JP2009123757A - Wiring board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board on which a solder ball can be positioned precisely and easily and which does not cause the dropout of the solder ball or the shorting of counterpart solder balls, and includes a solder connection pad excellent in the reliability of connection with the solder ball, and to provide a manufacturing method thereof. <P>SOLUTION: The wiring board includes an insulating board 1 and the solder connection pad 4 attached to the surface of the insulating board 1. The solder connection pad 4 is composed of a ring-shaped perimetric electrode 4a forming the perimetric portion of the solder connection pad 4 and a plurality of projections 4b projecting from the perimetric electrode 4a so that their widths become smaller toward the center c of the solder connection pad 4. Also, the manufacturing method thereof is provided. The solder connection pad 4 preferably has a center electrode 4c at the center c to which tips of the plurality of projections 4b are connected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wiring board used for mounting a semiconductor element or the like and a manufacturing method thereof.

  2. Description of the Related Art Conventionally, there is a wiring board as shown in FIG. 5 used for mounting a semiconductor element such as a semiconductor integrated circuit element. FIG. 5 is a cross-sectional view showing a conventional wiring board and solder balls. As shown in the figure, this wiring board 100 includes a copper foil or a copper plating film on the inside and surface of an insulating substrate 101 in which a plurality of insulating layers made of, for example, a glass-epoxy plate or an epoxy resin are laminated. A wiring conductor 102 made of is provided.

  In the central portion of the upper surface of the insulating substrate 101, a plurality of solder connection pads 103 for connecting a semiconductor element to which the electrodes of the semiconductor element are electrically connected via the solder bumps 106 are formed. A plurality of solder connection pads 104 for external connection are formed on the lower surface of the insulating substrate 101 and are electrically connected to the wiring conductors of the external electric circuit board via the solder balls 108.

  Solder resist layers 105 having openings 105a and 105b exposing the central portions of the solder connection pads 103 and 104 are formed on the upper and lower surfaces of the insulating substrate 101 so as to cover the outer peripheral portions of the solder connection pads 103 and 104. It is attached.

  Of the solder connection pads 103 and 104 exposed from the solder resist layer 105, the solder connection pad 103 has a solder bump 106 higher than the solder resist layer 105, and the solder connection pad 104 has a solder layer 107 lower than the solder resist layer 105. Are welded.

  The solder bumps 106 and the solder layer 107 previously welded onto the solder connection pads 103 and 104 are so-called pre-solder, and the workability of connecting the semiconductor element to the solder connection pad 103 and the solder to the solder connection pad 104 are described. This is to improve the joining workability of the ball 108.

  That is, the semiconductor element is mounted on the wiring board 100 by bringing the electrode of the semiconductor element into contact with the solder bump 106 welded to the solder connection pad 103 and heating and melting the solder bump 106.

  Further, the solder ball 108 is placed on the solder layer 107 welded onto the solder connection pad 104, and the solder layer 107 and the solder ball 108 are heated and melted, whereby the solder ball 108 is formed on the solder connection pad 104. The solder balls 108 are bonded and heated and melted in contact with the wiring conductors of the external electric circuit board, whereby the wiring board 100 is mounted on the external electric circuit board via the solder balls 108.

  Such a wiring board 100 is generally manufactured as follows. That is, first, solder connection pads 103 and 104 made of copper are formed on the upper and lower surfaces of the insulating substrate 101 in which the wiring conductors 102 made of copper are disposed inside and on the surface. Next, a solder resist layer 105 is deposited on the upper and lower surfaces of the insulating substrate 101 so that the central portions of the solder connection pads 103 and 104 are exposed. Solder is supplied to the surfaces of the solder connection pads 103 and 104 exposed from the solder resist layer 105. Next, the solder is heated and melted to weld the solder bumps 106 and the solder layer 107 onto the solder connection pads 103 and 104, respectively, thereby obtaining the wiring board 100.

However, the solder layer 107 deposited on the solder connection pad 104 has a shape in which the central portion is raised by the action of the surface tension, and the surface becomes a curved surface (see FIGS. 6A and 6B). . When the solder ball 108 is placed on such a solder layer 107, the solder ball 108 easily rolls on the solder layer 107, and accurate positioning becomes difficult, and the solder ball 108 is missing or short-circuited due to contact between the solder balls 108. There is a problem that occurs.
JP 2003-258156 A

  An object of the present invention is to provide a solder connection pad that can position a solder ball accurately and easily, does not cause a lack of a solder ball or a short circuit between solder balls, and has excellent connection reliability with the solder ball. And a manufacturing method thereof.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a solution means having the following constitution and have completed the present invention.
(1) A wiring board comprising an insulating substrate and a solder connection pad deposited on the surface of the insulating substrate, wherein the solder connection pad has a ring shape that forms the outer periphery of the solder connection pad A wiring board comprising: an outer peripheral electrode; and a plurality of projecting portions that project from the outer peripheral electrode toward a central portion of the solder connection pad so that the width thereof becomes narrower.
(2) The wiring board according to (1), wherein the solder connection pad has a center electrode with the tips of the plurality of protrusions connected to the center thereof.
(3) The wiring board according to (1) or (2), wherein a solder whose thickness increases from the center of the solder connection pad toward the outer peripheral electrode is welded onto the solder connection pad.

The method for manufacturing a wiring board according to the present invention includes a step of providing a solder connection pad on a surface of an insulating substrate and a step of welding solder onto the solder connection pad, the solder connection pad including an outer periphery of the solder connection pad. A ring-shaped outer peripheral electrode forming a portion, and a plurality of projecting portions projecting from the outer peripheral electrode toward the center portion of the solder connection pad so that the width thereof becomes narrower. Solder is welded so that the thickness increases from the center of the solder connection pad toward the outer peripheral electrode.
It is preferable that the solder connection pad has a center electrode with the tips of the plurality of protrusions connected to the center thereof.

  According to the present invention, the solder connection pad projects from the outer peripheral electrode forming the outer peripheral portion of the solder connection pad, and the width of the solder connection pad decreases from the outer peripheral electrode toward the central portion of the solder connection pad. It consists of a plurality of protrusions. As a result, when solder is supplied onto this connection pad and the solder is heated and melted, the surface tension acts on the solder connection pad from the center of the solder connection pad as described in (3) above. Solder (preliminary solder) whose thickness increases toward the outer peripheral electrode can be welded. When the solder ball is placed on the solder having such a shape, it is difficult for the solder ball to roll on the solder, and it is possible to prevent the solder ball from rolling out from the solder connection pad, thereby enabling accurate positioning. As a result, it is possible to suppress the occurrence of a short circuit due to lack of solder balls or contact between solder balls.

  Furthermore, when the solder connection pad according to the present invention is applied to the surface of the insulating substrate, a part of the surface of the insulating substrate is exposed from the region surrounded by the outer peripheral electrode and the protruding portion of the solder connection pad. For this reason, when a solder ball is placed on the solder welded onto the solder connection pad, a gap is formed between the lower part of the placed solder ball and the surface of the insulating substrate exposed in the region. In this state, when the solder and the solder balls are heated and melted and the solder balls are joined onto the solder connection pads, a cavity is formed between the insulating substrate exposed in the region and the formed solder. As a result, the stress generated due to the difference in thermal expansion coefficient between the solder and the solder connection pad can be reduced by releasing the stress to the cavity, so that the occurrence of cracks or the like in the solder is suppressed. Therefore, the connection reliability between the solder connection pad and the solder ball can be made excellent.

  In particular, as described in (2) above, when the center electrode of the solder connection pad has the center electrode connected to the tips of the plurality of protrusions, the tip of the probe for electrical testing is pressed against the center electrode for easy processing. An electrical test can be performed. In addition, since the outer peripheral electrode and the plurality of protruding portions are continuous through the central electrode, when solder is welded onto the solder connection pad, the molten solder flows uniformly on the pad, Solder having the shape as in (3) is easily welded. Further, when the center electrode is provided, the solder ball can be easily fixed to the center portion of the solder connection pad, whereby a solder connection portion having a uniform thickness can be formed in the solder connection pad after the solder ball is melted.

  Hereinafter, an embodiment of a wiring board and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a wiring board and solder balls according to the present embodiment. 2A is a plan view showing a solder connection pad for external connection in the wiring board shown in FIG. 1, and FIG. 2B is a broken cross-sectional view taken along the line I-I in FIG. FIG. 2C is a diagram showing a broken section taken along line II-II in FIG.

  As shown in FIG. 1, in the wiring board 15 according to the present embodiment, the insulating substrate 1 is formed by laminating a plurality of insulating layers 1b on the upper and lower surfaces of the insulating layer 1a, and the solder is formed on the outermost insulating layer 1b. A resist layer 5 is laminated. In the central portion of the upper surface of the insulating substrate 1, a plurality of solder connection pads 3 for connecting a semiconductor element, to which the electrodes of the semiconductor element are electrically connected via solder bumps 6, are formed. On the lower surface of the insulating substrate 1, a plurality of external connection solder connection pads 4 are formed which are electrically connected to the external electric circuit substrate via solder balls 8. A wiring conductor 2 that electrically connects the corresponding solder connection pad 3 and the solder connection pad 4 to each other is disposed from the upper surface to the lower surface of the insulating substrate 1. Solder bumps 6 are applied to the solder connection pads 3, and solder layers 7 are applied to the solder connection pads 4.

  The insulating layer 1a is a member that becomes a core of the wiring board 15, and is formed, for example, by impregnating a glass fabric in which glass fiber bundles are woven vertically and horizontally with a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin. The thickness of the insulating layer 1a is, for example, about 0.3 to 1.5 mm, and has a plurality of through holes 9 having a diameter of about 0.1 to 1 mm from the upper surface to the lower surface. A part of the wiring conductor 2 is attached to the upper and lower surfaces of the insulating layer 1 a and the inner surface of each through hole 9, and the upper and lower wiring conductors 2 are electrically connected through the through hole 9.

  Such an insulating layer 1a is manufactured, for example, by thermally curing an insulating sheet in which a glass fabric is impregnated with an uncured thermosetting resin, and then drilling the insulating sheet from the upper surface to the lower surface. The wiring conductors 2 on the upper and lower surfaces of the insulating layer 1a have a copper foil having a thickness of about 3 to 50 μm applied to the entire upper and lower surfaces of the insulating sheet for the insulating layer 1a, and the copper foil is etched after the sheet is cured. Thus, a predetermined pattern is formed. The wiring conductor 2 on the inner surface of the through hole 9 is provided with a copper plating film having a thickness of about 3 to 50 μm by an electroless plating method and an electrolytic plating method on the inner surface of the through hole 9 after the through hole 9 is provided in the insulating layer 1a. Formed by precipitation.

  The through hole 9 is filled with a hole filling resin 10 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin. The hole-filling resin 10 is for making it possible to form the wiring conductor 2 and each insulating layer 1b directly above and below the through-hole 9 by closing the through-hole 9, for example, an uncured paste-like heat A curable resin is filled into the through-holes 9 by screen printing, thermally cured, and then the upper and lower surfaces thereof are polished to be substantially flat. A plurality of insulating layers 1 b are laminated on the upper and lower surfaces of the insulating layer 1 a including the hole filling resin 10.

  Each insulating layer 1b laminated on the upper and lower surfaces of the insulating layer 1a has a thickness of about 20 to 60 μm, and has a plurality of through holes 11 having a diameter of about 30 to 100 μm from the upper surface to the lower surface of each layer. . Each insulating layer 1b is for providing an insulating interval for wiring the wiring conductor 2 with high density. A high-density wiring can be three-dimensionally formed by electrically connecting the upper wiring conductor 2 and the lower wiring conductor 2 via the through hole 11.

  Each such insulating layer 1b is formed by, for example, attaching an insulating film made of an uncured thermosetting resin having a thickness of about 20 to 60 μm to the upper and lower surfaces of the insulating layer 1a, thermosetting the film, and performing laser processing. The through-hole 11 is formed, and the next insulating layer 1b is sequentially stacked thereon in the same manner. The wiring conductor 2 deposited on the surface of each insulating layer 1b and in the through hole 11 has a thickness of about 5 to 50 μm in the surface of each insulating layer 1b and in the through hole 11 every time each insulating layer 1b is formed. It is formed by depositing a copper plating film on a predetermined pattern by a known pattern forming method such as a semi-additive method.

  The solder connection pads 3 for connecting semiconductor elements formed on the upper surface of the insulating substrate 1 and the solder connection pads 4 for external connection formed on the lower surface of the insulating substrate 1 are made of a copper plating film having a thickness of about 3 to 50 μm. Are electrically connected to the wiring conductor 2, respectively. The solder connection pad 3 functions as a terminal for connecting a semiconductor element, and the solder connection pad 4 functions as a terminal for connecting to an external electric circuit. Such solder connection pads 3 and 4 are formed, for example, by depositing a copper plating film in a predetermined pattern on the surface of the insulating layer 1b by a known semi-additive method.

  The solder bump 6 deposited on the surface of the solder connection pad 3 is made of lead-containing solder such as a lead-tin alloy, and functions as a connection member for connecting the solder connection pad 3 and the semiconductor element. The solder bump 6 is melted in a state where the electrode of the semiconductor element is in contact with the solder bump 6, whereby the solder connection pad 3 and the electrode of the semiconductor element are electrically connected via the solder bump 6. If the solder bumps 6 are previously attached to the solder connection pads 3, the workability of connecting the semiconductor elements to the solder connection pads 3 becomes extremely good.

  The solder bump 6 is formed by, for example, applying a solder paste containing a lead-containing solder powder made of a lead-tin alloy or the like on the solder connection pad 3 by a screen printing method and heating and melting the solder in the solder paste. It is deposited on the connection pad 3.

  The solder layer 7 applied to the solder connection pad 4 is made of lead-free solder such as tin-silver-copper alloy, for example, and prevents the solder connection pad 4 from being oxidized. When joining, it functions as a base metal for making the joining easy and strong. Then, the solder ball 8 is bonded to the solder connection pad 4 by heating and melting the solder layer 7 in a state where the solder ball 8 is in contact with the solder layer 7.

  The solder layer 7 is formed by, for example, printing and applying a solder paste containing lead-free solder powder made of tin-silver-copper alloy or the like on the solder connection pad 4 by a screen printing method and heating and melting the solder in the solder paste. To be applied onto the solder connection pads 4.

  Here, as shown in FIG. 2A, the solder connection pad 4 includes a ring-shaped outer peripheral electrode 4 a that forms the outer peripheral portion thereof, and the outer peripheral electrode 4 a toward the central portion c of the solder connection pad 4. It consists of four projecting portions 4b, 4b, 4b, 4b projecting so that the width becomes narrower. As a result, when the solder in the solder paste printed and applied on the solder connection pad 4 is heated and melted, the surface tension of the solder connection pad 4 as shown in FIG. The solder layer 7 can be deposited so that the thickness increases from the central portion c toward the outer peripheral electrode 4a. When the solder ball 8 is placed on the solder layer 7, it is difficult for the solder ball 8 to roll on the solder layer 7, and it is possible to prevent the solder ball 8 from rolling out of the solder connection pad 4, thereby enabling accurate positioning.

  Further, when the solder ball 8 is placed on the solder layer 7, as shown in FIG. 2C, the lower part of the placed solder ball 8, the outer peripheral electrode 4a, the protruding portions 4b, 4b,. A gap d is formed between the surface of the insulating layer 1b exposed in the region surrounded by the center electrode 4c described in the above. When the solder layer 7 and the solder ball 8 are heated and melted in this state and the solder ball 8 is joined to the solder connection pad 4, a cavity is formed between the insulating layer 1b and the solder to be formed. Thereby, the stress generated due to the difference in thermal expansion coefficient between the solder and the solder connection pad 4 can be released to the cavity and reduced, and the occurrence of cracks or the like in the solder can be suppressed. At this time, the bonded solder ball 8 is also bonded to the inner side surface of the outer peripheral electrode 4a and the side surface of the protruding portion 4b, so that the bonding surface between the solder connection pad 4 and the solder ball 8 becomes three-dimensional, and the solder The ball 8 is bonded firmly and with high reliability.

  The solder connection pad 4 has a central electrode 4c with the tips of the protruding portions 4b, 4b,. As a result, the electrical test can be easily performed by pressing the tip of the probe for electrical testing against the center electrode 4c. Further, when the center electrode 4c is provided, the outer peripheral electrode 4a and the protrusions 4b, 4b,... Are continuous through the center electrode 4c, so that the molten solder can be flowed uniformly on the pad. Thus, the solder layer 7 is easily formed in a shape as shown in FIG. Further, when the center electrode 4c is provided, the solder ball 8 is easily fixed to the center portion of the solder connection pad 4, thereby forming a solder connection portion having a uniform thickness in the solder connection pad 4 after the solder ball 8 is melted. can do.

  On the other hand, the solder resist layer 5 laminated on the outermost insulating layer 1b is formed by adding a filler such as silica or talc to a thermosetting resin such as an acrylic-modified epoxy resin. The solder resist layer 5 on the upper surface side has an opening 5 a that exposes the central portion of the solder connection pad 3, and is formed with a thickness thinner than the height of the solder bump 6. The solder resist layer 5 on the lower surface side has an opening 5 b that exposes the central portion of the solder connection pad 4, and is formed with a thickness larger than the height of the solder layer 7.

  These solder resist layers 5 increase the electrical insulation reliability between adjacent solder connection pads 3 or between solder connection pads 4, and increase the bonding strength of the solder connection pads 3 and 4 to the insulating layer 1b. To act.

  Further, since the thickness of the solder resist layer 5 is thinner than the height of the solder bump 6, when the semiconductor element is electrically connected to the solder connection pad 3 via the solder bump 6, the electrode of the semiconductor element and the solder bump 6 can be satisfactorily brought into contact with each other, and electrical connection between the semiconductor element and the solder connection pad 3 via the solder bump 6 is facilitated.

  In addition, since the solder resist layer 5 is thicker than the solder layer 7, a depression due to the opening 5 b of the solder resist layer 5 is formed on the solder layer 7, so that the solder balls 8 are formed on the solder connection pads 4. When bonding the solder balls 8, the solder balls 8 are well positioned in the depressions in the openings 5 b of the solder resist layer 5, and the solder balls 8 and the solder connection pads 4 can be easily bonded.

  Such a solder resist layer 5 has a thickness of about 10 to 50 μm. For example, an uncured resin paste for the solder resist layer 5 having photosensitivity adopts a roll coater method or a screen printing method to insulate the outermost layer. After coating on the layer 1b and drying it, exposure and development processes are performed to form openings 5a and 5b that expose the central portions of the solder connection pads 3 and 4, and then this is thermally cured. It is formed. Alternatively, after an uncured resin film for the solder resist layer 5 is stuck on the outermost insulating layer 1b, it is thermally cured, and then at a position corresponding to the central portion of the solder connection pads 3 and 4. By irradiating a laser beam and partially removing the cured resin film, it is formed to have openings 5a and 5b that expose the central portions of the solder connection pads 3 and 4.

  Next, another embodiment of the wiring board according to the present invention will be described in detail with reference to the drawings. FIG. 3A is a plan view showing a solder connection pad for external connection in the wiring board of this embodiment, and FIG. 3B shows a fractured surface taken along line III-III in FIG. FIG. 3A and 3B, the same components as those in FIGS. 1 and 2 described above are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIGS. 3A and 3B, the solder connection pad 20 for external connection according to this embodiment includes a ring-shaped outer peripheral electrode 20a and a central portion c of the solder connection pad 20 from the outer peripheral electrode 20a. , And four projecting portions 20b, 20b,... Projecting so that the width thereof becomes narrower. Even if the solder connection pad for external connection is configured in this way, the same effect as the solder connection pad 4 according to the above-described embodiment can be obtained. When performing an electrical test, an electrical test probe having a flat tip may be used. Other configurations are the same as those of the solder connection pad 4 according to the above-described embodiment.

  As mentioned above, although some embodiment concerning this invention was described, this invention is not limited to the above embodiment, A various improvement and change are possible within the range described in the claim. . For example, in the above-described embodiment, the description has been given of the case where the solder connection pad for external connection is configured in the shape according to the present invention among the solder connection pad for connecting the semiconductor element and the solder connection pad for external connection. Similarly, the solder connection pads for connection may be configured in the shape according to the present invention.

  Although the solder connection pads 4 and 20 having four protrusions have been described, the number of protrusions according to the present invention is not limited to this, and can be arbitrarily selected from a range of about 3 to 7. That's fine. Therefore, the number of protrusions may be three as shown in FIG. That is, the solder connection pad 25 shown in FIG. 4 has a ring-shaped outer peripheral electrode 25a and three protruding portions 25b that protrude from the outer peripheral electrode 25a toward the central portion c of the solder connecting pad 25 so that the width thereof becomes narrower. , 25b, 25b. Other configurations are the same as those of the solder connection pads 4 and 20 according to the above-described embodiment.

  The case where the solder layer 7 attached to the solder connection pad 4 is made of lead-free solder has been described, but lead-containing solder exemplified by the solder bump 6 may be used instead of the lead-free solder.

It is sectional drawing which shows the wiring board concerning one Embodiment of this invention, and a solder ball. (A) is a top view which shows the solder connection pad for the external connection in the wiring board shown in FIG. 1, (b) is a figure which shows the fracture surface of the II line | wire of (a), (c) is a figure which shows the fracture surface of the II-II line of (a). (A) is a top view which shows the solder connection pad for the external connection in the wiring board concerning other embodiment of this invention, (b) is a figure which shows the fracture surface of the III-III line of (a) It is. It is a top view which shows the solder connection pad for the external connection in the wiring board concerning further another embodiment of this invention. It is sectional drawing which shows the conventional wiring board and a solder ball. (A) is a top view which shows the solder connection pad for the external connection in the wiring board shown in FIG. 5, (b) is a figure which shows the fracture surface of the IV-IV line of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Insulation board | substrate 1a, 1b Insulating layer 2 Wiring conductor 3 Solder connection pad for semiconductor element connection 4, 20, 25 Solder connection pad for external connection 4a, 20a, 25a Peripheral electrode 4b, 20b, 25b Protrusion part 4c Center electrode 5 Solder resist layer 5a, 5b Opening 6 Solder bump 7 Solder layer 8 Solder ball 9 Through hole 10 Filling resin 11 Through hole 15 Wiring board

Claims (5)

  A wiring board comprising an insulating substrate and a solder connection pad deposited on the surface of the insulating substrate, wherein the solder connection pad includes a ring-shaped outer peripheral electrode forming an outer peripheral portion of the solder connection pad A wiring board comprising a plurality of projecting portions projecting from the outer peripheral electrode so as to narrow toward the center portion of the solder connection pad.   The wiring board according to claim 1, wherein the solder connection pad has a center electrode at a center portion of which the tips of the plurality of protrusions are connected.   3. The wiring board according to claim 1, wherein solder having a thickness increasing from a central portion of the solder connection pad toward the outer peripheral electrode is deposited on the solder connection pad. Providing a solder connection pad on the surface of the insulating substrate; and welding the solder on the solder connection pad;
The solder connection pad includes a ring-shaped outer peripheral electrode that forms an outer peripheral portion of the solder connection pad, and a plurality of protrusions that protrude from the outer peripheral electrode toward the central portion of the solder connection pad so that the width thereof is reduced. And
A method of manufacturing a wiring board, comprising: welding the solder on the solder connection pad so that the thickness increases from a central portion of the solder connection pad toward the outer peripheral electrode.   The method of manufacturing a wiring board according to claim 4, wherein the solder connection pad has a center electrode at a center portion of which the tips of the plurality of protrusions are connected.

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