FR2837982A1 - INTEGRATED CIRCUIT MODULE AND MANUFACTURING METHOD THEREOF - Google Patents

Abstract

An integrated circuit module comprises thermal contact pads (12) substantially in the same surface plane as the connection pads (6, 7) on the active faces of the components, a thermal contact pad corresponding to a conductive element of a component (1), connected to the ground plane thereof and located as close as possible to a hot spot, and heat conduction elements (12) passing through an interconnection structure of the collective wiring type (9), looking at said thermal contact pads (12), making it possible to connect these pads to a heat dissipation device (Dth). The thermal contact pads can be produced in the component manufacturing process, or collectively, in the module manufacturing process. Preferably, the thermal contact pads are formed on air bridges of power transistor.

Description

B 14079.3 AL

  INTEGRATED CIRCUIT MODULE AND METHOD

OF CORRESPONDING MANUFACTURE

  The present invention relates to an integrated circuit module and a corresponding manufacturing method. A more particularly interesting application relates to modules integrating power components, such as, for example, AsGa components of the MMIC type (acronym for MonolitElc Microwave Integratod Clrcuit), for which it is necessary to have good heat dissipation. Usually, heat dissipation is obtained by means of suitable elements providing a thermal path in the module considered, o between the rear face of the power components and a cooling device, such as a cold plate or a heat sink. The chaub points of the components are located on the front face. Hot spots

  typically correspond to junctions of power transistors.

  Also, the heat dissipation path in the component crosses it all 1 the substrate of the component itself, from the front face, to the rear face. In the invention, it has been sought to limit the heat exchanges to

inside the components.

  The solution found to this technical problem is to provide zo means of cooling by the front face of the components, by reducing

  as much as possible the heat dissipation by the back face.

  The invention applies more particularly to the field of integrated circuit modules, or MCM modules (acronym for Multl-Chip Module). These modules integrate different types of z components (silicon chips, surface wave filters, passive components ...), and their interconnection structure comes from so-called collective wiring technologies. According to these technologies, components are placed in an insulating substrate, so that the connection pads of these components are substantially in the same surface plane as the front face o of the insulating substrate. The substrate can be molded or etched. An interconnection structure of the collective wiring type is produced on the front face of the substrate, and makes it possible to interconnect the components with one another and to the outside. This structure comprises at least one layer of

  dielectric, metallized holes and a network of conductors.

  According to the invention, thermal contact areas are provided on the active face of certain components, corresponding to conductive elements electrically connected to the ground plane. Heat conduction elements are made in the interconnection structure to thermally connect these thermal contact pads to a heat dissipation device. These thermal contact areas are in practice located near hot spots. These are for example air bridges o power transistors. For example, a thermal contact area is made on an air bridge which contacts the emitters of the transistors

  elements of a HBT type power transistor (acronym

  Saxon for Heterojanction Bipolar Transisto4, or on an air bridge which contacts the sources of the elementary transistors of a power transistor of HEMT (High electron Mobility Transistor) type. These thermal contact areas are located substantially in the same surface plane

  as the connection pads and the front face of the insulating substrate.

  The invention therefore relates to an electronic component comprising an active face comprising conductive elements and zo connection pads, characterized in that it comprises a range of thermal contact at least on the active face, each range of thermal contact comprising an element of conductor electrically connected to the ground plane of the component, and a thermal contact surface comprising at least the

  contact surface with said conductive element.

  According to one aspect of the invention, the conductor element of a thermal contact area is an air bridge of a power transistor. Preferably, the surface of the thermal contact area covers

  substantially the surface of the power transistor.

  The invention also relates to an integrated circuit module comprising an insulating substrate, a plurality of electronic components including at least one component with one or more thermal contact pads, the components being placed in said substrate so that the connection pads are substantially in the same surface plane as the front face of the substrate, and an interconnection structure of collective wiring type ss arranged on said front face to connect the components together and to the outside, characterized in that the contact pads thermal are substantially in the same surface plane as the connection pads, and in that it comprises thermal conduction elements passing through said interconnection structure opposite said thermal contact pads

  making it possible to connect said pads to a heat dissipation device.

  The invention also relates to a method for manufacturing thermal contact pads on a component, comprising in particular the production of openings in a protective layer covering the active face of the

  component and filling of these openings with conductive material.

  o In a variant, provision is made to widen these thermal contact areas produced on the active faces of the components, in order to increase the surface

heat exchange.

  A method of manufacturing a module, in particular comprises the formation of holes passing through the interconnection structure, plugged with thermally conductive material, opposite the contact pads

  thermal on the active faces of the components.

  Other characteristics and advantages of the inventi on are detailed.

  in the following description, given by way of example, and with reference to

  o accompanying drawings in which: - Figure 1 is a longitudinal sectional view of a module according to the invention reported by surface mounting on a printed circuit bonded to a cooling circuit, - Figure 2 is a longitudinal sectional view of an example of an electronic circuit comprising integrated circuit modules according to the invention; FIGS. 3 and 4 are views in longitudinal and transverse section of a thermal conduction element on an air bridge of a power transistor serving as a thermal contact pad according to the invention, FIGS. 5 to 13 show steps for manufacturing an integrated circuit module in a molded substrate, including making thermal contact pads and corresponding thermal conduction elements, and FIG. 14 shows an example of a module obtained according to a

manufacturing variant.

  FIG. 1 shows an integrated circuit module M cooled by its front face according to the principle of the invention. For the sake of clarity, only one component 1 is represented in the module. This component is arranged in the substrate so that its connection pads 6, 7 are substantially in the same surface plane as the front face of the insulating substrate 2. For components such as component 1 which have their ground plane transferred o on the rear face (metallization of the rear face), it is necessary to ensure the electrical continuity of the ground plane with the front face of the module. At least one metallic layer (not shown) is usually provided between the component and the insulating substrate, which ensures this electrical continuity. This layer has a typical thickness of around 15 microns. The practical realization of this layer of metal of electrical continuity depends on the method of manufacturing the module M. In one example, the method of manufacturing the module uses a molded or etched substrate. This molded substrate can be made of any usual insulating material, such as ceramic, or resin, according to any known method. The layer of metal is then renlized zo according to any process suitable for covering the front face of the molded or etched substrate, before placing the components in cavities of the substrate, rear face of the components against the bottom of the cavity. In another example, the module manufacturing process uses a technique of molding a

  insulating substrate (resin) over the components, by their rear side.

  A technique for producing the electric continuity metal layer is described in patent application EP 0611 129 A2. According to this

  technique, a layer of metal is deposited on a flexible dielectric film.

  The film thus metallized is placed, metal face against the metallized rear face of the components. Resin molding can then be performed

Above.

  Preferably, the electrical continuity between the rear face of a component and the front face of the module is obtained by placing the component in a cavity of a block of conductive substrate, in the insulating substrate. The

  conductive substrate contributes to better cooling of the component.

  One such embodiment is shown in FIG. 1. The component 1 is placed in a cavity of a block of conductive substrate 3, typically a copper substrate. This conductive substrate is such that it is flush with the surface of the front face of the insulating substrate. The component is bonded by its rear face to the bottom of the cavity, with a conductive adhesive 4. There is thus continuity

  electrical of the ground plane between the rear face and the conductive substrate.

  An interconnection structure 9 of collective wiring type is produced in the usual way on the front face of the insulating substrate. This structure covers the entire surface of the module M and includes electrical connections which allow the interconnection of the module components and the connection to the outside. It generally comprises several layers of dielectric depending on the complexity of the routing to be carried out. For each layer, there are metallized holes, facing contact zones on a lower layer and corresponding conductors. In the example shown in FIG. 1, this interconnection structure 9 comprises two layers of polymer 9a and 9b. The first layer of polymer 9a especially comprises metallized holes opposite connection pads

  6, 7 of component 1, located on the active face of this component.

  The interconnection structure comprises a thermal conduction element 11, which passes right through it, and which comes into contact on a zo thermal contact pad 12 on the active face of the component 1, formed by a predetermined conductor connected to the plane component mass. In practice, this conductor is located near at least one hot spot of the component. It is for example, and as shown in FIG. 1, an air bridge of a power transistor. A power transistor in fact comprises various hot spots under the air bridge, at the junctions of the

  different elementary transistors which form it.

  The interconnection structure 9 comprises other heat conduction elements 13 a and 13 b, which pass through it right through, to come into contact with portions 14a and 14b of the conductive substrate 3, on the front face of the module. These portions form thermal contact areas by which the heat from the rear face of the component 1 placed

  in the conductive substrate will be able to dissipate.

  In general, the active face of the components is covered with a mechanical protection layer 5 which protects the conductors, in particular 3 the air bridges in the power components, and also ensures the planarization of the surface. This protective layer is typically a polymer layer of benzocyclobutene (BCB). Contact ranges

  thermal are formed by openings through this layer.

  In practice, the transverse thermal conduction elements of the interconnection structure 9 of the module correspond to openings made in this structure and, where appropriate, in the protective layer 5, up to the predetermined thermal contact areas. These openings are blocked with thermally conductive material, for example copper. By connecting these heat conduction elements to a cooling circuit, there is a heat dissipation which occurs by the front face of the module, by the active faces of the components, and by their

  rear side, via conductive substrates.

  In practice, the modules are usually mounted on the surface of multi-layer printed circuits, by means of suitable CMS transfer methods, typically by means of lead tin microbeads. In the example, the module M is thus mounted on the surface of a printed circuit C1. In addition to the microbeads b1, b2 usually provided on contact areas of the interconnection structure 9 of the module, there are microbeads b3 to b6 deposited on the surface of the interconnection structure, on the thermal conduction elements 1 3a, 12, 1 3b, and which participate in the thermal conduction. The module is transferred to the surface of the printed circuit C1, by reflow of the microbeads. This printed circuit is itself glued to a cooling circuit Dth, for example a cold plate or a drain

z thermal.

  The printed circuit C1 includes the usual interconnection layers (not shown), by which the module can be electrically connected to other modules or to the outside. According to the invention, it further comprises transverse holes 15, 16, 17 opposite the transverse thermal conduction elements of the modules, 1 3a, 12 and 1 3b respectively, provided with their microbeads. These holes in the printed circuit include inclusions of thermally conductive material, to ensure the continuity of the thermal conduction path from the thermal contact pads 1 4a, 12, and 1 4b from the module to the device for

ref roidissement Dth.

  The heat conduction elements in the printed circuits can be produced by drilling these printed circuits right through at the corresponding places. This drilling can be obtained mechanically or by laser ablation. The thermal conduction through these holes can be ensured by metal pins, held by gluing on the cooling circuit for example. It can also be provided by the cooling circuit itself, which then has any shape suitable for nesting in the holes 15, 16, 17 of the printed circuit. Or these holes can be plugged with thermally conductive material, by any known method. One can for example use a thermally conductive ink, such as a silver paste. Preferably, because copper is a very good thermal conductor, an electrolytic growth process of copper can be used in these holes. This can be obtained simply by sticking a copper foil on one side of the printed circuit, by providing, by drilling or saving the adhesive film, that there is no glue at the bottom of the holes and by placing the printed circuit in an electrolytic bath. The copper foil is connected to one of the electrolytic charging electrodes. The copper height obtained can then be adjusted, by polishing, and the surface of the plugged holes can be machined, so as to be adapted to the surface mounting of the module on this printed circuit. The printed circuit can then be drilled and metallized again and the copper foil can be etched, in order to make the electrical contacts between the two faces of the

printed circuit board.

  Preferably, the transverse heat conduction elements of the module interconnection structure and of the printed circuit on which the module is transferred, have substantially the same dimensions.

  than the associated thermal contact areas.

  The thermal ranges produced on the active face of

  components are as wide as possible, to promote cooling.

  o Several corresponding surface mounting microbeads are then provided, depending on the size of these ranges. In FIG. 1, there are thus two microbeads b4 and b5 for the thermal contact area 12

performed on component 1.

  With a module M according to the invention, it is thus possible to achieve the cooling of the components which it integrates, by its front face. In addition, the positioning of the components in a conductive substrate, and the formation of thermal contact areas on the front face of the module, on this conductive substrate, and on the periphery of these components, makes it possible to double the cooling by the active face. components of a cooling by

  the rear face, by the conductive substrate.

  A module according to the invention is particularly advantageous in applications where radio power is used, for example in antenna architectures using active transmit-receive modules. Indeed, the radio power that can be extracted from a power component directly depends on the ability to cool the component. And the Gallium arsenide substrates used to make the power components have a high thermal resistivity. By dogagating contact areas close to hot spots, on the active face of the

  component, we limit the heat dissipation that occurs through the AsGa substrate.

  This improves the radio performance of the component. By doubling the cooling of the active face, of cooling from the rear face, by means of thermal contact pads on the front face of the module, on the periphery of the component, on the conductive substrate, there is no need to provide a other cooling device from the rear side of the zo module (cold plate with openings made through the insulating substrate to the rear side of the components, with heat pad dissipation

or plugged holes for example).

  Figure 2 shows an example of a multi-electronic structure.

  module which can be carried out using the principle of the invention, by

  z example, to make an antenna.

  In this structure there is a heat sink Dth. On each side of the heat sink, there are two modules M, and M2 of integrated circuits, each mounted on the surface of a respective printed circuit, Cl ,, Cl2. The two circuits

  prints are each glued to one side of the thermal drain Dth.

  o The modules M and M2 each comprise a plurality of active or passive components. Some are placed in cavities of conductive substrates. Each cavity can include one or more components. The modules M and M2 and the printed circuits Cl, and Cl2 correspond to the module M and to the printed circuit Cl of FIG. 1. On the front face of the module M, there is thus a thermal contact area 20 on the active face of a component 22, placed in a cavity of a conductive substrate and a thermal contact pad 21, on the active face of a component 23. On the front face of the M2 module, there is a thermal contact pad 24, on the active face of a component 25 placed in a cavity of a conductive substrate 27 and a surface of thermal contact 26

of this conductive substrate 27.

  o Corresponding heat conduction elements in the interconnection structure INT, INT2 of the modules and in the printed circuits Cl, Cl2 ensure the continuity of the heat conduction path

  between each of these thermal contact areas and the thermal drain Dth.

  This continuity of the thermal conduction path appears clearly in FIG. 2, by solid lines 28, 29, 30 and 31 between the different ranges

  of thermal contact and the thermal drain Dth.

  The rear face of the modules can be used to transfer bulky passive elements, for example capacitors. The ground plane is then brought back to these rear, metallized faces, by means

  o of openings OO, O passing through the insulating substrates of the modular units.

  Finally, the electrical connections L, L2 between the two multilayer printed circuits Cl and Cl2 are provided by transverse transitions through the heat sink. These transitions can be ensured by miniature connectors or fuzz-buttons

  z5 maintained by gluing on the two printed circuits.

  Figures 3 and 4 show the longitudinal section views and

  transverse at a thermal contact area of a component.

  The active face of the component is generally covered with a mechanical protection layer 32, typically a polymer layer of so benzocyclobutene (BCB). A thermal contact area is formed by an opening in this protective layer 32, on an air bridge 33 of a power transistor, for example an HBT type transistor. The air bridge 33 interconnects the emitters of the elementary transistors, and passes

  above the bases b and the collectors c elementary transistors.

  - Over the surface of the component (and of the substrate), an interconnection structure 34 is produced. This structure may include one or more layers of dielectric (polymer), depending on the complexity of the routing to be performed. In this structure, a transverse thermal conduction element 35 is produced, facing the thermal contact area. This conduction element is typically formed by a hole passing through the entire interconnection structure and plugged with thermally conductive material. On this element 35, one then deposits at least one tin-lead microbead. This microbead typically has a diameter of 200 microns (106m). We will see in the manufacturing process of the module which will now be detailed, that we can widen the thermal contact range, so as to have a larger heat exchange surface. In particular, for a thermal contact range on a transistor air bridge, it is advantageous to have a thermal contact range whose surface substantially covers that of the power transistor. It is then expected that the corresponding heat conduction elements in the interconnection structure and in the printed circuit will have substantially the

same dimensions.

  Now, an example of a process for manufacturing such a zo module will be detailed, with reference to FIGS. 5 to 13. In this example, the insulating substrate is obtained by molding a resin by the rear face of the components. For this, a support substrate 36 is used. This support substrate may be a glass plate on which chromium 37 targets are produced. An adhesive material 38, for example a silicone resin, is deposited on the entire surface of the glass plate. The glass plate coated with the adhesive material forms a molding support. With the aid of the test patterns produced on the substrate, the active and passive components 39 are positioned on the adhesive material. These components are positioned with their active face carrying the connection pads against the glass plate. The adhesive material keeps the components in place, without sticking them

definitively.

  In the description of the modules, we saw that we placed

  preferably in conductive substrates the components for which it was necessary to ensure the electrical continuity of the rear face (ground plane). For these components, they are blocks 40 (or a matrix) of

  conductive substrate which is then positioned on the adhesive material.

  The components are integrated in a later step.

  It is then possible to mold resin from behind the components and the conductive substrates, to form the insulating substrate 41 (FIG. 6). Preferably, in order to limit the movement of the components due to the shrinking of the resin, a resin grid 42 previously molded is preferably used (FIG. 7). This grid is for example made by pouring a resin into a metal mold whose walls are o covered with Teflon. The resin may be an epoxy resin with a mineral filler having a high glass transition temperature. After annealing the resin, the grid can be easily separated from its mold (which can be reused). This grid is positioned on the glass plate (on the adhesive material) and the components are placed at the bottom of the cavities thus formed by

  s the grid, against the glass plate (Figure S).

  The molding resin can then be poured over the grid to coat the components (Figure 6). After the resin has hardened, the entire molded resin, the grid and the conductive components and substrates form a block which can be separated.

  zo of the molding support (glass plate + adhesive material).

  With such a method, the connection pads of the components and the conductive substrates are situated substantially in the same plane of

  surface as the front face of the insulating substrate formed by the molded resin.

  The surface of the resin is then metallized and metallic conductors are produced. This metallization can be in contact with the connection pads of certain components and with the conductive substrates. Cavities can then be produced in the conductive substrates 40. Typically, these substrates are copper blocks. The

  so cavities are formed by chemical etching.

  The components 43 are then bonded which must be placed in these cavities, rear face against the bottom of the cavity. A conductive adhesive 44 is used for this. The space left free between the components and the

  walls of the cavity can be blocked, by polymeric material for example.

  The depth of the cavities is substantially equal to the thickness of the components placed there added to that of the glue, so that the connection pads of these components 43 are substantially in the same plane as the front face of the insulating substrate. 41. In a practical example, the conductive substrate has a thickness of 500 microns or more and

  a cavity in the substrate has a depth of 150 microns.

  Other manufacturing methods can be used. For example, it is possible to start from a molded or etched substrate, with cavities of different thicknesses corresponding substantially to the thickness of the components and of the conductive substrates which must be placed there, added to the thickness of glue. If the insulating substrate is made by resin molding, the walls of the corresponding mold will preferably be covered with Teflon. The conductive components and substrates are then placed in the cavities of the insulating substrate and the spaces left free by the components in the cavities can be filled, for example with polymeric material. We then find the formation of cavities in the conductive substrates and the placement of components in these cavities,

like before.

  FIGS. 9 to 13 relate more particularly to the steps by which the thermal contact pads and the conduction elements

partners are realized.

  In these figures, a small portion of substrate 45 is shown, comprising a component 46. In the example, it is a conductive substrate, typically made of copper. It is itself integrated into an insulating substrate (not

s shown). The active face of the component includes different conductors including a bridge

  air 47 and connection pads 48, 49, for connecting the component to the outside. This active face can be covered with a mechanical protection layer 50, typically benzocyclobutene

  n / a (BCB), which will notably protect air bridges.

  In the example, the air bridge 47 is an air bridge of a power transistor. It is usually connected to the ground plane of the component on the rear face 51, by a metallized micro-hole 52 through the substrate of the component. It covers junctions of elementary transistors, s thermal heating seats. In a practical example, we can have a total dissipated power of 7.5 watts with an MMIC component (Microwave Monolithic Infegrated Circuit) of HPA type (High Power Amplifier) comprising seven identical elementary transistors, with twelve grid fingers dissipating 100 microns each the same power (7.5 wattsl7112). An order of magnitude of the dimensions of the conductor forming the air bridge in current technologies is 80 microns by 300 microns, where 300 microns corresponds to the length of the air bridge, which covers (over the length) the entire transistor. For comparison, the studs of

  connections are about 200 microns out of 200 microns.

  Preferably, provision is made for the thermal contact pad to have a surface which includes the contact surface on the conductor of the air bridge, and a surface around it. With a larger heat exchange surface, heat dissipation is improved. Particularly advantageously, if the surface of the thermal contact pad is enlarged so that it substantially covers the surface of the power transistor. In one example, a thermal contact range on an air bridge could have a surface of at least 300 microns by 700 microns, corresponding to the surface

of the transistor.

  zo A step of manufacturing thermal contact pads on the active face of a component comprises making openings in the mechanical protection layer 50 which usually covers the entire active face of the components, so as to release the connection pads 48 , 49 and the conductor forming the air bridge 47 (Figure 10), and the filling of these

  s openings with conductive material.

  This last step can be done for example as follows: depositing a film of photosensitive resin, and removing this resin on at least the surface released on the conductor forming the air bridge 47 and so preferably on a surface around (Figure 11); - chemical deposit of metal (copper), the resin forming a mask

  protection, in particular for the component connection pads.

  The resin film (metallized) is then removed, typically at

using solvents.

  Another method for widening the thermal contact range advantageously uses electrolytic recharging from the thermal contact ranges. Briefly, a thin metallic layer, typically copper, is deposited over the entire surface of the module, then this copper is crusted at the desired locations, that is to say preferably, over an area of

  extended contact around the air bridge.

  In more detail, such a method comprises the following steps: deposition of a thin metal layer 53, by puiverization. We

  o obtains a layer of approximately 1000 to 5000 angstroms (10 m) thick.

  - deposit of a thick layer of photosensitive resin on ib 54, and removal of this resin on the area released on the conductor of the air bridge 47, and preferably, on an area around it (Figure 10). The resin layer at a

  thickness of about 10 microns (106m) thick.

  - electrolytic recharge, using metallic layer 53

as electrode 55.

  - removal of the resin layer. This operation is typically

carried out using solvents.

  - removal of a thickness of metal layer substantially equal to zo the thickness of the first layer of metal 53. This operation is done

  typically by chemical micro-attack.

  In the end, we obtain the module shown in Figure 11, with a

  extended contact pad 56 above the air bridge 47.

  In the (common) case where the conductors on the active face are made of gold, it is planned to form the metal layer 53, to deposit by puérisation first of titanium-tungsten (TiW), on approximately 500 Angstroms, then of copper. The titanium-tungsten layer then forms a barrier between

gold and copper.

  This manufacturing process is in practice applied over the entire surface of the module, to form the thermal contact areas on the components. We can now make the interconnection structure 57 of collective wiring type, comprising one or more layers of dielectric, depending on the complexity of the routing to be performed. In general, the production of such a structure comprises, for each dielectric layer, a step of forming holes to reach areas of electrical connection on a lower layer, or to reach connection pads on the active face of the components, and a step of metallizing these holes and forming a network of conductors on the surface. In the example, the interconnection structure comprises two

  dielectric layers 57a and 57b.

  The first dielectric layer 57a is deposited over the entire surface of the module (Figure 12). Holes 58, 59 are made in this layer, by laser ablation or any other known method, above the connection pads 48, 49. The dimensions of the holes correspond to the dimensions of the connection pads. The surface of the layer 57a is then metallized and then etched to form a network of corresponding conductors.

at this routing level.

  The second dielectric layer 57b is deposited over the entire surface of the module. Holes corresponding to the connections to be made with the lower layer are made and a corresponding network of conductors

is carried out on the surface.

  According to the invention, holes are made through the entire interconnection structure o, here layers 57a and 57b, up to the thermal contact areas of the module: In the example, a first hole 62 is made with regard to the enlarged thermal contact pad 56. Another hole 63 is made at the periphery of the component, on the conductive substrate, so as to

  clear a thermal contact pad 64 on this substrate.

  s In practice, holes 60 to 63 are made in the same step,

  for example by laser drilling, which stops on the metal.

  A next step consists in plugging with holes the holes 62, 63 passing through the entire interconnection structure up to the thermal contact areas of the module. Then the electrical connection holes 60, 61 can be metallized and the network of conductors can be formed on the last layer 57b of the structure.

  interconnection, according to usual methods.

  The step of plugging the through holes 62, 63 can use electrolytic recharging, generally using a conductor of the ground plane as an electrode. The conductive substrate and its own thermal contact pads 64, and the thermal contact pads 56 of the component are short-circuited to ground. The recharging is done from the bottom of the holes 62, 63, to the surface of the dielectric material 57. Other methods can be used, such as for example the use of ink

  thermally conductive, such as silver paste.

  Finally, lead tin microbeads 65, 66 are deposited on the electrical connection zones of the interconnection structure. Other lead tin microbeads 67, 68, 69 are deposited on the thermal contact zones formed by the plugged holes 62 and 63. These microspheres for surface mounting are used one (65, 66) for electrical transmission,

  the others (67 to 69) to thermal conduction.

  FIG. 14 shows a variant of FIG. 13, according to which the electrical continuity is ensured not by a block of conductive substrate, but by a layer of metal 70. Thermal contact pads can be produced as for the block of conductive substrate , on a portion of layer 70, on the front face of the insulating substrate. The electrolytic charging process seen previously to plug the corresponding holes in

  the interconnection structure applies in the same way.

  Variants of the invention relate in particular to the formation o of the thermal contact pads. Indeed, the formation of these areas on the active faces of the components can be done before the integration of these components in the insulating substrate of the module, in the process of manufacturing these components and / or, collectively, in the process. manufacturing the module as more particularly described. In the first case, the layers of metal (53) and resin (54) cover the surface of the

  component. In the second, they cover the entire surface of the module.

  The invention which has just been described applies advantageously to integrated circuit modules comprising power components. It applies to manufacturing processes of the so collective wiring type which are inexpensive processes, and allows efficient cooling, by the front face of the modules, both by the active face of the components, and by their rear face, preferably via conductive substrates. It has been possible to measure in practice, in the example of an MMIC component integrated in a module as described in the invention, in a block of conductive substrate, that 50% of the heat dissipation could be done by the contact pads thermal on the active face of the components, the rest being dissipated by the rear faces, by the thermal contact pads in

periphery of the components.

Claims (18)

  1. Electronic component comprising an active face comprising conductive elements and connection pads (6,7), characterized in that it comprises a thermal contact area (12) at least on the active face, each thermal contact area comprising a conductor element electrically connected to the ground plane of the component, and a thermal contact surface comprising at least the   contact surface with said conductive element.   2. Component according to claim 1, characterized in that o the conductive element of a thermal contact area (12) is a bridge to power transistor air.   3. Component according to claim 2, characterized in that the surface of the thermal contact area substantially covers the surface of the power transistor.   4. Integrated circuit module comprising an insulating substrate (2), a plurality of electronic components including at least one component with one or more thermal contact pads (12) according to any one of   claims 1 to 3, the components being placed in said substrate in   so that the connection pads are substantially in the same surface plane as the front face of the substrate, and an interconnection structure of the collective wiring type (9), arranged on said front face to connect the components together and towards the exterior, module (M) characterized in that the thermal contact pads (12) are substantially in the same surface plane as the connection pads (6, 7), and in that it comprises thermal conduction elements (11) passing through said interconnection structure (9) opposite the said thermal contact pads enabling said pads to be connected to a o heat dissipation (Dth).   5. Module according to claim 4, comprising a component at least with a metallized rear face corresponding to the ground plane of the component, and a structure of conductive material (3) disposed between said component and the insulating substrate, and flush with the surface substantially in the same plane as the front face of the substrate to ensure the electrical continuity of the ground plane between the rear face of the component and the front face of the substrate, characterized in that it comprises at least one surface thermal contact pad (14a) of the insulating substrate, on a portion of said structure of conductive material, and a corresponding thermal o conduction element (13a), crossing the interconnection structure (9) of the module, making it possible to connect said pad to a dissipation device thermal (Dth).   6. Module according to claim 5, characterized in that said   structure of conductive material is a layer of metal (70).   7. Module according to claim 5, characterized in that said structure of conductive material is a block of conductive substrate (3), flush with substantially in the same surface plane as the front face of the insulating substrate (2), this block of conductive substrate comprising at least one cavity in which said component is placed, rear side against the bottom of the cavity.   8. Module according to any one of claims 4 to 7,   s characterized in that the heat conduction elements (11, 13a) of the interconnection structure include holes blocked by a material thermally conductive.   9. Module according to any one of claims 4 to 8,   characterized in that it comprises surface mounting elements arranged on the interconnection structure (9), on electrical connection zones (b1) and on the surface (b3, b4) of the heat conduction elements (13a, 11).   10. Electronic circuit comprising at least one module according to the preceding claim, mounted on the surface of a printed circuit (Cl), characterized in that a heat dissipation device (Dth) is mounted on the other face of the printed circuit and in that said printed circuit comprises transverse heat conduction elements (15, 16) opposite the heat conduction elements (13a, 11) of the interconnection structure (9) of said module.   11. Electronic circuit according to the preceding claim, characterized in that said thermal conduction elements (15, 16) of the printed circuit include holes passing through said printed circuit with   inclusion of thermally conductive material.   12. A method of manufacturing thermal contact pads on the active face of an electronic component, characterized in that it comprises the production of openings in a mechanical protection layer (50) covering the active face, to release the studs connection and predetermined conductive elements, said conductive elements corresponding to the thermal contact areas to be produced, and filling zo of said openings on the conductive elements with conductive material. 13. The manufacturing method according to claim 12, characterized in that the filling comprises the use of a mask obtained by z depositing a film or a layer of photosensitive resin (54), and removal of this resin on at least the surface of the conductive elements cleared in the opening stage.   14. The manufacturing method according to claim 13, characterized in that the localized removal of the resin is carried out on the surface of the   conductive elements released by the opening step and a surface around.   15. The manufacturing method according to claim 13 or 14, characterized in that the filling comprises the following steps: - deposition on the surface of a thin metallic layer (53) by puiperization, - localized deposition and removal of the resin (54) , - electrolytic recharging of metal from the thermal contact pads, using the metal layer (53) as the electrolytic recharging electrode, - removal of a thickness of metal corresponding to the thickness of the thin layer (53).   o 16. The manufacturing method according to any one of   claims 12 to 15, characterized in that it is applied to a module   integrated circuits comprising components (46) placed in an insulating substrate, so that the connection pads (48, 49) and components are substantially in the same surface plane as a front face of said substrate, the metal layers ( 53) and resin (54) being applied to   the entire front face of the substrate.   17. A method of manufacturing an integrated circuit module comprising placing components (46) in an insulating substrate, so that the connection pads (48, 49) of the components are substantially in the same surface plane as 'a front face of said substrate, a structure made of conductive material (45) which can be placed, between the rear face of certain components and the insulating substrate, and so as to be roughly flush in the same surface plane as the front face of the insulating substrate , - the production of an interconnection structure of the collective wiring type (57) on the front face of the substrate, characterized in that it comprises a step of forming holes (62) passing through said interconnection structure, for reach thermal contact areas formed by predetermined conductive elements (47) on the active face of the components, or by surface portions (64) of the structure of conductive material, and a step of bo uching of said holes   through with thermally conductive material.   18. The Solon manufacturing method of claim 16, characterized in that the step of plugging the through holes (62, 63) of the interconnection structure is carried out by electrolytic recharging of metal from the corresponding thermal contact pads, by connecting an electrode