Method for producing an electronic component

Abstract

A method for producing an electronic assembly (100) comprising a circuit carrier (10), at least one active electronic component (30) and at least one passive component (40), the method comprising connecting the active component (30) to the circuit carrier (10) by sintering using a first sintering compound (20) by applying pressure locally on the active component (30), the first sintering compound (20) and the circuit carrier (10) in the region of the active component (30), while connecting the passive component (40) to the circuit carrier (10) by pressureless sintering using a second sintering compound (20).

Description

Field of the Invention

[0001] The present invention relates to a method for producing an electronic assembly comprising a circuit carrier, at least one first electronic component, and at least one second component. Background Art

[0002] Such a method is well known, for example, in the manufacture of power modules. In this case, the connection and construction techniques used in power modules often draw on welding or pressure sintering methods for the thermal and mechanical connection of electronic components, where sintering methods are increasingly replacing conventional welding techniques. To produce a sintered connection, a press is required to generate a sintered connection between the electronic components to be interconnected by applying pressure and temperature over a specific period of time (possibly several minutes). For the sintering process, for example, semiconductor chips are arranged on a dry sintering pad and subjected to a specific pressure (uniaxial pressure or quasi-hydrostatic pressure). In this case, compared to quasi-hydrostatic pressure transfer, the uniaxial sintering process has the advantage of a shorter process time because the heat transfer to the sintered connection via a hard sintering die is more direct compared to the softer sintering die required for the quasi-hydrostatic process.

[0003] In addition to this pressure sintering method, sintering methods that are carried out without pressure are also known. For these methods, semiconductor or other electronic components are positioned in a wet sintering paste and sintered in a furnace without pressure for a relatively long period of time, which can be up to two hours at a specific temperature below the melting temperature of the sintering paste.

[0004] Particular problems arise in the manufacture of power modules when not only semiconductor elements but also passive electronic components such as thermal sensors, resistors, and additional connecting elements (which are soldered to a direct copper bond (DCB) as surface mount devices (SMDs)) are used. Although sintering techniques fundamentally exhibit higher reliability and fatigue strength of the connections produced in this way compared to welding techniques, sintering SMD components are generally excluded because these components may break when the pressure required for the sintering process is applied. Pressureless sintering can be considered for passive electronic components but is generally not used for active electronic components because due to the highly variable loads, these active electronic components can sometimes only be reliably mounted using a pressure sintering method. Therefore, rather demanding technical setups and procedural sequences must generally be implemented in order to be able to implement a sintering method for mounting active electronic components and a welding method for mounting passive electronic components without compromising the connections of the other electronic components in each case. Thus, the production of electronic assemblies comprising active and passive components is particularly time-consuming and labor-intensive. Summary of the Invention

[0005] Accordingly, an object of the present invention is to provide a method for producing an electronic assembly including at least one first electronic component (requiring pressure sintering) and at least one second electronic component (requiring pressureless sintering), which can be implemented effortlessly in a short time while still being able to form a reliable connection with high fatigue strength.

[0006] Typically, active components (especially power semiconductors with a high switching cycle) with particularly high requirements in terms of reliability require connections obtained by pressure sintering.

[0007] Again, typically, passive components (such as thermal sensors, current sensors, inductors, capacitors, and resistors) can be better connected using pressureless sintering.

[0008] The basic idea behind the present invention is to simultaneously implement the installation of passive electronic components and the installation of active electronic components in a single method step to form an electronic assembly, wherein the pressureless sintering process for installing passive electronic components and the pressure sintering process for installing active electronic components are carried out in parallel (i.e., substantially simultaneously). Due to the simultaneous implementation of the pressureless sintering process and the pressure sintering process, the electronic assembly can be produced in a single method step without combining different connection techniques in successive method steps, enabling a significant reduction in the complexity of the equipment and a shortening of the time required to produce the electronic assembly.

[0009] To effectively configure the method according to the present invention, method parameters that significantly shorten the time required to produce a fixed connection of passive components using a pressureless sintering method (which may typically take up to two hours) are preferably selected. For this purpose, for example, combinations of sintering pastes and process parameters capable of achieving a specific rapid sintering process within a few minutes are known from J Rudzki's “Aufbaukonzepte für die Leistungselektronik mit der Niedertemperatur-Verbindungstechnik” (Fortschritt-Berichte, VDI Reihe 21, Elektrotechnik (376) VDI-Verlag, Düsseldorf, 2006) [“Construction concepts for power electronics with low temperature connection technology” (Progress reports, VDI series 21, Electrical engineering (376), VDI-Verlag, Düsseldorf, 2006)].

[0010] In summary, the present invention enables the processing of some components with particularly high requirements in terms of reliability (such as active components, especially power semiconductors with a high switching cycle) using a pressure sintering process, while enabling the sintering of other components (such as passive components) that usually cannot withstand high thermomechanical loads without pressure. Therefore, even if a highly porous sintering compound is used to connect the passive components within the assembly (which is inherently less reliable), the connection established via pressureless sintering is sufficient for integrating the passive components into the assembly (although with low reliability).

[0011] In the present context, active electronic components are understood to be those components that enable a circuit to output any form of electrical signal with a power greater than that provided by the signal source. In this case, the active components assume a control function within the circuit, namely, in particular, (power) semiconductors. In this case, the active components are typically of a planar design and are integrated into the electronic component as die-attach components.

[0012] On the other hand, passive components are understood to be those components that do not have an amplifier effect and do not have a control function, such as, for example, thermal sensors, current sensors, inductors, capacitors, and resistors. Passive components are typically not of a planar design (partly due to their point mounting) and are fragile and sensitive to the applied pressure.

[0013] Therefore, according to the present invention, a method for producing an electronic assembly including a circuit carrier, at least one first electronic component, and at least one second component is proposed, in which the connection between the first component and the circuit carrier is achieved by sintering using a first sintering compound by locally applying pressure on the first component, the first sintering compound, and the circuit carrier in the first component region, while at the same time the connection between the second component and the circuit carrier is achieved by pressureless sintering using a second sintering compound.

[0014] At least one first component is preferably an active component.

[0015] At least one second component is preferably a passive component.

[0016] The sintering is preferably carried out under the application of a locally acting pressure, and the pressureless sintering is preferably carried out in a temperature range of 250°C to 400°C. The temperature is particularly preferably equal to or greater than 280°C and preferably at most 350°C.

[0017] The circuit carrier is preferably in the form of a direct copper bonded substrate (DCB).

[0018] In particular, the first component is selected from first components including semiconductors, power semiconductors, switches (such as IGBT transistors and MOSFET transistors made of silicon, silicon carbide or gallium nitride), and diodes, wherein the second component is formed, for example, as a surface mount device (SMD) and is most preferably selected from second components including thermal sensors, current sensors, inductors, capacitors, resistors, wires, thick wires and strips.

[0019] The locally acting pressure is further preferably applied uniaxially to the first component, the sintered compound and the circuit carrier in the first component area, such that preferably no pressure mold suitable for applying a quasi-hydrostatic acting pressure is used.

[0020] The sintered compound forming the connection between the electronic component and the circuit carrier is preferably a dry sintering paste or a sintering pad. In particular, it can be preferably provided that the sintered compound has been attached to the first component or the circuit carrier before connecting the first component to the circuit carrier. It is further preferably provided that the sintered compound has been attached to the second component or the circuit carrier before connecting the second component to the circuit carrier. Such a configuration enables the individual components constituting the assembly to be fully prepared, such that the filling process is greatly simplified and the sintering procedure can be implemented in a more time-saving manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be explained in more detail below with reference to exemplary embodiments, which are configured in a particularly preferred manner and are shown in the drawings, in which:

[0022] Figure 1 A first exemplary embodiment of an arrangement for performing the method according to the invention is shown, which is configured in a particularly preferred manner;

[0023] Figure 2 A second exemplary embodiment of an arrangement for performing the method according to the invention is shown, which is configured in a particularly preferred manner;

[0024] Figure 3 A third exemplary embodiment of an arrangement for performing the method according to the invention is shown, which is configured in a particularly preferred manner;

[0025] Figure 4 A fourth exemplary embodiment of an arrangement for performing the method according to the invention is shown; and

[0026] Figure 5 A fifth exemplary embodiment of an arrangement for performing the method according to the invention is shown. DETAILED DESCRIPTION OF THE INVENTION

[0027] A method for producing an electronic component including a circuit carrier, at least one active electronic component, and at least one passive component according to the present invention provides for connecting the active component to the circuit carrier by sintering using a first sintering compound by locally applying pressure on the active component, the sintering compound, and the circuit carrier in the area of the active component, while at the same time connecting the passive component to the circuit carrier by pressureless sintering using a second sintering compound.

[0028] In particular, it is provided that the method is carried out at a sintering temperature of 250 °C to 400 °C, especially at 280 °C to 350 °C. Due to the relatively high sintering temperature and the sintering paste (containing, for example, nanoparticles), the sintering process can thus be shortened to the range of a few seconds to 10 minutes. If a uniaxial pressure system is used, it is particularly advantageous to implement pressure sintering and pressureless sintering simultaneously. In this case, all components having the same height are sintered under uniaxial pressure, and other components are sintered without pressure (cf. Figures 1 to 5 ). In order for the passive components to be sintered without pressure, the pressing tool must have recesses at the locations where the passive components are located (cf. Figure 1 、 Figure 2 、 Figure 4 and Figure 5 ), or the passive components are lower than the active components sintered under pressure (cf. Figure 3 ).

[0029] In this case, the components for pressureless sintering are preferably not assembled in the wet paste; rather, the wet paste is pre-dried to form a sintering pad. Subsequently, the active and passive components are positioned on the dried pad, with the aim of reaching a high temperature (as described above) in a relatively short time (as described above), such that the pressing process and the pressureless process can be completed. The subsequent pressureless post-tempering of the sintered connection produced under pressure (which can be achieved within a few seconds) can preferably be achieved within the total time used for pressureless sintering.

[0030] In addition, sintering preforms can be used, which can be mounted both on the components provided for sintering and on the circuit carrier. Thus, the actual sintering procedure can be carried out even faster.

[0031] Finally, for sintering (the active components), a separation foil can be used, which, if necessary, has recesses in the area of the passive components to prevent pressure from being transmitted from the die to the passive components via the foil.

[0032] Figures 1 to 5Shows various different exemplary embodiments configured in a preferred manner of an arrangement for performing the method according to the invention. In particular, the figures show a component 100 manufactured using the method according to the invention. The component 100 includes a circuit carrier 10, which has a first metallization 12 on its underside and a second metallization 14 on its upper side. Such a construction (especially in the case of the metallizations 12, 14 of copper) is referred to as a direct copper bonded substrate (10, 12, 14).

[0033] A sintering compound 20 (formed in particular as a sintering pad) is provided in each case between the metallization 14 on the upper side and the active electronic component 30, and between the metallization 14 on the upper side and the passive component 40.

[0034] The connection of the active electronic component 30 to the circuit carrier 10 via the sintering compound 20 is achieved by applying pressure to the active component 30 via the (upper) die 200 of the sintering device under the simultaneous action of temperature. The connection of the passive component 40 to the circuit carrier 10 is simultaneously achieved by pressureless sintering using another sintering compound 20 under the action of temperature. For this purpose, in Figure 1 , Figure 2 and Figure 4 the exemplary embodiment shown, it is provided that the die 200 has a recess at the location of the passive component 40, such that the die 200 receives the passive component 40 without applying pressure to it. Alternatively, the component 100 is designed such that the passive component 40 is arranged lower overall or has a smaller total height compared to the active component 30, such that the die 200 cannot come into contact with the passive component 40.

[0035] Finally, Figure 5 shows the configuration of a separation foil 210 arranged between the component 100 to be sintered and the die 200. In order to prevent the die 200 from being able to apply pressure to the passive component 40 via the separation foil 210, the separation foil 210 is provided with a recess in the region of the passive component 40, such that the passive component 40 is not covered.

Claims

1. A method for producing an electronic component (100) comprising a circuit carrier (10), at least one active component (30) and at least one passive component (40), characterized in that, the active component (30) is connected to the circuit carrier (10) by sintering using a first sintering compound (20) by applying pressure locally on the active component (30), the first sintering compound (20) and the circuit carrier (10) in the area of the active component (30), while the passive component (40) is connected to the circuit carrier (10) by pressureless sintering using a second sintering compound (20).

2. The method according to claim 1, characterized in that, the sintering by applying pressure is carried out under the application of a locally acting pressure, and the pressureless sintering is carried out in a temperature range of 250 °C to 400 °C.

3. The method according to claim 1, characterized in that, the active component (30) is a semiconductor, and the semiconductor includes a power semiconductor.

4. The method according to claim 1, characterized in that, the active component (30) is a switch, and the switch includes an IGBT transistor or a MOSFET transistor.

5. The method according to claim 1, characterized in that, the active component (30) is a diode.

6. The method according to claim 1, characterized in that, the passive component (40) is a surface mount device (SMD).

7. The method according to claim 1, characterized in that, the passive component is selected from passive components including thermal sensors, current sensors, inductors, capacitors, resistors, wires and strips.

8. The method according to claim 2, characterized in that, the locally acting pressure in the area of the active component (30) is applied uniaxially to the active component (30), the first sintering compound (20), and the circuit carrier (10).

9. The method according to claim 1, characterized in that, the first sintering compound (20) and / or the second sintering compound (20) is a dry sintering paste or a sintering pad.

10. The method according to claim 1, characterized in that, before connecting the active component (30) to the circuit carrier (10), the first sintering compound (20) is attached to the active component (30) or the circuit carrier (10).

11. The method according to claim 1, characterized in that, before connecting the passive component (40) to the circuit carrier (10), the second sintering compound (20) is attached to the passive component (40) or the circuit carrier (10).

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