A method for making electrical connections

Abstract

A method for making electrical connections between printed circuits, electrical components and electronic components comprising the following steps: providing a rigid support (2; 102); coupling to the rigid support (2; 102) a film of dielectric material (2a) having a first face (3) facing the rigid support (2; 102) and a second visible face (4); forming on the second face (4) tracks (5) of electrically conductive material; forming first electrical connection areas (6) in electrical connection with the tracks (5) capable of being placed in electrical connection with the printed circuits, the electrical components and / or the electronic components; removing the film of dielectric material (2a) from the rigid support (2; 102). The film of dielectric material (2a) with the tracks (5) and the first electrical connection areas (6) constituting an electrical connection element (1; 100) between the printed circuits, the electrical components and / or the electronic components.

Description

[0001] A METHOD FOR MAKING ELECTRICAL CONNECTIONS DESCRIPTION

[0002] Field of application

[0003] The present invention is applicable to the sector of electronic and microelectronic packaging or electrical connection of components and parts of electronic circuits or integrated circuits.

[0004] More in detail, the present invention relates to a method for producing Printed Circuit Boards (PCBs) and flexible microelectronic components, compatible with alternative electrical connection methods to so-called wire bonding.

[0005] Prior art

[0006] In the production of printed circuit boards, integrated circuits and electronic components in general, great precision is required in making the electrical connections between the parts, increasingly organized according to complex and layered geometries.

[0007] In particular, one of the techniques mostly used to connect components and parts to the electronic circuit of which they must be part is wire bonding, that is, an electrical connection made with electrically conductive filaments and of particularly small dimensions (typically of the order of a few tens of p.m).

[0008] It is clear that great precision is required with this technology. In particular, great precision is required in the alignment of each filament with the relative electrical connection pad present in the microchip, in the quality of the welding between the filament and the pad, and in the control of the welding temperature in order to avoid damage to the microchip.

[0009] The automated positioning of the various components and parts of the electronic circuit and electrical connections undoubtedly improves the efficiency of the process, but has limitations linked not only to the size of the components treated, but also to their fragility. Moreover, welding technologies are constantly evolving, but remain susceptible to defects.

[0010] The semiconductor industry envisages the packaging step as a separate secondary step after the manufacture of the various components and parts of the electronic circuit. The silicon wafers in which they are first cut to separate the various components and parts of the electronic circuit, then they are electrically verified to discard the defective or qualitatively inadequate ones and subsequently sent to separate production facilities where the packaging is carried out.

[0011] This multi-step production approach, practiced in different production facilities using different machines, is one of the main sources of contamination of electronic components.

[0012] Moreover, there are cases where complex packaging may be necessary, which require the development of an advanced design that requires manufacturing steps also immediately following the assembly / electrical connection. An example is the need to make 2.5D and 3D high density interconnect connectors (interposers) or packaging, in which multiple electrical and / or electronic components as well as parts of the electronic circuit, produced separately, are coupled together within the same packaging (heterogeneous integration of a system in a SiP package). It is evident that in this case both the interconnection by wire bonding and the subsequent execution of the packaging in production structures different from those of the electronic components increases the executive complexity and the probability of damage and contamination of the same.

[0013] Presentation of the invention

[0014] The object of the present invention is to at least partially overcome the drawbacks noted above, by providing a method for making electrical connections between printed circuits, electrical components and electronic components which allows avoiding or at least limiting the possibilities of contamination of the components.

[0015] Another object of the present invention is to make available a method for making electrical connections between printed circuits, electrical components and electronic components that allows the use of wire bonding to be avoided, guaranteeing greater flexibility and less defect of electrical interconnection and greater mechanical stability of the bonding.

[0016] A further object of the present invention is to make available a method for making electrical connections between printed circuits, electrical components and electronic components that allows the development of complex packaging, including 3D, in a simple and customizable way based on the real components or real parts to be interconnected.

[0017] From all this it follows that another object of the invention is to allow the aforesaid electrical connection to be made directly in a single clean room, i.e. where the silicon wafer is machined to make a plurality of microchips even different from each other.

[0018] Accordingly, a further object of the present invention is to make available a method for making electrical connections between printed circuits, electrical components and electronic components that allows the electrical connection of such connections to be made with the microchip before the latter is separated from the production wafer.

[0019] Such objects, as well as others which will become clearer below, are achieved by a method for making a diode radiation sensor in accordance with the following claims, which are to be considered as an integral part of the present disclosure.

[0020] In particular, the method comprises a step of providing a rigid support to which at least one film of dielectric material having a first face facing the rigid support and a second visible face is coupled. It should be noted that a rigid support means a support made of any material of any shape as long as it is stiffer than the film made of dielectric material.

[0021] According to an aspect of the invention, on the second face of the film of dielectric material a plurality of tracks of electrically conductive material and a plurality of first electrical connection areas are formed in electrical connection with the tracks and capable of being placed in electrical connection at least with the printed circuits, the electrical components and / or the electronic components.

[0022] Subsequently there is a step of removing the film of dielectric material from the rigid support and overturning the film of dielectric material so that the second face faces the rigid support.

[0023] Then it is proceeded with re-coupling the film of dielectric material to the rigid support so that the first face is visible. In this way, it can be proceeded with forming one or more second tracks of electrically conductive material on the first face.

[0024] In particular, therefore, with the aforesaid steps of the method subject- matter of the invention, an electrical connection element is made comprising at least a film of dielectric material on which there are placed a plurality of tracks of electrically conductive material on both sides and a plurality of first electrical connection areas. With this element the desired electrical connections are made.

[0025] Advantageously, the electrical lines responsible for the connection between printed circuits and / or between these and the electrical and / or electronic components of the electronic circuit to be made consist of tracks deposited on a special support (the film in dielectric material), thereby ensuring their seal during assembly with the printed circuits and or electrical or electronic components as well as subsequently during their use.

[0026] Still advantageously, the execution of such electrical connections according to the present invention allows to guarantee precision in their realization in an easier way than the prior art.

[0027] Still advantageously, with the method of the invention the electrical connection element can be directly integrated and glued on the printed circuits or directly integrated or coupled with the electrical or electronic components. It follows that, advantageously, with the method of the invention the packaging can be performed at the wafer level, i.e. the electrical connection element can be integrated with printed circuits or electrical / electronic components before their separation from the wafer.

[0028] Still advantageously, therefore, with the method for making electrical connection of the present invention the electrical couplings can be made in a single clean room.

[0029] As a result, still advantageously, with the method of the invention the chances of contamination of the microchips can be decreased and complex even 3D packaging can be conveniently made.

[0030] Still advantageously, the connection method of the invention allows the removal of the support at any machining step to overturn the film in dielectric material and proceed with machining on the opposite face.

[0031] Still advantageously, these overturns can be multiple allowing complex machining and, in particular, to carry out machining on one side of the film which, on the opposite side, would be prevented by the presence of intermediate electrical connection elements. Basically, it is thus possible to work on one face on areas that would be in the shadow zone of machining made on the opposite face.

[0032] Still advantageously, it is observed that for all of the above the electrical connection element obtained by the method of the invention is performed separately (even if in the same environment), by printed circuits, electrical components and electronic components that said electrical connection element must interconnect.

[0033] Brief description of the drawings

[0034] Further features and advantages of the invention will become more apparent in light of the detailed description of some preferred, but not exclusive, embodiments of a method for making electrical connections between printed circuits, electrical components and electronic components according to the invention, illustrated by way of non-limiting example with the aid of the accompanying drawings, in which:

[0035] FIG. 1 depicts an electrical connection element according to the invention in perspective view;

[0036] FIG. 2 depicts a descriptive block diagram of a method for making electrical connections between printed circuits, electrical components and electronic components according to the invention;

[0037] FIG. 3 depicts a detail of a second variant embodiment of the method of FIG. 2;

[0038] FIGS. 4 to 7 depict different embodiment variants of the electrical connection element of FIG. 1 .

[0039] Detailed description of an exemplary preferred embodiment

[0040] With reference to the aforesaid figures, a method for making electrical connections between printed circuits, electrical components and electronic components is described. In other words, with the method of the present invention it is possible to connect printed circuits, electrical components, electronic components and any combination thereof.

[0041] In the present description and, in particular, in Figs. 1 and 2, an embodiment will be described where there is a single electrical connection element 1 obtained with the method of the invention, a single electronic component consisting of a microchip M and a single electronic circuit C in which the aforesaid microchip M is functionally inserted, but it is evident that this aspect, as will be illustrated with the aid of further figures, must not be limiting for the present invention, the number of connection elements, electrical and / or electronic components and electronic circuits being non-limiting characteristics for the invention. Moreover, according to further embodiment variants of the invention, the electrical connection element of the invention can be electrically connected to other electrical connection elements both according to the present invention and of a known type.

[0042] Also with the aid of Fig. 3, it is observed that the method of the invention provides for a step 50 of providing a rigid support 2. According to the embodiment being described, the rigid support 2 consists of a vetronite board, but this constitutes a non-limiting example for the present invention. According to a particular embodiment variant, moreover, the board is transparent.

[0043] Then there is a step of arranging a layer of adhesive material (not depicted in the figures) on the rigid support, a step indicated with 51 in the figure. This step serves to then be able to cling onto the rigid support, with a subsequent step 52, a film of dielectric material 2a having a first face 3 facing the rigid support 2 and a second visible face 4. The step indicated with 51, therefore, serves to make the coupling between the rigid support 2 and the film of dielectric material 2a and to guarantee stability to this coupling during the subsequent processing steps. However, such an embodiment should not be considered as limiting for the invention. In fact, what matters in the present invention is the aforesaid coupling. It can therefore also be made in different ways without any limit for the present invention.

[0044] Obviously, also the type of adhesive material is not a limiting characteristic for the present invention. With regard to the film of dielectric material 2a, it is typically made of polyimide, but also this aspect should not be considered limiting for the present invention, the material used for making the dielectric film can be any dielectric material.

[0045] According to an aspect of the invention, subsequently there is a step of forming or making (indicated with 53 in the figures), on the second face 4 of the film in dielectric material 2a, a plurality of tracks 5 in electrically conductive material. These tracks are the ones that constitute the electrical connection between the microchip M and the electronic circuit C.

[0046] In fig. 3 it is observed that the film in dielectric material 2a is already shaped in accordance with the electrical connection to be made (visible in fig. 1 ). In other words, the dielectric material film 2a was obtained with a previous operation of cutting a sheet of dielectric material. However, such aspect must not be considered as limiting for the present invention. According to some embodiment variants, in fact, the film made of dielectric material consists of the entire sheet which is first subjected to the machinings described above and subsequently cut with the desired shaping. In such cases, a step for setting up the cutting or engraving of the dielectric material is provided. This step allows the contours of any number of distinct individual electrical connection elements initially belonging to the same film of dielectric material to be shaped in any shape.

[0047] In other words, on the same film of dielectric material arranged on the same rigid support, it is possible to simultaneously make several electrical connection elements that will be advantageously separated with a cutting or engraving step.

[0048] Furthermore, this step can be used to make through holes (VIA) of any shape or to engrave any pattern in the film made of dielectric material.

[0049] Advantageously, the step just described can be carried out by means of known lithography and attachment techniques. This is advantageously due to the fact that this step can take place in the same machining environment where the electrical connection element of the invention is made. Moreover, this not only allows to speed up obtaining the finished product and to make it economically more advantageous, but also allows to avoid handling and transporting the product to another machining area to perform its cutting or engraving thereby subjecting it to risks of damage or contamination.

[0050] Among the cutting or engraving techniques are mentioned, for example, wet etching or mechanical or laser machining. Advantageously, etching of the present invention may include dry etching or plasma etching techniques, such as for example reactive ion etching or reactive ion etching or deep reactive ion etching. However, also this aspect should not be considered limiting for the present invention, as there are embodiment variants of the present invention where such a step is not provided.

[0051] During the step indicated with 53 of forming the tracks 5, typically, but not necessarily, there is also the formation on the second face 4 of the film in dielectric material 2a of a plurality of first electrical connection areas 6 in electrical connection with the tracks in electrically conductive material 5 and capable of being placed in electrical connection with the microchip M and the electronic circuit C.

[0052] According to the embodiment being described, said steps of forming tracks 5 and first electrical connection areas 6 are carried out with a photolithographic technique. In more detail, provision is made for a film of electrically conductive material, not represented in the figures, which is coupled to the second face 4 of the film of dielectric material 2a.

[0053] Subsequently, the masking of the film of electrically conductive material is carried out, thus drawing the tracks 5 and the electrical connection areas 6. Subsequently, any unmasked electrically conductive material is removed by a normal known process.

[0054] Obviously, even that aspect of the invention should not be considered as limiting for different embodiment variants. For example, both the tracks and the electrical connection areas may be made by direct deposition of electrically conductive material onto the dielectric material film. Mixed embodiment variants are not excluded where only the tracks or only the electrical connection areas are performed with the photolithographic technique, while the remaining are performed by deposition.

[0055] In any case, according to the embodiment being described, the electrically conductive material is aluminium, but also this aspect must not be considered limiting for different embodiment variants according to which the electrically conductive material is for example copper.

[0056] According to another aspect of the invention, after making tracks 5 and electrical connection areas 6 there is a step of removing, indicated with 54, the film of dielectric material 2a from the rigid support 2. The electrical connection element 1 was then obtained which was ready to be stably coupled to the microchip M.

[0057] Advantageously, the electrical lines responsible for the connection between the microchip M and the electronic circuit C consist of tracks 5 formed on a special support (the film in dielectric material 2a), thereby ensuring their seal during assembly with the microchip M as well as subsequently during its use.

[0058] Still advantageously, the execution of such electrical connections allows to guarantee precision in their realization in an easier way compared to the prior art. In particular, resting on a rigid support promotes both precision and manageability throughout the construction of the electrical connection element 1

[0059] Still advantageously, therefore, with the method for making the electrical connection between microchip M and electronic circuits C just described, such electrical couplings can be made directly in the same clean room in which the microchip M is made or in general one or more of the electrical and / or electronic components that will be electrically connected to the printed circuit with the electrical connection element 1 of the invention are made.

[0060] It follows, still advantageously, that with the method of the invention the electrical connection element 1 can be, as will be seen shortly, directly coupled to the microchip M. Moreover, still advantageously, with the method of the invention the packaging can be performed at the wafer level (wafer level packaging), i.e. the electrical connection element 1 can be integrated with the microchip M before its separation from the wafer.

[0061] As a result, still advantageously, with the method just described, the chances of contamination of the microchip M have been reduced and even 3D complex packaging can be carried out with convenience.

[0062] It is noted that, still advantageously, the method described above allows to realize embodiment variants, an example of which is visible in fig. 4, where the coupling between the electrical connection element 100, the microchip M and / or the electronic circuit C takes place when the electrical connection element 100 is still arranged on the rigid support 102.

[0063] So far we have seen the execution of a single-layer or monolayer electrical connection element. However, also this aspect should not be considered limiting for the present invention, as there are embodiment variants of the present invention where the electrical connection element is multilayer. In such a case, before the removal of the electrical connection element from the rigid support there are some additional steps in the method which, actually, repeat some of the steps described so far.

[0064] In particular, there is a step of coupling to the visible face, and above the newly formed tracks, a further film of dielectric material. A plurality of further tracks in electrically conductive material and a plurality of further first electrical connection areas in electrical connection with the aforesaid further tracks in electrically conductive material are then formed on the latter. One or more of these further areas, moreover, are used for electrical connections between different layers. In this case there will be ways (known in the field of multilayer printed circuits or multilayer PCBs) made at electrical connection areas of the first layer and further electrical connection areas of additional layers.

[0065] In the embodiment described above, the coupling between films of dielectric material and the rigid support was made by means of adhesive. In the present variant, the same also happens between the various films in dielectric material. However, also in this case the union between the films can be obtained in any alternative way.

[0066] The steps indicated in the previous embodiment are then repeated with 51, 52, 53. These steps of adhesive deposition, further film in dielectric material and formation of further tracks and further electrical connection areas can be repeated any number of times in accordance with the design parameters of the electronic circuit to be made and the electrical connections to be made. In this way, a multilayer electrical connection element is made.

[0067] In this case too, advantageously, this operation is favoured and facilitated by the arrangement of the whole on a rigid support that allows a correct control of the electrical connection element being made without the risk of pollution or damage to the same. Moreover, especially in the multilayer case, the presence of the rigid support allows the extreme precision of the machining.

[0068] According to other embodiment variants, some layers are made of materials different from the dielectric material films of the other layers. In some cases the change relates to the type of dielectric material used, but in other cases the change relates to the material in the sense of using non-dielectric materials such as, by way of a non-limiting example, lead. This allows to apply the present invention to particular fields of art such as electromedical instrumentation or the execution of antennas for the transceiving of signals in frequency.

[0069] According to another aspect of the invention, second tracks and electrical connection areas are also made on the first face 3 of the film in dielectric material 2a.

[0070] In this sense, after completing the machining on the second face 4 of the film in dielectric material 2a, the same film 2a is detached from the rigid support 2, it is overturned and re-coupled to the rigid support 2 with the second face 4 facing the rigid support 2 and the first visible face 3.

[0071] It is then proceeded with the formation of the second tracks and the electrical contact areas also on the first face 3.

[0072] Moreover, according to further embodiment variants, also on the first side it is proceeded, similarly to what was done on the second face, with the creation of a multilayer.

[0073] Advantageously, the connection method of the invention allows the removal of the support 2 at any machining step to overturn the film in dielectric material 2a and proceed with machining on the opposite face.

[0074] Still advantageously, these overturnings can be multiple allowing complex machining and, in particular, to carry out machining on one face of the film 2a which, on the opposite face, would be prevented by the presence of intermediate electrical connection elements. Basically, it is thus possible to work on one face on areas that would be in the shadow zone of machining made on the opposite face.

[0075] Still advantageously, it is observed that for all the above the electrical connection element 1 obtained by the method of the invention is made separately (even if in the same environment), by printed circuits, electrical components and electronic components that said electrical connection element will have to interconnect.

[0076] According to another aspect of the main embodiment being described, electrical or electronic components 10 are also coupled to the faces 3, 4 of the dielectric film 2a, for example, to make resistive or impedance adaptations on the electrical connections. Still, there are also further electrical and electronic components 11 made directly on the film in dielectric material 2a giving a suitable shape to the tracks 5.

[0077] In any case, once the electrical connection element 1 has been made, it is possible to proceed, always within the same clean room where the wafer microchips M (or in general components or parts of the electronic circuit to be executed) are made, to the electrical connection between them and the electrical connection element 1.

[0078] According to the embodiment being described, the microchips M to which the relative electrical connection elements must be connected are provided in wafers. Before cutting the wafer, at each microchip M, having a plurality of second electrical connection areas (not visible in the figures) a corresponding electrical connection element 1 is partially arranged superimposed so that the first electrical connection areas 6 of the latter are at the second electrical connection areas of the microchip M. Subsequently, it is proceeded with a step of electrical connection (with mechanical stability) between the first electrical connection areas 6 and the second electrical connection areas on the microchip M.

[0079] It should be noted that, as seen above, such operations should not be considered limiting for the invention. For example, it has previously been seen that according to some embodiment variants, instead of moving the electrical connection elements by connecting them to the respective microchips on the wafer, it is also possible to provide for cutting the wafer and moving the microchips towards the respective electrical connection elements and performing the stable electrical connection thereof.

[0080] From what has been said, it can be immediately understood how with the method of the invention it is possible to make electronic circuits where with the same electrical connection element of the invention it is possible to connect several microchips, several electrical and electronic components and several circuit parts at the same time. Two examples of such embodiment variants are depicted in figs. 5 and 6.

[0081] Moreover, it can be equally immediately understood how with the method of the invention it is possible to make complex electronic circuits where there are microchips, circuit parts and electrical connection elements according to the invention arranged as a multilayer. An example of this is visible in fig. 7.

[0082] In light of the foregoing, it can be understood that the method for making electrical connections between printed circuits, electrical components and electronic components of the invention achieves all the set purposes.

[0083] In particular, the method allows to avoid or at least limit the possibilities of contamination of the microchips or electrical / electronic components to be used.

[0084] Moreover, it makes it possible to avoid the use of wire bonding, guaranteeing greater ease and fewer defects in electrical interconnection.

[0085] In addition, the method of the invention allows the development of complex 3D packaging in a simple and customizable way based on the actual microchips to be interconnected.

[0086] On closer inspection, therefore, the method of the invention allows the aforesaid electrical connection to be made directly in the clean room, i.e. where the silicon wafer is processed to make a plurality of components that are also different from each other.

[0087] The invention is subject to numerous modifications and variations, all falling within the appended claims. All the details may be replaced by other technically equivalent elements, and the materials may be different according to requirements, without departing from the scope of protection of the present invention.

Claims

CLAIMS1 . A method for making electrical connections between printed circuits, electrical components and electronic components comprising the following steps: providing a rigid support (2; 102); coupling to said rigid support (2; 102) at least one film of dielectric material (2a) having a first face (3) facing said rigid support (2; 102) and a second visible face (4); forming on said second face (4) of said at least one film of dielectric material (2a) one or more tracks (5) of electrically conductive material; forming on said second face (4) of said at least one film of dielectric material (2a) one or more first electrical connection areas (6) in electrical connection with said tracks (5) of electrically conductive material and capable of being placed in electrical connection at least with said printed circuits, said electrical components and / or said electronic components; removing said at least one film of dielectric material (2a) from said rigid support (2; 102); overturning said at least one dielectric film (2a) so that said second face (4) of said at least one dielectric film (2a) faces said rigid support (2; 102); coupling again said at least one film of dielectric material (2a) to said rigid support (2; 102) so that said first face (3) is visible; forming on said first face (3) of said at least one film in dielectric material (2a) one or more second tracks in electrically conductive material, said at least one film of dielectric material (2a) with said one or more tracks (5) of electrically conductive material, said one or more second tracks of electrically conductive material and said one or more first electrical connection areas (6) constituting an electrical connection element (1; 100) at least among said printed circuits, said electrical components and / or said electronic components.

2. Method according to claim 1 wherein before said step of removing (54) said at least one film of dielectric material (2a) from said rigid support (2; 102) the following steps are repeated one or more times: coupling to said at least one film of dielectric material (2a) at leastone further film of dielectric material; forming on said at least one further film in dielectric material one or more further tracks in electrically conductive material; forming on said at least one further film in dielectric material one or more further first electrical connection areas in electrical connection at least with said further tracks in electrically conductive material, so as to provide a multilayer electrical connection element.

3. Method according to one or more of the preceding claims, further comprising the following steps after said step of removing (54) said at least one film of dielectric material (2a) from said rigid support (2; 102): providing said one or more printed circuits and / or said one or more electrical or electronic components provided with a plurality of second electrical connection areas; arranging said at least one film of dielectric material (2a) at least partially superimposed on said printed circuits and / or said electrical components and / or said electronic components so that at least one of said first electrical connection areas (6) is at least at one of said second electrical connection areas; stably and electrically connecting said at least one of said first electrical connection areas (6) with said at least one of said second electrical connection areas.

4. Method according to one or more of the preceding claims, wherein at least said step of forming (53) on said second face (4) of at least one film in dielectric material (2a) said plurality of tracks (5) in electrically conductive material comprises the following steps: providing a film of electrically conductive material; coupling to said at least one film of dielectric material (2a) said film of electrically conductive material; masking on said film of electrically conductive material said plurality of tracks (5); removing from said film of electrically conductive material all unmasked electrically conductive material.

5. Method according to one or more of claims 1 to 3, wherein at leastsaid step of forming (53) on said second face (4) of said at least one film of dielectric material (2a) said plurality of tracks (5) of electrically conductive material comprises a step of depositing electrically conductive material on said second face (4) of said at least one film of dielectric material (5) to form said tracks (5).

6. Method according to one or more of the preceding claims, wherein said electrically conductive material is copper.

7. Method according to one or more of claims 1 to 5 wherein said electrically conductive material is aluminium.

8. Method according to one or more of the preceding claims, wherein said electrically dielectric material is polyimide.

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