JP2005209844A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board with a capacitor element in which reliability of electric insulation is enhanced at a connection pad for the capacitor element by protecting a solder resist layer against cracking due to action of thermal stress, incident to solder connection of the connection pad and the capacitor element, on the opening of the solder resist layer. <P>SOLUTION: On the surface of an insulating substrate 1 for mounting a semiconductor element, a solder resist layer 10 having a plurality of connection pads 5a and 5b composed of a conductor layer being connected electrically with the electrodes of a capacitor element 8 through a solder 9, and a rectangular opening 10c for exposing the plurality of connection pads 5a and 5b is formed. The solder resist layer 10 is provided, at each corner part in the opening 10c, with a part not forming the conductor layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wiring board used for mounting electronic components such as semiconductor elements.

  Conventionally, a wiring board used for mounting a semiconductor element such as a semiconductor integrated circuit element includes an insulating substrate in which a plurality of insulating layers made of, for example, a glass-epoxy plate or an insulating layer made of an epoxy resin are stacked and A wiring conductor made of a conductor layer such as a copper foil or a copper plating film is disposed on the surface. The wiring conductor includes a ground wiring conductor for supplying a ground potential to the semiconductor element, a power supply wiring conductor for supplying a power supply potential, and a signal for inputting and outputting signals between the semiconductor elements. And wiring conductors. In addition, a plurality of first connection pads for grounding, power supply, and signal for electrically connecting the electrodes of the semiconductor element via solder bumps are formed at the center of the upper surface of the insulating substrate. A second connection pad for external connection, which is electrically connected to a wiring conductor of the external electric circuit board via a solder ball, is formed on the outer periphery of the lower surface of the first and second connection pads. The connection pads are electrically connected to the corresponding wiring conductors.

  Furthermore, in a wiring board on which a recent highly integrated and high-speed semiconductor element is mounted, for example, a capacitor element electrically connected to a grounding conductor or a power supply conductor in the center of the lower surface of the insulating substrate A plurality of pairs of third connection pads for connection are formed, and capacitor elements such as ceramic chip capacitors are electrically connected between the ground wiring conductor and the power supply wiring conductor on these third connection pads. It is connected via solder so as to be connected. This capacitor element is decoupled to prevent malfunction of the semiconductor element by suppressing the fluctuation of the ground potential and the power supply potential by being electrically connected between the wiring conductor for grounding and the wiring conductor for power supply. Functions as a capacitor.

  Furthermore, a solder resist layer made of a thermosetting resin is formed on the upper and lower surfaces of the insulating substrate. The solder resist layers have openings that expose the central portions of the first connection pad, the second connection pad, and the third connection pad. Has been. By forming such solder resist layers on the upper and lower surfaces of the insulating substrate, the electrical insulation of each connection pad can be maintained well, and the bonding of these connection pads to the insulating substrate becomes strong. Yes.

  In such a wiring board, solder bumps are previously welded to the first connection pads in order to facilitate electrical connection with the semiconductor element.

  Then, the semiconductor element is placed on the solder bump welded to the first connection pad so that the electrode abuts, and the semiconductor bump is heated and melted by heating and melting the solder bump welded to the first connection pad. The electrode of the semiconductor element is mounted on the wiring substrate and electrically connected to the first connection pad via the solder bump.

Further, by placing the solder ball on the second connection pad and heating and melting the solder ball, the solder ball is welded on the second connection pad, and this solder ball is placed on the wiring conductor of the external electric circuit board. The wiring board is mounted on the external electric circuit board via the solder balls and the semiconductor element mounted on the wiring board is electrically connected to the external electric circuit board. The Rukoto.
JP 2002-204046 A JP-A-9-153673

  By the way, in such a conventional wiring board with a capacitor element, the opening of the solder resist layer that exposes the central part of the connection pad for connecting the capacitor element has a rectangular shape. However, when the opening of the solder resist layer that exposes the connection pad for connecting the capacitor element has a square shape, the heat generated during operation of the semiconductor element on the wiring board to which the capacitor element is connected and the temperature change in the external environment When heat is repeatedly applied, the thermal stress due to the solder connecting the capacitor element to the connection pad for connecting the capacitor element acts heavily on the corners of the opening of the solder resist layer, and as a result, the solder resist layer Cracks are generated in the solder resist layer starting from the corners of the openings, and the electrical insulation reliability of the connection pads for connecting the capacitor elements is greatly reduced.

  The present invention has been devised in view of such conventional problems, and its purpose is to prevent the thermal stress caused by the solder connecting the capacitor element connection pads and the capacitor elements from being formed at the corners of the openings of the solder resist layer. It is an object of the present invention to provide a wiring board with a capacitor element having a high electrical insulation reliability in a connection pad for connecting a capacitor element without causing a crack in a solder resist layer due to a large effect on the solder resist layer.

  A wiring board according to the present invention includes a plurality of connection pads formed of a conductor layer in which electrodes of a capacitor element are electrically connected via solder on the surface of an insulating substrate on which a semiconductor element is mounted, and the center of the plurality of connection pads A solder resist layer having a quadrangular opening that exposes each portion is formed, and the connection pad is provided with a portion where the conductor layer is not formed at a position located at each corner of the opening. It is characterized by this.

  The wiring board of the present invention is a portion located at the corner of the opening of the solder resist layer that exposes the center of each of the plurality of connection pads made of a conductor layer to which the electrode of the capacitor element is electrically connected via solder. Since the conductor layer non-forming portion is provided on the solder resist layer, when the capacitor element is connected to the capacitor element connecting connection pad exposed in the opening of the solder resist layer via solder, the non-conductor at the corner of the opening is formed. Since the solder does not get wet on the portion, thermal stress due to the solder is not applied to the corner of the opening of the solder resist layer. Accordingly, it is possible to provide a wiring board with a capacitor element that is excellent in electrical connection reliability in a connection pad for connecting a capacitor element, without causing cracks in the solder resist layer from starting at the corners of the opening. it can.

  Next, the wiring board of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of the best mode for carrying out the wiring board of the present invention. In the figure, 1 is an insulating substrate composed of an insulating layer 1a and an insulating layer 1b, and 2a, 2b and 2c are respectively Ground, power, and signal first connection pads, 3a, 3b, and 3c are ground, power, and signal second connection pads, 4a, 4b, and 4c are ground, power, and Signal wiring conductors, 5a and 5b are third connection pads, 6 is a solder bump, 7 is a solder layer, 8 is a capacitor element, 9 is solder, and 10 is a solder resist layer.

  In this example, the insulating substrate 1 is formed by laminating two insulating layers 1b made of thermosetting resin on the upper and lower surfaces of the insulating layer 1a made by impregnating glass fabric with thermosetting resin, A solder resist layer 10 is formed on the outermost insulating layer 1b. In addition, first connection pads 2a, 2b, and 2c for grounding, power supply, and signal are formed at the center of the upper surface of the insulating substrate 1 so that the electrodes of the semiconductor elements are electrically connected via the solder bumps 6, respectively. In addition, on the outer peripheral portion of the lower surface of the insulating substrate 1, second connection pads 3a, 3b, 3c for grounding, power supply, and signal that are electrically connected to an external electric circuit board via solder balls 11, respectively. For the grounding to electrically connect the corresponding first connection pads 2a, 2b, 2c and the second connection pads 3a, 3b, 3c to each other from the upper surface to the lower surface of the insulating substrate 1, respectively. Power supply and signal wiring conductors 4a, 4b, and 4c are provided. In addition, third connection pads 5a and 5b electrically connected to the ground wiring conductor 4a and the power supply wiring conductor 4b are formed at the center of the lower surface of the insulating substrate 1. Solder bumps 6 are welded to the first connection pads 2a, 2b, 2c, and solder layers 7 are welded to the second connection pads 3a, 3b, 3c. Further, the capacitor element 8 is connected to the third connection pads 5 a and 5 b through the solder 9.

  The insulating layer 1a is a member that becomes the core of the wiring board of this example, and is formed by impregnating a glass fabric in which glass fiber bundles are woven vertically and horizontally with a thermosetting resin such as epoxy resin or bismaleimide triazine resin, The thickness is about 0.3 to 1.5 mm, and a plurality of through holes 12 having a diameter of about 0.1 to 1 mm are provided from the upper surface to the lower surface. A part of the wiring conductors 4a, 4b, 4c made of a conductor layer is deposited on the upper and lower surfaces and the inner surfaces of the respective through holes 12, and the upper and lower wiring conductors 4a, 4b, 4c pass through the through holes 12. Is electrically connected.

  Such an insulating layer 1a is manufactured 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 4a, 4b, and 4c on the upper and lower surfaces of the insulating layer 1a have a copper foil having a thickness of about 3 to 50 μm adhered to the entire upper and lower surfaces of the insulating sheet for the insulating layer 1a. It is formed into a predetermined pattern by etching after curing. Further, the wiring conductors 4a, 4b, 4c on the inner surface of the through hole 12 have a thickness of about 3 to 50 μm by electroless plating and electrolytic plating on the inner surface of the through hole 12 after the through hole 12 is provided in the insulating layer 1a. It is formed by depositing a copper plating film.

  Furthermore, the insulating layer 1a is filled with a resin column 13 made of a thermosetting resin such as an epoxy resin or a bismaleimide triazine resin in the through hole 12 thereof. The resin pillar 13 is for making it possible to form the wiring conductors 4a, 4b, 4c and the respective insulating layers 1b directly above and below the through-hole 12 by closing the through-hole 12, and is an uncured paste-like heat A curable resin is filled in the through-holes 12 by screen printing, thermally cured, and then the upper and lower surfaces thereof are polished to be substantially flat. Two insulating layers 1b are laminated on the upper and lower surfaces of the insulating layer 1a including the resin pillars 13, respectively.

  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 14 having a diameter of about 30 to 100 μm from the upper surface to the lower surface of each layer. . Each of these insulating layers 1b is for providing an insulating interval for wiring the wiring conductors 4a, 4b, 4c with high density. A high density wiring can be formed in three dimensions by electrically connecting the upper wiring conductors 4a, 4b, 4c and the lower wiring conductors 4a, 4b, 4c through the through holes 14. Each of the insulating layers 1b has an uncured thermosetting resin insulating film having a thickness of about 20 to 60 μm attached to the upper and lower surfaces of the insulating layer 1a. And the next insulating layer 1b is sequentially stacked thereon in the same manner. Note that the wiring conductors 4a, 4b, 4c deposited on the surface of each insulating layer 1b and in the through-holes 14 are formed on the surface of each insulating layer 1b and in the through-holes 14 every time each insulating layer 1b is formed. It is formed by depositing a copper plating film having a thickness of about 50 μm in a predetermined pattern by a known pattern forming method such as a semi-additive method or a subtractive method.

  Further, the first connection pads 2a, 2b, 2c formed on the upper surface of the insulating substrate 1, and the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b formed on the lower surface of the insulating substrate 1. Is formed by a conductor layer made of a copper plating film having a thickness of about 3 to 50 μm, and is electrically connected to the corresponding wiring conductors 4a, 4b and 4c, respectively. The first connection pads 2a, 2b, 2c serve as terminals for connecting semiconductor elements, and the second connection pads 3a, 3b, 3c serve as terminals for connecting to an external electric circuit. 5a and 5b function as terminals for connecting the capacitor element 8, respectively. The first connection pads 2a, 2b, 2c, the second connection pads 3a, 3b, 3c, and the third connection pads 5a, 5b are formed on the surface of the insulating layer 1b by a known semi-additive method or subtractive method. Is formed by depositing a copper plating film in a predetermined pattern. A solder bump 6 is welded to the first connection pads 2a, 2b, 2c, and a solder layer 7 is welded to the second connection pads 3a, 3b, 3c. The capacitor element 8 is connected to the third connection pads 5 a and 5 b via the solder 9.

  The grounding, power supply, and signal wiring conductors 4a, 4b, and 4c disposed from the upper surface to the lower surface of the insulating substrate 1 are used to electrically connect each electrode of the semiconductor element to an external electric circuit. The wiring conductors 4a and 4b for grounding and power supply include a wide area conductor pattern, and the wiring conductor 4c for signal includes a thin strip-shaped conductor pattern. Yes. The grounding and power supply wiring conductors 4a and 4b function as conductors for supplying a ground potential and a power supply potential to the semiconductor elements, and also function as shields for electromagnetically shielding the signal wiring conductor 4c. The signal wiring conductor 4c functions as a conductor for taking signals into and out of the semiconductor element. For example, the signal wiring conductor 4c is given a predetermined characteristic impedance when the wiring conductor 4a for grounding or the wiring conductor 4b for power supply and the signal wiring conductor 4c face each other with the insulating layer 1b interposed therebetween. The

  The solder bump 6 welded to the surface of the first connection pads 2a, 2b, 2c is made of, for example, a lead-tin alloy, and a connection member for connecting the first connection pads 2a, 2b, 2c and the semiconductor element. Function as. Then, by melting the solder bump 6 in a state where the electrode of the semiconductor element is in contact with the solder bump 6, the first connection pads 2 a, 2 b, 2 c and the electrode of the semiconductor element are electrically connected via the solder bump 6. Will be connected. As described above, by soldering the solder bump 6 to the first connection pads 2a, 2b, and 2c in advance, the workability of connecting the semiconductor element to the first connection pads 2a, 2b, and 2c is extremely good. Become.

  The solder layer 7 welded to the second connection pads 3a, 3b, 3c prevents oxidation of the second connection pads 3a, 3b, 3c and solder balls to the second connection pads 3a, 3b, 3c. 11 is made of a tin-silver-copper alloy having a melting point higher than that of the solder bump 6, which functions as a base metal for making the bonding easy and strong when bonding. Then, the solder ball 11 is bonded to the second connection pads 3a, 3b, 3c by heating and melting the solder ball 11 in a state where the solder ball 11 is in contact with the solder layer 7. At this time, according to the wiring board of the present invention, since the solder layer 7 is welded to the second connection pads 3a, 3b, 3c, the solder balls 11 are joined to the second connection pads 3a, 3b, 3c. In this case, the solder layer 7 effectively prevents the second connection pads 3a, 3b, 3c from being oxidized, and as a result, the second connection pads 3a, 3b, 3c and the solder balls 11 are firmly bonded. Therefore, even after the wiring board is mounted on the external electric circuit board, even if heat generated during operation of the semiconductor element or heat accompanying temperature change of the external environment is repeatedly applied over a long period of time, the solder ball 11 is connected to the second connection. The pads 3a, 3b and 3c are not detached from each other, and the electrical connection between the semiconductor element mounted on the wiring board and the external electric circuit can be kept good.

  The capacitor element 8 connected to the third connection pads 5a and 5b via the solder 9 is generally a ceramic chip capacitor and has a pair of electrodes at both ends thereof. The capacitor element 8 functions as a so-called decoupling capacitor, one electrode is connected to the third connection pad 5a for grounding, and the other electrode is connected to the third connection pad 5b for power supply. Yes. Then, by supplying electric charges to the ground wiring conductor 4a and the power supply wiring conductor 4b via the third connection pads 5a and 5b, it is possible to suppress fluctuations in the ground and the power supply potential. The solder 9 connecting the capacitor element 8 to the third connection pads 5 a and 5 b is made of solder having the same composition as the solder layer 7 and has a melting point higher than that of the solder bump 6. Thus, since the melting point of the solder 9 connecting the capacitor element 8 to the third connection pads 5a and 5b is higher than the melting point of the solder bump 6, the semiconductor element is connected to the first connection pads 2a, 2b and 2c. When connecting via the solder bump 6, the capacitor element 8 is heated to a temperature not lower than the melting point of the solder bump 6 and lower than the melting point of the solder 9 to melt only the solder bump 6, thereby connecting the capacitor element 8 to the third connection pads 5 a, The semiconductor element can be connected in a state of being firmly fixed to 5b.

  Also, the solder resist layer 10 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, and a solder resist layer on the upper surface side. If it is 10, it has an opening 10a that exposes the central part of the first connection pads 2a, 2b, 2c, and is thinner than the solder bump 6. Further, in the case of the solder resist layer 10 on the lower surface side, the opening 10b exposing the central part of the second connection pads 3a, 3b, 3c and the opening exposing the central part of the third connection pads 5a, 5b, respectively. 10 c and thicker than the solder layer 7 and substantially the same thickness as the solder 9.

  These solder resist layers 10 enhance the electrical insulation reliability between the first connection pads 2a, 2b, 2c, between the second connection pads 3a, 3b, 3c and between the third connection pads 5a, 5b. In addition, the bonding strength of the first connection pads 2a, 2b, 2c, the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b to the insulating layer 1b is increased.

  Since the solder resist layer 10 has a thickness lower than that of the solder bump 6, the semiconductor element is electrically connected to the first connection pads 2 a, 2 b, 2 c via the solder bump 6. Since the electrode of the element and the solder bump 6 can be satisfactorily contacted, the electrical connection between the semiconductor element and the first connection pads 2a, 2b, 2c via the solder bump 6 is facilitated.

  Further, since the solder layer 7 is thinner than the solder resist layer 10, depressions due to the openings 10 b of the solder resist layer 10 are formed on the solder layer 7, so that the second connection pads 3 a, 3 b, When the solder ball 11 is bonded onto the 3c, the solder ball 11 is well positioned in the recess in the opening 10b of the solder resist layer 10, and the solder ball 11 and the second connection pads 3a, 3b, 3c are bonded. Becomes easy.

  Such a solder resist layer 10 has a thickness of about 10 to 50 μm, and an uncured resin paste for the solder resist layer 10 having photosensitivity adopts a roll coater method or a screen printing method as an outermost insulating layer. After coating on 1b and drying it, exposure and development processes are performed to provide first connection pads 2a, 2b, 2c, second connection pads 3a, 3b, 3c and third connection pads 5a, 5b. The openings 10a, 10b, and 10c that expose the central part of the film are formed, and then are thermally cured. Alternatively, after an uncured resin film for the solder resist layer 10 is stuck on the outermost insulating layer 1b, it is thermally cured, and then the first connection pads 2a, 2b, 2c and the second The positions corresponding to the connection pads 3a, 3b, 3c and the third connection pads 5a, 5b are irradiated with laser light, and the cured resin film is partially removed to remove the first connection pads 2a, 2b, 2c, The second connection pads 3a, 3b and 3c and the third connection pads 5a and 5b are formed to have openings 10a, 10b and 10c.

  Furthermore, in the wiring board of the present invention, as shown in FIG. 2, the third connection pads 5a and 5b are portions where the conductor layer is not formed at the corners of the opening 10c of the solder resist layer 10. A is provided, and at least a part of the non-formed portion A of the conductor layer is exposed in the opening 10c. Thus, since the third connection pads 5a and 5b are provided with the non-formed portion A of the conductor layer at the position located at each corner of the opening 10c of the solder resist layer 10, the third connection pads 5a and 5b Since the solder 9 connecting the pads 5a, 5b and the capacitor element 8 does not get wet with the non-formed portion A of the conductor layer provided at the portion located at the corner of the opening 10c, the corner of the opening 10c The solder 9 and the solder resist layer 10 do not come into contact with each other, and as a result, the thermal stress due to the solder 9 is not applied to the corner of the opening 10 c of the solder resist layer 10. Therefore, there is provided a wiring board with a capacitor element that is excellent in electrical connection reliability in the third connection pads 5a and 5b without causing cracks at the corners of the opening 10c in the solder resist layer 10. can do.

  In addition, it is preferable that a part of the non-formed portion A of the conductor layer is exposed in the opening 10c and the remaining part is covered with the solder resist layer 10. When a part of the non-formed portion A of the conductor layer is exposed in the opening 10c and the remaining part is covered with the solder resist layer 10, the conductor layer is not exposed at the corners of the opening 10c. It can prevent very effectively that the solder 9 contacts the soldering resist layer 9 in a corner | angular part. On the other hand, when the entire conductor layer non-formed portion A is exposed in the opening 10c, the conductor layer is exposed at the corner of the opening 10c, so that the solder passes through the conductor layer and the corner of the opening 10c. As a result, the thermal stress due to the solder 9 is applied to the corners of the opening 10c of the solder resist layer 10, and there is a risk that the solder resist layer 10 may crack.

  Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the non-formed portion A of the conductor layer has a triangular shape. However, as shown in FIG. 3, the non-formed portion A of the conductor layer has a corner portion of the opening 10c as shown in FIG. It may be L-shaped along. Thus, by forming the non-formed portion A of the conductor layer in an L shape along the corner of the opening 10c, the connection pads 5a, 5b and the capacitor element 8 are connected to the solder 9 with a wide bonding area of the solder 9. It is possible to connect firmly through. It goes without saying that the non-forming portion A may have another shape.

It is sectional drawing which shows the example of the best form for implementing the wiring board of this invention. It is a principal part top view of the wiring board of this invention. It is a principal part top view in another example of embodiment of the wiring board of this invention.

Explanation of symbols

1: Insulating substrates 5a, 5b: Connection pads 8 to which the electrodes of the capacitor element 8 are connected: Capacitor element 9: Solder 10: Solder resist layer 10c: Opening A: Non-formed portion of the conductor layer

Claims (1)

A rectangular shape in which a plurality of connection pads made of a conductor layer to which electrodes of capacitor elements are electrically connected via solder are exposed on the surface of an insulating substrate on which a semiconductor element is mounted, and central portions of the plurality of connection pads are exposed. The wiring board is characterized in that a solder resist layer having a plurality of openings is formed, and the connection pad is provided with a portion where the conductor layer is not formed in a portion located at each corner of the opening. .

Images