Semiconductor assembly

Abstract

Semiconductor assembly (20) comprising: - at least one semiconductor component (1) which has external contacts (3) arranged in a grid on its underside (4), - a substrate (10) for receiving the at least one semiconductor component (1), wherein the substrate (10) has a first main surface (11) on which a number of contact terminal surfaces (13) are arranged, wherein - the contact connection surfaces (13) are arranged in a grid on the first main surface (11), - the contact surfaces (13) in an edge area (17) of the grid extend outwards beyond a grid dimension, - the contact connection surfaces (13) are formed in a round shape in an inner area (16) of the grid, - the contact connection surfaces (13) in the edge area (17) of the grid have an oval shape, and - the contact connection surfaces (13) in a corner area (18) of the grid are round and have a larger diameter than contact connection surfaces (13) in an inner area (16) of the grid, and wherein - the external contacts (3) of the semiconductor component (1) are soldered to the contact terminals (13) of the substrate (10) forming solder connections (19), wherein the solder connections (19) are arranged centered on the contact terminals (13) in an inner area (16) of the grid and the external contacts (3) are arranged eccentrically on the contact terminals (13) in an outer area (17) of the grid.

Description

[0001] The present invention relates to a semiconductor assembly comprising at least one semiconductor component and a substrate for receiving the at least one semiconductor component.

[0002] Reliability issues often arise when soldering semiconductor components to higher-level substrates, especially when soldering BGA components. The different expansion coefficients of the substrate and the semiconductor component can cause the solder joints between them to crack.

[0003] Various approaches to prevent this are known. For example, underfill materials are known that are introduced into the space between the semiconductor component and the substrate to absorb the effects of temperature cycles. Another option is edge bonding, an epoxy resin that is applied specifically to the particularly vulnerable corner areas of BGA packages. However, these measures are often inadequate and also require additional production steps. For this reason, some manufacturers have already dispensed with the use of contacts in corner or edge areas for signal transmission.

[0004] Document US 6,400,019 B1 discloses that the connection strength between the external terminals and the wiring substrate of a semiconductor device can be improved without producing a large-sized semiconductor device. This is achieved by disposing a plurality of bump electrodes on the outer periphery of the backside of an intermediate substrate on which a semiconductor chip constituting a CSP Type 1 semiconductor device is mounted. The bump electrodes are larger in size in the direction intersecting the sides of the intermediate substrate than in the direction along the sides of the intermediate substrate.

[0005] JP 2001-68594 A discloses that a reinforcement bump having the same or larger cross-sectional area than that of a signal bump is arranged at a corner portion near a BGA square vertex to improve the strength of a package. Furthermore, a reinforcement pad having the same or larger surface area than that of a signal pad is arranged at a corner portion near the square vertex of the area array to improve the strength of a packaging board. A surface area or arrangement position of the reinforcement bump is increased compared to the cross-sectional area of ​​the reinforcement bump, or shifted toward the corner side of the outer peripheral side compared to the arrangement position, thereby obtaining a BGA chip-sized packaging body in which stress tends not to be centered at an electrode junction portion.

[0006] Document KR 10 2005 0 061 199 A discloses that a plurality of pads formed on a peripheral edge of a PCB have an elliptical shape, and that a plurality of solder balls of a BGA package are adhered to the plurality of pads. The elliptical pads are arranged outside the peripheral edge of the printed circuit board, and the circular pads are arranged inside the peripheral edge of the printed circuit board. The elliptical pads arranged on the peripheral edge of the printed circuit board have a size of 0.41 mm in an x-direction and 0.3 mm in a y-direction.

[0007] It is therefore an object of the present invention to provide a semiconductor assembly having at least one semiconductor component and a substrate for receiving the at least one semiconductor component, which has increased reliability of solder connections, in particular in edge and corner regions of the semiconductor component, and is also easy to manufacture.

[0008] This problem is solved by the subject matter of the independent patent claim. Advantageous embodiments and further developments are the subject matter of the dependent claims.

[0009] According to one aspect of the invention, a semiconductor assembly is provided, comprising at least one semiconductor component having external contacts arranged in a grid on its underside, and a substrate for receiving the at least one semiconductor component. The semiconductor component is, in particular, a so-called BGA component having external contacts in the form of solder balls.

[0010] According to the invention, the substrate has a first main surface on which a number of contact pads are arranged. The contact pads are provided to be connected to external contacts of the semiconductor component in a soldering process. The contact pads are arranged in a grid on the first main surface, with contact pads extending outward beyond a grid dimension in an edge region of the grid.

[0011] The grid is defined by the distances between adjacent contact pads in both directions of the first main surface. These distances a2 and b2 correspond to the distances a1 and b1 between adjacent external contacts of the semiconductor component. They are typically the same across the entire grid, although the horizontal distances a1, a2 do not necessarily have to correspond to the vertical distances b1, b2. However, all contact pads have the same distance from their nearest neighbors in the first direction of the first main surface, and the same distance in the second direction of the first main surface.

[0012] The substrate has modified contact pads in its edge regions. Edge regions are those regions of the grid in which contact pads are not surrounded on all sides by neighboring contact pads, but have no neighboring contact pad on at least one side. A special case of an edge region is a corner region in which a contact pad has even fewer neighboring contact pads, namely only two neighboring contact pads in the case of a square or rectangular grid. The inner region of the grid is understood here and below to be regions of the grid in which contact pads are surrounded on all sides by neighboring contact pads and have the maximum number of nearest neighbors, i.e. four nearest neighbors in the case of a square or rectangular grid.

[0013] According to the invention, contact pads arranged in an edge region of the grid extend outward beyond the grid dimension. Extension is understood to mean that the contact pads have a larger area than contact pads in an inner region of the grid. Outward extension is understood to mean that the additional area extends exclusively outward, i.e., away from an inner region of the grid.

[0014] The substrate has the advantage that conventional semiconductor components can be arranged on it with a uniform pitch, since the position of the contact pads remains unchanged. However, at the particularly vulnerable contact pads at the edge of the grid, a larger area and thus more material is available for a solder connection. This has the advantage of providing a solder connection with a larger volume and larger contact area to both the substrate and the semiconductor component, which is less susceptible to defects.

[0015] Enlarging the contact pads outwards not only has the advantage that the pitch of the semiconductor component to be arranged on them can be maintained, but it also takes advantage of the fact that more space is available in the edge area of ​​the substrate and can be used to enlarge the contact area and the solder volume than in an inner area of ​​the grid.

[0016] According to the invention, the contact pads are round in an inner region of the grid, and the contact pads in an edge region of the grid have an oval shape. The oval shape of the contact pads results from the fact that the round contact pads in the edge region have been extended outwards.

[0017] According to the invention, the contact pads in a corner region of the grid are round and have a larger diameter than contact pads in an inner region of the grid. Here, the round, enlarged shape of the contact pads is achieved by extending the contact pads in the corner regions outward in several, at least two, directions. The round shape is advantageous because it is particularly simple.

[0018] In the semiconductor assembly according to the invention, the external contacts of the semiconductor component are soldered to the contact pads of the substrate, forming solder connections. The external contacts in an inner region of the grid are arranged centered on the contact pads, and external contacts arranged in an edge region of the grid are arranged eccentrically on the contact pads.

[0019] The eccentric arrangement of the external contacts on the contact pads in the edge region results from the fact that the contact pads in the edge region extend outward beyond the pitch, while the pitch on the semiconductor component is uniform. The external contacts, which are arranged in a uniform pitch, are therefore not centrally positioned above the contact pads in the edge region.

[0020] The semiconductor assembly has the advantage that the larger contact pads in the edge region provide more solder material for the solder connections formed there, making these solder connections more reliable. Furthermore, it has the advantage that no modifications to the semiconductor component, and in particular to the arrangement of its external contacts, are necessary, since the semiconductor component and the substrate still have the same pitch, and the external contacts thus fit onto the contact pads. The contact pads arranged in the edge region simply have an additional, extended surface area.

[0021] According to one embodiment, each contact pad has a solder layer. This layer is printed, in particular, in the form of a solder paste. The solder layer is applied to all contact pads in a uniform thickness. This results in a larger volume of solder on the contact pads arranged in the edge regions of the grid, which is available for forming a solder connection with the semiconductor component.

[0022] The substrate can in particular be designed as a PCB substrate and comprise an electrically insulating material on which the contact pads and optionally conductor tracks and / or through-contacts are applied.

[0023] According to one embodiment, the solder connections have a larger volume in an edge region of the grid than in an inner region of the grid. The largest solder volume is available in corner regions, which have the most extensive contact pads. The increased solder volume results from the increased area of ​​the contact pads in the edge or corner regions with the same thickness of the applied solder layer.

[0024] Embodiments of the invention are described below by way of example with reference to schematic drawings. Fig. 1 shows a bottom view of a semiconductor device for forming a semiconductor assembly according to an embodiment of the invention; Fig. 2 shows a view of a first main surface of a substrate according to an embodiment of the invention; Fig. 3 shows a semiconductor assembly according to an embodiment of the invention with a semiconductor component and a substrate before soldering the semiconductor component and Fig. 4 shows a sectional view of the semiconductor assembly according to Fig. 3 after soldering the semiconductor component.

[0025] Fig. Figure 1 shows a semiconductor component 1 in a view of the underside 4 of its housing 2. The semiconductor component 1 shown in a section is, in particular, a BGA component that has at least one semiconductor component arranged within the housing 2, which can be contacted via external contacts 3 and connected to a higher-level substrate. The external contacts 3 are solder balls that are melted in a reflow process to connect the semiconductor component 1 to a higher-level substrate.

[0026] The external contacts 3 are arranged in a rectangular grid on the underside 4 of the housing 2. They are spaced apart from their nearest neighbors by the distances a1 and b1 in the first and second directions, respectively, in the plane of the underside 4. The distances a1 in the first direction are the same for all external contacts 3 of the semiconductor component 1. The same applies to the distances b1 in the second direction. In the case of a square grid, a1 = b1.

[0027] Fig. 2 shows a substrate 10 on which a semiconductor device such as that shown in Fig. 1 shown. In this case, Fig. 2 only a section of such a substrate 10 is shown.

[0028] The substrate 10 has a first main surface 11 on which a number of contact pads 13 are arranged. The contact pads 13 are arranged in a rectangular grid on the first main surface 11 and are spaced a2 and b2 from their nearest neighbors in both directions of the plane of the first main surface 11.

[0029] The contact pads 13 are intended for connection to external contacts 2 of the semiconductor component 1. Therefore, the pitch of the semiconductor component 1 corresponds to that of the substrate 10, i.e., a1 = a2 and b1 = b2. In the case of a square pitch, a1 = a2 = b1 = b2. However, a rectangular pitch can also be selected, with a1, a2 ≠ b1, b2.

[0030] The contact pads 13 on the substrate 10 are formed as metallization on the electrically insulating substrate, which can be, for example, a PCB substrate. A layer of solder paste 14 is arranged on the contact pads 13. The contact pads 13 are surrounded by a layer of solder resist 15, which prevents the solder material from running during a reflow process.

[0031] The grid of contact pads 13 has an inner region 16 as well as an edge region 17 and a corner region 18. The inner region 16 is defined by the fact that contact pads 13 arranged there are surrounded on all sides by further contact pads 13. Contact pads 13 in the edge region 17, however, have no adjacent contact pads 13 on at least one side. Contact pads 13 in the corner region 18, of which Fig. 2 only one is shown, have no adjacent contact pads 13 on two sides.

[0032] The contact pads 13 in the inner region 16 of the grid are round with a diameter D that is approximately the same size as the diameter of the external contacts 3 of the semiconductor component 1 or slightly larger. The external contacts 3 of the semiconductor component 1 are in Fig. 2 are indicated by dashed lines to illustrate their position relative to the contact pads 13.

[0033] The contact pads 13 in the edge region 17 of the substrate 10 have an oval shape, wherein their smaller diameter essentially corresponds to the diameter D of the contact pads 13 in the inner region 16.

[0034] The contact pads 13 in the corner region 18 of the substrate 10 are again round and have a diameter D' that is larger than the diameter D of the contact pads 13 in the inner region 16. It corresponds approximately to the larger diameter of the oval-shaped contact pads 13 in the edge region 17.

[0035] Again Fig. As can be seen from Figure 2, it is intended that the external contacts 3 of the semiconductor component 1 are arranged centered on the contact pads 13 of the inner region 16 of the substrate 10. However, they are arranged eccentrically on the contact pads 13 of the edge region 17 and thus also of the corner region 18, since these contact pads 13 have been enlarged outwards and thus asymmetrically to the grid of the external contacts 3.

[0036] Fig. 3 shows a sectional view of a semiconductor assembly 20 with the Fig. 1 shown semiconductor component 1 and the one in Fig. 2 before soldering the external contacts 3 onto the contact pads 13. In this view, it can be seen that the external contacts 3 of the semiconductor component 1 are arranged on contact pads 5 of the housing 2 and have the shape of solder balls.

[0037] Fig. 4 shows the semiconductor assembly 20 according to Fig. 3 after soldering the external contacts 3 onto the contact pads 13. It can be seen that the external contacts 3 are fused with the solder paste 14 on the contact pads 13 to form solder connections 19, which are arranged in the inner region 16 of the grid, centered relative to the contact pads 13 and the contact pads 5. However, in the edge region 17, the solder connections 19 are arranged eccentrically relative to the contact pads 13.

[0038] In the edge region 17, the solder connections 19 have a larger diameter than in the inner region 16 because more solder material is available in the edge region 17 to form the solder connection 19 due to the larger contact connection surface 13 and thus the larger volume of solder paste 14. The solder connection 19 thus also has a larger surface area on the contact connection surfaces 13 and, if applicable, also on the contact surfaces 5 in the edge regions 17 and is more reliable and less susceptible to cracking.

Claims

[1] Semiconductor assembly (20) comprising: - at least one semiconductor component (1) having external contacts (3) in a grid on its underside (4), - a substrate (10) for receiving the at least one semiconductor component (1), wherein the substrate (10) has a first main surface (11) on which a number of contact pads (13) are arranged, wherein - the contact pads (13) are arranged in a grid on the first main surface (11), - the contact connection surfaces (13) in an edge region (17) of the grid are extended outwards beyond one grid dimension, - the contact connection surfaces (13) in an inner region (16) of the grid are round, - the contact pads (13) in the edge region (17) of the grid have an oval shape, and - the contact connection surfaces (13) in a corner region (18) of the grid are round and have a larger diameter than contact connection surfaces (13) in an inner region (16) of the grid, and wherein - the external contacts (3) of the semiconductor component (1) are soldered to the contact pads (13) of the substrate (10) to form solder connections (19), and wherein the solder connections (19) are arranged centered on the contact pads (13) in an inner region (16) of the grid, and the external contacts (3) are arranged eccentrically on the contact pads (13) in an edge region (17) of the grid. [2] A semiconductor assembly (20) according to claim 1, wherein each contact pad (13) comprises a solder layer. [3] Substrate (10) according to one of claims 1 to 2, wherein the substrate (10) is formed as a PCB substrate. [4] Semiconductor assembly (20) according to one of claims 1 to 3, wherein the solder connections (19) have a larger volume in an edge region (17) of the grid than in an inner region (16) of the grid.

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