Patent Application
20080192967
This application claims priority of German application No. 10 2007 005 862.6 filed Feb. 6, 2007, which is incorporated by reference herein in its entirety.
The present invention relates to a circuit arrangement, in particular for a hearing device, having an SMD component and a further electronic component. In the present context a hearing device is understood to mean in particular a hearing aid, but can also refer to a headset, earphones and the like.
Hearing aids are wearable hearing devices that are designed to provide hearing assistance to the hearing-impaired. In order to accommodate the numerous individual requirements, different designs of hearing aids are provided, such as behind-the-ear (BTE) hearing aids and in-the-ear (ITE) hearing aids, e.g. including concha hearing aids or completely-in-the-canal (CIC) hearing aids. The hearing aids cited by way of example are worn on the outer ear or in the auditory canal. In addition, however, bone conduction hearing aids and implantable or vibrotactile hearing aids are also available on the market. With said devices, the damaged hearing is stimulated either mechanically or electrically.
The main components of hearing aids essentially include an input transducer, an amplifier and an output transducer. The input transducer is generally a receiving transducer, e.g. a microphone, and/or an electromagnetic receiver, e.g. an induction coil. The output transducer is mostly implemented as an electroacoustic converter, e.g. a miniature loudspeaker, or as an electromechanical converter, e.g. a bone conduction receiver. The amplifier is typically integrated into a signal processing unit. This basic layout is shown in
The principal objective in the continuing development of hearing aids and other hearing devices is their miniaturization. This applies in particular also to the signal processing unit, which is typically mounted on a printed circuit board (PCB substrate). Conversely, a further aim is to integrate more and more functions into a hearing aid, with the result that the space requirement therein increases. In order to avoid having to increase the size of a hearing aid, however, the circuit arrangement must be designed proportionally more compactly.
In order to enable more components to be accommodated on a hearing aid circuit board, it was always necessary in the prior art to increase the size of the surface area of the board accordingly. An improvement in the compactness of the circuit board that was in many cases assembled from integrated circuits and SMD components was not achieved thereby.
An arrangement consisting of a substrate, a semiconductor component disposed thereon and a lead frame mounted in turn thereon is known from the patent specification U.S. Pat. No. 6,472,737 B1. The semiconductor component is connected both to the substrate and to the lead frame by way of bond wires.
The publication DE 40 17 217 A1 also describes an electronic component having a lead frame, a semiconductor chip and a flat capacitor. The flat capacitor is provided with a connecting contact area on both its upper face and its lower face. Furthermore, the capacitor is mounted with its lower face in an electrically conductive connection on the lead frame, and the semiconductor chip is disposed in an electrically conductive connection on the upper face of the capacitor. An electrically conductive adhesive establishes an electrical connection between the semiconductor chip and the capacitor. Bond wires are used for the purpose of electrically contacting the lead frame to the capacitor and the semiconductor chip.
Furthermore, the European patent specification EP 0 575 051 B1 discloses stacked multi-chip modules consisting of semiconductor dice and an interconnect medium which is supported by a mounting surface of a carrier component. The interconnect medium is a connecting substrate which is stacked on a surface of the semiconductor die. The components are electrically connected to one another by means of a wire bonding technique.
Also known from the publication US 2002/0076076 A1 is a condenser microphone assembly. An integrated circuit (IC) or an application-specific integrated circuit (ASIC) can be provided under the base of the microphone assembly.
The object of the present invention is to improve the compactness of a circuit board and in particular a hearing aid circuit board.
This object is achieved according to the invention by means of a circuit arrangement, in particular for a hearing device, having an SMD component and a further electronic component, wherein the SMD component and the electronic component are electrically interconnected by means of a wire bond connection. In this context the term “electronic component” is understood to refer to any active or passive component, such as a printed circuit board, substrate, SMD component, integrated circuit, etc.
Thus, it is advantageously possible to mount SMD components onto virtually any substrates and to realize the electrical contacting thereof in a very compact manner. Moreover, SMD components can be used which generally have smaller dimensions than other comparable components.
Preferably the circuit arrangement has a carrier and, as the further electronic component, a second integrated circuit which is mounted on the carrier, the SMD component being mounted on the second integrated circuit and electrically connected to the second integrated circuit by means of bond wires. A suitable carrier may include, for example, a printed circuit board (PCB), an LTCC substrate and the like.
Alternatively, the circuit arrangement may be equipped with a carrier and a first integrated circuit, mounted directly on the carrier, as well as a second integrated circuit, mounted on the first integrated circuit, and the SMD component, mounted directly on the carrier, the SMD component being electrically connected to the second integrated circuit by means of bond wires.
Space can advantageously be saved by stacking the SMD component or the second integrated circuit onto the first integrated circuit on the printed circuit board or, as the case may be, the carrier. In this way a higher level of miniaturization can be achieved. Moreover, it is particularly advantageous if the first or second integrated circuit is connected directly to the SMD component via bond wires. This makes the connections shorter and in addition the connections can be laid directly.
In a special embodiment, the SMD component can be mounted onto the second integrated circuit or the carrier, with at least one further integrated circuit being inserted at the same time. A correspondingly large amount of space on the carrier can be saved as a result of this multiple stacking.
Equally, at least a third integrated circuit can be mounted between the first integrated circuit and the second integrated circuit. Obviously this also leads to a saving of space on an amplifier or hearing aid circuit board at least in the lateral direction.
The integrated circuits may be application-specific integrated circuits (ASICs). With ASICs specifically there is namely the problem that their degree of integration is not as high as in the case of standard ICs.
The first integrated circuit can be mounted on the carrier using flip-chip, CSP, BGA or wire bonding technology. This means that the principle of stacking integrated circuits and/or SMD components with one another and interconnecting them via bond wires can be applied to all possible types of integrated circuits.
The SMD component can include for example a piezoelectric crystal. In this case there is the further advantage that the oscillations of the piezoelectric crystal are not transmitted directly via the printed circuit board to another oscillation-sensitive component when the SMD crystal is mounted on another component. No direct transmission of the oscillations takes place even when the SMD crystal is mounted on the carrier and an oscillation-sensitive component is mounted on an integrated circuit.
According to another embodiment, the SMD component is electrically connected by means of one of the bond wires to a bond pad on the carrier and from there by means of another of the bond wires to the second integrated circuit. This can be advantageous when space conditions are very restricted on the second integrated circuit or the SMD component.
As has already been indicated above, a circuit arrangement according to the invention can be used particularly advantageously in a hearing aid. In this case it is possible on the one hand to exploit the increased degree of miniaturization and on the other hand to benefit from a reduction in oscillation transmission as a result of the stacking technology and wire-bonding interconnect technology.
The present invention is explained in more detail below with reference to the accompanying drawings, in which:
The exemplary embodiments described in more detail below represent preferred embodiments of the present invention.
The circuit arrangement shown by way of example in
An SMD crystal 13 which is based on the piezoelectric principle and provides an oscillation frequency or clock frequency is mounted directly onto the second ASIC 12. The SMD crystal 13 is attached to the second ASIC 12 in turn in accordance with any of the aforementioned bonding techniques (gluing, soldering, etc.). The bonding step is labeled M3 in
In the example shown in
The layout depicted in
1. A higher degree of miniaturization can be achieved by stacking the ASIC and SMD components.
2. Stacking the ASIC and SMD components one on top of the other enables more effective use of a circuit layout in the vertical direction.
3. The wire bonding technique permits a short and direct connection between, for example, an ASIC and an SMD component.
4. The first ASIC 11 can be mounted on the PCB substrate 10 using any assembly technologies, such as flip-chip, wire bonding, CSP, BGA, etc.
5. Any types of multi-layer substrates can be used as the printed circuit board: e.g. multi-layer PCB substrates, multi-layer thick-film substrates, multi-layer LTCC (Low Temperature Co-fired Ceramic) substrates, multi-layer LTCC substrates with countersunk bonding space (cavity).
6. As a result of the vertical stacking, the oscillations of the SMD crystal 13 are not transmitted directly via the PCB substrate 10, but at most are transmitted attenuated by the intermediate components and the connecting materials such as adhesive, metal or solder. This enables a better attenuation to be achieved particularly for the emission of higher frequencies. The oscillation transmission or structure-borne sound transmission via the bond wires is practically irrelevant.
A second ASIC 22 is adhesively bonded, soldered or attached by some other means onto the first ASIC 21. This attachment step is labeled M5 in
An SMD crystal 23 is also soldered or attached by some other means onto the PCB substrate 20. The attachment step is labeled M6 in
The SMD crystal 23 is wired to the second ASIC 22 by means of bond wires 24, analogously to the example shown in
The exemplary embodiment according to
1. The bond wires enable a short and direct connection from an ASIC to the SMD component.
2. The first ASIC 21 can be mounted on the PCB substrate 20 using any assembly technology, such as flip-chip, wire bonding, CSP, BGA, etc.
3. All the aforementioned multi-layer substrates can be used.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 005 862.6 | Feb 2007 | DE | national |
