Bump-on-conductor (BAL) structure and procedure for forming the BAL structure

Abstract

Method for forming a bump-on-conduit setup, hereinafter referred to as BAL setup, comprising: Forming a contact line (18) on a substrate (16); Generating an enlarged wetting area (40) of the contact line (18), wherein the enlarged wetting area (40) comprises several indentations (42) on only one side wall (28) of the contact line (18); and Applying solder (22) over the enlarged wetting area (40) of the contact line (18) to electrically connect the contact line (18) to a conductive column (20), wherein the multiple indentations (42) on only one side wall (28) of the contact line (18) are completely covered by the conductive column (20).

Description

BACKGROUND

[0001] In a package or assembly, such as a flip-chip package (flip-chip-scale package, fcCSP), an integrated circuit (IC) or semiconductor wafer is mounted onto a substrate (e.g., a printed circuit board, PCB, or other carrier for integrated circuits) via a bump-on-line (BAL) connection. The BAL connection is made by soldering to electrically connect the bump or protrusion of the IC to the substrate's conductor.

[0002] Given the increasing demand for smaller packages, attempts are frequently made to reduce the distance between adjacent bumps, also known as bump pitch or bump spacing. One way to reduce bump spacing is to reduce the distance between adjacent metal conductors.

[0003] Unfortunately, reducing the distance between adjacent metal conductors can have undesirable or detrimental consequences. For example, a solder bridge can form during the BAL connection process during reflow or reflow if the adjacent metal conductors are too close together.

[0004] Document US 2013 / 0127042A1 discloses a BAL connection comprising a contact line on a substrate, a conductive column, and a solder element between the contact line and the conductive column to electrically connect the contact line to the conductive column.

[0005] Document US 2013 / 0001769A1 discloses a BAL structure in which a conductive column covers two indentations 230A, each located on the opposite side walls of a contact line.

[0006] Document US 2011 / 0074024A1 also discloses a BAL structure, wherein several indentations are formed on both side walls of a contact line. Further prior art relating to the subject matter of the invention can be found in document US 2012 / 0061824A1.

[0007] The invention provides a method for forming a BAL structure according to claim 1 and a BAL connection according to claim 12. Embodiments are specified in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following descriptions together with the accompanying drawings, in which: Fig. 1 shows a top view of an embodiment of a bump-on-line (BAL) assembly in a package (where the die or semiconductor wafer has been removed) for easier illustration; Fig. 2 a sectional view of the embodiment of the BAL structure of Fig. 1 along line 2-2 shows; Fig. 3 a sectional view of the embodiment of the BAL structure of Fig. 1 along line 3-3 shows; Fig. Figures 4 to 6 together show an embodiment of a process sequence used to produce the embodiment of the BAL structure of the Fig. 1 to 3 are used; Fig. 7 to 8 indentations are shown, which are located in the contact line of the embodiment of the BAL structure. Fig. 1 can be formed; Fig. Figure 9 shows the dimensions of the conductive column in relation to the contacting line section under the conductive column; Fig. 10 to 11 provide a set of images which illustrate the increased distance between the solder element and the adjacent conductor in the embodiment of the BAL setup of the Fig. 1 compared to a BAL connection; and Fig. 12 to 13 embodiments of methods for producing the BAL structure of the Fig. Show 1.

[0009] Corresponding numbers and symbols in different figures generally refer to corresponding parts, unless otherwise stated. The figures are drawn to clearly show the relevant aspects of the embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION OF EXAMPLE FORMS OF EXECUTION

[0010] The manufacture and use of the present embodiments are explained in detail below. However, it should be noted that the disclosure provides many applicable inventive concepts that can be implemented in a wide variety of specific contexts. The specific embodiments described are purely exemplary and do not limit the scope of the disclosure.

[0011] The present disclosure is described with reference to embodiments in a specific context, namely a package that includes a bump-on-line (BAL) connection. However, the concepts of the disclosure can also be applied to other packages, interconnect configurations, or semiconductor structures.

[0012] Together they show Fig. Figures 1 to 3 describe a bump-on-line (BAL) configuration 10 for a package 12. As explained in more detail below, the BAL configuration 10 offers numerous advantages over BAL configurations formed using other approaches. For example, the BAL configuration 10 allows for a more uniform distribution of solder across the contact line. This inhibits or prevents the formation of solder bridges between adjacent lines in a bump design with close spacing. Additionally, the BAL configuration 10 provides a more robust and reliable electrical connection for the package 12.

[0013] As shown, the BAL assembly 10 is designed such that it incorporates a semiconductor wafer 14 (in Fig. 2 and Fig. 3) electrically (and in some embodiments structurally) connects to a substrate 16. According to one embodiment, the semiconductor wafer 14 comprises one or more integrated circuits from a plurality of different integrated circuits that have been isolated from a wafer. According to one embodiment, the substrate 16 may, for example, be a printed circuit board. In some embodiments, the semiconductor wafer 14 and the substrate 16 may each comprise additional components, layers, structures, or elements that have been omitted for the sake of simplicity.

[0014] As in Fig. As shown in Figure 1, the BAL assembly 10 comprises a landing trace, a conductive column 20, and a solder element 22. The landing trace lies on the substrate 16 next to at least one adjacent conductor 30. As explained below, the landing trace 18 has a reduced length or may be truncated or shortened relative to the adjacent conductor 30. In other words, the landing trace 18 may be shorter than the adjacent conductor 30.

[0015] As in the Fig. As shown in Figures 2 and 3, the contact line 18 is supported by the substrate 16. In one embodiment, the contact line 18 is arranged entirely above an upper surface of the substrate 16. In another embodiment, the contact line is at least partially embedded in the substrate 16. The contact line 18 is formed from a conductive metal, such as copper (Cu), but can also be formed from other suitable conductive metals.

[0016] Fig. Figure 1 further shows that the contact line 18 of the BAL assembly 10 includes an end 24 of the contact line 18. The end 24 can also be referred to as the distal end. The end 24 has an end face 26 located between opposing side walls 28. In embodiments where the contact line 18 is shorter than the adjacent line 30, the distal end 24 of the contact line 18 is offset relative to the distal end 24 of the adjacent line 30. In other words, the contact line 18 and the adjacent line 30 are misaligned in their positioning on the substrate 16 with respect to each other.

[0017] As in the Fig. As shown in Figures 2 to 3, the conductive column 20 is connected to the semiconductor wafer 14. The conductive column 20 is formed from a conductive metal, such as copper (Cu), but can also be formed from other conductive metals in a suitable manner. The conductive column 20 can be referred to as a bump or under-bump metallization (UBM).

[0018] As in the Fig. As shown in Figures 1 to 2, the conductive column 20 extends at least to the distal end 24 of the contact line 18 and, in some embodiments, may extend beyond the distal end 24. In other words, a region 32 of the conductive column 20 extends at least to the end face 26 of the underlying contact line 18. According to one embodiment, the conductive column 20 extends beyond the underlying contact line 18, such that the region 32 of the conductive column 20 projects beyond the end face 26 of the underlying contact line 18. According to one embodiment, the conductive column 20 has a width 34 that is greater than the width 26 of the underlying contact line 18.

[0019] According to one embodiment, the contact line 18 and the conductive column 20 can have a variety of suitable shapes. In other words, the contact line 18 and the conductive column 20 are not limited to the shapes shown in the Fig. The shapes shown in Figures 1 to 3 are limited. For example, the contact wire 18 can have a square shape, a round shape, an oval shape, etc., instead of a rectangular shape. Similarly, the conductive column 20 can also have a rectangular shape, a square shape, a round shape, and so on, instead of an oval shape.

[0020] As in the Fig. As shown in Figures 1 to 3, the solder element 22 (e.g., a solder joint) is located between and around the conductive column 20 and the contact line 18. The solder element 22 is suitable for electrically connecting the conductive column 20, which extends from the semiconductor plate 14, to the contact line 18, which is located on the substrate 16.

[0021] In one embodiment, the solder element 22 contacts both side walls 28 of the contact line 18 and rests against both side walls 28 of the contact line 18. In another embodiment, the solder element 22 also contacts the end surface 26 of the contact line 18 and rests against the end surface 26 of the contact line 18. The solder element 22 can be a solder paste, a solder ball, or another suitable molten metal alloy used for joining components and which has a lower melting point than the components.

[0022] Because the conductive column 20 extends at least to the distal end 24 of the contact line 18 and can protrude beyond it, as shown in the Fig. As shown in Figures 1 to 2, it is possible for the solder element 22 to distribute itself evenly across both side walls 28 of the contact line 18. By distributing itself along both side walls 28, the volume of the solder is reduced on each side of the contact line 18 compared to wetting only one of the two side walls 28 with solder. In other words, the volume of the solder is distributed across both side walls 28 instead of accumulating along only one of the side walls 28.

[0023] Because the solder volume is distributed across the two side walls 28 of the contact line 18, the distance between the solder element 22 and the adjacent line 30 is reduced compared to the case where the entire solder element 22, or most of it, accumulates only along the side wall 28 of the contact line 18 facing the adjacent line 30. This allows the distance between the contact line 18 and the adjacent line 30 to be reduced, for example, to provide a smaller overall package 10.

[0024] According to one embodiment, the volume of the solder is distributed between the two side walls 28 and the end surface 26 of the contact line 18. In this embodiment, the distance between the solder element 22 and the adjacent line 30 can be reduced even further compared to the case in which the solder element 22 accumulates only along the side wall 28 of the contact line 18 that faces the adjacent line 30.

[0025] In one embodiment, the contact line 18 can be smaller than the adjacent line 30 from the outset. Under such circumstances, the section 38 of the contact line 18, which is located in Fig. 4, which is shown by dashed lines, has not been manufactured. In another embodiment, the contact line 18 and the adjacent contact line 18 can be approximately the same length if sufficient space is available at the distal end 24 of the contact line 18 for the conductive column to extend to or beyond the distal end 24. In other words, if the distal end 24 of the contact line 18 is spaced from the vicinity of the substrate 16 in such a way that a soldered connection is possible, then the contact line 18 and the adjacent contact line 18 can be approximately the same length.

[0026] The Fig. Figures 4 to 6 schematically show an embodiment of a process sequence used to manufacture the BAL structure 10. Fig. 1 to 3 are used. As in Fig. As shown in Figure 4, the contact line 18 and the adjacent line 30 are formed on the substrate 16. In one embodiment, the section 38 (shown by dashed lines) of the contact line 18 is omitted during the manufacturing process, so that the contact line 18 has a shorter length than the adjacent line 30.

[0027] In one embodiment, the contact line 18 and the adjacent line 30 are initially formed with the same length, and subsequently, section 38 can be removed to provide a contact line 18 of a shorter length. Section 38 of the contact line 18 can be removed, for example, by etching. Section 38 of the contact line can also be removed by suitable methods such as laser cutting, laser burning, selective etching, mechanical cutting, etc.

[0028] Fig. Figure 5 shows that if the contact line 18 is made shorter than the adjacent line 30, or if section 38 of the contact line 18 is removed, an increased wetting area 40 (in Fig. 5 (shown in dashed lines) is generated or manufactured. In one embodiment, the enlarged wetting area 40 comprises an end face 26 of the contact line 18. In another embodiment, the enlarged wetting area 40 comprises the end face 26 and at least a portion of both side walls 28 of the contact line 18. The enlarged wetting area 40 provides more area or additional surfaces for the solder element 22 to spread over and around it.

[0029] Fig. Figure 5 shows that the conductive column 20 is arranged above the contact line 18. In one embodiment, the conductive column extends at least to the distal end 24 of the contact line 18. In another embodiment, the conductive column 20 projects beyond the distal end 24 of the contact line 18. In other words, the area 32 surrounding the conductive column 20 projects beyond the end face 26 of the underlying contact line 18, as shown in Figure 5. Fig. 5 is shown.

[0030] Referring to Fig. 6. The solder element 22, initially provided between the contact line 18 and the conductive column 20, is melted after the conductive column 20 has been positioned. As soon as the solder element 22 cools, the contact line 18 is electrically connected to the conductive column 20. Fig. 6 The solder element 22 extends along both side walls 28 and the end surface 26 of the contacting line 18. This reduces the extrusion of the solder element 22 in the direction of the adjacent line 30 compared to other BAL connections.

[0031] As in the Fig. As shown in Figures 7 to 8, in one embodiment one or more indentations 42 can be formed in the contact line 18 to create or contribute to the enlarged wetting area 40 (shown in dashed lines) of the contact line 18. In other words, the indentations 42 can be formed instead of, or in addition to, the removal of the section 38 of the contact line 18 shown in Figure 7 to 8. Fig. Figure 4 shows the indentations formed in the contact line 18. The indentations 42 in the contact line 18 provide a surface for the solder element 22 to be occupied or occupied during melting. This reduces the extrusion of the solder element 22 towards the adjacent line 30 compared to other BAL connections.

[0032] As in Fig. As shown in Figure 7, the indentations 42 can be formed in a "herringbone" pattern or structure. As in Fig. As shown in Figure 8, the indentations 42 can also be configured in a "comb" pattern. The indentations 42 can also be configured in a variety of other suitable patterns. For example, the indentations can be configured in symmetrical or asymmetrical patterns, in patterns with uniform or uneven spacing between the indentations 42, etc. Furthermore, the indentations 42 can have a variety of suitable shapes. For example, the indentations can have a square shape, a rectangular shape, a semicircular shape, an oval shape, etc.

[0033] Fig. Figure 9 shows the adjacent conductor 30 to the side of the contact conductor 18. As can be seen, the solder element 22 and the conductive column 20 are shown above the contact conductor 18. The conductive column 20 has a diameter R. The contact conductor 18 has a length L, which corresponds to the section of the contact conductor 18 that lies within the area 32 surrounding the conductive column 20.

[0034] In one embodiment, the length L of the contact line 18 within the environment 32 of the conductive column 20 is approximately 20% to 100% of the diameter R of the conductive column 20. The lower limit of 20% was chosen because the process variation for the overall assembly is approximately 20% of the diameter R of the conductive column 20. Therefore, it is proposed that the length L of the contact line 18 be 20% or more of the diameter R of the conductive column 20 to ensure that the conductive column has a suitable connection to the contact line 18. Otherwise, an electrical break could be found after the assembly process because the conductive column 20 does not make contact with the contact line 18.In one embodiment, the conductive column 20 is positioned such that the length L of the contact line 18 within the environment 32 of the conductive column 20 is less than 100% of the diameter R of the conductive column 20. In other words, the equation 1 / 5 R ≤ L ≤ R is satisfied.

[0035] Fig. Figures 10 to 11 show a first image 44 and a second image 46, which illustrate the increased distance between the solder element and the adjacent conductor when the process described herein is used. In fact, as in Fig. As shown in Figure 10, a distance D1 between the solder element and the adjacent conductor in the BAL connection 52 is smaller than a distance D2 between the solder element and the adjacent conductor when the embodiment of the BAL assembly 10 is used. In other words, the distance D2 in Fig. 11 far greater than the distance D1 in Fig. 10, because in the BAL setup 10 of Fig. 11 the wetting with the plumb element 22 is promoted along both side walls.

[0036] In Fig. Figure 12 shows a method 60 for forming the BAL structure 10. In block 62, the contact line 18 is formed on the substrate 16. In block 64, the conductive column 20 is positioned above the contact line 18 such that the conductive column 20 extends at least to the end 24 of the contact line 18. In block 66, the solder element 22 is melted between the contact line 18 and the conductive column 20 to electrically connect the contact line 18 to the conductive column 20.

[0037] In Fig.Figure 13 shows a method 70 for forming the BAL structure 10. In block 72, the contact line 18 is formed on the substrate 16. In block 74, a section of the contact line 18 is removed to create an enlarged wetting area 40. In block 76, solder is applied over the enlarged wetting area 40 of the contact line 18 to electrically connect the contact line to the conductive column 20.

[0038] Based on the preceding explanations, a person skilled in the art will recognize that the BAL structure 10 controls or minimizes solder extrusion. Furthermore, the BAL structure 10 enables a more uniform distribution of solder across the contact line. This reduces the risk of solder bridging in packages with small bump spacing. In other words, in an (I / O) design with small bump spacing, the undesired formation of solder bridges between adjacent traces is inhibited or prevented. Additionally, the BAL structure 10 provides a more robust and reliable electrical connection for the package 12 by modifying an existing design for trace patterns or structures without significant additional process costs.

Claims

[1] Method for forming a bump-on-conduit setup, hereinafter referred to as BAL setup, comprising: Forming a contact line (18) on a substrate (16); Generating an enlarged wetting area (40) of the contact line (18), wherein the enlarged wetting area (40) comprises several indentations (42) on only one side wall (28) of the contact line (18); and Applying solder (22) over the enlarged wetting area (40) of the contact line (18) to electrically connect the contact line (18) to a conductive column (20), wherein the multiple indentations (42) on only one side wall (28) of the contact line (18) are completely covered by the conductive column (20). [2] Method according to claim 1, wherein the multiple indentations (42) are formed in a comb pattern. [3] Method according to claim 1, wherein the multiple indentations (42) have a square shape, a rectangular shape, a semicircular shape, or an oval shape. [4] Method according to any one of the preceding claims, further comprising: Applying solder (22) over the enlarged wetting area (40) of the contact line (18) to electrically connect the contact line (18) to the conductive column (20) such that a width of the contact line (18) within a circumference of the conductive column (20) is smaller than a diameter of the contact line (18). [5] Method according to one of the preceding claims, wherein the multiple indentations (42) in the contact line (18) have an area which is occupied by the solder (22) during melting. [6] Method according to one of the preceding claims, wherein the enlarged wetting area (40) comprises an end surface (26) of the contact line (18). [7] Method according to one of the preceding claims, wherein the enlarged wetting area (40) comprises an end surface (26) of the contact line (18) and a section of both opposite side walls (28) of the contact line (18). [8] Method according to claim 6 or 7, further comprising removing a section (38) of the contact line (18) to create the enlarged wetting area (40). [9] Method according to claim 6 or 7, further comprising removing a section (38) of the contact line (18) such that a length (L) of the contact line (18) within an environment (32) of the conductive column (20) is 20% to 100% of a diameter (R) of the conductive column (20). [10] Method according to any one of claims 6 to 9, further comprising aligning the conductive column (20) such that a surrounding area (32) of the conductive column (20) extends at least to an end (24) of the contact line (18). [11] Method according to any one of claims 6 to 9, further comprising aligning the conductive column (20) such that a surrounding area (32) of the conductive column (20) extends beyond an end (24) of the contact line (18). [12] Bump-on-line connection, hereinafter referred to as BAL connection, comprising for one package: a contact line (18) on a substrate (16), wherein the contact line (18) has an enlarged wetting area (40) comprising several indentations (42) on only one side wall (28) of the contact line (18); and a solder element (22) on the enlarged wetting surface (40) of the contact line (18) which electrically connects the contact line (18) and a conductive column (20), wherein the multiple indentations (42) on only one side wall (28) of the contact line (18) are completely covered by the conductive column (20). [13] BAL connection according to claim 12, wherein the multiple indentations (42) are formed in a comb pattern. [14] BAL connection according to claim 12, wherein the multiple indentations (42) have a square shape, a rectangular shape, a semicircular shape, or an oval shape. [15] BAL connection according to one of claims 12 to 14, wherein a width of the contacting line (18) within a circumference of the conductive column (20) is smaller than a diameter of the contacting line (18). [16] BAL connection according to one of claims 12 to 15, wherein the multiple indentations (42) in the contact line (18) have an area occupied by the solder element (22). [17] BAL connection according to one of claims 12 to 16, wherein a surrounding (32) of the conductive column (20) extends at least to an end (24) of the contact line (18). [18] BAL connection according to one of claims 12 to 16, wherein the conductive column (20) extends beyond an end (24) of the contact line (18). [19] BAL connection according to one of claims 12 to 18, wherein the contact line (18) has a shorter length than an adjacent line (30) in the package (12). [20] BAL connection according to one of claims 12 to 19, wherein the solder element (22) contacts an end face (26) and opposite side walls (28) of the contacting line (18).

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