WO2007104700A2

WO2007104700A2 - A process for manufacturing a supporting element for an electronic circuit and the supporting element obtained thereby

Info

Publication number: WO2007104700A2
Application number: PCT/EP2007/052189
Authority: WO
Inventors: Diego Bortot
Original assignee: Elettrolab S.R.L.
Priority date: 2006-03-10
Filing date: 2007-03-08
Publication date: 2007-09-20
Also published as: ITTV20060031A1; WO2007104700A3

Abstract

The invention refers to a manufacturing process of a supporting element (1) for an electronic circuit. The process according to the invention enables a plurality of electrically isolated seats (4) to be obtained in a metallic base (2). These seats are suitable for containing the leg wires (100) of electronic components (200) assembled on said supporting element.

Description

A PROCESS FOR MANUFACTURING A SUPPORTING ELEMENT FOR AN ELECTRONIC CIRCUIT AND THE SUPPORTING ELEMENT OBTAINED THEREBY

DESCRIPTION

The present invention refers to a manufacturing process of a supporting element for electronic circuitry.

It is common knowledge that electronic circuits - and particularly one-sided, two-sided and multi-layer printed circuits, for instance - are assembled on dedicated supporting elements, or boards, whereon the components of the electronic circuit are installed. Generally speaking, these supporting elements comprise an insulating base (made of epoxy glass, for instance) on which one or more layers of insulating supporting material and one or more layers of conductive metallic material are deposited. These layers are then processed in order to define traces for connecting the various components in the electronic circuit. The electronic components are then installed on the supporting element according to the layout of the electronic circuit. The components are assembled after arranging suitable through holes in line with the various positions of the electronic components, inserting the leg wires on the electronic components in said through holes and then soldering the legs to the supporting element.

In some applications, such as in the field of lighting technology and/or the automotive industry, for instance, or in other areas of industrial electronics, it may be necessary to extract the heat produced by the electronic circuit. For this purpose, supporting elements are used that comprise a base made of a metallic material with a high thermal conductivity, such as aluminum. Successive insulating and metallic layers are then deposited on this base, which are subsequently processed in order to define the traces for connecting the circuit's components.

The presence of a metallic base has certain drawbacks, however, during the assembly of the electronic components.

In fact, the above-described conventional assembly technologies, which are known to be inexpensive and capable of ensuring a remarkable mechanical sturdiness, become unsuitable because any contact between the leg wires of the electronic circuit's components and the metallic base would cause an electrical short circuit of the electronic circuit.

Other known assembly techniques, and surface-mounting assembly techniques in particular, are consequently used to assemble the components. Although they ensure a greater degree of circuit integration, such techniques have the drawback of being relatively expensive and affording a mechanically less sturdy connection of the electronic components to the supporting element.

The main technical aim of the present invention is thus to realize a manufacturing process of a supporting element for an electronic circuit that enables the above-described drawbacks to be overcome.

As part of said aim, the first object of the present invention is to realize a manufacturing process that enables the assembly of the electronic components using methods capable of ensuring an excellent mechanical sturdiness of the connection between the supporting element and the electronic component despite the presence of a metallic base in the supporting element.

Another, not necessarily last, object of the present invention is to realize a manufacturing process that is easy to implement and at a competitive cost.

This aim and these objects, as well as other objects that will come to light from the subsequent description and attached drawings are achieved, according to the invention, by a manufacturing process, according to the following claim 1.

In a further aspect, the invention also refers to a supporting element for an electronic circuit, according to the following claim 12.

Further characteristics and advantages of the present invention will become easier to understand with reference to the description provided below and to the attached figures, provided simply for illustrative and non-restrictive purposes, wherein: figure 1 shows a processing step in the manufacturing process of a supporting element for an electronic circuit according to the present invention; figure 2 shows another processing step in the manufacturing process, according to the present invention; figure 3 shows another processing step in the manufacturing process, according to the present invention; figure 4 shows another processing step in the manufacturing process, according to the present invention; figure 5 shows an electronic component mounted on a portion of the supporting element for an electronic circuit manufactured by means of the manufacturing process according to the present invention.

With reference to the above-mentioned figures, the present invention refers to a manufacturing process of a supporting element 1 for an electronic circuit. The supporting element 1 comprises at least one base 2 made of a metallic material (e.g. aluminum), the purpose of which is to dissipate at least a part of the heat produced by the components in the electronic circuit.

The manufacturing process, according to the invention, comprises a stage wherein at least a first cavity 3 is arranged in the base 2. The first cavity 3 is obviously situated in a position where a leg wire 100 of a component 200 of the electronic circuit being assembled has to be connected to the supporting element 1. The first cavity 3 is preferably a cavity passing through the full thickness of the first base 2 and is preferably obtained by drilling. The first cavity 3 advantageously has a larger diameter than the diameter of the leg wire 100. The manufacturing process, according to the invention, also comprises a stage wherein at least one seat 4, electrically isolated from the first base 2, is arranged inside the first cavity 3. As shown in figure 5, the seat 4 is suitable for containing the leg wire 100 and for keeping said leg wire 100 electrically isolated from the first base 2. The seat 4 is preferably an electrically isolated channel passing through the full thickness of the first base 2. The seat 4 has a smaller diameter than the diameter of the through cavity 3. Moreover, the seat 4 has a diameter that substantially corresponds, subject to the obvious mechanical tolerances, to the diameter of the leg wire 100 to install in the seat 4, thus ensuring a secure fitting of the leg wire 100 in the seat 4.

With reference to figures 2-4, the manufacturing stage wherein the above-described seat 4 is arranged, preferably comprises a step wherein a predefined quantity of insulating material 40, e.g. an epoxy resin or equivalent material, is deposited on the surfaces 21 and 22 of the first base 2 so as to fill the first cavity 3 with said insulating material (figure 2). The insulating material 40 may be deposited using known surface deposition and/or injection and/or molding methods.

There is also a subsequent step wherein at least a portion 400 of the insulating material 40 is removed in order to obtain a layer of insulating material 41 that covers the inside walls of the first cavity 3 (figure 3). Clearly, the layer of insulating material 41 dimensionally defines the seat 4 for containing the leg wire 100. The portion 400 of the insulating material 40 is preferably removed by means of a drilling process, which is advantageously performed after the insulating material 40 has solidified. The thickness of the layer 41 coincides essentially with the difference between the diameter of the first cavity 3 and that of the seat 4. Said thickness is calculated as a function of the level of electrical insulation that has to be afforded by the layer 41, which depends substantially on the electrical voltage existing between the leg wire 100 and the first base 2.

Moreover, there is advantageously a subsequent step involving the removal of the portions 401 of the insulating material 40 that have been deposited on the surfaces 21 and 22 of the first base 2, but outside the first cavity 3 (figure 2). The portions 401 can be removed using methods known to the sector, such as a lapping process, or a process for the selective removal of material by means of suitable chemical agents.

The result of the above-described manufacturing processes is illustrated in figure 4, showing the first base 2, which comprises at least one electrically-isolated seat 4 suitable for containing a leg wire 100 and keeping it isolated from the first base 2. Clearly, the first base 2 may comprise a plurality of seats 4, arranged using the previously-described steps/stages, each of said seats 4 being suitable for containing a leg wire 100 of a component of an electronic circuit to assemble on the supporting element 1.

Moreover, a further embodiment of the manufacturing process, according to the invention,

(not shown) includes the preparation of a plurality of seats 4 inside the first cavity 3, so as to obtain a greater integration in the assembly of the electronic circuit.

The manufacturing process, according to the present invention, also comprises several stages for the deposition of insulating/metallic layers needed for the subsequent preparation of the traces for connecting the components in the electronic circuit.

The manufacturing process, according to the invention, thus comprises a stage wherein one or more second layers 23 of insulating material with appropriate dielectric properties are deposited on the surfaces 21 and 22 of the first base 2.

This stage is immediately followed by a stage wherein one or more third layers 24 of metallic material are deposited on said second layers 23. Clearly, the purpose of the second layers 23 is to support the third layers 24 and to isolate them electrically from the first base 2. The third layers 24 are used to arrange the connection traces (not shown) on the electronic circuit. The layers 23 and 24 can be deposited using known methods, such as selective depositing and/or pressing process. Of course, depending on the type of electronic circuit required, the layers 23 and 24 can be deposited on one or both surfaces 21 and 22 of the first base 2.

These stages can also take place at different times in the above described manufacturing process, according to need. For instance, they may precede the stage wherein the first cavity 3 is arranged, in which case, the preparation of the first cavity 3 also involves removing portions of the layers 23 and 24 as well as of the base 2. Alternatively, these stages may be completed immediately after the processing step wherein the cavity 3 is filled with the insulating material 40, in which case, the subsequent step for removing the portion 400 of the insulating material 40 to arrange the seat 4 also includes removing portions of the layers 23 and 24. According to a further variant, these stages may take place after the stage for the preparation of the seat 4, in which case the layers 23 and 24 are deposited on the outside of the seat 4, so as to avoid obstructing said seat.

Finally, the manufacturing process, according to the invention, may also include a stage wherein the traces connecting the components in the electronic circuit are arranged on the third layers 24. This stage can be executed using methods already known in the field of manufacturing of supporting elements for electronic circuits. After the connection traces have been arranged, they can be covered with a further insulating and protective layer 50, such as a layer of resist. Then the components 200 of the electronic circuit can be assembled on one or both sides of the supporting element 1, according to need and depending on the type of electronic circuit required. The leg wires 100 of the components 200 are inserted in the seats 4, and said components 200 are advantageously fixed definitively to the supporting element 1 by soldering 60. It should be noted that, if necessary, the insides of the seats 4 can be metal- covered by means of a metallic layer deposited over the layer 41.

In practice, it has been demonstrated that the manufacturing process, according to the invention, enables the above-mentioned objects to be achieved.

The preparation of seats 4 in the first metal base 2, which are electrically isolated therefrom, enables the electrical continuity to be achieved between the two sides of the supporting element 1, since the leg wires 100 of the components 200 can pass through the first base 2, without the risk of a short circuit. Adequate heat sinking is consequently assured and, at the same time, conventional methods can be used to install the electronic components, despite the presence of a metallic base in the supporting element. Moreover, any type of electronic component is suitable for use (even if it is not of the surface-mounted type) in the assembly of the electronic circuit. All the above features enable a more sturdy connection and a considerable reduction in the manufacturing costs of the electronic circuit. Finally, it has been verified in practice that the manufacturing process, according to the present invention, has no particular difficulties from the point of view of its implementation. In fact, it is easy to complete at a limited, economically competitive cost and demands no excessive investments.

Claims

1. A manufacturing process of a supporting element for an electronic circuit, said supporting element comprising at least a first base made of a metallic material suitable for dissipating at least a part of the heat generated by the components in said electronic circuit, characterized in that it comprises the following stages: arranging a first cavity in said first metallic base; arranging at least one seat inside said first cavity that is electrically isolated from said first base and suitable for containing a leg wire of a component of said electronic circuit, thereby keeping said leg wire electrically isolated from said first base.

2. A manufacturing process, according to claim 1, characterized in that said first cavity is a cavity passing through the thickness of said first base.

3. A manufacturing process, according to one or more of the previous claims, characterized in that said seat isolated electrically from said first base is a channel passing through the thickness of said first base.

4. A manufacturing process, according to claim 3, characterized in that said second through cavity has a smaller diameter than that of the first through cavity.

5. A manufacturing process, according to claim 4, characterized in that said second through cavity has a diameter substantially coinciding with the diameter of the leg wire contained inside said second through cavity.

6. A manufacturing process, according to one or more of the previous claims, characterized in that a plurality of said seats electrically isolated from said first base is arranged inside said first cavity, each of said seats being suitable for containing a leg wire of a component of said electronic circuit, in order to keep said lead wire electrically isolated from said first metallic base.

7. A manufacturing process, according to one or more of the previous claims, characterized in that said stage of manufacturing said seat electrically isolated from said first base comprises the following steps: depositing a predefined quantity of insulating material, so as to fill said first cavity with said insulating material; removing at least a portion of said insulating material, so as to obtain a layer of insulating material suitable for covering the inside walls of said first cavity, said layer of insulating material defining said seat electrically isolated from said first base.

8. A manufacturing process, according to claim 7, characterized in that said stage of arranging said seat electrically isolated from said first base comprises the following step: removing the portions of said insulating material deposited on the outside of said first cavity.

9. A manufacturing process, according to one or more of the previous claims, characterized in that it comprises the following stages: depositing one or more second layers of insulating material; depositing one or more third layers of metallic material on said second layers.

10. A manufacturing process, according to one or more of the previous claims, characterized in that it also comprises the following stage: arranging traces for connecting the components in said electronic circuit on said third layers.

11. A supporting element for an electronic circuit characterized in that it is obtained by means of a manufacturing process, according to one or more of the previous claims.

12. A supporting element for an electronic circuit comprising at least a first base of metallic material suitable for dissipating at least a part of the heat produced by the components of said electronic circuit, characterized in that said first base comprises at least one seat electrically isolated from said first base and suitable for containing a leg wire of a component of said electronic circuit, thereby keeping said leg wire electrically isolated from said first base.

13. A supporting element, according to claim 12, characterized in that said seat electrically isolated from said first base is a channel passing through the thickness of said first base.