Connection strip for discrete and power electronics

Abstract

Embodiments of the present disclosure relate to a connection strip for discrete electronic devices and power electronic devices. The present disclosure relates to an electronic device comprising: a connection strip comprising: an arcuate portion having a first side opposite a second side, the second side being a convex side of the arcuate portion, the first side comprising one or more concave sides, the second side comprising one or more convex sides opposite respective concave sides; a contact layer of a first material covering the second side, and a flat bond end on each end of the arcuate portion; and a support.

Description

Technical Field

[0001] This disclosure relates to a connection strip for discrete electronic devices and / or power electronic devices, and discrete electronic devices and / or power electronic devices coupled by the connection strip. Background Technology

[0002] As is well known, the semiconductor die of an integrated electronic device (whether a discrete component, a more complex circuit, or a microelectromechanical system) is bonded to a support that carries a connection area, and is electrically connected to these connection areas, and possibly to other power sources or discrete devices, through a connection structure formed by wires or conductive strips (so-called clips).

[0003] When the electronic device is a power supply device, the connection structure is designed to have sufficient current capacity relative to the required current. Furthermore, considering the application and specific operating conditions, these connection structures should be designed to have sufficient durability. Summary of the Invention

[0004] One or more embodiments of the present invention provide a solution for electrically connecting semiconductor dies and devices, overcoming the shortcomings of the prior art.

[0005] According to the present invention, a connecting strip, an electronic device, and a bonding method are provided.

[0006] An electronic device is one example. This electronic device includes a support, at least one die comprising semiconductor material on the support, and connecting strips.

[0007] The connecting strip has a first side and a second side opposite to the first side. The first side is in contact with at least one core.

[0008] The connecting strip includes a flat engagement end that engages with the support member, and the connecting strip elastically presses against the at least one core.

[0009] The connecting strip includes multiple die connection protrusions on a first side between the flat joint ends. The multiple die connection protrusions resiliently press the at least one die to form an electrical connection.

[0010] The connecting strip includes multiple recessed areas located on the first side between the flat joint ends. Each recessed area is located between adjacent die connection protrusions.

[0011] Multiple recessed areas do not contact at least one core.

[0012] In some embodiments, the connecting strip includes a plurality of protruding regions and a plurality of recessed regions located on the second side.

[0013] Each protruding area on the second side corresponds to a corresponding recessed area on the first side. Each recessed area on the second side corresponds to a corresponding protruding area for the core connection on the first side.

[0014] In some embodiments, a first side of the connecting strip includes a contact layer, and a second side of the connecting strip includes an elastomer. The contact layer is in electrical contact with at least one die and defines the first side of the connecting strip.

[0015] In some embodiments, the thickness of the elastomer is at least three times the thickness of the contact layer. Attached Figure Description

[0016] To better understand the invention, embodiments thereof are now described by way of non-limiting example, with reference to the accompanying drawings, wherein:

[0017] Figure 1 This is a side view of a system formed by two semiconductor dies;

[0018] Figure 2 This is a side view of another system formed by two semiconductor dies;

[0019] Figure 3 It is used for Figure 2 A perspective view of the electrical connection solutions for semiconductor dies;

[0020] Figure 4 It is used for Figure 2 A perspective view of another electrical connection solution for a semiconductor die;

[0021] Figure 5 This is a side view showing another possibility for connecting semiconductor dies;

[0022] Figure 6 It is a perspective view of a semiconductor die;

[0023] Figure 7 It is a side view of a strip that can be used for electrical connections in electronic devices;

[0024] Figure 8 It is along Figure 7 Section line VIII-VIII cut Figure 7 The cross-section of the connecting strip;

[0025] Figure 9 yes Figure 7 The perspective bottom view of the connecting strip;

[0026] Figure 10 yes Figure 7 The side view of the connecting strip shows the two-step process of attaching the connecting strip to the support.

[0027] Figure 11This is a perspective view of a molded support member that can be used to connect a power supply device;

[0028] Figure 12 It is Figure 7 The connecting strip is welded to Figure 11 A perspective view of the steps on the support; and

[0029] Figure 13 yes Figure 12 Side view of the welding process. Detailed Implementation

[0030] Figure 1 An apparatus comprising two semiconductor dies 1 is shown, each die 1 integrating its own power element, integrated circuit, or any other electronic or microelectromechanical component. The die 1 is bonded to a support 3 (e.g., a printed circuit board), which is typically made of an insulating material and has contact areas 4 for a conductive material (e.g., a metal such as copper). The die 1 is attached to the support 3 via bonding areas 5 (e.g., conductive or non-conductive solder bonding areas).

[0031] exist Figure 1 In this configuration, the die 1 is connected to the corresponding contact area 4 via the first wire 7 (one for each die 1); in addition, the dies 1 are connected together via the second wire 8.

[0032] Figure 2 Another system is shown, in which two dies (again designated by 1) are joined together. The conductors are typically made of aluminum and joined by welding; the clips are typically made of copper or bronze to provide sufficient rigidity in the elastic areas. The joining can be fusion welding or powder welding (sintering).

[0033] Figures 3-6 Showing Figure 2 A specific embodiment of the connection shown.

[0034] For example, in Figure 3 In this configuration, two dies 11 are attached to a support 12 via a bonding layer 13, which is a DBC (Direct Bonded Copper) multilayer. The top layer of the properly shaped support 12 forms a die contact area 15 and an outer contact area 16. Depending on the required current capacity, wires 14 of variable thickness couple the dies 11 together and bond them to the outer contact area 16.

[0035] exist Figure 4 In this configuration, the top surface of the die 17 is engaged to the outer contact area 18 via a top clip 19. A bottom clip 20 engages the bottom surface of the die 17 to a plate 22 engaged to a support 23. Clips 19 and 20 are typically pre-folded from a planar strip to form multiple bends.

[0036] Figure 5A die 25 is shown bonded to a support 26 by a bottom solder layer 27. The support 26 is part of a metal lead frame and also forms first and second external contact areas 30, 33. A metal clip 29, typically made of copper, electrically connects the power die 25 to the first external contact area 30. The metal clip 29 includes a first planar portion 29A and a second planar portion 29B. The first planar portion 29A is bonded to the power die 25 by a top solder layer 28 of conductive material, which occupies most of the die 25's area. The second planar portion 29B is bonded to the first contact area 30 by another solder layer 31, also made of conductive material. Aluminum conductors 32 bond different portions of the surface of the power die 25 to the second external contact area 33, and have a lower current capacity than the metal clip 29.

[0037] Figure 6 The diagram illustrates securing a die 35 to a multi-layered ceramic support 36. Specifically, the support 36 has a top layer 40 that is conductive, for example coated with a silver alloy, and is shaped to form external contact areas 41A and die contact areas 41B. The die 35 is secured to the die contact areas 41B by a first bonding area 42 formed from a pre-coated sintering paste. A second bonding area 43 is applied between the top surface of the die 35 and a copper foil 45 having a plating (e.g., a NiPdAu plating (not shown)). Copper power bonding wires 46 are soldered to the copper foil 45 and some of the external contact areas 41B for electrical connections to the die 35. Another aluminum bonding wire 47 bonds the contact pads 48 of the die 35 to the corresponding external contact areas 41A.

[0038] Figure 1-6 Some methods in the relevant technologies are described. In all the electrical connection solutions shown, there are solder durability issues. In fact, due to the difference in the coefficient of thermal expansion (CTE) between the bonded wires or clips and the silicon chip, the solder may degrade, and the wires or clips may separate (bonding phenomenon), especially under thermal changes and / or mechanical stress.

[0039] Generally, welded joints are more flexible than sintered joints, but neither technique provides sufficient reliability in certain applications, such as the automotive industry.

[0040] To improve adhesion and durability, wet metal-based techniques have been developed, such as forming stacks of metal layers (typically Ti-Ni-Au or Ag), which allows the top of the die to be wetted and soldered to the clip. This material stack can also be formed on the back side of the die to allow it to be bonded to the support 36. However, these techniques are costly and require expensive soldering materials.

[0041] Figure 7-9 A connecting strip 50, also known as a clip, is shown for electrically connecting one or more semiconductor dies together and / or connecting them to contact areas. One or more semiconductor dies may integrate discrete electronic components, circuits, or other electronic and / or microelectromechanical components. Typically, at least one die integrates power components and / or high-current components. For example, one or more dies may integrate power devices such as IGBTs, diodes, high-voltage or low-voltage MOS transistors, silicon-based or silicon carbide-based devices.

[0042] exist Figure 7-13 In the illustrated embodiment, the connecting strip 50 is used to connect two dies (in...) Figure 10-13 (Specified by 72, 73) are in contact with each other and with the support 70; however, the connecting strip 50 may be used to contact a single die with one or more contact areas on the support, or simply to couple multiple dies together.

[0043] Specifically, the connecting strip 50 is made of a conductive elastic material and has an elongated shape that can be folded to define an overall arched or curved shape.

[0044] In its undeformed state, before being welded to the support 70, the connecting strip 50 has a concave side 50A and a convex side 50B, and is designed to be fixed to the support 70 on its convex side 50B, as discussed in more detail below.

[0045] The connecting strip 50 has an end 51 and is designed to be fixed to a support 70 at the end 51 so as to hold the cores 72, 73 against the support 70.

[0046] In the illustrated embodiment, the connecting strip 50 is formed from a series of flat portions. Furthermore, the ends 51 are flat to facilitate welding.

[0047] Specifically, the connecting strip 50 has at least a protruding region and a recessed region on its convex side 50B. In the illustrated embodiment, both the concave side 50A and the convex side 50B have protruding and recessed regions.

[0048] Specifically, the protruding and recessed regions on the concave side 50A are designated by 52A and 53A, respectively; the protruding and recessed regions on the convex side 50B are designated by 52B and 53B, respectively. Furthermore, each protruding region 52A on the concave side 50A corresponds to a recessed region 53B on the convex side 50B, and each recessed region 52A on the concave side 50A corresponds to a protruding region 52B on the convex side 50B.

[0049] Specifically, in Figure 7 In this design, the connecting strip 50 is configured to contact four contact pads arranged on two different dies (see reference below). Figure 11The convex side 50B has four protruding regions 52B, interspersed with three recessed regions 53B; the protruding regions 52B on the convex side 50B correspond to the recessed regions 53A on the concave side 50A.

[0050] Here, the end 51 is formed by a protruding region 52B on the convex side 50B.

[0051] The protruding areas 52B on the convex side 50B are generally flat, so they can press down flat against the contact pads on the surfaces of the dies 72 and 73 and the support 70 (see...). Figure 11 As described above.

[0052] Connecting strip 50 Figure 7 and 8 The figure shows an elastomer 61 coated with a contact layer 62.

[0053] The elastomer 61 may be copper or a copper alloy, such as bronze, and has a rectangular cross-section (see [reference]). Figure 8 Its thickness ranges from 300μm to 1mm, especially between 300 and 800μm.

[0054] The contact layer 62 is made of a material that is softer than the elastomer 61; for example, it can be aluminum, and its thickness is less than that of the elastomer 61, for example, between 50 μm and 100 μm. Alternatively, it can be a silver alloy, and its thickness is between 3 and 5 μm.

[0055] The width W of the connecting strip is 50. Figure 8 The thickness is between 2 and 5 mm.

[0056] The connecting strip 50 can be manufactured by hot-laminating an aluminum layer onto copper or bronze, cutting it into strips, and then winding it around a coil. The coil is then folded to obtain protruding and recessed areas 52A, 52B, 53A, 53B and then segmented.

[0057] exist Figure 10 In the diagram, the connecting strip 50 is represented by a solid line in its undeformed state before being joined to the support member 70, and by a dashed line in its deformed state after being joined to the support member 70.

[0058] Here, the support 70 is formed of multiple layers, such as DBC (Direct Bonded Copper) multilayer, and two dies 72 and 73 have been attached to it.

[0059] In the example shown (see also...) Figure 11The substrate 70 includes a bottom layer 80 of a conductive material (e.g., copper); an intermediate layer 81, which is electrically insulating and typically a ceramic material, such as alumina (Al₂O₃) or aluminum nitride (AlN); and a top layer 82 made of a conductive material (e.g., copper). The top layer 82 is suitably shaped to form contact areas. In the example shown, the top layer 82 forms the die contact area specified by 83A, and dies 72, 73 and two connection contact areas specified by 83B are bonded thereto.

[0060] The die contact area 83A and the connection contact area 83B are aligned with each other, so that the connecting strip 50 can be arranged on and in contact with the connection contact area 83B and the dies 72 and 73.

[0061] Dies 72 and 73 have contact pads 85 (in the example shown, the first die 72 has one contact pad 85 and the second die 73 has three contact pads 85); the contact pads 85 are typically made of aluminum, for example, with a thickness of 4-9 μm.

[0062] As mentioned above, and can be in Figure 10 As can be seen, the connecting strip 50 is arranged such that the convex side 50B faces the support 70 and the cores 72 and 73, and is welded to the support 70.

[0063] Specifically, the connecting strip 50 is arranged such that the protruding area 52B on its convex side 50B is located at the die 72 and 73, more precisely, at the contact pad 85, and the end 51 is located at the connecting contact area 83B. In order to enable soldering, the connecting strip 50 is pressed at the end 51 and undergoes deformation and flattening.

[0064] After welding, the device consisting of cores 72 and 73, support 70 and connecting strip 50 can be encapsulated and indicated by 95.

[0065] In this way, the connecting strip 50 forms an electrical contact between the contact pads 85 of the dies 72 and 73 and the connection contact area 83B of the support 70, and there is no intermediate bonding material between the connecting strip 50 and the dies 72 and 73.

[0066] Due to the joint, and due to the connecting strip 50, especially through the protruding area 52B ( Figure 7 and Figure 9 The elastic pressure applied to the contact pads 85 causes the contact layer 62 to deform to adapt to the microstructure of the contact pads 85 of the dies 72 and 73 (and may also partially deform), thereby forming a tight mechanical contact between them, thus achieving optimal electrical contact.

[0067] The joining of the connecting strips 50 can be performed using ultrasonic technology, as shown in the following reference. Figure 12-13 As stated above.

[0068] Specifically, an ultrasonic device (e.g., an ultrasonic welding electrode with a welding head 90) can be used to perform the bonding.

[0069] The welding head 90 may have a handling system, such as a suction system, for picking up and holding the connecting strip 50, and has a width approximately equal to that of the connecting strip 50. In particular, the welding head 90 has welding portions 91 arranged at a distance to position itself at the ends 51 of the connecting strip 50 and to apply pressure to these ends 51 during welding.

[0070] For example, the welding portion 91 of the welding head 90 can be tungsten carbide, and a pressure between 3 MPa and 5 MPa is applied at 50 kHz. Welding can be performed at room temperature; thus, any heat that may be generated (typically below 200°C) will not damage the dies 72 and 73, especially dies manufactured using silicon carbide technology. Furthermore, since the bonding pressure is applied only to the end 51 of the connecting strip 50, and the only pressure acting on the dies 72 and 73 is the elastic pressure generated by the connecting strip 50 after bonding, the dies 72 and 73 are not damaged.

[0071] The connecting strip 50 and device 95 described herein have many advantages.

[0072] The connecting strip 50 can actually be manufactured at a low cost and has high durability and reliability. It is capable of carrying high currents, minimizing parasitic effects, has high temperature resistance, and can be joined using ultrasonic technology or simply by sintering.

[0073] The device 95, including the connecting strip 50, has high reliability and connection strength.

[0074] In fact, one or more dies are fixed in a flexible, non-plastic manner, so the blockage is particularly resistant to vibration and mechanical stress even over time.

[0075] Furthermore, since no bonding material is provided between the connecting strip 50 and the cores 72 and 73, and the cores 72 and 73 are held in place only by the pressure of the connecting strip 50, there is no area where deterioration will occur under temperature changes, especially under temperature fluctuations, such as when adding or not adding material, or when wires are joined or soldered between different materials.

[0076] Since the aluminum contact pads 85 and the contact layer 62 are partially in contact with the same material, there is no difference in their thermal coefficients, thus eliminating any cause of failure due to thermal stress caused by different coefficients of thermal expansion (CTE).

[0077] The elastic stress generated by the deformation ensures that the contact pads 85 of the connecting strip 50 and the cores 72 and 73 maintain reliable contact for a period of time.

[0078] In particular, compared with the aforementioned known wet metal processes, the bonding process can be implemented at a lower cost.

[0079] Finally, it is obvious that modifications and variations can be made to the connecting strips, electronic devices, and electrical connection methods described and illustrated herein without departing from the scope of the invention.

[0080] For example, the connecting strip can be other conductive elastic materials; the end joints can be achieved by sintering instead of ultrasonic welding; the die can integrate different types of electronic components and circuits, or be formed from a packaged device with external contact areas for electrical connection in complex systems and / or supports.

[0081] In addition, the elastomer 61 may be coated with a contact layer only in certain portions, such as in the contact area with the core or cores 72, 73 and at the end 51.

[0082] For example, the core may not be welded, but it is kept in contact with the support only by the elasticity of the connecting strip.

[0083] A conductive elastic material connecting strip (50) having an arched portion having a concave side (50A) and a convex side (50B), the connecting strip (50) can be generally described as including a flat joint end (51).

[0084] The convex side (50B) may have at least one die connection protrusion (52B), two support connection protrusions (51) and two recessed areas (53B), the support connection protrusions forming the joint end (51) of the connecting strip (50), and each recessed area (53B) may extend between the die connection protrusion (52B) and the corresponding support connection protrusion (51).

[0085] The connecting strip may include an elastomer (61) with a contact layer (62) coated on one side.

[0086] The elastomer (61) may be copper or a copper alloy, such as bronze.

[0087] The contact layer (62) can be a softer material than the elastomer (61), especially an aluminum or silver alloy.

[0088] The thickness of the elastomer (61) can be between 300 μm and 1 mm, and the thickness of the contact layer (62) can be between 50 and 100 μm in the case of aluminum, and between 3 and 5 μm in the case of silver alloy.

[0089] An electronic device may be summarized as including a support (70), at least one die (72, 73) comprising a semiconductor material, and a connecting strip (50), wherein the connecting strip (50) is made of a conductive elastic material and has a first side and a second side (50B, 50A), the first side (50B) being in contact with at least one die (72, 73), wherein the connecting strip (50) may further include a flat engagement end (51) engaged with the support (70) and resiliently pressing at least one die to electrically connect at least one die (72, 73) to the support (70).

[0090] The first side (50B) of the connecting strip (50) may have: at least one die connection protrusion (52B); two support connection protrusions (51) and two recessed regions (53B); the support connection protrusions form the connection ends (51) of the connecting strip (50); each recessed region (53B) extending between the die connection protrusion (52B) and the corresponding support connection protrusion (51); and the die connection protrusions may be in elastic and electrical contact with at least one die (72, 73).

[0091] The connecting strip (50) may include an elastomer (61) with a contact layer (62) coated on one side, wherein the contact layer (62) is elastically electrically contactable with the at least one die (72, 73) and defines a first side (50B) of the connecting strip.

[0092] The elastomer (61) may be copper or a copper alloy, such as bronze, and the contact layer (62) may be an aluminum or silver alloy.

[0093] The thickness of the contact layer (62) can be less than that of the elastomer (61).

[0094] The thickness of the elastomer (61) can be between 300 μm and 1 mm, and the thickness of the contact layer (62) can be between 50 and 100 μm in the case of aluminum and between 3 and 5 μm in the case of silver alloy.

[0095] A method for bonding at least one die (72, 73) to a support (70) by means of a connecting strip (50), the at least one die (72, 73) being generally comprising a semiconductor material, and the connecting strip (50) being made of a conductive elastic material having an arched portion having concave and convex sides (50A, 50B) and having a bonding end (51), the method comprising: arranging at least one die (72, 73) on the support (70); arranging the connecting strip (50) on at least one die (72, 73) with the convex side (50B) facing at least one die; deforming the connecting strip (50) to contact the bonding end (51) with the support (70), and bonding the bonding end (51) of the connecting strip (50) with the support (70) to make the connecting strip (50) directly electrically contact at least one die (72, 73) and elastically pressing it onto the support (70).

[0096] The joint end (51) may include ultrasonic welding.

[0097] The joint end (51) may include sintering.

[0098] The various embodiments described above can be combined to provide further embodiments.

[0099] These and other changes can be made to the embodiments based on the detailed description above. Generally, the terminology used in the following claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments and the full scope of equivalents enjoyed by these claims. Therefore, the claims are not limited to this disclosure.

Claims

1. An electronic device, comprising: Connecting strip, the connecting strip comprising: An arched portion having a first side opposite to a second side, the second side being a convex side of the arched portion, the first side including one or more concave sides, and the second side including one or more convex sides opposite to a corresponding concave side; The first material contact layer covers the second side, and Flat joint ends, at each end of the arch; and Support member, wherein the support member is provided with: The first die has a first contact pad; and The second die has at least two second contact pads, and the first contact pad and the at least two second contact pads are each coupled to one of the one or more convex sides. The first contact pad and the at least two second contact pads comprise the first material. The flat joint end is configured to engage with the support member such that the one or more convex sides of the second side are coupled to the first die and the second die.

2. The electronic device of claim 1, wherein the convex side has at least one die connection protrusion, two support connection protrusions and two recessed regions, the support connection protrusions forming a flat joint end of the connection strip, and wherein each recessed region extends between the die connection protrusion and the corresponding support connection protrusion.

3. The electronic device of claim 1, wherein the arched portion comprises an elastomer on the second side coated with the contact layer.

4. The electronic device according to claim 3, wherein the elastomer comprises copper or a copper alloy.

5. The electronic device of claim 3, wherein the first material is a material softer than the elastomer.

6. The electronic device according to claim 5, wherein the first material comprises an aluminum or silver alloy.

7. The electronic device of claim 6, wherein the elastomer has a thickness in the range of 300 µm to 1 mm, and the contact layer, when made of aluminum, has a thickness in the range of 50 µm to 100 µm.

8. The electronic device of claim 6, wherein the elastomer has a thickness in the range of 300 µm to 1 mm, and the contact layer, when made of a silver alloy, has a thickness in the range of 3 µm to 5 µm.

9. An electronic device, comprising: Support components, including: First conductive layer; A first insulating layer, on the first conductive layer; and The second conductive layer is on the first insulating layer; At least one die includes a semiconductor material on the second conductive layer; An aluminum contact pad, on said at least one die, the aluminum contact pad having a first thickness in the range of 4µm to 9µm; and The connecting strip has a first side and a second side opposite to the first side, the first side including an aluminum contact layer coupled to the aluminum contact pad. The connecting strip includes a flat engaging end that engages with the support member, and the connecting strip resiliently abuts against the at least one die, such that one or more convex sides of the first side are coupled to the at least one die. The second side includes one or more concave sides, and the first side includes one or more convex sides opposite to the corresponding concave side.

10. The electronic device of claim 9, wherein the first side of the connecting strip has at least one die connection protrusion, two support connection protrusions and two recessed regions, the support connection protrusions forming a flat joint end of the connecting strip, each recessed region extending between the die connection protrusion and a corresponding support connection protrusion, and wherein the die connection protrusion is in elastic and electrical contact with the at least one die.

11. The electronic device of claim 9, wherein the connecting strip includes an elastomer coated with a contact layer on one side, wherein the contact layer is in elastic and electrical contact with the at least one die and defines the first side of the connecting strip.

12. The electronic device of claim 11, wherein the elastomer is made of copper or a copper alloy.

13. The electronic device of claim 12, wherein the thickness of the contact layer is less than the thickness of the elastomer.

14. The electronic device of claim 12, wherein the elastomer has a thickness in the range of 300 µm to 1 mm, and the contact layer has a thickness in the range of 50 µm to 100 µm.

15. The electronic device of claim 12, wherein the elastomer has a thickness in the range of 300 µm to 1 mm.

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