Semiconductor device

Abstract

The present invention provides a semiconductor device that prevents solder balls from adhering to an insulating circuit substrate and an insulating layer. The semiconductor device includes a base plate, an insulating circuit substrate, and granular material. The insulating circuit substrate includes an upper surface for holding a semiconductor element and a lower surface bonded to the surface of the base plate via a bonding material. The granular material adheres to the surface of the base plate that is located outside the insulating circuit substrate when viewed from above. The bonding material is conductive. The granular material is formed from the same material as the bonding material.

Description

Technical Field

[0001] The present invention relates to semiconductor devices. Background Art

[0002] In the assembly process of a semiconductor power module, an insulating circuit substrate on which a semiconductor chip (semiconductor element) is mounted is joined to a heat sink via solder.

[0003] Patent Document 1 discloses a semiconductor device including a first solder resist layer provided along the periphery of a bonding region on a heat sink to be bonded to a substrate. The first solder resist layer is cut at a certain position along the periphery.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-100864 Summary of the Invention

[0005] Solder balls generated when the insulating circuit substrate and the base plate are joined adhere to the insulating circuit substrate or the insulating layer (solder resist layer). If a potential difference occurs between the insulating circuit substrate and the base plate, discharge may occur between the insulating circuit substrate and the base plate through the solder balls.

[0006] In order to solve the above-mentioned problems, the present invention provides a semiconductor device that prevents conductive particulate matter from adhering to an insulating circuit board and an insulating layer.

[0007] The semiconductor device according to the present invention includes a base plate, an insulating circuit substrate, and granular material. The insulating circuit substrate includes an upper surface for holding a semiconductor element and a lower surface bonded to a surface of the base plate via a bonding material. The granular material adheres to a surface of the base plate that is located outward of the insulating circuit substrate when viewed from above. The bonding material is conductive. The granular material is formed from the same material as the bonding material.

[0008] Effects of the Invention

[0009] According to the semiconductor device of the present invention, conductive particles are prevented from adhering to the insulating circuit substrate and the insulating layer.

[0010] The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a plan view showing the structure of the semiconductor device in the first embodiment.

[0012] Figure 2 This is a cross-sectional view showing the structure of the semiconductor device in the first embodiment.

[0013] Figure 3This is a cross-sectional view showing the structure of a semiconductor device in the second embodiment.

[0014] Figure 4 This is a cross-sectional view showing the structure of a semiconductor device in a third embodiment.

[0015] Figure 5 sectional views showing the manufacturing process of the semiconductor device in the third embodiment. DETAILED DESCRIPTION

[0016] <Implementation Method 1>

[0017] Figure 1 as well as Figure 2 A top view and a cross-sectional view respectively illustrate the structure of the semiconductor device according to the first embodiment. Figure 2 Shown in Figure 1 The cross section at AA' is shown in FIG.

[0018] The semiconductor device includes a base plate 1 , an insulating pattern 2 , an insulating circuit substrate 3 , a semiconductor element 4 , and granular materials 6 .

[0019] The base plate 1 holds the insulating circuit board 3 and the semiconductor element 4. The base plate 1 is formed of a metal such as copper or aluminum. The base plate 1 in the first embodiment is a heat sink having a function of dissipating heat generated by the semiconductor element 4.

[0020] The insulating pattern 2 is formed on an insulating layer 2A provided on the surface of the base plate 1. The insulating pattern 2 includes a bonding opening 2B and a peripheral opening 2C. The insulating layer 2A is, for example, a solder resist layer, and in this case, the insulating pattern 2 is a solder resist pattern.

[0021] The bonding opening 2B is provided corresponding to the setting position of the insulating circuit substrate 3. The bonding opening 2B is formed in such a manner that the surface of the base plate 1 is exposed from the insulating layer 2A. The insulating layer 2A is not provided on the inner side of the bonding opening 2B. The side surface of the insulating pattern 2 forming the bonding opening 2B is located further outside than the outer edge of the insulating circuit substrate 3 when viewed from above. The shape of the bonding opening 2B has a similar relationship to the shape of the insulating circuit substrate 3, for example. The bonding opening 2B in embodiment 1 has a rectangular shape that is larger than the insulating circuit substrate 3. In the manufacturing process of the semiconductor device, the insulating pattern 2 of the bonding opening 2B makes it easy to position the insulating circuit substrate 3. In addition, the side surface of the insulating pattern 2 forming the bonding opening 2B has a function of blocking the bonding material 5 described later.

[0022] Peripheral opening 2C is positioned outside of bonding opening 2B. In the first embodiment, peripheral opening 2C surrounds bonding opening 2B. Peripheral opening 2C is formed so that the surface of base plate 1 is exposed from insulating layer 2A. Peripheral opening 2C and bonding opening 2B form a rectangular frame-shaped insulating pattern 2.

[0023] The insulating circuit substrate 3 is composed of an insulating plate 3A and metal patterns 3B provided on the upper and lower surfaces of the insulating plate 3A. The metal pattern 3B on the upper surface is bonded to the semiconductor element 4 via a bonding material (not shown). In other words, the insulating circuit substrate 3 holds the semiconductor element 4. The metal pattern 3B on the lower surface is bonded to the surface of the base plate 1 exposed from the bonding opening 2B via a bonding material 5. In other words, the insulating circuit substrate 3 is bonded to the surface of the base plate 1 via the bonding material 5 arranged inside the bonding opening 2B. The bonding material 5 is conductive. For example, the bonding material 5 is solder 5A.

[0024] The semiconductor element 4 is formed, for example, from a semiconductor such as Si or a so-called wide-bandgap semiconductor such as SiC or GaN. The semiconductor element 4 is a power semiconductor element or a control IC (Integrated Circuit) for controlling the power semiconductor element. Examples of the semiconductor element 4 include an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and a Schottky barrier diode. Alternatively, the semiconductor element 4 may be an RC-IGBT (Reverse-Conducting IGBT) in which an IGBT and a freewheeling diode are formed within a single semiconductor substrate.

[0025] Granular particles 6 are fixed to the surface of the base plate 1 exposed through the peripheral opening 2C. Granular particles 6 are formed from the same material as the bonding material 5. When the bonding material 5 is solder 5A, granular particles 6 are granular solder 6A. The adhesion of granular particles 6 to the base plate 1 is greater than the adhesion of granular particles 6 to the insulating layer 2A. Alternatively, the wettability of the base plate 1 to the granular particles 6 is greater than the wettability of the insulating layer 2A to the granular particles 6.

[0026] Although not shown in the figure, the semiconductor device of Embodiment 1 may further include a housing and an encapsulating material. The housing has a frame shape when viewed from above. The housing accommodates the insulating circuit substrate 3 and the semiconductor element 4 within its frame shape. The encapsulating material has insulating properties and fills the space inside the housing. In this case, the lower surface of the granular material 6 contacts the surface of the base plate 1, and the surface of the granular material 6 other than the lower surface contacts the encapsulating material.

[0027] The following describes an example in which the bonding material 5 is solder 5A. In the reflow process, which is one of the manufacturing processes of the semiconductor device, the insulating circuit substrate 3 is bonded to the surface of the base plate 1 via the solder 5A. At this time, the solder 5A is in a molten state. When the insulating circuit substrate 3 is mounted on the solder 5A, the solder 5A may sometimes fly around the bonding opening 2B. Figure 1 As shown, the insulating pattern 2 is not formed directly below the end of the insulating circuit substrate 3. In other words, the insulating pattern 2 ensures a sufficient distance between the end of the insulating circuit substrate 3 and the surface of the base plate 1. Furthermore, the solder 5A adheres more easily to the surface of the base plate 1 than to the insulating layer 2A. Therefore, the solder 5A that scatters from the bonding opening 2B is efficiently discharged to the outside of the insulating circuit substrate 3.

[0028] The discharged solder 5A adheres to the surface of the base plate 1 at the peripheral opening 2C in a molten state, forming granular solder 6A. Granular solder 6A is firmly fixed to the surface of the base plate 1, preventing the formation of solder balls. Consequently, the possibility of discharge caused by solder balls is reduced.

[0029] In summary, the semiconductor device of Embodiment 1 includes a base plate 1, an insulating circuit substrate 3, and granular material 6. The insulating circuit substrate 3 includes an upper surface that holds a semiconductor element 4 and a lower surface that is bonded to the surface of the base plate 1 via a bonding material 5. The granular material 6 is attached to the surface of the base plate 1 that is located outside the insulating circuit substrate 3 when viewed from above. The bonding material 5 is conductive. The granular material 6 is formed of the same material as the bonding material 5.

[0030] This semiconductor device prevents solder balls from adhering to the insulating circuit substrate 3 and insulating layer 2A. For example, during the semiconductor device manufacturing process, even if solder 5A scatters from the bonding opening 2B, the scattering solder 5A is efficiently discharged to the outside of the insulating circuit substrate 3. In other words, in this structure, the solder 5A adheres to or moves on the insulating layer 2A, preventing it from adhering to the insulating circuit substrate 3. The discharged solder 5A adheres to the surface of the base plate 1 exposed from the peripheral opening 2C, forming granular solder 6A. Compared to the insulating layer 2A, the granular solder 6A is more firmly fixed to the base plate 1. The granular solder 6A once attached to the base plate 1 is less likely to peel off. Therefore, the possibility of discharge caused by solder balls is reduced. In other words, even if a potential difference occurs between the insulating circuit substrate 3 and the base plate 1, the possibility of discharge between the insulating circuit substrate 3 and the base plate 1 is reduced.

[0031] <Implementation Method 2>

[0032] A semiconductor device according to Embodiment 2 will be described. Embodiment 2 is a subordinate concept of Embodiment 1. In Embodiment 2, the same components as those in Embodiment 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0033] Figure 3 This is a cross-sectional view showing the structure of a semiconductor device in accordance with Embodiment 2. As in Embodiment 1, no insulating pattern 2 is formed directly below the end of the lower surface of insulating circuit substrate 3. In Embodiment 2, the width L of insulating pattern 2 between bonding opening 2B and peripheral opening 2C is smaller than the distance H from the surface of base plate 1 to the lower surface of insulating circuit substrate 3. Consequently, solder 5A is more efficiently discharged to the outside of insulating circuit substrate 3.

[0034] The discharged solder 5A adheres to the surface of the base plate 1 at the peripheral opening 2C in a molten state, forming granular solder 6A. Granular solder 6A is firmly fixed to the surface of the base plate 1, making it less likely to form solder balls. This reduces the possibility of discharge caused by solder balls.

[0035] <Implementation Method 3>

[0036] A semiconductor device according to Embodiment 3 will be described. In Embodiment 3, the same components as those in Embodiment 1 or 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0037] Figure 4 This is a cross-sectional view showing the structure of a semiconductor device according to Embodiment 3. The structure other than the insulating pattern 2 is the same as that of Embodiment 1. The frame shape of the insulating pattern 2 is located inward of the outer edge of the insulating circuit substrate 3 when viewed from above. In other words, the side surface of the insulating pattern 2, which forms the peripheral opening 2C, is located inward of the outer edge of the insulating circuit substrate 3 when viewed from above.

[0038] Figure 5 This is a cross-sectional view illustrating the manufacturing process of a semiconductor device according to Embodiment 3. When the insulating circuit substrate 3 is bonded to the base plate 1 via solder 5A, the position of the insulating circuit substrate 3 is determined by a jig 7. The frame shape of the insulating pattern 2 is located inward of the position where the insulating circuit substrate 3 is set when viewed from above, so the jig 7 is in direct contact with the surface of the base plate 1. Consequently, the accuracy of determining the position of the insulating circuit substrate 3 is improved. Furthermore, the surface of the base plate 1 is exposed through a peripheral opening 2C between the jig 7 and the frame shape of the insulating pattern 2. The solder 5A that scatters during bonding adheres to the surface of the base plate 1 between the jig 7 and the side surface of the insulating pattern 2 in a molten state. This then forms granular solder 6A. The granular solder 6A is firmly fixed to the surface of the base plate 1, making solder balls less likely to form. As a result, the possibility of discharge caused by solder balls is reduced.

[0039] Furthermore, the present invention can freely combine the various embodiments, or appropriately modify or omit the various embodiments.

[0040] Description of the label

[0041] 1 Base plate, 2 Insulation pattern, 2A Insulation layer, 2B Opening for bonding, 2C Peripheral opening, 3 Insulation circuit board, 3A Insulation plate, 3B Metal pattern, 4 Semiconductor element, 5 Bonding material, 5A Solder, 6 Granular material, 6A Granular solder, 7 Jig

Claims

1. A semiconductor device comprising: base plate; an insulating circuit substrate including an upper surface for holding a semiconductor element and a lower surface bonded to a surface of the base plate via a bonding material; and a granular material fixed to the surface of the base plate on the outer side of the insulating circuit substrate when viewed from above, The bonding material has electrical conductivity, The granular material is formed of the same material as the bonding material, The semiconductor device further includes an insulating pattern formed on an insulating layer provided on the surface of the base plate. The insulating pattern comprises: a bonding opening formed so as to expose the surface of the base plate from the insulating layer; as well as a peripheral opening formed so as to surround the entire periphery of the bonding opening and expose the surface of the base plate from the insulating layer; The insulating circuit substrate is bonded to the surface of the base plate via the bonding material disposed inside the bonding opening. The granular matter is attached to the surface of the base plate exposed from the peripheral opening, The entire side surface of the insulating pattern forming the peripheral opening is located inside the outer edge of the insulating circuit substrate in a plan view.

2. The semiconductor device according to claim 1, wherein A width of the insulating pattern between the bonding opening and the peripheral opening is smaller than a distance from the surface of the base plate to the lower surface of the insulating circuit substrate.

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