower surfaces of the second substrate (200) to which the dry film is attached (b). Afterwards, a pattern can be formed by removing the dry film at the mask placement position through an exposure process (c). At this stage, half-etching can be performed through masking on the upper surface to form a piece (220). Afterwards, when the etching process is performed, the second substrate (200) in the area where the dry film is not present can be etched by an etchant (d). Afterwards, the dry film can be peeled off to form a second substrate (200) having a pattern formed thereon. Here, the second substrate (200) may be a half-etched substrate.

[0093] The following describes the process further. A dry film may be attached to the upper surface of the second substrate (200) on which a pattern is formed, and a photosensitive coverlay film may be attached to the lower surface of the second substrate (200) to form a second solder resist layer (720) (f). In step (f), the upper dry film serves to maintain the alignment of the pieces (220) of the second substrate (200), and the photosensitive coverlay film may be used to form the second solder resist layer (720) to perform full etching. Thereafter, a pattern or cavity may be formed in a desired area on the lower surface of the second substrate (200) to which the photosensitive coverlay film is attached, and a masking process may be performed on an area for forming a second joining hole (721) in the second solder resist layer (720) (g). After this, a pattern can be formed on the lower surface of the second substrate (200) by removing the second solder resist layer (720) at the mask placement location through an exposure process (h). After this, when etching is performed, additional half-etching is performed on the lower surface of the area where half-etching was performed on the upper surface in step (c) of the second substrate (200), resulting in a full-etched form, so that a piece (220) can be formed on the second substrate (200) (i). After this, the dry film attached to the upper surface of the second substrate (200) is peeled off (j), and a photosensitive coverlay film can be attached to the upper surface of the second substrate (200) (k). If the photosensitive coverlay film is attached to the upper surface of the second substrate (200) before step (k), there is a concern that additional half-etching of the masked area may occur, so the photosensitive coverlay film can be attached to the upper surface of the second substrate (200) after step (j) of peeling the dry film. After this, a masking process can be performed on an area for forming a first bonding hole (711) of a first solder resist layer (710) on the upper surface of the second substrate (200) (l), and by removing the photosensitive coverlay film at the mask arrangement position through an exposure process, the first solder resist layer (710) can be arranged on the upper surface of the second substrate (200) to support the piece (220) of the second substrate (200).In this case, a first bonding hole (711) can be formed in the first solder resist layer (710) (m).

[0094] 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 at least one of the upper or lower surfaces of the second substrate; A MEMS structure disposed on the second substrate; and A MEMS microphone including a capacitor disposed on the second substrate and spaced apart from the MEMS structure.

2. In paragraph 1, The second substrate includes a first cavity exposing the first main pad of the first substrate upward, A MEMS microphone, wherein the solder resist layer includes a second cavity having a shape corresponding to the cavity.

3. 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 MEMS microphone including a second solder resist layer disposed on the lower surface of the second substrate.

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

5. In paragraph 4, The above polyimide is a MEMS microphone including a photosensitive polyimide.

6. In paragraph 1, A MEMS microphone wherein the solder resist layer includes a photosensitive coverlay film.

7. In paragraph 6, A MEMS microphone in which the photosensitive coverlay film is disposed on at least one of the upper and lower surfaces of the second substrate and attached to the second substrate through an exposure process and an etching process.

8. In paragraph 3, The above second substrate, A MEMS microphone comprising a base substrate and at least one independent piece spaced apart from the base substrate by a space 9. In paragraph 8, The first solder resist layer includes at least one first bonding hole at a position overlapping the upper surface of the piece in the vertical direction, A MEMS microphone in which the first solder resist layer covers the separation space and supports the patch of the base substrate and the piece.

10. In paragraph 9, A MEMS microphone in which the second solder resist layer overlaps the lower surface of the piece in a vertical direction and includes at least one second coupling hole having a larger size than the first coupling hole.

Images