The invention concerns a method for production of an electronic assembly and an electronic assembly.
Such a method is known from DE 10 2008 009 220 A1 and from DE 10 2010 014 579 A1.
The task of the present invention is to provide an improved method and an improved electronic assembly.
This task is solved in terms of the method by
1.1 Providing an electrically-conducting film, especially a support film,
1.2 Providing at least one electrical component with at least one electrical contact site,
1.3 Application of an adhesive between the electrical component and the surface of the electrically-conducting film,
1.4 Arrangement of at least one component with at least one electrical contact site on the surface of the electrically-conducting film and fastening of the at least one component by formation of an adhesive joint between the electrical component and the surface,
1.5 Providing a support, especially from a flexible material,
1.6 Lamination of the film with the support so that the at least one electrical component is arranged between the film and support and formation of mechanical and electrical connection between the electrical contact site of the at least one electrical component and the electrically-conducting film by low-temperature sintering of nanoparticles, especially from gold, silver, nickel or copper or from an alloy of these metals, lamination of the film occurring simultaneously with low-temperature sintering,
1.7 Structuring of the electrically-conducting film to conductor tracks and/or cooling surfaces.
Variant [sic; variants (Ausführungformen)] of the invention are particularly advantageous, since lamination and low-temperature sintering can occur in the same process step essentially simultaneously. This is made possible, on the one hand, by using nanoparticles, which permit low-temperature sintering in a temperature range that is also suitable for lamination of the film and, on the other hand, by previous fastening of the at least one electrical component on the surface of the electrically-conducting film. By this fastening it is ensured that the electrical component is situated in the correct location when the support for subsequent lamination is applied to the film and the component situated in the space and that the component cannot slide.
“Electrical component” is understood to mean here especially housed and unhoused electronic components, like integrated semiconductor chips, for example, so-called bare chips (or bare dies), as well as discrete electrical or electronic components, like capacitors.
Such an electrical component ordinarily has a side on which one or more electrical contact sites are provided for electrical contacting of the component. This side of the component is also referred to as “active side” of the component. In particular, if the component is a bare die, the electrical contact sites are formed as so-called contact pads.
The support can be preimpregnated fibers (i.e., a so-called prepreg), which are understood to mean here an uncured thermosetting plastic matrix. For example, the support can be a liquid crystalline polymer (LCP), which is particularly advantageous for production of biocompatible implants, or another support material.
According to one embodiment of the invention an electrically conducting film whose surface is coated with nanoparticles is used as starting material. The at least one electrical component is then fixed on the surface of the electrically-conducting film by an adhesive, which is applied outside the electrical contact sites of the component. The adhesive is preferably a nonconducting adhesive, i.e., a so-called a nonconducting adhesive (NCA) or nonconducting paste (NCP). If the electrical component is a bare die, which is surrounded outside the electrical contact sites by a passivation layer, the adhesive joint is produced by means of this adhesive between the passivation layer and the surface of the electrically-conducting film.
According to one embodiment of the invention, an electrically-conducting film whose surface need not be coated with nanoparticles is used as starting material. In this case an adhesive containing the nanoparticles is used. The adhesive is applied to the at least one electrical contact site of the electrical component in order to fix the electrical component on the surface of the electrically-conducting film. The support is then applied in order to laminate the film with the support and at the same time conduct low-temperature sintering. In this case the nanoparticles contained in the adhesive joint are sintered. This embodiment of the method according to the invention is particularly advantageous, since the nanoparticles that are required for subsequent low-temperature sintering are also applied simultaneously by application of the adhesive.
According to one embodiment of the invention low-temperature sintering is conducted as “pressureless” low-temperature sintering. “Pressureless” is understood here to mean that low-temperature sintering is not conducted at the usually employed high pressures of, say, 200 bar, but at a much lower pressure, as is also used for lamination, i.e., at a pressure of, say, 15-20 bar.
Appropriate adhesives or pastes that contain the nanoparticles for such pressureless low-temperature sintering are known per se from the prior art, for example, from DE 10 2008 039 828 A1 and are commercially available from Heraeus under the trade names mAgic Adhesive and mAgic Paste.
A particularly efficient and material-saving production method is made possible on this account, since the amount of employed nanoparticles can be minimized. The joint so produced is also particularly mechanically stable and has good electrical contact properties owing to the covalent bonds of the nanoparticles that lead to limited contact resistance.
According to one embodiment of the invention the size of the nanoparticles is chosen so that they are relatively chemically inert at room temperature so that no spontaneous sintering occurs at room temperature. On the other hand, the size of the nanoparticles can be chosen sufficiently small so that the reactivity of the nanoparticles in comparison with macroscopic particles is already increased in the temperature range required for lamination so that formation of covalent chemical bonds occurs between the nanoparticles so that they are sintered to each other.
According to one embodiment of the invention the adhesive can be an LCP. This is particularly advantageous if the support is also formed by an LCP, especially with respect to thermal loadability and long-term stability of the resulting electronic assembly, which is particularly advantageous for application in the medical field, especially for implants.
In another aspect the invention concerns a method for production of an electronic assembly in which before lamination of the film with the support the at least one component arranged on the electrically-conducting film is enclosed with a filler material from a polymer, in which case low-temperature sintering already occurs in this enclosure step. This is particularly advantageous, if the resulting intermediate product must be transported from one production stage to another in a discontinuous process and also for the mechanical stability of the resulting electronic assembly.
In a further aspect the invention concerns an electronic assembly which was produced according to the method of the invention. This can be an implant, like an electronic module for an insulin pump, a pacemaker or an implantable hearing aid.
Provision of the film advantageously occurs by supplying individual foil sections cut to size or by supplying an endless film from a roll.
Provision of the at least one electrical component preferably occurs by supplying it on an endless film or supply in a magazine.
Arrangement of the at least one electronic component preferably occurs in automated fashion with an insertion robot or by hand, especially by means of templates or position markers in or on the film.
Provision of the support can occur by supplying individual support sections cut to size or by supplying an endless support from a roll.
Lamination of the film with the support preferably occurs by exerting a contact pressure on the film in the direction of the support, especially with simultaneous influence of heat.
Structuring of the electrically-conducting film to conductor tracks and optionally cooling surfaces advantageously occurs by direct structuring, for example, with a laser, or by generation of a positive or negative mask and subsequent etching.
The film is advantageously wound on a roll with the support and at least one electrical component after structuring of the film.
It can be prescribed in a modification of the invention that enclosure of at least one electrical component occurs after arrangement of the component on the film with a filler material from the polymer, especially a thermoplastic, thermosetting plastic or elastomer.
Filling of the filler advantageously occurs in predefined form, especially by casting, foaming, extrusion or lamination.
In a modification of the invention it can be prescribed that generation of at least one additional support layer occurs on the conductor tracks generated by structuring, in which case this is preferably insulating and/or dielectric and/or it contains additional conductor tracks.
In particular, application of at least one reinforcement layer, preferably several reinforcement layers on the support or support layer can occur after step 1.6. It can also be prescribed as an alternative that the support is optionally removed after step 1.6.
In a modification of the invention cutting out of the support in a predetermined shape can occur to form the electronic assembly, especially before and/or after lamination with the circuit board in step 1.6.
The electrically-conducting film can then consist of metal, especially copper, electrically-conducting plastic or electrically-conducting ceramic, on whose surface a layer of silver or a silver compound and/or a three-dimensional structure from metallic nanoparticles is optionally present at least in areas and is optionally reinforced by a support film.
It can be prescribed in particular that the electrically-conducting film on the side facing the at least one electrical component be smooth or roughened or have a bump structure.
It can be prescribed that the at least one electrical component is a passive or active component, especially a chip, in which case it is provided preferably outside the contact sites with a protective coating, especially a lacquer, i.e., a so-called passivation layer.
In a modification it can be prescribed that the protective coating be electrically insulated and/or a dielectric. The support can advantageously be a film, especially from metal, plastic or ceramic, a mat from natural materials, for example, plant fibers, a leather section, a textile section or section from another fabric or composite material or a circuit board, ceramic support or glass support.
In a modification of the invention it can be prescribed that the support is given a reinforcement layer and especially one made of metal, plastic or ceramic, from natural materials, like plant fibers, from leather, from textile or another fabric or composite material or a circuit board, ceramic support or a glass support.
The at least one electrical component can have at least one contact side in which at least one electrical contact site is arranged, in which case the at least one electrical contact site is preferably plane with the corresponding contact side.
The contact site advantageously consists of copper or a copper compound, on whose surface a layer of silver or a silver compound and/or a three-dimensional structure from metallic nanoparticles can optionally be present.
In a modification it can be prescribed that a section of the electrically conducting film is formed as a heat-removing contact area (film cooling section) on the at least one electrical component.
In a modification of the invention it can be prescribed that a cooling element or cooling channel is connected to the film cooling section and/or the at least one electronic component.
Additional details, features and advantages of the invention are apparent from the patent claims, whose wording becomes a content of the description by reference, the following description of preferred embodiments of the invention and with reference to the drawings.
In the drawings:
a shows an enlarged section of
b shows an enlarged depiction of a contact site of the component of
Corresponding or identical elements of the different embodiments are subsequently marked with the same reference numbers.
A robot arm grasps one or more components 5 from the film and places them on defined sites on the coated surface 30 of film 3. An adhesive is then applied between component 5 and the surface 30 of electrically-conducting film in order to fix the component by formation of an adhesive joint, in which case joint 7 is an adhesive joint.
The adhesive can be applied before positioning of one of the components 5 on the surface 30 of the film, As an alternative or in addition the adhesive can also be applied robotically, outside the electrical contact sites 5c on the active side, i.e., the contact side 5b of component 5. Another possibility is that the component is initially positioned by the robot arm on the surface 30 of the electrically-conductive film in order to arrange the component there and that subsequently the adhesive to produce the adhesive joint is applied, for example, by applying the adhesive along the side edge of the component (cf. also the embodiments according to
The adhesive joint produced in this way fixes the component 5 mechanically on film 3 without contacting it electrically. In this embodiment the adhesive 20 (cf.
According to one embodiment of the invention a film of thermoplastic polymer is unwound from an additional roll and placed on the arrangement of
In this step low-temperature sintering, i.e., to form a mechanical and electrical connection 23 between the contact sites 5c and surface 30, can already occur if the rolls are sufficiently warm.
A film of plastic composite material, in the present case glass fibers arranged in an epoxy resin, is now unwound from an additional roll and placed on the arrangement of
As shown in
A laser beam directed onto film surface 3u evaporates predetermined sections of film 3. The remaining sections of film 3 form conductor tracks 11 and electrically unbonded cooling section 13, see
Additional layers 9a and 9b are laminated onto the upper side in
The laminated layers 9, 9a, 9b and 19 with the electrical components 5 situated in them are separated by a laser beam into individual electronic assemblies. A partially broken down perspective view of the assembly 1 produced in this way is depicted in
a shows in a perspective view the film 3 with two electronic components 5.1 and 5.2, which are formed here as so-called bare dies.
b shows a top view of film 3 with the components 5.1 and 5.2 fixed on it by the adhesive joint. To form the adhesive joint between component 5.1 and film 3 adhesive 20 is applied along the lateral cutting edge 21 (cf. also
On the other hand, the adhesive 20 for fixation of component 5.2 on film 3 is applied spot-like in the area of the corners of component 5.2, as also shown in
c shows the corresponding sectional views. It is particularly advantageous here in both cases that the possible active surface for electrical contacting of components 5.1 and 5.2 is not reduced or only insignificantly so by formation of the adhesive joint. In particular, despite formation of the adhesive joint, essentially the entire bottom of components 5.1 and 5.2, i.e., the contact side 5b, is available for electrical contacting with film 3 and also the tops of components 5.1 and 5.2.
Adhesive 20 is applied to film 3 on the upper side 30 in
In a further process step electronic components are now positioned by means of appropriate devices on the locations at which adhesive 20 was previously applied so that the contact sites 5c of the components come in contact with adhesive 20; this is shown as an example in
These electronic components 5 are pressed on so that the adhesive points of the adhesive 20 are squeezed and only cover the contact sites 5c of the electronic components 5 and adhesive it relative to film 3. This state is depicted in
In a subsequent process step, which is not absolutely essential, an enclosure of filler material 19, for example, a polymer mass, can be applied around the electronic components 5, which encloses individual or all electronic components in a separate or common enclosure. Through this process sintering of the nanoparticles contained in adhesive 20 can be initiated in order to produce the joints 23 (cf.
The enclosure extends outside the electronic components 5 up to the upper side 30 of film 3 in
Since the enclosure encloses components 5 and extends up to film 3, and optionally also enters into a type of gluing with film 3, a mechanically stable block is formed on this account. The enclosure preferably also extends between the contact sites, as shown in
Subsequent to the process step whose result was shown in
In a further step the film 3 provided with the enclosure is laminated with a circuit board support 9, which comes to lie on the side of film 3 on which the electronic components 5 are also arranged (cf. the arrangement according to
In a further step the film 3 is now structured on its free side 8 so that conductor tracks are now generated.
This electronic assembly, however, can be further processed and further configured.
The two joined assemblies here differ from the simple assembly of
From the nonactive side of the electronic components 5 metallized cooling channels 15 lead through the circuit board support 9 to the middle cooling layer 12 so that the heat can be taken off here.
It is shown as an example in
An additional embodiment of the method proposed by the invention is depicted in
Whereas in
In a first process step the conducting film 33 is structured so that contact pads 35 are formed on the support film 34, which correspond to the connection sites 5c of the electronic components being attached.
Such an electronic component 5 is shown in
The adhesive 20 is an adhesive with nanoparticles distributed in the adhesive. An adhesive layer is therefore formed, which is present between the contact pads 35 and the connection sites 5c of the electronic component 5. In this way the electronic component 5 is connected with its connection sites 5c facing the contact pads 35, that is initially only via adhesive joints.
The electronic component 5 can then be surrounded with an enclosure of a filler material 19, again from a polymer mass, which encloses the entire electronic component 5, including the contact pads 35 and extends to the support film 34. This result is shown in
The support film 34 can then be separated, which is shown in
The electronic component 5 can then be positioned on the structured film so produced in the same manner, fastened with adhesive 20, as was shown in
The electronic assemblies, as shown in
The method proposed by the invention makes it possible to achieve significantly increased surface utilization on electronic circuit supports. Additional layers with components positioned in the narrow space can be produced, both active and passive components. The passive and active electronic components can be encapsulated cost effectively so that high reliability is achieved. Risky mixed techniques, namely soldering, gluing and wire bonding can be avoided in manufacture. Through a planar initial structure reproducible HF transitions can be achieved. It is a particular advantage that no separate process step is required to form the electronic connections, since this occurs by low-temperature sintering together with enclosure or lamination and that a particularly stable mechanical connection and an electrical connection with limited contact resistance as well as limited length simultaneously results from this, which is advantageous for high frequency applications.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2012/059476 | 5/22/2012 | WO | 00 | 12/19/2014 |