Electronic component containing a capacitor

The present invention is to provided with one or more capacitors).

Is designated in the present specification under the general term of "component" any passive or active component, any discrete component or any number of components forming a hybrid circuit or integrated.

As is known, it is frequent that a component or an electronic circuit requires one or more auxiliary capacitors, in particular for the decoupling, which cannot be integrated on the same substrate that the component under consideration. The one or more capacitors are added on the printed-circuit board that carries the component and its housing, y occupying a large area compared to that of component, which is in contradiction with the trouble of density increase which is set at the current hardware.

Furthermore, as is known, the connections between the component and its capacitor have parasitic inductances, which increases with the length of the plug, which themselves give rise to parasitic voltages disturbing recognition logic levels. For the high performance integrated circuits, these parasitic voltages tend, to become very important, by a mechanism comprehended further, and then it is necessary to minimize the value of the parasitic inductance, and thus the length of the connections, by placing the capacitor as close as possible to its component. However, there is a minimum length of necessary connections between the component and the capacitor, while being worn by the printed circuit board, which can conduct length in some cases to an unacceptable level of interference voltages.

In the, it is known for utilizing the housing of the component to make a capacitor, both increase compactness and minimize the length of the connections. It is known for example by French patent application of 2,4 56,388 THOMSON-CSF on behalf of a capacitor in the base of the case. However, this solution is little adapted to certain applications, especially those that employ or power components with a high degree of integration, due to heat dissipation of these components that is important:

the base of a housing is to have particular thermal properties which may not be compatible with the production of a capacitor.

It is known further French patent application

n^e the name of the Company 2 529,386 computing Aéronautique Space Militaire and of use the cover of the housing to make a capacitor. This structure, if it avoids the previous problem, however, results in some cases difficulties of realization that, when fastening the cap on the base, it is necessary to provide both sealing the cap on the base and making of the electrical connections of the capacitor with the rest of the circuit.

II is also known of French patent application

n^e 2 550,045 the name of the Company and computing Space Militaire Aéronautique capacitive of performing the function using a discrete component disposed within the housing, above the electronic component and resting on the base of the case. It is thus advantageously avoid previous problems and even minimize the length of the connections between the capacitor and the electronic component. However it has limitations that can be disturbing in certain applications. Indeed, the discrete component fixed to the receptacle by its electrical connections, it is necessary that the material is adapted thermally the material for the housing, in particular in the expansion coefficient; for the hardware performance, the housings are géhéralement alumina, which required for the capacitor materials which are convenient to be in the low dielectric constant, thereby limiting the value of the capacitance of the capacitor. Furthermore, the insertion of a discrete component in the housing is, when the component is somewhat bulky, lead to change the shape of the housing (in particular its cover), disadvantage is industrially.

The present aim of the invention is to prevent or minimize the limitations of known devices and improve their performance by the fact that the capacitive function is performed by at least one discrete component, attached to the electronic component itself, the component off subsequently optionally encapsulated in a housing.

Therefore, in particular, the length of the connections component-capacitor is minimized, the capacitor being directly placed on the component; further, it is possible to use a standard housing due to the compactness of the component assembly-capacitor; further, it is no longer necessary to adapt the capacitor thermally the material of the housing.

Other objects, features and results of the invention shall become apparent from the following description, given by way of non-limiting example and illustrated by the appended Figures which represent:

-figure 1, a cross-sectional view of a first embodiment of the invention;

-figure 2, a view of the top of the preceding figure;

-figure 3, a top view of a second embodiment of the invention;

-figure 4, a cross-sectional view of a third embodiment of the invention.

On these different figures, the full scale has not been observed for the clarity of the disclosure and, on the other hand, the same references relate to the same elements.

On Figures 1 and 2, is represented an electronic component 1, carried by the base 3 a housing on which it is attached for example by means of a metallization 31. The base 3 is covered by a cover 4, a sealing manner by a seal 41.

For example, the housing represented is of the type "CHIP CARRIER", i.e. a housing in which the connecting pins are replaced by metallizations, marked 32, formed on the lower face of the base 3. In the example represented, the base 3 consists of three parts: a carrier wafer 33, carrying the component 1 on the upper surface, covered by a first annular plate 34, disposed around the component 1, and by a second annular plate 35, disposed thereon and recessed relative thereto. Thus that it is known, of demitrous , marked 36, are provided on the periphery of the base 3 to allow the passage of conducting tracks forming connections 37 towards the pins 32. The component 1 is having bond pads 11 which are connected by wires (flexible) connection 12 to the conductive tracks 38 deposited on the top face of the ring 34 and extending between the rings 34 and 35 to join the tracks 37 to the bond pads 32 of the housing.

According to the invention, the component 1 has on its face which is opposite to the base 3 (its upper side in Figure) a capacitor 2, attached thereto such as by an attachment layer 13. In the example represented, the capacitor 2 is a stacked capacitor having a plurality of electrodes 23 superimposed (five in the example), connected alternately to two distinct connection pads, marked 21 and 22, located on the periphery of the capacitor 2. These pads are connected by connecting wires 14, similar to the wires 12, to the pads 11 of the component 1.

In the alternative embodiment shown in Figure, the capacitor 2 is provided with a wiring level marked 24, on which are arranged the Bollards 21 and 22.

The fixing layer 13 may be for example, an adhesive type flexible elastomer. Such adhesive has the advantage of avoiding the possible mechanical mismatch due to differences in value of the coefficients of expansion of the material constituting the component 1 and the dielectric of the capacitor 2. In order to achieve a precise gluing (the studs 11 of the component are not to be coated), may be to one of following known techniques :.

-pre-crosslinking of the elastomer constituting the adhesive;

-screen printing the adhesive on the entire surface or checkerboard 5

-peripheral slot on the bottom of the capacitor.

In this embodiment, the outer dimension of the capacitor 2 is preferably less than and close to that of the component 1, to expose the pads 11 of the component 1 but while allowing lead wires 14 of minimum length.

Indeed, as is known, the connections produce parasitic inductances, which increase with their length. These inductances (L) induce parasitic voltages (AV) according to the formula:

4V = L. $

where 2 is the current there through and t the time. Or, at present, integrated circuits tend to admit a number of parallel bits progressively larger and switching times-shorter, thereby increasing the term ^ ; parallel, the values of the power supply voltage has apt to decrease. Therefore, AV interfering voltages become too large to allow good recognition logic levels, and may even become higher than the supply voltages for, if the term L is not sufficiently small.

11 is to be noted that a capacitor as 2 reduces in some cases the number of pads required. for the housing 32. Indeed, when the component 1 is an integrated circuit, the number of pads required for power supply of the circuit (typically two voltages and a mass) may easily reach 20% of the total number of pads, whether to operate the distribution at various points in the circuit. II is then possible to connect the capacitor in a single point (pad 32), or optionally, a few points, to each external supply voltage, and using in that the electrodes each form an equipotential plane for distributing the supply voltage to the n considered Bollards (11) of the component 1 which require the, n up to several tens and being in any case greater than the number of pads 32 to which each electrode is connected.

Figure 3 represents, viewed from above, a second embodiment of the invention.

On Figure 3, is represented, for example, the common base of the housing than in Figure 2, in other words a base "CHIP CARRIER" to three levels, carrying an electronic component 1 includes a plurality of bond pads 11 at its periphery.

In this embodiment, the capacitive function is performed by a plurality of capacitor elements, marked 23, of the type called " CHIPSE " is commonly used in hybrid circuit technology. Each of the capacitors 23 is fixed to the component 1 in the same way as on the capacitor 2 figures claims. Each of the capacitors 23 is provided with two connection regions, respectively marked 2k and 25, and the interconnect 23-1 capacitor component is performed by flexible wires marked connection lk, as previously.

For example, is represented one of the capacitors 23 connected to bonding pads (marked 15) of the component 1 which are not located at the component periphery.

By way of example, if it is has a component 1 on the order of 10 mm x 10 mm requiring a capability decoupling nH 60, six capacitors can be installed such as 23, of 10 nH each, the dimensions of which are substantially of the order of 1 mm to 2 mm x 1.2.

Note that, in either of the preceding embodiments the lead wires of the (of) capacitor (s) may connect the latter directly to the tracks (38) of the housing, without passing by the studs (11) of the component (1).

Figure 4 represents another embodiment of the invention.

On this figure, Je is found electronic component 1 having bond pads 11, arranged for example at its periphery and also in various points of its surface.

The capacitor 2 is deposited directly on the upper side of the component 1, which carries the Bollards 11, in successive steps:

-a first step of depositing the dielectric material 27, by providing specific areas 28 for the connections of the capacitor electrodes;

-a second step of depositing a conductive material to form the first electrode of the capacitor, marked 26 to be connected by the area 28 to one of the pads 11 of the component 1 j

a step of depositing of the dielectric material 27 again on the electrode 26,5

-a step of depositing a second electrode, marked 25, to be connected to another pads 11 of the component 1;

-a step of depositing a new dielectric layer 27, etc...

For example, the dielectric material 27 may be organic (polyimide, polycarbonate, etc...) with electrodes in copper or aluminum for instance, or mineral (silicon nitride, silica, alumina, etc...) with electrodes e.g. aluminium.

In the various embodiments described above, the capacitors are arranged on the top face of the component 1, which carries the bonding pads (11). It is of course be located on the underside of said component. However, the thermal conductivity of the dielectric materials is generally low, heat dissipation can have difficulties in certain applications.

Furthermore, the component 1 with its ^ or its capacitor;

may, as shown in Figures 1 to 3, be placed in a s

housing. However, it can also be located directly on a hybrid circuit for example.

Finally, the above the has been by way of non-limiting example. Thus that the leads described (14, 12) may be replaced by any known means as located by conductive adhesive bonding, or soldering.