Substrate with solder mounting lands

Abstract

A substrate (1) having lands for soldering comprises: metallic bottom plates (4); metallic peripheral walls (5) erected from a peripheral edge of the bottom plates (4), respectively; solder accommodating spaces (6) each of which is formed by the peripheral wall (5) and the bottom plate (4), and in which a solder for electrical connection to a terminal of an electronic component is to be accommodated; lands (3) for soldering each of which includes the solder accommodating space (6) and is formed by the bottom plate (4) and the peripheral wall (5); and a substrate body (2) on which the lands (3) for soldering are placed, and which is electrically connected to the lands (3) for soldering.

Description

[Technical Field]

[0001] The present invention relates to a substrate having solder mounting lands for solder mounting electronic components. [Background technology]

[0002] A solder mounting technique is known in which electronic components such as circuit components and semiconductor elements are placed in predetermined positions on a substrate body and then fixedly connected using solder to electrically connect the electronic components to a conductor pattern formed on the substrate body. During this solder mounting, lands made of a conductive material formed on the surface of the substrate body are connected to the terminals of the electronic components using solder. During solder mounting, a solder resist is arranged around the lands, which defines the bonding area during solder mounting (see, for example, Patent Document 1). When embedding electronic components, the substrate body is laminated with prepreg interposed therebetween, and the electronic components are embedded in the prepreg to form a multilayer substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-027917 Summary of the Invention [Problem to be solved by the invention]

[0004] However, solder resist has a lower glass transition point than prepreg (because solder resist is made of a photosensitive material and contains acrylic, which has low heat resistance), and a higher thermal expansion coefficient, resulting in poor heat resistance during reflow. As a result, stress concentrates on the solder resist due to the difference in thermal expansion during reflow, causing it to shear. When this shear occurs, delamination begins at the solder resist. Because solder resist has a thermal expansion difference with the copper material that forms the conductive layer (land), delamination is known to occur not only between the solder resist and prepreg, but also between the solder resist and the land, and even within the solder resist. While the use of solder resist is undesirable from the standpoint of delamination, some kind of structure is required to block the solder during solder mounting.

[0005] The present invention has been made in consideration of the above-mentioned prior art, and has as its object to provide a substrate having solder mounting lands that are free from delamination. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a substrate with solder mounting lands, comprising: a metal bottom plate; a metal peripheral wall erected from the peripheral edge of the bottom plate; a solder accommodating space formed by the peripheral wall and the bottom plate to accommodate solder for electrically connecting to terminals of an electronic component; solder mounting lands including the solder accommodating space and formed by the bottom plate and the peripheral wall; and a substrate main body on which the solder mounting lands are placed and which is electrically connected to the solder mounting lands.

[0007] Preferably, the electronic components are mounted on the substrate body via the solder mounting lands and the solder, and the electronic components are disposed within an insulating layer made of an insulating material.

[0008] Preferably, the lower side of the inner wall surface of the peripheral wall is tapered so that the diameter gradually increases.

[0009] Preferably, the bottom plate and the peripheral wall are made of copper.

[0010] Preferably, the bottom plate is made of copper, and the peripheral wall is made of Ni, Au, or Pd.

[0011] Preferably, the bottom plate and the lower side of the peripheral wall including the taper are made of copper, and the upper side of the peripheral wall including the taper is made of Ni, Au or Pd.

[0012] Preferably, the exposed surface of the portion of the solder mounting land made of copper, excluding the lower surface of the bottom plate, has a surface roughness of 0.1 μm or more and 10 μm or less.

[0013] Preferably, the mounting surface of the bottom plate, which is the surface on the solder receiving space side, is covered with a surface treatment layer made of Ni, Au, Ag or Sn. [Effects of the Invention]

[0014] According to the present invention, the solder mounting land has a bottom plate and peripheral wall both made of metal, and therefore does not use a resin material such as solder resist on the peripheral wall. This eliminates stress concentration during reflow, and delamination can be suppressed. Furthermore, the solder mounting land is made of metal, which improves its heat resistance. This delamination prevention effect is particularly pronounced when electronic components are embedded within an insulating layer. Furthermore, the solder mounting land itself has an uneven shape on the bottom plate and peripheral wall, so that when stacked with an insulating layer interposed, the solder mounting land and the insulating layer interlock, enhancing adhesion.

[0015] In addition, because the inner wall of the peripheral wall is tapered on the underside, the solder penetrates into this, making it difficult for the solder to come out of the solder-receiving space. This improves the tensile strength of the component, preventing it from coming out when pulled. Furthermore, the tapered surface increases the area of the mounting surface, which is the surface of the bottom plate facing the solder-receiving space, increasing the contact area with the solder and improving the tensile strength of the solder. Furthermore, because a large amount of solder can be accommodated, it is possible to prevent the solder from overflowing if there is a large amount of solder, which can cause a short circuit with adjacent conductive circuits, etc.

[0016] Furthermore, if both the bottom plate and the peripheral wall are made of copper, the prepreg and copper have high adhesion when laminated with an insulating layer, resulting in a laminated substrate with strong adhesion. Furthermore, it can be manufactured relatively inexpensively compared to other metals. Furthermore, if the peripheral wall is formed on the bottom plate by copper plating, the adhesion between the bottom plate and the peripheral wall is higher than with other metals.

[0017] Furthermore, by forming the bottom plate from copper and all or part of the peripheral wall from Ni, Au, or Pd, solder corrosion of copper to the peripheral wall can be reduced, which is particularly noticeable when the peripheral wall is narrow.

[0018] Furthermore, if the exposed copper surface is provided with surface roughness, when stacked with an insulating layer interposed therebetween, the solder mounting lands and the insulating layer can be engaged to enhance adhesion.

[0019] Furthermore, by providing a surface treatment layer made of Ni, Au, Ag, or Sn, Ni, Au, Ag, or Sn has high solder wettability, and the spreading of solder during solder mounting can be improved. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of a substrate having a solder mounting land according to the present invention. [Figure 2] 1 is a schematic plan view of a substrate having solder mounting lands according to the present invention. [Figure 3]1 is a schematic cross-sectional view of a substrate having solder mounting lands according to the present invention with an electronic component mounted thereon. [Figure 4] 1 is a schematic cross-sectional view of a substrate having solder mounting lands according to the present invention with an electronic component built in. FIG. [Figure 5] FIG. 2 is a schematic cross-sectional view showing an example of a solder mounting land. [Figure 6] FIG. 10 is a schematic cross-sectional view showing another example of a solder mounting land. [Figure 7] FIG. 10 is a schematic cross-sectional view showing yet another example of a solder mounting land. [Figure 8] FIG. 10 is a schematic cross-sectional view showing yet another example of a solder mounting land. [Figure 9] FIG. 10 is a schematic cross-sectional view showing yet another example of a solder mounting land. DETAILED DESCRIPTION OF THE INVENTION

[0021] As shown in FIG. 1, a substrate 1 with solder mounting lands according to the present invention includes solder mounting lands 3 mounted on a substrate body 2. The substrate body 2 has an insulating layer made of an insulating material and further includes plated through-holes and a conductor pattern for electrical connection to the solder mounting lands 3. The solder mounting lands 3 include a metal bottom plate 4 and a metal peripheral wall 5 extending from the periphery of the bottom plate 4. The space formed by the bottom plate 4 and the peripheral wall 5 forms a solder-receiving space 6. That is, the solder mounting land 3 is formed by the bottom plate 4 and the peripheral wall 5, including the solder-receiving space 6. As shown in FIG. 2, if the bottom plate 4 is circular in plan view, the peripheral wall 5 will be cylindrical. The peripheral wall 5 is formed continuously in the circumferential direction. The shape of the bottom plate 4 in plan view is not limited to a circular shape and may be angular. The height of the peripheral wall 5 is approximately 5 μm to 20 μm, depending on the amount of solder used during reflow.

[0022] As shown in FIG. 3, the solder mounting lands 3 are electrically connected to terminals 8 of the electronic component 7 via solder 9. That is, the electronic component 7 is mounted on the board body 2 via the solder mounting lands 3 and solder 9. A component-mounted board on which an electronic component 7 is mounted in this manner is also a board 1 having solder mounting lands according to the present invention. Furthermore, as shown in FIG. 4, the electronic component 7 may be disposed within an insulating layer 10 made of an insulating material (e.g., prepreg). A component-embedded board in which an electronic component 7 is embedded in this manner is also a board 1 having solder mounting lands according to the present invention.

[0023] As described above, the solder mounting lands 3 have a bottom plate 4 and peripheral wall 5 both made of metal, and therefore no resin material such as solder resist is used on the peripheral wall 5. This eliminates stress concentration during solder reflow when mounting the electronic component 7, thereby suppressing delamination. Furthermore, since the solder mounting lands 3 are made of metal, heat resistance is also improved. This effect of preventing delamination is particularly pronounced when the electronic component 7 is embedded within the insulating layer 10. Furthermore, since the solder mounting lands 3 themselves have an uneven shape on the bottom plate 4 and peripheral wall 5, when stacked with the insulating layer 10 interposed between them, the solder mounting lands 3 and the insulating layer 10 interlock with each other, enhancing adhesion. This allows for a high-quality laminated substrate to be obtained.

[0024] As shown in FIG. 5 , a gradually expanding taper 11 is formed on the lower side of the inner wall surface of the peripheral wall 5 of the solder mounting land 3. Therefore, the solder-receiving space 6 is wider at the bottom than at the top. Because the taper 11 is formed on the lower side of the inner wall surface of the peripheral wall 5, the solder enters the space below the taper 11 during solder mounting. This makes it difficult for the solder to escape from the solder-receiving space 6. This improves the tensile strength of the electronic component 7 and prevents the electronic component 7 from being pulled out. Furthermore, the taper 11 increases the area of the mounting surface 12, which is the surface of the bottom plate 4 facing the solder-receiving space 6 (the mounting surface 12 expands by the amount of the expansion caused by the taper 11), thereby increasing the contact area with the solder and improving the tensile strength of the solder. The expansion of the mounting surface 12 depends on the amount of solder used during reflow, but is typically between 0.1 μm and 10 μm. Furthermore, the taper 11 widens the solder receiving space 6 downwards, allowing it to receive a large amount of solder, preventing the solder from overflowing if there is a large amount of solder, thereby preventing short circuits with adjacent conductive circuits, etc.

[0025] As for the materials of the bottom plate 4 and the peripheral wall 5, both may be formed of copper as shown in Fig. 5. Alternatively, as shown in Fig. 6, the bottom plate 4 may be formed of copper and the peripheral wall 5 may be formed of Ni, Au, or Pd. Alternatively, as shown in Fig. 7, the bottom plate 4 and the lower side of the peripheral wall 5 including the taper 11 may be formed of copper, and the upper side of the peripheral wall 5 including the taper 11 may be formed of Ni, Au, or Pd. In this case, the material of the peripheral wall 5 changes midway along the taper 11. The peripheral wall 5 is formed on the bottom plate 4 by plating deposition.

[0026] If both the bottom plate 4 and the peripheral wall 5 are made of copper, the prepreg and copper have high adhesion when laminated with the insulating layer 10, resulting in a laminated board with strong adhesion. Furthermore, it can be manufactured relatively inexpensively compared to other metals. Furthermore, if the peripheral wall 5 is formed on the bottom plate 4 by copper plating, the adhesion between the bottom plate 4 and the peripheral wall 5 is higher than with other metals. On the other hand, by forming the bottom plate 4 from copper and all or part of the peripheral wall 5 from Ni, Au, or Pd, solder corrosion of copper to the peripheral wall 5 can be reduced. This effect is particularly pronounced when the width of the peripheral wall 5 is small. For example, the width of the peripheral wall 5 is usually designed to be 10 μm or more and 500 μm or less. However, if the width of the peripheral wall 5 is less than 10 μm, there is a high probability of solder corrosion occurring when the peripheral wall 5 is made of copper. Reducing the width of the peripheral wall 5 is effective in ensuring the size of the mounting surface 12, so forming the peripheral wall 5 from Ni, Au, or Pd, which does not cause solder corrosion, is particularly effective.

[0027] 8, the exposed copper surface of the solder mounting land 3, excluding the lower surface of the bottom plate 4, has a surface roughness 13 of 0.1 μm or more and 10 μm or less. If the exposed copper surface has surface roughness 13, when laminated with an insulating layer 10 in between, the solder mounting land 3 and the insulating layer 10 can be engaged to improve adhesion.

[0028] 9, the mounting surface 12 of the bottom plate 4, which faces the solder receiving space 6, may be covered with a surface treatment layer 14 made of Ni, Au, Ag, or Sn. By providing the surface treatment layer 14 made of Ni, Au, Ag, or Sn in this way, Ni, Au, Ag, or Sn has high solder wettability, which can improve the spreading of solder during solder mounting. In this case, the other copper portions have surface roughness 13, which ensures high solder wettability while also ensuring adhesion to the insulating layer 10. [Explanation of symbols]

[0029] 1: substrate with solder mounting lands, 2: substrate body, 3: solder mounting lands, 4: bottom plate, 5: peripheral wall, 6: solder accommodating space, 7: electronic component, 8: terminal, 9: solder, 10: insulating layer, 11: taper, 12: mounting surface, 13: surface roughness, 14: surface treatment layer

Claims

1. A metal base plate and a metal peripheral wall extending from the peripheral edge of the bottom plate; a solder receiving space formed by the peripheral wall and the bottom plate, for receiving solder for electrically connecting with a terminal of an electronic component; a solder mounting land including the solder receiving space and formed by the bottom plate and the peripheral wall; a substrate body on which the solder mounting lands are placed and which is electrically connected to the solder mounting lands; The lower side of the inner wall surface of the peripheral wall is formed with a taper that gradually increases in diameter, A substrate having solder mounting lands, characterized in that the bottom plate is formed of copper and the peripheral wall is formed of Ni, Au or Pd, or the bottom plate and the lower side of the peripheral wall including the taper are formed of copper and the upper side of the peripheral wall including the taper is formed of Ni, Au or Pd.

2. 2. A substrate with solder mounting lands according to claim 1, wherein the electronic component is mounted on the substrate body via the solder mounting lands and the solder, and the electronic component is disposed within an insulating layer made of an insulating material.

3. 2. A substrate having a solder mounting land according to claim 1, characterized in that the exposed surface of the portion of the solder mounting land made of copper, excluding the lower surface of the bottom plate, has a surface roughness of 0.1 μm or more and 10 μm or less.

4. 4. The substrate having solder mounting lands according to claim 3, wherein the mounting surface of the bottom plate facing the solder receiving space is covered with a surface treatment layer made of Ni, Au, Ag or Sn.

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