Component with a chip in a cavity and a stress-reduced mounting

Abstract

Component (B) comprising: - a chip (C1) with an electrical connection (EA), - a housing (G) with a cavity (H) in which the chip is arranged and an electrical conductor (EL1), - a mechanically flexible conductor connector (LV) connecting the electrical connection (EA) of the chip (C1) to the electrical conductor (EL1), which has a lower stiffness than the chip (C1) and a higher stiffness than a bond wire and which is mechanically deformable, wherein: - the housing (G) has an opening (OF) through which the chip (C1) is in contact with the atmosphere surrounding the component (B), and: - the chip (C1) is a sensor, - the chip (C1) is operated at an electrical, mechanical or acoustic operating frequency, and: - the natural frequency of the mechanical oscillator consisting of the chip (C1) and the mechanically flexible conductor connectors (LV) is less than 0.8 times the operating frequency of the chip (C1).

Description

The invention relates to components having a chip which is arranged in a cavity and fastened in a voltage-reduced manner.Electrical components, in particular those which are intended to be used in portable devices, are intended to be as robust as possible, small-sized and cost-effective to produce.The publication US 2009 / 01 27 697 A1 discloses an electrical component in a housing.DE 10 2004 044 982 A1 relates to a pressure sensor device having a receptacle for receiving a pressure sensor.DE 43 06 268 A1 relates to a housing for gas sensors, in which a sensor is arranged in a cantilevered manner in the housing, fastened merely via bonding wires.US 2007 / 00 69 354 A1 relates to a semiconductor sensor device.U.S. Pat. No. 6,482,013 B2 relates to a contact spring on which a component can be arranged.An object of the present invention is to specify components with a chip which is arranged in a cavity and fixed in a voltage-reduced manner and has improvements over known components. In particular, an improved chip is intended to cover a greater field of application or the chip arranged in the cavity is intended to be better protected against external mechanical influences.These objects are achieved by the structural elements according to the independent claims. The dependent claims indicate further and advantageous embodiments.In one variant, the component comprises a chip with an electrical connection, a housing with a cavity and a mechanically flexible line connector. The chip is disposed in the cavity of the package. The housing further comprises an electrical lead. The mechanically flexible line connector connects the electrical terminal of the chip to the electrical line. The mechanically flexible line connector has a lower stiffness than the chip and is mechanically deformable. The chip is substantially fixed by the flexible line connector. The housing of the component has an opening through which the cavity is in contact with the atmosphere surrounding the component. The chip is a sensor.The chip can be fixed exclusively by the flexible line connector. The flexible lead connector has higher rigidity than a conventional bonding wire.The above-cited publication discloses a component with a chip in a cavity. The chip is connected to electrical contacts of the housing by a mechanically flexible line connector. The component of the present invention is improved over components known from the prior art in that the component can be used as a sensor because of the opening in the housing, wherein the sensor is in contact with the atmosphere surrounding the component via the housing opening and can detect corresponding parameters such as temperature, pressure, air humidity, sound pressure, gas composition or the like.In various embodiments, the chip is a pressure sensor, a sound sensor, an optical sensor or a sensor for detecting a gas composition.In one embodiment, the diameter of the opening is less than 100 μm. It is also possible that the diameter of the opening is substantially 100 μm.In an alternative variant, the component comprises a chip with an electrical connection. The component further comprises a housing having a cavity, an electrical line and a cover. The chip is disposed in the cavity and the lid covers the cavity. The component further comprises a mechanically flexible line connector, which connects the electrical terminal of the chip to the electrical line. The mechanically flexible line connector has a lower stiffness than the chip and is mechanically deformable. The cover of the housing comprises a polymer layer having an optical absorption factor of >95% in the wavelength range between 400 nm and 1100 nm.Such a component, the cover of which has a high optical absorption factor in the visible wavelength range, is suitable for receiving light-sensitive chips. In particular, chips comprising a semiconducting material may benefit from reduced light incidence. Due to the width of the energy gap of semiconducting material, such chips can react with disturbances to light incidence.Alternatively, it is also possible to use a semiconductor chip or another chip reacting to optical stimuli, for example if the cover has a defined light incidence opening.In a third variant, the component comprises a chip with an electrical connection and a housing. The package further includes a cavity in which the chip is disposed and an electrical lead. The component further has a mechanically flexible line connector, which connects the electrical terminal of the chip to the electrical line. The mechanically flexible line connector has a lower stiffness than the chip and is mechanically deformable. The line connector is secured at two spaced apart locations on the inside of the cavity.The number of mechanical fixings can be different-for example depending on the selected variant.The mechanically flexible line connector fulfils two tasks in all variants: on the one hand, it serves for the electrical interconnection of the chip with the electrical line of the component. On the other hand, it serves as a mechanical fastening of the chip in the cavity of the housing. The low stiffness of the flexible lead connector reduces mechanical stresses between the chip and the package. In particular, mechanical stresses which occur on account of different coefficients of thermal expansion can thus be easily reduced. The use in mobile devices often requires increased mechanical stability and robustness of the components used. Mobile devices are particularly at risk of dropping or jamming.By attaching the flexible line connector to the inside of the cavity at two spaced apart locations, its mechanical stability is improved without stress jeopardizing the chip. In particular, a mechanically flexible line connector better resists torsional forces without sacrificing its flexibility with respect to bending.Since the flexible line connector serves not only as a mechanical fastening but also as a switching element, the reliability is increased if the flexible line connector should break at one location. The redundancy due to the second fastening point, which can also be an electrical contact point, thus increases the reliability.In one embodiment of the above-mentioned components, the inside of the cavity, the surfaces of the chip or the line connector are covered with a polymer film of a thickness <=10 μm. It is in particular possible that the inside of the cavity, the surfaces of the chip and the line connector are covered with a polymer film. A thin polymer film acts as a passivation layer and can protect surfaces arranged in the interior of the cavity from corrosion or contamination by substances located in the surrounding atmosphere. This is relevant in that the cavity in the component can be connected to the surrounding atmosphere via an opening in the housing. The polymer film may comprise parylene.In one embodiment, the housing comprises a ceramic, e.g., an HTCC (High Temperature Co-fired Ceramics) or an LTCC (Low Temperature Co-fired Ceramics).In one embodiment of this embodiment, the package comprises multi-layer HTCC or multi-layer LTCC. Metallization levels are arranged between dielectric layers of the HTCC or LTCC. The metallization planes overlap in total with the base area of the cavity to an extent of at least 80% of the base area of the cavity. Metals have a high degree of absorption in the visible optical wavelength range. Even if the ceramic material is highly transparent, for example due to the walls being made very thin, good optical shielding or good RF shielding is still provided.The hollow space can be covered on the inside with an additional metallization layer.In addition, passive circuit components such as capacitive elements, inductive elements or resistive elements may be integrated as structured metallizations in the metallization levels.The chip is operated at an electrical, mechanical or acoustic operating frequency. The chip can be operated, for example, at a mechanical working frequency and can be a rotation rate sensor. The chip and the one or more mechanical flexible line connectors necessarily form a mechanical oscillator; due to the mechanically flexible mounting of the chip, the chip can oscillate as suspended from a spring. The natural frequency of the mechanical oscillator consisting of the chip and the mechanically flexible line connectors is here less than 0.8 times the operating frequency of the chip. If the chip is a MEMS chip and comprises vibrating component structures or component structures that can be excited to vibrations, it is provided to select the natural frequencies of the chip systems with line connectors on the one hand and the component structures on the other hand such that the coupling of the vibration modes of these vibrations is minimized.In one embodiment, a further chip and a further electrical line are arranged in the cavity. The further chip is connected to the electrical line or the further electrical line.It may be preferred to arrange more than one chip in the cavity. In particular if the component is to function as a sensor, it is advantageous to arrange an ASIC chip (ASIC= Appli Specific Integrated Circuit= Anwendungs Specific Integrated Circuit) in addition to a MEMS chip which has electromechanical component structures. Then, both chips, e.g. the MEMS chip and the ASIC chip, can be interconnected with one another.In one embodiment, an ASIC chip or a MEMS chip is interconnected as a chip.A method for producing a component according to the invention comprises the steps:providing a first case having a concave portion and an electric lead, a chip having an electric terminal, and a lid,forming a mechanically flexible line connector, which is connected to the electrical line of the first housing part, in the concave section,arranging the chip in the concave portion,connecting and interconnecting the electrical terminal of the chip with the line connector,creating and at least partially closing a cavity by placing the lid over the concave portion.In one embodiment of the production method, a patterned sacrificial layer is produced in the concave section before the line connector is formed. A portion of the lead connector is formed on the sacrificial layer. The sacrificial layer is removed before the line connector is connected and interconnected to an electrical terminal of the chip.Conventional methods for manufacturing devices with flexible line connectors provide for the flexible line connector to be patterned on a sacrificial layer and first for the electrical line connector to be connected to the chip. The sacrificial layer is then removed. The advantage of this sequence is that the sacrificial layer can build up a mechanical counterpressure when the chip is pressed onto the flexible line connector for contacting.However, the invention now provides for the sacrificial layer to be removed first and then for the chip to be arranged and connected in the cavity. The absence of the sacrificial layer is accepted in this case. It is advantageous in this case in the method according to the invention that the chip is not contaminated with chemicals or substances which are used during the removal of the sacrificial layer, for example by etching.In one embodiment, the sacrificial layer is patterned by means of a resist layer, wherein the resist layer comprises a film.In an embodiment, the surfaces of the concave portion, the lead connector, the chip, and at least a part of the lid are covered with a polymer film.The invention is explained in more detail below with reference to exemplary embodiments and schematic figures.The following are shown: FIG. 1 shows a component with a chip in a concave section of a housing, FIG. 2 shows a component with an opening in the housing, FIG. 3 shows a component with a cover, FIG. 4 shows a component with two flexible line connectors, which are each fastened at two spaced-apart points on the inside of the cavity, FIG. 5 shows a housing of multilayer design, FIG. 6 shows a perspective view of the component, FIG. 7 shows a component with a first and a second chip, FIG. 8 shows a component with a protective film on the inside of the cavity, FIG. 9 shows a component having two chips and a flexible line connector which is connected to an electrical line via.FIG. 1 shows a component B with a housing G. An electrical line EL 1 is arranged on the underside of the housing G. A chip C1 is arranged in the cavity H of the housing G. The chip C 1 comprises an electrical terminal EA on its underside. The electrical terminal EA of the chip C 1 is connected to the electrical line EL 1 via a mechanically flexible line connector LV. At the same time, the mechanically flexible line connector serves as a mechanical receptacle of the chip C 1 in the housing G.The cavity of the housing is designed as a cuboidal depression in which the chip C 1 is arranged; the upwardly directed opening of the depression represents the opening OF of the component B.FIG. 2 shows an embodiment of the component B in which the housing G has a lower part and an upper part. In the upper part of the housing G, an opening OF is arranged, via which the chip C 1 is in contact with the atmosphere surrounding the component.FIG. 3 shows a component in which the cavity of the housing G is covered by a cover D. The cover D is not transparent at all or less in the visible wavelength range. The chip C 1 arranged in the cavity is thus well protected from any harmful or undesired light incidence.FIG. 4 shows the arrangement of two mechanically flexible line connectors LV on the lower surface of the cavity H. A chip C 1, characterized by a rectangle drawn with dashed lines, is arranged in the cavity H. On the lower upper side of the cavity, a first electrical line EL 1 and a second electrical line EL 2 are arranged. One of the flexible line connectors LV is connected and connected to one of the electrical lines EL 1, EL 2 at two points S 1, S 2 in each case. Each of the mechanically flexible line connectors LV comprises an electrical terminal EA, which is configured in a planar manner and via which the line connector is connected and connected to an electrical terminal of the chip. The interconnection can be effected, for example, via bumps.FIG. 5 shows a multilayer housing G. Metallization levels ME are arranged between the layers of the housing which are embodied in an electrically insulated manner. Capacitive elements KE and inductive elements IE are structured in metallization planes ME. These impedance elements are connected via vias through the housing G to electrical connections EA on the underside of the housing G or via electrical lines and the mechanically flexible line connector LV to electrical connections on the underside of the chip C 1.FIG. 6 shows a perspective view of the cavity of a component according to the invention. For the sake of better clarity, no chip is arranged in the cavity. Four mechanically flexible line connectors LV are arranged on the underside of the cavity. Each of the mechanically flexible line connectors comprises a connection pad as an electrical connection EA for contacting a chip.To improve the shielding from light or electromagnetic interference, the walls of the cavity may be metallized.FIG. 7 shows an embodiment of the component, wherein a second chip C 2 is arranged in the cavity in addition to the one chip C 1. Both chips are connected and interconnected to the housing G via mechanically flexible line connectors LV. In addition, the first chip C 1 is connected and interconnected to the housing G via a mechanically stiff connection MSV. The chip C 1 may be, for example, an acceleration sensor. It can then be advantageous for the chip C 1 to directly follow all movements of the housing G. For this purpose, the mechanically rigid connection MSV transmits the acceleration forces that the housing G experiences directly on the first chip C 1. Because the chip C 1 is connected to the housing G via a mechanically flexible line connector LV in addition to the mechanically rigid connection MSV, the application of stresses caused by different thermal expansion coefficients is effectively reduced.It is possible that one of the chips is fixed not with a flexible line connector but in a conventional manner-for example by flip-chip connections or by means of an adhesive.Fig. 8 shows an embodiment of the invention, wherein the surface of the cavity is covered with a protective layer S. The protective layer S covers only the inside of the cavity but not the surfaces of the lead connectors and the chip C1. This ensures the sensor functionality of the chip C 1. If a coating on the line connectors, the electrical lines and the chips does not interfere, it is also possible to cover their surfaces with a protective layer.However, all inner surfaces may be covered. Then, a selective covering, which can be complicated in the production process, is not necessary.FIG. 9 shows an embodiment of a component with two chips. One of the chips C 2 is connected to an electrical line EL 1 by means of a flexible line connector LV and via a through-connection DK. The electric line EL 1 is disposed in an inner layer of the multilayer case G. The connection point of the flexible line connector to the housing is arranged directly above the through-connection. It is also possible for the flexible line connector to be configured to be arranged in a straight line and vertically.Components according to the invention are not limited to the described exemplary embodiments. Variations which comprise, for example, still further chips, line connectors, electrical lines or housing parts such as housing lower parts or covers or arbitrary combinations thereof likewise represent exemplary embodiments according to the invention.List of reference charactersB component C 1, C 2 chip D cover DK through-connection EA electrical connection EL 1, EL 2 electrical line G housing H cavity IE inductive element KE capacitive element LV mechanically flexible line connector ME metallization plane MSV mechanically rigid connection OF opening S protective layer / protective film S 1, S 2 fastening points of the line connector on the inside of the cavity

Claims

Component (B) comprising - a chip (C1) having an electrical terminal (EA), - a housing (G) having a cavity (H) in which the chip is arranged and an electrical line (EL1), - a mechanically flexible line connector (LV) which connects the electrical terminal (EA) of the chip (C1) to the electrical line (EL1), which has a lower rigidity than the chip (C1) and a higher rigidity than a bonding wire and which is mechanically deformable, wherein - the housing (G) has an opening (OF) through which the chip (C1) is in contact with the atmosphere surrounding the component (B), and - the chip (C1) is a sensor, the chip (C1) is operated at an electrical, mechanical or acoustic operating frequency, and the natural frequency of the mechanical oscillator consisting of the chip (C1) and the mechanically flexible line connectors (LV) is less than 0.8 times the operating frequency of the chip (C1).Component (B) according to the preceding claim, wherein the chip (C1) is a pressure sensor, a sound sensor, an optical sensor or a sensor for detecting a gas composition.Component according to one of the preceding claims, wherein the diameter of the opening (OF) is <=100 μm.Component according to one of the preceding claims, wherein the cover (D) comprises a polymer layer having an optical absorption degree >95% in the wavelength range between 400 nm and 1100 nm.The device according to any of the preceding claims, wherein the line connector (LV) is fixed at two spaced apart locations on the inside of the cavity (H) and comprises a terminal via which the line connector is connected to the electrical terminal (EA) of the chip.The device according to any of the preceding claims, wherein the inside of the cavity (H) and the surfaces of the chip (C1) and the lead connector (LV) are covered with a polymer film of thickness <=10 μm.The component according to any one of the preceding claims, wherein the housing (G) comprises ceramic, HTCC or LTCC.Component according to the preceding claim, wherein - the housing (G) comprises multilayer HTCC or multilayer LTCC, - metallization levels (ME) are arranged between the layers, and - the metallization levels (ME) overlap the base area of the cavity (H) in total to at least 80% of the base area of the cavity (H).Component according to one of the preceding claims, wherein the cavity (H) is covered on the inside with a metallization layer.Component according to one of the preceding claims, wherein a further chip (C2) and a further electrical line (EL2) are arranged in the cavity (H) and the further chip (C2) is connected to the electrical line (EL1) or the further electrical line (EL2).Component according to one of the preceding claims, wherein an ASIC chip or a MEMS chip is interconnected as chip (C1, C2).

Images