Patent Application
20130192338
The present invention relates to a portable electronic device.
Miniaturization and wireless technologies have enabled portable electronic devices to process information in a ubiquitous way.
The more sensors are integrated into smart phones or tablet computers, for example, the more information can be gathered the user may make use of.
The problem to be solved by the present invention is therefore to provide an arrangement for a chemical sensor in a portable electronic device.
This problem is solved by a portable electronic device according to the features of claim 1. The portable electronic device comprises a chemical sensor for measuring a property of at least one analyte. The chemical sensor is arranged inside a housing of the portable electronic device. An opening in the housing is provided for exposing the chemical sensor to a fluid to be analyzed. Such fluid may be a fluid in an environment of the portable electronic device. In this context, a fluid may at least comprise a liquid or a gas. Such fluid may contain one or more ingredients. The detection of a chemical substance also denoted as analyte contained in such fluid may be of interest to a user. Analytes may be, for example, CO2, NOX, ethanol, CO, ozone, ammonia, formaldehyde, or xylene without limitation. The chemical sensor is adapted to detect at least one property of at least one analyte. Hence, a fluid supplied to the chemical sensor may be analyzed by means of the chemical sensor as to if and which of the one or more chemical substances the chemical sensor is sensitive to are present in the fluid supplied. It is always subject to a design of the chemical sensor as to how many analytes and/or how many different properties of an analyte the chemical sensor is receptive to. Typically, such chemical sensor is capable of detecting/measuring a property of the one or more analytes assigned, which property may, for example, be a concentration of the analyte in a sample which sample specifically may be air surrounding the device. Other properties may be, for example, chemical properties such as a binding energy of the analyte. Or, the chemical sensor may comprise at least one receptor of a sensor material, e.g. in form of a layer, to which an analyte may bond to and as such modify an electrical property of the sensor material such as its electrical conductance, which principle preferably is applied in metal oxide chemical sensors, or an optical property of the sensor material such as its transmission rate, for example. Then, the electrical or optical property of a combination of the analyte and the receptor is measured and allows a conclusion as to the analyte, such as by way of comparison to a property of the receptor measured without the presence of the analyte. It is noted that in case of detecting multiple different analytes—which may be different chemical elements or chemical compounds—it is not required to always measure the same property per analyte. Different properties may be measured for different analytes.
Specifically, the chemical sensor may be a gas sensor for detecting one or more substances in a gas.
The portable electronic device may further comprise a housing, and an opening in the housing. For the reason, that the chemical sensor is arranged within the housing, there is an access required for the fluid or at least analytes of the fluid to access the chemical sensor inside the housing. Such access in form of an opening in the housing may, for example, be of small scale, such as, for example, of a diameter of between 0.1 mm and 3 mm. By means of the opening in the housing the chemical sensor is sufficiently exposed to the environment for providing reasonable measurements as to the analyte/s the sensor is prone to. On the other hand, the chemical sensor is sufficiently protected from contamination which in turn supports an accurate and stable performance. In a majority of cases, the fluid may be a gas, and especially be the air surrounding the portable electronic device. Hence, in a sample application it may be of interest to identify if such air may contain analytes the chemical sensor is prone to. Specific applications may include the detection of toxic gases, the detection of ethanol in a users breath, or the detection of other substances. The opening may be arranged in a front wall, a bottom wall, or a side wall of the housing, and, for example, may take the form of a cavity. An arrangement in a cavity of the housing shall be included in the term “inside” the housing.
In a preferred embodiment, the portable electronic device further comprises a conductor board, which specifically may be a flexible conductor board, and in a further embodiment may be a flexible printed circuit board. In another variant a processing unit is connected to the chemical sensor via the conductor board. The processing unit may be any microprocessor present in the device, since many portable electronic devices such as smart phones or tablet computers require considerable computing capability. While the processing unit not necessarily needs to be arranged on the conductor board and may be arranged elsewhere, it is preferred that the chemical sensor not only is electrically connected to the conductor board but also is arranged on or attached to the conductor board. Hence, the conductor board may form a support for the chemical sensor such that the chemical sensor is mechanically and electrically coupled to the conductor board.
Hence, any portable electronic device such as a mobile phone, and in particular a smart phone, a handheld computer, an electronic reader, a tablet computer, a game controller, a pointing device, a photo or a video camera, or a computer peripheral—which listing is not limited—may in addition to its original function provide chemical information as to its environment. The user may learn about chemical substances and compositions present in the devices surroundings, and may use, transmit or else analyse such information. For the reason that such portable electronic device typically includes interfaces to a remote infrastructure, such information may be transmitted elsewhere and used elsewhere. In an alternative, the user himself/herself may benefit from the information provided by the chemical sensor in that actions can be taken in response to detected analytes, including but not limited to analytes representing toxic substances. Such portable electronic device as a result may primarily be designed for computing and/or telecommunication and/or other tasks in the IT arena, and now may be enhanced by the function of providing chemical information as to its environment.
Preferably, the chemical sensor not only is capable of measuring a single analyte, but instead is designed for measuring one or more properties of multiple different analytes. Hence, the chemical sensor may be understood as a sensor device for detecting one or even more properties of more than one analyte. Specifically, the sensor may for this purpose be embodied as a sensor array. In such sensor array, each sensor cell may provide a layer of a material exhibiting different absorption characteristic such that each cell of the sensor array may specifically be sensitive to a different analyte and as such may enable the portable electronic device to detect the presence or absence or concentration of such analyte. In other variants, each sensor cell may provide a sensor material, e.g. in form of a layer, and also denoted as receptor, to which an analyte may bond to and as such modify an electrical property of the sensor material such as its electrical conductance, which principle preferably is applied in metal oxide chemical sensors, or an optical property such as its transmission rate, for example. However, a sensor cell of such sensor array may in one embodiment exhibit not only sensitivity to a core analyte, but also to analytes other than the core analyte since such sensor cell may exhibit a cross-sensitivity to one or more analytes possibly representing core analytes for other cells. In another embodiment, the chemical sensor may be a single sensor cell, e.g. with a single layer, which however, may be receptive to multiple different analytes. Such single cell may, in one embodiment, be receptive to different analytes only under different operating conditions. For example, the sensor cell may be receptive to a first analyte x when being heated to a first temperature tx, and may be receptive to a second analyte y when being heated to a second temperature ty which is different from the first temperature tx. In another variant, a sensor array may comprise multiple sensor cells wherein at least one of the multiple sensor cells—and in another variant preferably all of the multiple sensor cells—is designed such that such cell/s may be sensitive to different analytes under different operating conditions such as under different temperatures. In such specific embodiment, each of such cell/s may be provided with an individual heater.
However, the chemical sensor even if designed for detecting multiple different analytes may be based on one of the following measurement principles without limitation:
A chemomechanical principle, in which a chemical reaction is transformed into a surface acoustic wave, or into a cantilever resonance, for example. Alternatively, there may be thermal sensing concepts applied, e.g. by making use of pellistors which may serve as a catalytic thermal sensor in which heat is generated during combustion. Alternatively, the chemical sensor may rely on optical detection, such as in form of a microspectrometer, or an NDIR, or may make use of electrochemical reactions such as being enabled by solid state electrolytes in combination with voltammetric, potentiometric, or conductometric measurement principles. Chemiresistors may also be used, such as conducting and carbon-loaded polymers, preferably in a low-temperature arena, or, metal-oxide sensors such as tin oxide, gallium oxide, indium oxide, zinc oxide, which preferably may be applied in a high temperature-arena. ISFET (ion-selective FET) may also be used, as well as chemocapacitors wherein it is preferred to use a polymer as active material.
Given that in a preferred embodiment the chemical sensor is arranged on an electrical conductor board such as a circuit board, the chemical sensor may be arranged between the conductor board and a wall of the housing which wall comprises the opening. Preferably the chemical sensor faces the opening and is located underneath the opening. In such scenario, the chemical sensor may be sandwiched between the conductor board and the wall of the housing with the opening. This improves a support for the chemical sensor and enhances the fixture of the sensor device within the housing. Still, the chemical sensor may be arranged close to the opening such that the chemical sensor has a quick response time and such that a sufficient amount of gas may be forwarded to the chemical sensor.
The conductor board may be embodied as a printed circuit board, i.e. a relatively stiff circuit board. In a different embodiment, the conductor board may be embodied as a flexible printed circuit board which is flexible and can be bent in order to follow a shape of the housing or its interior, for example.
In case of a sensor array the individual sensor cells may be embodied as discrete sensor cells arranged on the conductor board. In a different embodiment, the sensor cells may be represented by multiple chips the sensing structures are integrated in. Here, each individual chip may be packaged, i.e. encapsulated, and arranged on the conductor board. In an alternative arrangement, such multiple sensor chips may comprise a common package, such that these chips are encapsulated by a common encapsulation, which package finally is arranged on the conductor board. In a further embodiment, the sensor cells are monolithically integrated into a common sensor chip with a common substrate for all sensor cells. Such monolithic sensor chip may still be encapsulated and be arranged on and electrically connected to the conductor board.
In the arrangement illustrated above, the chemical sensor may be fixed in its position—which preferably may be a position directly underneath the opening in the housing—by a clamp mechanism in which two housing halves may be clamped together with at least the conductor board and the chemical sensor arranged in between. Preferably, a support element is arranged between a lower half of the housing and the conductor board such that this support element will help to have the chemical sensor be pressed against the upper housing half. For this purpose, the support element may be of elastic nature, in one embodiment.
In such scenario, but also in other scenarios, it may be beneficial that a seal is arranged between the chemical sensor and the housing for sealing the opening against an interior of the housing. Such seal may be applied on top of the chemical sensor, and, for example, be glued thereto or otherwise attached thereto, however, without covering the sensitive structure of the chemical sensor, but preferably encircling the sensitive structure instead. On top of the chemical sensor may include on top of the sensor chip, or on top of an encapsulation of the sensor chip. When clamping the housing together, the seal preferably is arranged such that it encloses the opening in the housing. Alternatively, the seal may be glued or otherwise attached to the housing and specifically to its inner wall thereby enclosing the opening in the housing wall such that when clamping the housing together, the seal preferably rests on the chemical sensor and encloses the sensitive structure. In a third alternative, the seal is placed between the chemical sensor and the housing without being attached to any of these elements and is held between these elements when the housing halves are clamped together. In all variants, the seal may take the form of a seal ring, i.e. a closed structure, and be of a photoresist such as SU8, or epoxy material, or a material with elastic properties, for example. In other variants, a sealing compound may be applied between the chemical sensor and the housing where needed. After being hardened such sealing compound provides for the sealing function.
In another embodiment, a seal ring may be arranged between the conductor board and the wall of the housing comprising the opening. The seal may be of an arbitrary ring structure and be made of an appropriate material. It may enclose the chemical sensor. When clamping the two house halves together, the seal, and if present, the support element may be compressed, thereby improving the sealing function.
The seal may be preferred not only for protecting the inside of the portable electronic device, but also improving the chemical measurements, the response time in particular: For the reason that the seal prevents any gas from entering—by diffusion, for example—into the housing through the assigned opening, no transient sensor states, where the gas concentration in dead volumes of the housing are equilibrated by gas exchange processes through the assigned opening among others, can occur. In such transient states the gas concentration the sensor is exposed to is governed by the exact nature of the exchange process through the assigned opening and lies in between the gas concentration in the surrounding and the one in the dead volumes of the mobile device.
In a different embodiment, the chemical sensor may not be arranged underneath the opening in the housing with its sensitive structure facing the opening. Here, a side wall of the housing, instead of one of the top and bottom walls, may comprise the opening while the chemical sensor still is arranged on a conductor board orthogonal to such side wall.
In yet another alternative, the conductor board may be arranged in between the chemical sensor and the wall of the housing comprising the opening. Hence, the chemical sensor is arranged on the back side of the conductor board. In this scenario, the chemical sensor chip may be flip chip mounted to the conductor board such that the sensitive element faces the conductor board. In order to now expose such chemical sensor sufficiently to the environment, the conductor board may have an opening for allowing the fluid from the outside to reach the chemical sensor.
The opening in the housing may, in a preferred embodiment, be covered by a membrane at least permeable to analytes of interest or permeable to the gas of interest, by a grid, by slits or by a bezel. By such means, the chemical sensor and the interior of the housing may be protected.
Instead of providing a single opening in the housing there may be provided two or more openings in the housing, two of which openings may be arranged on opposite walls of the housing such that gas may circulate though the interior of the device thereby getting in touch with the chemical sensor arranged inside the housing between the two openings.
In another embodiment, the opening may be an opening already existing in the housing for a different purpose. In case of the device being embodied as a mobile phone or a voice controllable computing device, a small opening in the housing may be provided for a microphone. The chemical sensor may be arranged underneath/in such opening for the microphone together with the microphone. Another opening may be provided for a speaker of the mobile phone. The chemical sensor may be arranged underneath/in such opening for the speaker together with the speaker. In a different embodiment, there may be a dedicated opening for the chemical sensor and an associate sensor if any. Such dedicated opening may be arranged in the housing elsewhere subject to different criteria such as space, connectivity, etc.
In another embodiment, there may be at least one additional sensor provided. Such at least one additional sensor may be a sensor/sensors out of the following list of sensors:
Preferably, a temperature sensor and/or a humidity sensor are provided, as these sensor/s may help in compensating temperature induced and/or humidity induced signal variations in a signal of the chemical sensor. Preferably the temperature sensor and/or the humidity sensor may be arranged in proximity to the chemical sensor, for example in the same opening.
Irrespective of the kind of additional sensor applied to the system, such additional sensor may make use of the same opening as the chemical sensor does for getting access to the environment. Hence, such opening may be used by both or even more sensors if applicable. The sensors may preferably be both arranged on the conductor board in close proximity. In another variant, the two or more sensors may be arranged on different conductor boards. In any case, in such combination, the chemical sensor may be an individual sensor also denoted as sensor cell, or may include an array of chemical sensor cells such as described above. As a further alternative, the conductor board may carry the additional sensor and one or more chemical sensor arrays and/or one or more individual chemical sensor of a discrete type.
In another embodiment, two or more openings may be provided in the housing for granting access to the sensors inside wherein one opening may be assigned to one of the sensors.
In another preferred embodiment, in which at least one additional sensor is used, the at least two sensors may be arranged in a common encapsulation, for example in a common mould compound encapsulating the two or more sensor chips the sensor structures are integrated in. In case two or more integrated sensor chips are used, these chips may be arranged on a lead frame or a different intermediary electric carrier, and subsequently may be encapsulated by a common encapsulation with at least connect pads remaining accessible in such encapsulation. The encapsulation may be formed such that sensitive structures of the sensor chips are not covered by the encapsulation either. Such package may then be bonded to the conductor board, and preferably may be assigned to a common opening in the housing wall. Especially, the chemical sensor and a humidity sensor may be arranged on such intermediary carrier and may be encapsulated together. The result is a compact package which package may be arranged even in small openings. An access opening in the encapsulation may be common to the chemical sensor and the humidity sensor, or separate access openings may be provided in the encapsulation. Other sensor chips such as a microphone may be added to such package, too, if desired. In any case, in any of the above embodiments, the package may contain a chemical sensor in form of an individual sensor cell of a discrete type, or may include an array of chemical sensor cells monolithically integrated on a common substrate. As a further alternative, the package may contain the additional sensor and one or more monolithically integrated chemical sensor arrays and/or one or more individual chemical sensor of a discrete type. In case a seal is provided, a single seal ring, for example, may be applied encircling the sensor structures of both the chemical sensor and the additional sensor. Such seal ring may be applied between the package and the housing wall.
In another embodiment, the chemical sensor and at least one additional sensor may be monolithically integrated in a common chip. Such chip includes a common substrate, on/in which the at least two different sensor structures representing at least two different sensor functions are integrated. Preferably, the sensors may be the chemical sensor and a humidity sensor, however other combinations such as the chemical sensor and a temperature sensor and/or a microphone may be envisaged, too. In such example, the humidity sensor may include a polymer layer deposited on the semiconductor substrate. The chemical sensor may include at least one more polymer layer susceptible to the one or more subject analytes. In another embodiment, the chemical sensor may comprise a thinned substrate portion in combination with one or more metaloxide layers. After having manufactured such monolithic sensor chip in which different sensor functions are integrated, the resulting chip may be packaged, too, i.e. preferably cast into a mould compound which resulting package may then, for example, be SMD mounted to the conductor board. In any case, in any of the above embodiments, the monolithically integrated chip may contain a chemical sensor in form of an individual sensor cell, or may include an array of chemical sensor cells, or a combination of, in addition to the monolithically integrated additional sensor. In case a seal is provided, a single seal ring, for example, may be applied encircling the sensor structures of both the chemical sensor and the additional sensor. Such seal ring may be applied between the package if present and the housing wall or between the chip and the housing wall.
In a very specific embodiment, the conductor board may be formed by at least a part of a wall of the housing, and preferably by the wall that comprises the opening. Conductors may be applied to the inside surface of such wall, and electronic elements including the sensor chip containing the chemical sensor and possibly other sensors may directly mechanically and electrically be connected to the wall of the housing thereby electrically connecting the conductors on the wall. Specifically, the chemical sensor may be arranged across the opening with its sensitive structure facing the opening.
Other advantageous embodiments are listed in the dependent claims as well as in the description below.
The embodiments defined above and further aspects, features and advantages of the present invention can also be derived from the examples of embodiments to be described hereinafter and are explained with reference to the drawings. In the drawings the figures illustrate in
Same or similar elements are referred to by the same reference numerals across all Figures.
Prior to further embodiments, it is noted that the chemical sensor 12 may generally take different appearances in terms of packaging:
In a first embodiment, the chemical sensor may comprise a chip, preferably comprising a semiconductor substrate containing the sensitive structure/s on its top surface for example. Through-silicon-vias may provide an electrical connection between the top surface and a back side of the chip. At the back side of the chip, the through-silicon-vias may lead into contact pads which are provided with solder bumps. The chemical sensor 12 may then be pressed against a conductor board to be mounted to (SMD mounting), possibly under impact of heat, such that an electrical connection as well as a mechanical fixture is built between the chemical sensor and the conductor board. This variant of a chemical sensor package in the following is also denoted as TSV-variant (for through-silicon-vias).
In a different embodiment, the chip is first mounted to an intermediate carrier such as a leadframe where the chip may be bonded to. Then the chip and the leadframe may be encapsulated in a moulding process, preferably with the sensitive structure being relieved from the encapsulation such that an access opening is formed in the encapsulation, which access opening may be referred to as 121 in the drawings. Contact pads on the lead frame may also remain free from encapsulation material. Such contact pads may also be provided with solder bumps. This variant of a chemical sensor package in the following is also denoted as mould-variant.
In a third variant, the chip as such with the sensitive structure and contact pads on the same surface is applied to a conductor board with the sensitive structure facing the conductor board. This variant of a chemical sensor in the following is also denoted as a flip-chip-variant.
It is noted that in all of the following embodiments, a seal—although not shown—may preferably be applied between the chemical sensor and the housing, or between the conductor board and the housing if applicable. The seal in the first instance encloses the opening in the housing and the sensitive structure while in the second instance it encloses the opening in the housing and the chemical sensor as such.
The chemical sensor 12 is arranged in close proximity underneath the opening 211 in the front wall 21 of the housing such that the sensitive structure is exposed to any gas in the environment of the tablet computer that may diffuse into the interior of the housing through the opening 211. The printed circuit board 3 may be fixed elsewhere within the housing, and preferably may carry a processing unit for analyzing the signal supplied by the chemical sensor 12. The chip representing the chemical sensor 12 may additional hold integrated electronic circuitry. In a very preferred embodiment, the electronic circuitry and the sensitive structure may both be realized by the very same manufacturing process such as a CMOS and possibly other additional processes such as MEMS processes. In such scenario, the chemical sensor chip may already provide a linearized digital signal, which may be supplied via conductors on the printed circuit board 3 to the processing unit.
For the embodiments according to
The embodiment of
In an alternative, the support element 5 may be of elastic nature, too, and may generate a force acting on the conductor board for holding it is a defined position. Of course, both, an elastic support element 5 and an elastic seal ring 123 may be used in combination.
In such embodiment, a seal may preferably be applied by casting a seal material between the conductor foil 6 and the front side of the chemical sensor chip without covering the sensitive structure of the chemical sensor chip.
In
While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practised within the scope of the following claims.
