JP2005191121A - Process for producing wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board with a capacitor element in which a connection pad and a semiconductor element can be connected well through a solder bump. <P>SOLUTION: After a first solder paste 21 is printed on second connection pads 3a, 3b and 3c and third connection pads 5a and 5b, a solder layer 7 and an underlying solder layer 9a are welded by thermally melting solder powder of first solder paste 21. After second solder paste 22 is printed subsequently on first connection pads 2a, 2b and 2c, a solder bump 6 is welded by thermally melting solder powder of the second solder paste 22. After third solder paste 23 is printed subsequently on the underlying solder layer 9a, a capacitor element 8 is mounted on the third solder paste 23 and connected through the solder 9 by thermally melting solder powder of the third solder paste 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  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.

  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 joined on the second connection pad, and the solder ball is placed on the wiring conductor of the external electric circuit board. The circuit 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.

By the way, in such a wiring board with a capacitor element, as the solder for connecting the capacitor element to the third connection pad, solder having a melting point higher than that of the solder bump welded to the first connection pad is used. . This is because when the semiconductor element is connected to the first connection pad, the electrode of the semiconductor element and the first connection pad are solder bumped with the capacitor element firmly fixed without melting the solder for connecting the capacitor element. This is because it is possible to make a good connection through the connection. Further, in such a wiring board with a capacitor element, the capacitor element is connected to the third connection pad provided at the center of the lower surface of the insulating substrate, and the solder bump is welded to the first connection pad provided on the upper surface of the insulating substrate. In order to do this, the solder paste is printed on the third connection pad provided at the center of the lower surface of the insulating substrate in a state where the insulating substrate is placed on the printing table with the lower surface side facing up, The capacitor element is placed on the solder paste, the solder in the solder paste is heated and melted to connect the capacitor element and the third connection pad via the solder, and then the insulating substrate to which the capacitor element is connected is mounted. After the solder paste for solder bumps is printed on the first connection pad in a state where the capacitor element is placed on the printing table with the capacitor element facing down, the capacitor Manufacturing method for forming a solder bump to the first connection pads by heating and melting the solder in the solder paste at a temperature lower than the melting point of the solder for connecting the child is adopted.
JP 2002-204046 A

  By the way, according to such a conventional method for manufacturing a wiring board with a capacitor element, a capacitor element is connected to a third connection pad provided at the center of the lower surface of the insulating substrate, and then formed at the center of the upper surface of the insulating substrate. In order to prevent the insulating substrate from rattling or the capacitor element from coming into contact with the print table when the solder paste is printed on the first connection pad, the printing table A method is employed in which a concave portion capable of accommodating a capacitor element is formed at a position corresponding to the central portion of the lower surface of the insulating substrate, and printing is performed while the capacitor element is floated from the table.

  However, with the recent demand for thinning the wiring board, the insulating board is also thinned to about 0.5 to 1 mm, and therefore the insulating board is easily bent by an external force. Then, when a capacitor element is connected to the central portion of the lower surface of the insulating substrate and a solder bump is welded to the central portion of the upper surface of the insulating substrate using the conventional manufacturing method to the thinned insulating substrate in this manner, When the solder paste is printed on the first connection pad formed on the insulating board, the insulating substrate is bent by the printing pressure at a portion corresponding to the concave portion provided on the printing table. The solder paste cannot be printed uniformly on all, resulting in large variations in the size of the obtained solder bumps. As a result, the obtained wiring board has a problem that it is difficult to connect the first connection pad and the electrode of the semiconductor element satisfactorily through the solder bump.

  Further, in the conventional wiring substrate as shown in Patent Document 1, since the second connection pad is exposed, when solder bumps are welded to the first connection pad, or to the third connection pad. When the capacitor element is connected via solder, the surface of the second connection pad is easily oxidized. When the surface of the second connection pad is oxidized, heating is performed when solder balls are welded to the second connection pad. The molten solder ball does not wet well on the second connection pad, and as a result, the bonding between the second connection pad and the solder ball becomes weak, and the wiring board is mounted on the external electric circuit board. Later, when heat generated during operation of the semiconductor element or heat accompanying temperature changes in the external environment is repeatedly applied over a long period of time, the solder balls are detached from the second connection pads due to the stress generated by the heat, and are disposed. Keeping the electrical connection between the semiconductor element and the external electric circuit mounted on the substrate well had a problem that it is difficult.

  The present invention has been devised in view of such a conventional problem, and the object thereof is not to greatly vary the size of solder bumps welded to the first connection pads to which the semiconductor elements are electrically connected. Another object of the present invention is to provide a wiring board with a capacitor element capable of satisfactorily connecting an electrode of a semiconductor element to a first connection pad via a solder bump. Further, after the solder ball is welded to the second connection pad for external connection, the second connection pad and the solder ball are firmly bonded and mounted on the external electric circuit board via the solder ball. Even if heat generated during operation of the semiconductor element or heat due to temperature change in the external environment is repeatedly applied over a long period of time, the semiconductor element is electrically connected to the external electric circuit through the solder balls. An object of the present invention is to provide a wiring board with high electrical connection reliability.

  The method for manufacturing a wiring board according to the present invention includes a first connection pad electrically connected to a semiconductor element on an upper surface, a second connection pad electrically connected to an external electric circuit board on a lower surface, and a capacitor element on a lower surface. Solder bumps are welded to the first connection pads of the insulating substrate on which the third connection pads to which are electrically connected are formed, and the melting points of the second connection pads are higher than the solder bumps A method of manufacturing a wiring board, wherein a solder layer is welded and the capacitor element is electrically connected to the third connection pad via solder having the same composition as the solder layer, wherein the second connection After printing the solder layer and the first solder paste which becomes a part of the solder on the pad and the third connection pad, the solder powder in the first solder paste is heated and melted to melt the second contact. A step of welding the solder layer to the pad and a base solder layer to be a part of the solder to the third connection pad, and after printing the second solder paste to be the solder bump on the first connection pad A step of heating and melting the solder powder in the second solder paste to weld the solder bumps to the first connection pads, and a third solder paste that becomes the remainder of the solder on the base solder layer After the capacitor is printed, the capacitor element is placed on the third solder paste and the solder powder in the third solder paste is heated and melted to place the capacitor element on the third connection pad. And a step of connecting via a wire.

  Furthermore, in the method for manufacturing a wiring board according to the present invention, preferably, a solder resist layer having an opening exposing the second connection pad and the third connection pad is formed on the lower surface of the insulating substrate. Each thickness of the solder layer and the base solder layer is thinner than the solder resist layer.

  Furthermore, the method for manufacturing a wiring board according to the present invention is preferably characterized in that the surface of the solder bump is coated with a flux when the solder powder in the third solder paste is heated and melted. It is.

  Furthermore, the method for manufacturing a wiring board of the present invention is preferably characterized in that the viscosity of the first solder paste is lower than the viscosity of the third solder paste.

  In the method for manufacturing a wiring board according to the present invention, before the capacitor element is connected to the lower surface of the insulating substrate, the second solder bump is formed on the first connection pad to which the semiconductor element on the upper surface of the insulating substrate is electrically connected. The second solder paste can be uniformly printed on all of the first connection pads without bending the insulating substrate when the second solder paste is printed. As a result, a wiring board with a capacitor element that has a solder bump of uniform size on the first connection pad and that can satisfactorily connect the electrode of the semiconductor element to the first connection pad via the solder bump. Can be provided. Also, after welding the solder layer and the base solder layer to the third connection pad for connecting the capacitor element to the second connection pad for external connection, a third solder paste is printed on the base solder layer, and then The capacitor element is placed on the third solder paste and the solder powder in the third solder paste is heated and melted to connect the capacitor element to the third connection pad via the solder. A sufficient amount of solder can be connected to the third connection pad, and the second connection pad can be covered with a thin solder layer, which effectively oxidizes the second connection pad. Is prevented. As a result, the solder ball can be firmly bonded to the second connection pad, and a wiring board having high connection reliability with the external electric circuit board via the solder ball can be provided.

  Furthermore, in the method for manufacturing a wiring board according to the present invention, a solder resist layer having openings for exposing the second connection pads and the third connection pads is formed on a lower surface of the insulating substrate, and the solder When the thickness of each of the layer and the underlying solder layer is thinner than the solder resist layer, the solder layer and the underlying solder layer may be another member when the second solder paste for forming solder bumps is printed on the first connection pad. It is possible to effectively prevent contamination of other members by the solder layer or the base solder layer.

  Furthermore, in the method of manufacturing a wiring board according to the present invention, when the solder powder in the second solder paste is heated and melted, the surface of the solder bump is covered with a flux. It is possible to effectively prevent the solder bumps from being oxidized and deformed when the powder is heated and melted.

  Furthermore, in the method for manufacturing a wiring board according to the present invention, when the viscosity of the second solder paste is lower than the viscosity of the third solder paste, it is easy to cover the second connection pads with a thin solder layer. It is.

  Next, a method for manufacturing a wiring board with a capacitor element of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of a wiring board with a capacitor element manufactured by the manufacturing method of the present invention. In the figure, reference numeral 1 denotes an insulating substrate composed of an insulating layer 1a and an insulating layer 1b. Are first connection pads for grounding, power supply, and signal, respectively, 3a, 3b, and 3c are second connection pads for grounding, power, and signal, respectively, and 4a, 4b, and 4c are grounding and power supply respectively 5 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 disposed 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 4 a, 4 b, 4 c is attached to the upper and lower surfaces and the inner surface of each through hole 12, and the upper and lower wiring conductors 4 a, 4 b, 4 c are electrically connected via the through hole 12. It is connected to the.

  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 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. 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 arranged from the upper surface to the lower surface of the insulating substrate 1 are electrically conductive for connecting each electrode of the semiconductor element to the external electric circuit substrate. If the wiring conductors 4a and 4b for grounding and power supply function as a path, they include a wide area conductor pattern, and the wiring conductor 4c for signals includes a thin strip-shaped conductor pattern. 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.

  Further, the solder layer 7 welded to the second connection pads 3a, 3b, 3c prevents the second connection pads 3a, 3b, 3c from being oxidized, and the solder balls 11 are applied to the second 3a, 3b, 3c. When joining, it functions as a base metal for making the joining easy and strong, and is made of solder having the same composition as the solder 9 described later. 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.

  The capacitor element 8 connected to the 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, for example, a tin-silver-copper alloy 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.

Further, the solder resist layer 10 formed 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, for example.
The solder resist layer 10 on the upper surface side has an opening that exposes the central portion of the first connection pads 2a, 2b, and 2c and is thinner than the height of the solder bump 6. In addition, the solder resist layer 10 on the lower surface side has an opening that exposes the center of the second connection pads 3a, 3b, 3c and the center of the third connection pads 5a, 5b, and The thickness is larger than the thickness of the solder layer 7 and smaller than the thickness of 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 resin layer 1b is increased.

  When the solder resist layer 10 is thinner than 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. Therefore, the electrical connection between the semiconductor element and the first connection pads 2a, 2b, and 2c via the solder bump 6 is facilitated.

  Further, since the solder resist layer 10 is thicker than the solder layer 7, a depression due to the opening of the solder resist layer 10 is formed on the solder layer 7. Therefore, the solder resist layer 10 is formed on the second connection pads 3 a, 3 b and 3 c. When the solder balls 11 are joined, the solder balls 11 are well positioned in the recesses in the openings of the solder resist layer 10, and the joining of the solder balls 11 and the second connection pads 3a, 3b, 3c is facilitated.

  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 is applied to the outermost resin layer by using a roll coater method or a screen printing method. 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. After forming the opening part which exposes, this is formed by thermosetting. Alternatively, after an uncured resin film for the solder resist layer 10 is stuck on the outermost resin layer 1b, it is thermally cured, and then the first connection pads 2a, 2b, 2c and 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, 3c and the third connection pads 5a, 5b are formed to have openings.

  Next, an example in which the above-described wiring board with a capacitor element is manufactured according to the manufacturing method of the present invention will be described.

  First, as described above, the first connection pads 2a, 2b, and 2c whose semiconductor elements are electrically connected to the upper surface and the second connection pads 3a and 3b that are electrically connected to the external electric circuit board are connected to the lower surface. , 3c and the third connection pads 5a, 5b are formed on the lower surface, and the first connection pads 2a, 2b, 2c and the second connection pads 3a, 3b, 3c and the third connection pad are formed on the upper and lower surfaces. An insulating substrate 1 on which a solder resist layer 10 having an opening exposing 5a and 5b is formed is prepared.

  Next, as shown in FIG. 2A, the insulating substrate 1 is turned upside down 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 are A low-viscosity first solder paste 21 containing a lead-free solder powder such as tin-silver alloy or tin-silver-copper alloy having a viscosity of 30 to 150 Pa · s by screen printing using a metal mask. Print. Thus, by printing the low-viscosity first solder paste 21 having a viscosity of 30 to 150 Pa · s on the second connection pads 3a, 3b, and 3c and the third connection pads 5a and 5b, the second solder paste 21 is printed. The surfaces of the connection pads 3a, 3b, 3c and the third connection pads 5a, 5b can be uniformly covered with a small amount of the thin first solder paste 21. In addition, when the viscosity of the first solder paste 21 is less than 30 Pa · s, the first solder paste 21 greatly bleeds when printing the first solder paste 21, and it becomes difficult to print well. On the other hand, if it exceeds 150 Pa · s, the viscosity of the first solder paste 21 is so high that it is difficult to spread, so that the surfaces of the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b are a little thin. It becomes difficult to cover with the first solder paste 21. Therefore, the viscosity of the first solder paste 21 is preferably in the range of 30 to 150 Pa · s.

  Next, as shown in FIG. 2B, the solder powder in the first solder paste 21 is heated and melted to weld the solder layer 7 to the second connection pads 3a, 3b, 3c and the third solder paste. A base solder layer 9a to be a part of the solder 9 is welded to the connection pads 5a and 5b. At this time, the first solder paste 21 printed on the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b has a low viscosity and is printed thinly and uniformly. When the solder in the paste 21 melts, it spreads thinly and evenly on the surfaces of the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b, and the second connection pads 3a, 3b, 3c, A thin solder layer 7 and a base solder layer 9a having a uniform thickness are welded to the surfaces of the third connection pads 5a and 5b. Thus, the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b are welded to the surfaces of the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b. , 3b, 3c and third connection pads 5a, 5b are effectively prevented from being oxidized or discolored by the solder layer 7 or the base solder layer 9a. The solder layer 7 welded to the second connection pads 3a, 3b, 3c and the base solder layer 9a welded to the third connection pads 5a, 5b are thinner than the solder resist layer 10. Then, as will be described later, when the solder paste 22 for the solder bump 6 is printed on the first connection pads 2a, 2b, 2c, the printing is not hindered and other members are contaminated. There is nothing. Therefore, the thickness of the solder layer 7 welded to the second connection pads 3a, 3b, 3c and the thickness of the base solder layer 9a welded to the third connection pads 5a, 5b should be smaller than the thickness of the solder resist layer 10. It is preferable to keep it. Further, the solder layer 7 welded to the second connection pads 3a, 3b, 3c and the base solder layer 9a welded to the third connection pads 5a, 5b have a thickness of less than 1 μm. The connection pads 3a, 3b, 3c and the third connection pads 5a, 5b cannot be satisfactorily covered, and the second connection pads 3a, 3b, 3c and the third connection pads 5a, 5b are oxidized or discolored. There is a danger of coming. Accordingly, the thickness of the solder layer 7 deposited on the second connection pads 3a, 3b, 3c and the base solder layer 9a deposited on the third connection pads 5a, 5b is preferably 1 μm or more.

  Next, as shown in FIG. 2C, lead-tin having a melting point lower than that of, for example, the solder layer 7 or the base solder layer 9a is formed on the first connection pads 2a, 2b, 2c formed on the upper surface of the insulating substrate 1. A second solder paste 22 containing solder powder made of an alloy is printed by a screen printing method using a metal mask. At this time, since the capacitor element 7 is not connected to the lower surface of the insulating substrate 1, the second solder paste 22 is applied to all of the first connection pads 2a, 2b, 2c without causing the insulating substrate 1 to bend. Can be printed uniformly. Further, each of the thickness of the solder layer 7 welded to the second connection pads 3a, 3b, 3c and the base solder layer 9a welded to the third connection pads 5a, 5b is thinner than the thickness of the solder resist layer 10. When the second solder paste 22 is printed on the first connection pads 2a, 2b, and 2c, the solder layer 7 and the base solder layer 9a do not come into contact with other members, and the solder layer 7 and the base Contamination to other members by the solder layer 9a is effectively prevented.

  Next, as shown in FIG. 2D, the solder powder in the second solder paste 22 is heated and melted to weld the solder bumps 6 onto the first connection pads 2a, 2b, 2c. At this time, since the second solder paste 22 is uniformly printed on all the first connection pads 2a, 2b, and 2c, the solder bumps 6 having a uniform size can be formed.

  Next, as shown in FIG. 2 (e), the surface of the solder bump 6 is covered with a flux 31. By covering the surface of the solder bump 6 with the flux 31 in this way, the solder bump 6 is formed when the capacitor element 8 is connected to the third connection pads 5a and 5b via the solder 9 as will be described later. Oxidation and deformation due to heat can be effectively prevented. In order to cover the surface of the solder bump 6 with the flux 31, the flux adhering when the solder bump 6 is welded is temporarily removed, and then a paste-like flux 31 is newly screened on the center of the upper surface of the insulating substrate 1. What is necessary is just to print so that the solder bump 6 may be covered by printing. The reason why the flux 31 is newly printed is that the solder bump 6 is covered with a highly active flux because the effect of preventing oxidation and deformation of the solder bump 6 due to heat is high. In addition, when it is not necessary to consider the oxidation and deformation of the solder bump 6, it is not always necessary to cover the surface of the solder bump 6 with the flux 31.

  Next, as shown in FIG. 2 (f), the insulating substrate 1 is turned upside down and the same composition as the base solder layer 9a is formed on the base solder layer 9a welded onto the third connection pads 5a and 5b. After the third solder paste 23 containing the solder powder and having a higher viscosity than the first solder paste 21 is printed by screen printing using a metal mask, the third solder paste 23 is printed on the printed third solder paste 23. A capacitor element 8 is placed. At this time, since the viscosity of the third solder paste 23 is higher than that of the first solder paste 21, the shape of the printed third solder paste 23 can be easily maintained, so that the third solder paste 23 is printed thickly on the base solder layer 9a. can do. Therefore, as described later, a sufficient amount of solder is used when the solder powder in the third solder paste 23 is heated and melted to connect the capacitor element 98 to the third connection pads 5a and 5b via the solder 9. 9 can be secured.

  If the viscosity of the third solder paste 23 is less than 160 Pa · s, it is difficult to print the third solder paste 23 having a sufficient thickness on the underlying solder layer 9a, and on the other hand, it exceeds 450 Pa · s. Then, when printing the third solder paste 23, the omission of the paste from the metal mask becomes worse, and it tends to be difficult to print a uniform amount of the third solder paste 23. Therefore, the viscosity of the third solder paste 23 is preferably 160 to 450 Pa · s.

  By the way, the printing table used for printing the third solder paste 23 is provided with a recess capable of accommodating the solder bump 6 at a position corresponding to the central portion of the insulating substrate 1 to which the solder bump 6 is welded. As a result, printing is performed with the central portion of the insulating substrate 1 floating from the printing table, so that the insulating substrate 1 bends at the time of printing, but the insulating substrate 1 bends to the printing amount of the printed third solder paste 23. Even if there is a variation caused by the above, since the capacitor element 8 is small and has few electrodes, it can be placed on the third solder paste 23 without any problem.

  Next, as shown in FIG. 2G, the third connecting pad 5a is obtained by heating and melting the solder powder and the base solder layer 9a in the third solder paste 23 on which the capacitor element 8 is placed. , 5b is electrically connected to the capacitor element 8 via the solder 9. At this time, if the surface of the solder bump 6 is covered with the flux 31, even if heat is applied to the solder bump 6 when the solder powder and the base solder layer 9a in the third solder paste 23 are melted, the solder bump 6 is soldered. Since the surface of the bump 6 is protected by the flux 31, it is possible to effectively prevent the solder bump 6 from being oxidized and deformed by heat. Finally, the remaining flux 31 is removed to complete a wiring board with a capacitor element having solder bumps 6 of uniform size.

  Thus, according to the method for manufacturing a wiring board of the present invention, the solder bumps 6 of uniform size are provided, and the electrodes of the semiconductor element are satisfactorily applied to the first connection pads 2a, 2b, 2c via the solder bumps 6. In addition, it is possible to provide a wiring board with a capacitor element that is capable of being connected to the semiconductor device and having excellent connection reliability capable of firmly bonding the solder ball 11 to the second connection pads 3a, 3b, and 3c. .

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

It is sectional drawing which shows an example of the wiring board manufactured by the manufacturing method of this invention. (A)-(g) is sectional drawing for every process for demonstrating the manufacturing method of the wiring board of this invention.

Explanation of symbols

1: insulating substrates 2a, 2b, 2c: first connection pads 3a, 3b, 3c: second connection pads 5a, 5b: third connection pads 6: solder bumps 7: solder layers 8: capacitor elements 9: solder 9a: base solder layer 21: first solder paste 22: second solder paste 23: third solder paste 31: flux

Claims (4)

A first connection pad electrically connected to the semiconductor element on the upper surface, a second connection pad electrically connected to the external electric circuit board on the lower surface, and a third electrically connected capacitor element to the lower surface A solder bump is welded to the first connection pad of the insulating substrate on which the connection pad is formed, and a solder layer having a melting point higher than that of the solder bump is welded to the second connection pad. A method of manufacturing a wiring board in which the capacitor element is electrically connected to a connection pad via a solder having the same composition as the solder layer, the solder connected to the second connection pad and the third connection pad. After printing the first solder paste that becomes a part of the layer and the solder, the solder powder in the first solder paste is heated and melted to form the solder layer and the third on the second connection pad. A step of welding a base solder layer that becomes a part of the solder to the connection pad, and a second solder paste that becomes the solder bump is printed on the first connection pad, and then the solder in the second solder paste Heating and melting powder to weld the solder bumps to the first connection pads; and printing a third solder paste on the base solder layer to form the remainder of the solder; Placing the capacitor element on the paste and heating and melting the solder powder in the third solder paste to connect the capacitor element onto the third connection pad via the solder. A method for manufacturing a wiring board. A solder resist layer having an opening for exposing the second connection pad and the third connection pad is formed on the lower surface of the insulating substrate, and the thicknesses of the solder layer and the base solder layer are determined by the solder. 2. The method for manufacturing a wiring board according to claim 1, wherein the thickness of the resist layer is smaller than that of the resist layer. The solder bump is deposited on the first connection pad, and then the surface of the solder bump is covered with a flux, and then the solder powder in the third solder paste is heated and melted. Item 3. A method for manufacturing a wiring board according to Item 2. 4. The method of manufacturing a wiring board according to claim 1, wherein the viscosity of the first solder paste is lower than the viscosity of the third solder paste. 5.

Images