An electronic product, a body and a method of manufacturing

Description of equivalent WO 2004016055 A1

0001An electronic product, a body and a method of manufacturing

0002The invention relates to an electronic product comprising a body provided with a threedimensional shape that is derived from the product and incorporates structurally at least part ofthe product shape.

0003The invention also relates to a body suitable for use as a product part in a desired product and provided with a threedimensional shape that is derived from the product and incorporates structurally at least part ofthe product shape.

0004The invention further relates to a method of manufacturing a body suitable for use as a product part in a desired product and provided with a threedimensional shape that is derived from the product and incorporates structurally at least part ofthe product shape, comprising the steps of:

0005- providing a foil having a releasable layer and a pattern of conductor tracks;

0006- attaching electrical elements to the conductor tracks;

0007- providing the body of electrically insulating material by a molding technique, therewith encapsulating the electrical elements and mechanically anchoring the conductor tracks in the body; and

0008- removing the releasable layer.

0009Contemporary products increasingly contain electronic components. Vehicles are full of electronic components that fulfill sensor functions and allow the operation of task with only a push on a button. Clothes and other articles are provided with electronics that can be read out wirelessly. Consumer electronics products ranging from shavers and coffee- machines to television sets, remote controls and mobile phones are bodies that include more functionality than in the past and also need to have a beautiful shape. In order to fulfill the desire ofthe provision of electronics anywhere, the electronics can be attached to plastic parts, including housings that provide the shape ofthe desired products and appliances. There are various ways of attachment.

0010One of them is the use of a printed circuit board, to which the electronic components are attached and electrically contacted. The printed circuit board is provided inside a housing, such that it is not visible from the outside, or visible only to the extent that is desired. The disadvantage ofthe printed circuit board is however, that it takes considerable space and that it is in need of substantial assembly. The need for assembly can even limit the freedom of choosing the shape ofthe product. Another way of attachment is the provision ofthe electronics on a label at a surface by means of adhesive. This is particularly an option wherein the label includes a transponder or wherein the body is a product part that will be surrounded by a housing. The use of adhesive however has the disadvantage that it is not always very robust. Moreover, electrical contacting ofthe components is not made easy, since it must be done either contactlessly or with a limited number of contacts.

0011In short, there is a need for such macroscopic bodies as housings and products parts in or to which any desired electronic components can be provided in a mechanically stable manner without limiting the freedom of design ofthe product shape.

0012It is therefore a first object ofthe invention to provide an electronic product of the kind mentioned in the opening paragraph, in which electronics are integrated without limiting the freedom ofthe designer and without making the body or the product mechanically or chemically vulnerable. This object is achieved in that the body comprises an electrically insulating material and comprises a pattern of electrical conductors, which pattern includes contact pads for external contacting, that are exposed at a surface, which conductors are mechanically anchored in the body, a plurality of electric elements being encapsulated in the body and being electrically connected to the pattern of electrical conductors. According to the invention, the electric elements and the pattern of conductors are embedded in the body. The body therewith does not only provide a structural shape ofthe product and/or to provide an esthetically desired appearance and/or a mechanical support for the product. The body is in fact also the encapsulation for the electric elements and functions as the circuit board for the attachment of electric contacts for external contacting. It is an advantage ofthe body ofthe invention that its manufacture can be very straightforward and is hardly in need of assembly. Generally, the process flow ofthe manufacture includes a first step in which a foil is provided with a releasable layer and thereon the pattern of conductors. In a second step this foil is provided at a desired location in a mould and is overmoulded by the electrically insulating material in the desired shape. In a third step the releasable layer is removed from the body of electrically insulating material. The mechanical anchoring ofthe conductors is for instance achieved in that the releasable layer is slightly etched before provision ofthe molding material, such as to create underetch. A suitable combination of materials is the use of copper for the pattern of conductors and the use of Al for the releasable layer. This has the advantage that both the patterning of the copper conductors and the removal ofthe releasable layer can be realized with wet-chemical etching without deteriorating the other layers.

0013In principle, the complete pattern of conductors will be present at the surface ofthe body. Some additional steps maybe taken however, that lead to the encapsulation of the conductors inside the body. First of all, a foil or spring assembly or alternative electrical connectors may be connected to the contact pads before the molding and be partly overmoulded together with the formation ofthe body. This provides a very robust integration of such a connector in the body. An alternative connector is for instance a connector to which a battery can be connected. Secondly, the pattern of conductors may be overmoulded in a separate step after the provision ofthe body. Thirdly, and particularly in combination with the use ofthe underetch for the anchoring, the pattern may include conductors with a relatively small and with a relatively large width. By a suitable choice ofthe underetch time, the small conductors can be included completely in the body, whereas the large ones will at least partially be present at the surface ofthe body. In a fourth elaboration, the releasable foil is substantially removed in a first area before the molding process, without removing the pattern of conductors in that area. The conductors in the first area can thereafter be provided with an encapsulation from all sides.

0014The electrically insulating material is preferably a polymer material, that is suitable for use in combination with molding techniques, particularly insert molding and has a good chemical and mechanical stability. Examples include polystyrene, polypropene, polyvinylchloride, polyphenylene sulfide.

0015It is particularly preferred that an additional coating is provided at the foil so as to improve the adhesion between any metal and the insert moulded polymer. A first example is the use of a material that melts on heating. Elements to be attached with solder balls to the pattern of conductors can first be provided on this material, that is heated thereafter. This process is further described in the non-prepublished application WO- D303/02292 (PHNL020471). A second example is the provision of a coating after that the elements have been assembled on the pattern of conductors. The coating can then be provided not only at the interface ofthe conductors and the insert moulded material, but also at the interface ofthe elements and the insert moulded material. A suitable class of materials to be used for the coatings are copolymers. Particularly suitable appear to be vinyl copolymers of acrylic acid and alkyl acrylates.

0016It is furthermore preferred for good encapsulating properties ofthe molding material that it comprises fillers for absorption of moisture. Particularly suitable for this aim are silica or other metal oxides such as aluminum oxide and magnesium oxide. These fillers may be porous matrices.

0017The use of a foil of a releasable layer and a pattern of conductors thereon is per se known from EP-A 1,187,205. However, said application discloses the use thereof for chip scale packaging of integrated circuits. These are electronic components with typical dimensions in the order of 3 * 3 mm² or less, and the shape ofthe body herein follows the shape ofthe encapsulated electronic component. The insulating material is therein provided with transfer molding. In the present invention, however, the shape ofthe body is not based on that ofthe embedded components, but on that ofthe product of which the body is a part. In general, the dimensions of the body will thus be larger than that of an integrated circuit, and it will not have the shape of a rectangular block, such as an integrated circuit. Suitable dimensions are for instance at least 0.5 to 0.5 cm , and often more than 3 to 3 cm , and in one or more directions even 10 cm or even 1 m. To be sure, it is not necessary that the foil will have dimensions comparable to those ofthe body. The use of such a foil is further known from GB-A 2,229,864 as well as from

0018US-A 5,738,797. However, the known methods relate to the manufacture of a circuit board. It is not disclosed therein, that the circuit board can be used as encapsulation for electric components. It is not disclosed either, that the circuit board has a sufficient mechanical stability to act as the structural element in a product. hi a preferred embodiment, means are present for mechanical attachment of a device, component or carrier to the body. As the skilled person will understand, there is a variety of means that can be provided as part ofthe mould. This includes cavities and throughholes in the first place. It also includes any clamping means, threads for engagement with a thread of an external component and any edges, protrusions and corners as desired. The advantage hereof is that the electronic product can be a truly integrated system, wherein some elements are present at the surface ofthe body and others are integrated into the body. An example hereof is for instance a display, wherein the display is present at the surface, but wherein the display driver is hidden inside the body. Another example is for instance a radio: the loudspeaker is present at the surface, and the electronics are hidden inside the body. Such electronics do not only include passive components such as resistors, capacitors and inductors and protective components such as diodes, but also signal processing units. However, such signal processing unit could be integrated also with one ofthe elements at the surface, as is the case with an image sensor. Furthermore, with a small radio, it is an advantage that any electronics or user functionality needed in addition, such as a display or buttons can be part ofthe same product. Either they are integrated in the body, or they are present at the surface that has a shape fitted for mechanical attachment. It is even possible that such electronics or functionality is partly overmoulded and thus anchored in the body. Particularly in this embodiment, the body acts as system integrator of various elements and components. It provides mechanical stability and shape. This is done not only in that the product has at least partly the shape ofthe body, but also in that any components attached to the body are given their position. Moreover, due to the versatile possibilities of the molding process, not only the position, but also the angle with respect to the surface of the body can be determined. This is particularly relevant for the optimal operation of microphones, cameras, displays and the like.

0019In a further embodiment, the electronic device comprises a sensing or transmitting first element provided at the surface ofthe body for radiation of a first kind and an auxiliary second element for processing or providing ofthe radiation, the first and second element having a predetermined spatial interrelationship to each other to allow their functioning, which is defined in the body, the first element being electrically connected to the pattern of electrical conductors in the body. The number of electronic devices being constructed from a first and a second element that need to be in a mutual interrelationship is large. A good example is a camera with a lens and a image sensor. In this case the body acts also defines the locations ofthe individual elements and therewith achieves the system integration, that previously needed to be dealt with separately.

0020A variety of electronic products is enabled with the invention. Electronic components could be introduced in the arms of a chair. Also, the electronics needed for switching and for power conversion in a coffee machines or a water boiler could be integrated in that part constituting a leg ofthe machine. In the example of a mobile phone or a remote control, the body may be a product part with a display and to which any buttons and any further RF electronics are attached afterwards. The product part can finally be provided with a separate housing. In the example of a dashboard the body ofthe dashboard will be the main structural part, as it currently is. The body is of course not only suitable for a dashboard at the front side of a vehicle, but can also be used at the doors and back side. The invention also relates to a body for use in the product. Circuit boards included in a plastic part of a certain shape are for instance known from GB-A 2,229,864. In this embodiment the pattern of conductors is bent so as to provide any required shape. However, the known circuit board does not include any electric elements, and it appears disadvantageous to do a bending operation either before or after the placement of elements on a foil. Nevertheless, a full flexibility ofthe required three-dimensional shape ofthe body is desired, such that the body can function as the system integrator giving mechanical support. It is therefore a second object ofthe invention to provide a body that fulfills these objects.

0021This second object is achieved in a body suitable for use as a product part in a desired product and provided with a threedimensional shape that is derived from the product and incorporates structurally at least part ofthe product shape, which body comprises an electrically insulating material and comprises a pattern of electrical conductors, which pattern includes contact pads for external contacting which conductors are mechanically anchored in the body, a plurality of electric elements being encapsulated in the body and being electrically connected to the pattern of electrical conductors, wherein the conductors are present at a surface only partially.

0022In the invention, the conductors are present at the surface ofthe body only at certain areas, whereas in other areas they are hidden inside the body. There are particularly two methods for achieving this functionality. First of all, the pattern of conductors may be overmoulded in a separate step after the provision ofthe body. This is a simple and straightforward implementation, however, with the limitation that the products need to be brought back into a mold after removal ofthe releasable layer, and with the limitation that the molding ofthe additional features may not affect the shape ofthe already moulded body negatively. In a second, preferred method, the releasable foil is substantially removed in a first area before the molding process, without removing the pattern of conductors in that area. The conductors in the first area can thereafter be provided with an encapsulation from all sides.

0023Although not preferred in assembly, it nevertheless may be that the surface of the body includes a first and a second face which mutually includes an angle unequal to 180 °C and wherein the pattern of conductors extends along the first and the second face. This is particularly suitable if the pattern of conductors comprises a plurality of tracks are positioned in parallel and need to be fitted to the desired shape. It is furthermore suitable, if electric components need to be attached and contacted at different faces, particularly at opposed faces.

0024In another embodiment, the pattern of conductors includes contact pads for contacting a component that can be assembled to the surface ofthe body, and the shape ofthe body is fitted for assembly ofthe active device. For many applications, it is advantageous that any further active devices can be assembled to the surface ofthe body. Examples of such active devices are integrated circuits and other such semiconductor devices, which may be too expensive for integration in the body; display devices, speakers, microphones and lenss that need to be provided at the surface ofthe body in order to fulfill their functions; and other devices for which integration is not preferred.

0025In a further elaboration hereof, the surface ofthe body is provided with a cavity in which the active device fits, hi this manner the active device is given a mechanical protection.

0026The invention further relates to a method of manufacturing a body suitable for use as a product part in a desired product and provided with a threedimensional shape that is derived from the product and incorporates structurally at least part ofthe product shape.

0027It is a third object ofthe invention to provide such a method with an improved freedom of design ofthe product shape. This object is achieved in that it comprises the steps of: - providing a foil having a releasable layer and a pattern of conductor tracks, the pattern comprising an first area that is to be hidden in the body;

0028- removing the releasable layer from the first area to the extent that any conductor tracks;

0029- attaching electrical elements to the conductor tracks; - providing the body of electrically insulating material by a molding technique, therewith encapsulating the electrical elements and mechanically anchoring the conductor tracks in the body; and

0030- removing the releasable layer to the extent that it is present at a surface ofthe body. In this method, integration is achieved by suitably patterning the releasable layer before provision ofthe mould. This leads to an efficient method with a good result.

0031The removal ofthe releasable layer before the insertion into the mold is preferably done by cutting. This results therein that the releasable layer is also integrated in the body. That is not problematic if the releasable layer is not too thick. Furthermore, it has the advantage that the first area is provided with some mechanical stability after the cutting. Alternatively, other methods such as localized dry of wet etching or irradiation with ultraviolet light could be used. The type of removal is also dependent on the specific foil in use. The releasable layer can in principle be a layer of a metal, such as Al, Cu, or steel, organic material, and a ceramic material such as glass or silicium. The resolution ofthe patterning is preferably in the range of millimeters to centimeters. However, with an automation, ofthe local patterning higher resolution can be achieved.

0032The method has its main benefit if also electric elements are integrated in the body, but is in principle also applicable for a body without any embedded electric elements. Another aspect ofthe invention resides in an electrically insulating body that comprises a flexible portion. Such a flexible portion may be used for a specific connection to a component, so as to adapt the body to the desired shape or to act as a contacting portion. Such is flexible portion is achievable in that the insulating material is provided in more than one step, in each of which steps desired insulating materials are used, such that a first portion is provided with an elastic insulating material and a second portion is provided with a hard, non-elastic insulating material.

0033Examples of non-elastic materials are thermoharders, epoxides, standard injection molding materials such as polyphenylenesulfide, polystyrene, nylons, polyester PET, PBT and PCT, polyetherimide, polyethersulphone, polyarylsulphone, polysulphone, polyetherketone, polyetheretherketone. The materials may be strengthened with glass fibers or desired particles as known to the skilled person. Particularly they are provided with any cross-linking agent which rigidifi.es the a structure and is initiated by heating. Examples of elastic materials are thermoplastic materials without or substantially without any such cross- linking agent. Particularly suitable are polyimide and benzocyclobutene. Any other elastic and non-elastic materials will be apparent to the skilled person.

0034As compared to the body known from GB-A 2,229,864 it is a clear advantage that the resulting body is fitted for many more shapes. This is particularly suitable for integration ofthe body is a casing with limited space. It is also advantageous with bodies of larger dimensions, particularly if the body has a threedimensional shape derived from the product in which it is used. The edges ofthe body may be made flexible, therewith reducing any damage to the body when inserted in a casing. An intermediate portion between a first and a second rigid portion may be flexible, so as to allow bending ofthe rigid portion with respect to each other. Alternatively, a mainly flexible body may be provided with rigid portions, at which it can be mechanically and electrically contacted. In a suitable embodiment, the flexible portion is provided with conductors according to a desired pattern. The flexible portion has the same function as a flexfoil, but need not to be assembled to it. Therewith, a problem of electrical contacting is reduced substantially. The body according to this aspect ofthe invention, is preferably provided with conductors that are present at a surface ofthe body at least partially. As explained above, the conductors may be hidden in the inside ofthe body in various ways. It is furthermore preferred that the conductors are mechanically anchored, so as to provide a good adhesion between conductors and the body. It may well be that the pattern of conductors extends over a first and a second face ofthe body, or even extends to a third face opposed to the first face. In many applications it will further be preferred that any electrical elements are embedded in the body. Examples of elements include diodes, resistors, capacitors, inductors, transformers, integrated circuits. Therewith the body, having a threedimensional shape and including the desired elements is really a system of its own, that does not need any wireless transmission of energy and data, but can make use of conventional galvanic coupling.

0035The electronic device can be used for many applications. Applications in the field of mobile communication, consumer electronics and automotive electronics are particularly preferred in view ofthe miniaturization and increase of functionality in those areas. Any components attachable to the body are particularly components that provide a user interface, and components that are too vulnerable or expensive or else to be integrated. The body can be provided with any cavities, holes and other mechanical attachment means for adequate location and attachment of these components. For their electric contacting, they will be connected to the pattern of conductors. Signal processing units may be hidden in the body. The body can also define the system if two or more components need a spatial interrelationship for their proper functioning, such as a lens and an image sensor in the example of a camera.

0036If the flexible portion is used for contacting, it can be very helpful a connector is present at one end ofthe flexible portion or at a rigid portion connected to that end. It is the advantage ofthe body of this invention that any suitable connector can be integrated in the body by overmolding.

0037With respect to the manufacturing of this body having a flexible portion, it is observed that the exact implementation of such process is open to engineering optimization by the skilled person. The expression 'first mold' and 'second mold' is understood in the context of this application to include both the implementation with separate moldings and the implementation with one mold having two or more chambers. For both processes it appears suitable to use an insertion molding process. As mentioned above, any additional coatings can be used to improve the adhesion between metal and the insertion moulded material. The releasable layer is chosen to desire. Good results have been obtained with a foil with copper patterns and a releasable layer of aluminum. Alternatively, the patterns can be of Al, and the releasable layer is of copper. Copper could be used as well for both the releasable layer and the pattern of conductors, with a suitable barrier in between of both. However, silicon and an organic, UN-releasable material could be used as releasable layers as well.

0038These and other aspects ofthe invention will be further explained with reference to the figures, in which identical components have been given the same reference numerals and in which: Fig. 1 shows a first embodiment ofthe body in a diagrammatic perspective view;

0039Fig. 2 shows a first embodiment ofthe device comprising the body shown in Fig. 1 in a diagrammatic perspective view;

0040Fig. 3 shows a first embodiment ofthe body in a diagrammatic perspective view; and

0041Fig. 4 shows a first embodiment ofthe device comprising the body shown in Fig. 3 in a diagrammatic perspective view.

0042Fig. 1 shows a first embodiment ofthe electrically insulating body 2 according to the invention. Fig. 2 shows the corresponding electronic device 10. The body is manufactured in the following manner. First a carrier plate is provided, which comprises a first releasable layer, here with a thickness of 30 μm and made of Al, on which a second, electrically conductive layer is present. The second layer is in this case made of copper and has a thickness of 10 μm. This second layer is patterned into conductors through a mask of silicon oxide by etching with an aqueous solution of ferrichloride. This solution leads also to some etching ofthe Al, leading to underetch under the conductors.

0043Hereafter, in this embodiment, the carrier plate is bent in the desired shape and provided in the mold. Electric elements, such as resistors, capacitors and diodes, and optionally also integrated circuits can now be provided on the conductors. Solder is used to provide an electrical connection between the conductors and the electric elements, but anisotropically conducting adhesive can be used alternatively. Then, any suitable synthetic resin, for instance PPS (= PolyPhenylene Sulphide) is injected in the mold and the body 2 is formed by injection molding. Finally, the releasable layer ofthe carrier plate is removed. The body 2 of this example is made to be suitable for a variety of active devices that are to be assembled at the surface ofthe body. This procedure yields not only openings 20, but also a cavity 60 with a side 61 and a bottom 62, the conductor pattern extending up to the bottom 62. The cavity 60 is suitable for accommodating elements such as a loudspeaker 63 and a buzzer 64, as shown in Fig. 2. The openings 20 are suitable for the formation of cameras, that are constructed through the assembly of a lens 40 and a photosensitive semiconductor element 30. The two cameras are positioned in opposite directions, for which reason the conductor pattern extends from the first side 2A via the second side 2B to the third side 2C. The shape ofthe body 2 is not derived from the size ofthe components, but from the product in which it has to be used. This body is made to fit in the upper part of a mobile phone, in the area above the display. Although not shown in this embodiment, it can be provided with clamping means to be attached more easily to the housing ofthe mobile phone. Fig. 3 shows a second embodiment ofthe body 2 ofthe invention. Fig. 4 shows the corresponding device 10. The body in this example is the carrier for a large number of desired electronic elements of a mobile phone. These are in particular the elements which provide the interface to the user. The shape ofthe body 2 is chosen such that it forms the basic carrier plate of any components in the mobile phone. To this body 2 not only the desired electronic elements can be attached, but also any RF part ofthe mobile phone can be attached.

0044At the rear side 2C (not shown) ofthe body 2, conductors 1 provide interconnections between the elements, and connection regions are present for the placement of elements which implement the required control functions. It is also possible for a contacting region for a flexible foil or a connector to be defined at that side. Connections are present for a semiconductor element 30 of a camera, a loudspeaker 63, a buzzer 64, a display 65, keys 66, a touchscreen 67, lamps 68 (preferably light-emitting diodes) and a microphone 69. The areas for these elements are indicated in Fig. 9 by their reference numerals followed by A (for example 30A). It is noted that the body has the advantage that a direct connection between (the semiconductor elements 30 of) the cameras and the picture screen 65 and the keys 66 and/or the touchscreen 67 is also possible without connections having to be realized by means of connectors or flexible foils. The number of connections may thus be advantageously reduced, and the camera 41 and the picture screen 65 can be mutually attuned in the assembly.

0045It is further noted that the conductors 1 in this embodiment lie in a recess at a side, whereby possible damage is prevented. Such damage, however, is improbable, anyway when such a manufacturing method is used (with the underetched copper conductors) that leads to a recessed position ofthe conductor pattern. The conductor pattern providing the drive ofthe touchscreen 67 comprises a flexible portion in this embodiment. This is formed in that a portion ofthe carrier plate is provided with an elastic synthetic resin such as polyimide instead of PPS. Connectors and flexible connections between two portions ofthe body 2 can also be integrated in this manner. It is further noted that although not explicitly shown, the body is very suitable for integration of electric elements that are needed for a proper operation. Examples hereof are capacitors, resistors, transformers, diodes for ESD protection, transistors and other switches, and possibly also integrated circuits such as a display driver.

0046It is also noted that the threedimensional shape of the shown conductor pattern is not absolutely necessary. A simpler version which extends in only two dimensions can be made as well. Moreover, part ofthe conductors can be provided inside the body in a simple way, in that the carrier plate is substantially cut away at those areas in which the conductors need to be embedded in the body. The cutting is done such that the conductors are separated from each other. The resulting conductors will be embedded in the body including the releasable layer. The resulting body can thus have the shape to accommodate the active devices as good as possible and to be suitable for integration in and attachment to the housing ofthe apparatus, in this case a mobile phone.