JP4383253B2 - Wiring board - Google Patents

Description

  The present invention relates to semiconductor integrated circuit elements such as IC and LSI, LD (semiconductor laser), LED (light emitting diode), PD (photodiode), CCD, line sensor, image semiconductor and other optical semiconductor elements, piezoelectric vibrator, crystal The present invention relates to a wiring board on which a vibrator such as a vibrator and other various electronic components are mounted.

  Semiconductor integrated circuit elements such as IC and LSI, LD (semiconductor laser), LED (light emitting diode), PD (photodiode), CCD, line sensor, optical semiconductor element such as image sensor, piezoelectric vibrator, crystal vibrator, etc. As a wiring board on which vibrators and other various electronic components are mounted, a substrate in which a wiring conductor made of a metal material such as copper, silver, palladium, or gold is formed on an insulating base made of a glass ceramic sintered body is often used. It has come to be. This wiring board includes, for example, an insulating base formed by laminating a plurality of insulating layers made of a glass ceramic sintered body such as a borosilicate glass-aluminum oxide system, a wiring conductor formed inside the insulating base, and an insulating base And a plurality of connection pads arranged on the outer periphery of the lower surface.

  In addition to mounting electronic components on the upper surface of the insulating substrate, the electrodes for signal, grounding, power supply, etc. of the electronic components are connected to the corresponding wiring conductors via solder or bonding wires, and the electronic components are resinized as necessary The electronic device is completed by sealing with a cap. Then, the plurality of connection pads arranged on the outer peripheral portion of the lower surface of the insulating base are connected to the circuit wiring of the corresponding external electric circuit board via conductor bumps made of solder or the like, so that the electronic device can Mounted on a circuit board.

Further, as a conventional technique, in order to suppress the occurrence of cracks in the conductor bumps due to the thermal stress caused by the difference in thermal expansion coefficient between the insulating base and the external electric circuit board, the connection pad on the lower surface of the insulating base is used. It is known that a dummy conductive pad is formed in a region in which no is formed, and this dummy conductive pad is joined to an external electric circuit board via solder or the like. For example, Patent Documents 1 and 2 listed below disclose such conventional techniques.
JP 2004-31934 A JP 2001-332663 A

  However, in the conventional wiring board, a solder pool is generated between the conductive pad and the circuit wiring of the external electric circuit board, and a gap is formed between the electronic component storage package and the external circuit board. There was a possibility that the bonding with the bumps would be insufficient. As a result, cracks occur in the joint surface between the connection pad and the conductor bump, the joint surface between the conductor bump and the circuit wiring of the external electric circuit board, etc. There was a possibility of destruction. In particular, instead of the conventional tin-lead eutectic solder, so-called lead-free solder such as tin-silver, tin-silver-copper, etc. has come to be frequently used as a material for the conductor bump, and such a problem is remarkable. It has become something. That is, in the case of lead-free solder, since the soldering temperature is high and it is difficult to deform, the thermal stress acting on the joint portion between the connection pad and the conductor bump is further increased. Cracks are likely to occur on the joint surface, the joint surface between the conductor bump and the circuit wiring of the external electric circuit board, and the like.

  The present invention has been completed in view of the above-described problems in the prior art, and an object thereof is to suppress the occurrence of mechanical breakage on the joint surface between the connection pad and the conductor bump, the conductor bump itself, or the like. It is possible to provide a wiring board excellent in mechanical connection and electrical connection reliability to an external electric circuit board.

A wiring board according to the present invention comprises an insulating substrate formed by laminating a plurality of insulating layers and having a recess formed in the center of the lower surface, a wiring conductor formed inside the insulating substrate, and the lower surface of the insulating substrate. formed and arranged in the peripheral portion, the plurality of connection pads which are wire conductors electrically connected, have a conductive pad formed on the bottom surface of the recess, the peripheral portion of the bottom surface of the recess, the conductive pad The non-formation region is provided .

  In the wiring board of the present invention, it is preferable that at least one of a ground conductor layer and a power supply conductor layer is formed inside the insulating base, and the conductive pad is formed of the ground conductor layer or the power supply conductor layer. It is electrically connected to this.

  The wiring board of the present invention is preferably characterized in that a plurality of the conductive pads are formed on the bottom surface of the recess.

In the wiring board of the present invention, the conductive pad is formed on the bottom surface of the concave portion formed in the central portion of the lower surface of the insulating base, so that the solder for joining the conductive pad and the wiring conductor of the external electric circuit board is provided. Is accommodated in the recess, and as a result, it is possible to prevent a gap from being generated between the electronic component storage package and the external circuit board, and to improve the bonding strength between the connection pad and the wiring conductor of the external electric circuit board. It becomes possible. In addition, it is possible to suppress mechanical damage on the joint surface between the connection pad and the conductor bump, the conductor bump itself, and the like, and the mechanical connection to the external electric circuit board and the reliability of the electric connection are possible. A wiring board excellent in performance can be provided. In addition, since the conductive pad non-formation region is provided in the periphery of the bottom surface of the recess, it is possible to prevent the insulating layer from being chipped due to the stress generated in the conductive pad.

In the wiring board of the present invention, preferably, the insulating base has at least one of a ground conductor layer or a power conductor layer formed therein, and the conductive pad is electrically connected to the ground conductor layer or the power conductor layer. by there, it is possible to suppress the generation of stray capacitance in the conductive pads, to suppress a delay or the like of the electrical signal sent isopropylidene by the wiring conductor, it is possible to provide a wiring board having excellent electrical characteristics. And the area of the conductor for grounding or a power supply can be increased, the supply function of a grounding voltage or a power supply voltage can be improved, and a wiring board with more excellent electrical characteristics can be provided.

  In the wiring board of the present invention, it is preferable that a plurality of conductive pads are formed on the bottom surface of the concave portion, so that thermal stress that tends to act greatly along the outer peripheral edge portion of the conductive pads is applied to the plurality of conductive pads. It can be effectively dispersed by the pad, and it is more effective that mechanical damage such as cracks occurs on the joint surface between the conductive pad and the conductive bump, the joint surface between the conductive pad and the insulating base, etc. Therefore, it is possible to provide a wiring board excellent in reliability of electrical connection and mechanical connection to an external electric circuit board.

  Next, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  A first example of the wiring board of the present invention will be described with reference to FIG. FIG. 1A is a bottom view showing the configuration of the first example of the wiring board of the present invention, and FIG. 1B is a cross-sectional view taken along the line XX ′ in the wiring board of FIG. It is. The wiring substrate 111 according to the first example of the present invention includes an insulating base 101 formed by laminating a plurality of insulating layers, a wiring conductor 102 formed inside the insulating base 101, and a connection pad formed on the insulating base 101. 103 and conductive pad 104.

  The insulating base 101 has an upper surface on which electronic components are mounted and a lower surface facing the upper surface. The lower surface of the insulating base 101 is a mounting surface for the external electric circuit board. In the central portion of the upper surface of the insulating base 101, a concave portion (mounting portion 105) for mounting electronic components is formed. A recess 106 is also formed at the center of the lower surface of the insulating substrate 101. The recess 106 is formed by removing a part (central portion) of the insulating layer 101a in the outermost layer (lowermost layer) of the insulating layers constituting the insulating base 101.

  The insulating base 101 is made of an electrically insulating material such as a glass ceramic sintered body, an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, a silicon nitride sintered body, and a silicon carbide sintered body. Consists of. Here, a method of manufacturing the insulating base 101 when the insulating base 101 is made of a glass ceramic sintered body will be described. First, a glass ceramic raw material powder such as silicon oxide and aluminum oxide is mixed with a suitable organic binder and solvent to form a slurry, and this is formed into a sheet by using a doctor blade method to form a plurality of ceramic green sheets. To manufacture. Thereafter, the ceramic green sheets are formed into an appropriate shape by cutting or punching, and a plurality of them are laminated. Finally, the laminated ceramic green sheets are fired at a temperature of about 1000 ° C. in a reducing atmosphere, whereby the insulating base 101 is manufactured.

  The insulating base 101 is a semiconductor integrated circuit element such as an IC or LSI, an LD (semiconductor laser), an LED (light emitting diode), a PD (photodiode), a CCD, a line sensor, an optical semiconductor element such as an image sensor, a piezoelectric vibrator, It functions as a base for supporting a vibrator such as a quartz vibrator and other various electronic components (not shown). In the example shown in FIG. 1, the insulating base 101 has a shape in which a portion (mounting portion 105) for storing an electronic component is formed on the upper surface, but may be a flat plate.

  The wiring conductor 102 is formed inside the insulating base 101, a part thereof is exposed to the mounting portion 105 of the insulating base 101, and the other part is led out to the side surface of the insulating base 101.

  The connection pads 103 are arrayed on the periphery of the lower surface of the insulating base 101. The connection pad 103 is formed so as to extend to a plurality of notches 107 formed on the side surface of the insulating base 101. Further, the connection pad 103 is electrically connected to the wiring conductor 102 via a conductor layer 108 formed in the notch 107.

  Here, the wiring conductor 102 and the connection pad 103 function as a conductive path for electrically connecting an electronic component mounted on the mounting portion 105 to an external electric circuit. An electrode of an electronic component is electrically connected to a portion of the wiring conductor 102 exposed to the mounting portion 105 via a bonding wire, solder, or the like. Then, the connection pad 103 is connected to an external electric circuit (not shown) via a conductor bump (not shown) made of solder or the like, so that the electrode of the electronic component is electrically connected to the external electric circuit. The Further, the wiring conductor 102 and the connection pad 103 are made of a metal material such as copper, silver, palladium, gold, tungsten, molybdenum, or manganese. For example, if the wiring conductor 102 and the connection pad 103 are made of copper, a metal paste produced by kneading copper powder together with an organic solvent and a resin binder is printed on a ceramic green sheet serving as the insulating base 101. The wiring conductor 102 and the connection pad 103 shown in FIG. 1 are formed.

  The notch 107 on the side surface of the insulating substrate 101 extends the connection pad 103 to the side surface of the insulating substrate 101 to expand the area, and forms a large meniscus of the conductor bump bonded to the connection pad 103. The connection pad 103 and the conductor bump have a function of further strengthening the bonding. The notch 107 is formed by providing a groove-like notch on the side surface of the ceramic green sheet to be the insulating base 101 by punching using a mold or the like. If the wiring substrate 111 is manufactured in a multi-cavity configuration in which the region to be the wiring substrate 111 is arranged vertically and horizontally on the main surface of the mother substrate, through holes are formed in the boundary lines of the regions to be the wiring substrates 111. The wiring substrate 111 having the notch 107 on the side surface can be formed by dividing the mother substrate along the boundary line of the region to be the wiring substrate 111. The through hole is divided along the dividing groove (boundary line), and becomes a notch 107 on the side surface of each wiring board 111. According to this method, a large number of wiring boards 111 having notches 107 can be manufactured in a lump, so that the productivity of the wiring board 111 can be improved.

  The conductor layer 108 can be formed using the same metal material as that of the wiring conductor 102 and the connection pad 103. If the conductor layer 108 is made of copper, the conductor layer 108 is prepared by kneading copper powder with an organic solvent and a resin binder. The formed metal paste is printed on the inner surface of the cutout portion 107 of the ceramic green sheet to be the insulating base 101.

  The conductive pad 104 is formed on the bottom surface of the recess 106 provided on the lower surface of the insulating base 101. Here, the bottom surface of the recess 106 refers to the surface of the insulating layer inside the insulating layer on which the connection pad 103 is formed. In the example shown in FIG. 1, the central portion of the insulating layer 101a where the connection pad 103 is formed is removed, and a recess 106 is formed there. The bottom surface of the recess 106 is the surface of the insulating layer 101b inside the insulating layer 101a.

  In the example shown in FIG. 1, a conductive pad 104 is formed on the surface of the insulating layer 101b. The conductive pad 104 can be formed using the same metal material as that of the wiring conductor 102 and the connection pad 103. For example, if the conductive pad 104 is made of copper, it is prepared by kneading copper powder together with an organic solvent and a resin binder. The formed metal paste is formed by, for example, printing on the central portion of the portion that becomes the bottom surface of the recess 106 in the ceramic green sheet that becomes the insulating substrate 1. This conductive pad 104 is a strength of electrical connection and mechanical connection between the connection pad 103 of the wiring board 111 (or an electronic device in which an electronic component is mounted on the wiring board 111) and the circuit wiring of the external electric circuit board. It has the function of improving. That is, the bonding strength between the wiring board 111 and the external electric circuit board can be improved by bonding the conductive pad 104 to a dummy connection conductor or the like formed on the external electric circuit board via solder or the like. It becomes possible. Then, it is possible to suppress the occurrence of mechanical destruction such as cracks on the joint surface between the connection pad 103 and the conductor bump and the conductor bump itself, and to electrically connect the connection pad 103 and the circuit wiring of the external electric circuit board. The reliability of mechanical connection can be improved.

  Here, when the thickness of the conductive pad 104 is less than 10 μm, the bonding strength of solder or the like tends to be insufficient, and when it exceeds 35 μm, the bonding strength to the insulating layer tends to decrease due to internal stress. Therefore, it is preferable that the conductive pad 104 has a thickness of 10 to 35 μm.

  FIG. 1A shows a configuration in which a plurality of connection pads 103 are formed at the same arrangement interval on each side of the lower surface of the insulating base 101. The structure formed in each corner | angular part of a lower surface may be sufficient.

  Moreover, it is preferable that the recessed part 106 shall be 0.05 mm or more in depth. If the thickness is less than 0.05 mm, the solder formed between the conductive pad 104 and the wiring conductor of the external electric circuit board is not sufficiently stored in the recess 106, and a gap is generated between the wiring board 111 and the external wiring board. In some cases, it becomes impossible to form a fillet between the connection pad 103 and the conductor bump, and the reliability of electrical connection and mechanical connection between the connection pad 103 and the circuit wiring cannot be sufficiently improved. .

  In the wiring substrate 111 of the present invention, at least one of the ground conductor layer 109 and the power supply conductor layer 110 is formed inside the insulating base 101, and the conductive pad 103 is electrically connected to the ground conductor layer 109 or the power supply conductor layer 110. It is good to be connected. With such a configuration, it is possible to suppress the generation of stray capacitance in the conductive pad 104, to suppress the occurrence of a delay of an electric signal transmitted by the wiring conductor 102, and the wiring board having excellent electrical characteristics. 111 can be provided.

  Further, the connection pads 103 for grounding and power supply are electrically connected to the conductive pads 104, so that the area of the conductor for grounding and power supply can be increased, and the electrons mounted on the wiring board 111 can be increased. It becomes possible to more reliably and stably supply the ground voltage and the power supply voltage to the components.

Further, the periphery of the bottom surface of the recess 106, Ru provided a non-forming region of the conductive pads 104. That is, the conductive pad 104 is formed away from the insulating layer 101a. With this configuration, it is possible to prevent the insulating layer 101a from being chipped due to stress generated in the conductive pad 104. Further, since the stress generated in the conductive pad 104 tends to concentrate on the corner of the conductive pad 104, the conductive pad 104 may be formed away from the insulating layer 101 a at the corner of the bottom surface of the recess 106.

  As described above, the wiring board 111 of the present invention has the conductive pad 104 formed on the bottom surface of the concave portion 106 formed in the central portion of the lower surface of the insulating base 101, so that the conductive pad 104 and the conductive pad 104 are formed in the concave portion 106. Solder for joining the wiring conductor and the like of the external electric circuit board is accommodated, and the joining strength between the connection pad 103 and the conductor bump can be improved. Further, it is possible to suppress the occurrence of mechanical breakage on the joint surface between the connection pad 103 and the conductor bump, the conductor bump itself, and the like, and the mechanical connection and the electric connection of the external electric circuit board can be suppressed. The wiring board 111 with excellent reliability can be provided.

  Next, a second example of the wiring board of the present invention will be described with reference to FIG. FIG. 2A is a bottom view showing the configuration of the second example of the wiring board of the present invention, and FIG. 2B is a cross-sectional view taken along line XX ′ in the wiring board of FIG. It is. In the wiring substrate 211 of the second example of the present invention, a plurality of conductive pads 204 a and 204 b are formed on the bottom surface of the recess 106 provided at the center of the lower surface of the insulating base 101. Other configurations are the same as those of the wiring substrate 111 of the first example of the present invention shown in FIG. In the wiring board 211 of the second example of the present invention, the same components as those of the wiring board 111 of the first example of the present invention shown in FIG.

  The conductive pad 204 a and the conductive pad 204 b are connected to a ground conductor layer or a power supply conductor layer formed inside the insulating base 101 through a through conductor formed inside the insulating base 101. FIG. 2 shows an example in which the conductive pad 204 a and the conductive pad 204 b are connected to the ground conductor layer 109.

Further, the periphery of the bottom surface of the recess 106, conductive pads 204a, Ru provided a non-formation region of 204b. Nachi Suwa, conductive pads 204a, and 204b, are formed apart from the insulating layer 101a. With this configuration, it is possible to prevent the insulating layer 101a from being chipped due to stress generated in the conductive pads 204a and 204b. Further, since the stress generated in the conductive pads 204a and 204b tends to concentrate on the corners of the conductive pads 204a and 204b, the conductive pads 204a and 204b are separated from the insulating layer 101a at the corners of the bottom surface of the recess 106. It may be formed.

  According to the wiring substrate 211 of the second example of the present invention, the plurality of conductive pads 204a and 204b are formed on the bottom surface of the concave portion 106 provided in the central portion of the lower surface of the insulating base 101. The thermal stress in 211 can be effectively dispersed. That is, the thermal stress generated on the lower surface of the wiring board 211 can be distributed to each of the plurality of conductive pads 204a and 204b. Then, by dispersing the thermal stress, it is possible to suppress mechanical destruction such as cracks generated on the joint surface between the conductive pad and the conductive bump such as solder and the joint surface between the conductive pad and the insulating base 101. The reliability of electrical connection and mechanical connection to the external electric circuit board can be further improved.

(A) is a bottom view showing a first example of the embodiment of the wiring board of the present invention, and (b) is a cross-sectional view taken along line X-X ′ of the wiring board shown in FIG. 1 (a). (A) is a bottom view which shows the 2nd example of embodiment of the wiring board of this invention, (b) is sectional drawing in the X-X 'line | wire of the wiring board shown to Fig.2 (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Insulation base | substrate 102 ... Wiring conductor 103 ... Connection pad 104 ... Conductive pad 105 ... Mounting part 106 ... Concave part 107 ... Notch part 108 ... Conductor layer 109- ..Grounding conductor layer 110 ... Power supply conductor layer 111 ... Wiring board

Claims (3)

An insulating base formed by laminating a plurality of insulating layers and having a recess formed in the central portion of the lower surface, a wiring conductor formed inside the insulating base, and an array formed on the periphery of the lower surface of the insulating base, a plurality of connection pads the wired conductor electrically connected, have a conductive pad formed on the bottom surface of the recess, the peripheral portion of the bottom surface of the recess, provided with a non-forming region of the conductive pad A wiring board characterized by that.   The insulating base has at least one of a ground conductor layer and a power conductor layer formed therein, and the conductive pad is electrically connected to the ground conductor layer or the power conductor layer. The wiring board according to claim 1.   The wiring board according to claim 1, wherein a plurality of the conductive pads are formed on the bottom surface of the recess.

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