JP2005277164A - Wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board which can surely prevent the matter that mechanical teardown is generated on a bonding surface between a connection pad and a conducting bump, a conducting bump itself, etc. over long period of time, even when the connection pad becomes small and the conducting bump is formed of lead free solder, and which wiring board is excellent in reliability of mechanical and electrical connection to an external electric circuit board. <P>SOLUTION: The wiring board 9 is provided with an insulating substrate 1 which is constituted by laminating a plurality of insulators, a wiring conductor 2 formed inside the insulating substrate 1, a plurality of the connection pads 3 which are arranged and formed on an outer peripheral part of a lower surface of the insulating substrate 1 so as to respectively protrude to a plurality of notched parts 1a formed on a side surface of the insulating substrate 1, and electrically connected to the wiring conductor 2 at the notched parts 1a, a conducting pad 4 formed in a center section of a lower surface of the insulating substrate 1, holes 5 of not penetrating which were formed on periphery of the conducting pad 4 of the lower surface of the insulating substrate 1, and conductors 6 formed on internal surfaces of the holes 5 of not penetrating. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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. A wiring board on which a vibrator and other various electronic components are mounted generally includes a plurality of insulating layers made of an insulating material such as an aluminum oxide sintered body, a glass ceramic sintered body, and an aluminum nitride sintered body. Insulating base, a wiring conductor formed inside the insulating base, and a plurality of connection pads arranged on the outer periphery of the lower surface of the insulating base.

  On the side surface of the insulating base, a plurality of cutouts are usually formed corresponding to the portions where the connection pads are formed, and a part of the wiring conductor is led to the cutouts. In addition, a connection pad extends on the inner side surface of the notch, and the connection pad and the wiring conductor are electrically connected at the extended portion.

  In addition to mounting electronic components on the top 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 if necessary, The electronic device is completed by sealing the component with resin or a cap.

  Thereafter, the electronic device is connected to the external electric circuit by connecting a plurality of connection pads arranged on the outer peripheral portion of the lower surface of the insulating base to the circuit wiring of the corresponding external electric circuit board via conductor bumps made of solder or the like. Mounted on the board.

  Here, in the conventional wiring board, thermal stress is generated due to the difference in thermal expansion coefficient between the insulating base and the board of the external electric circuit, and this thermal stress causes the bonding surface between the conductor bump and the connection pad to There is a problem that mechanical breakage such as a crack is likely to occur in the conductor bump itself, and the reliability of external connection of the wiring board is likely to be lowered.

  For such a problem, a conductive pad is formed in a portion of the lower surface of the insulating substrate where the connection pad is not formed, and this conductive pad is connected to the external electric circuit board, and the connection pad and the circuit wiring of the external electric circuit board are connected. The bonding between the electronic component storage package and the external electric circuit board is reinforced by bonding via the same solder as the solder for forming the conductive bump to be connected, and the mechanical bump such as the conductive bump due to the thermal stress as described above A technique for preventing the destruction is known.

The central part of the bottom surface of the insulating substrate where the connection pad is not formed is the largest. If a large conductive pad is formed here, the bonding of the electronic component storage package to the external electric circuit board is effectively reinforced. It is considered that mechanical damage such as cracks can be prevented from occurring on the joint surface between the conductor bump and the connection pad and the conductor bump itself.
JP 2004-31934 A JP 2001-332663 A

  However, when a conductive pad is formed at the center of the lower surface of the insulating substrate and bonded to the external electric circuit board, the overall bonding between the electronic component storage package and the external electric circuit board is effectively reinforced. Therefore, it is possible to effectively prevent the mechanical destruction of the joint surface between the connection pad and the conductor bump and the conductor bump itself in the use and usage of the conventional wiring board, but the conductive pad. Since a large thermal stress is concentrated along the peripheral edge of the conductive layer, cracks occur in the bonding surface between the conductive pad and the insulating base, the bonding surface between the conductive pad and solder, etc., starting from the peripheral portion of the conductive pad, During long-term use, the effect of reinforcement by the conductive pad becomes insufficient, and there is a possibility that mechanical damage is likely to occur on the joint surface between the connection pad and the conductor bump and the conductor bump itself, Electrical for parts the electric circuit board, tended to be as insufficient long-term reliability of the mechanical connection.

  In particular, with the recent miniaturization of the wiring board (the length of one side is about 2 mm or less), the area of the connection pad is further reduced, and the conventional tin-lead eutectic is used as a material for the conductor bump. Instead of solder, so-called lead-free solders such as tin-silver and tin-silver-copper are used frequently, and the soldering temperature of lead-free solder is high and it is difficult to deform. Since the absorbing action is low, the thermal stress acting on the joint portion of the conductive pad is becoming larger, etc., and cracks are more likely to occur on the joint surface between the conductive pad and solder, etc. The deterioration of long-term reliability of electrical and mechanical connections to such external electric circuit boards has become remarkable.

  In addition, when lead-free solder or the like is used as the conductor bump, the soldering temperature is high and the thermal stress is larger as described above. Therefore, the bonding surface between the connection pad and the conductor bump or the conductor bump itself is mechanically bonded. It becomes difficult to reliably prevent the occurrence of destruction.

  The present invention has been devised in view of the above-described conventional problems, and the purpose of the present invention is to provide a connection pad even if the connection pad becomes smaller or the conductor bump is formed of lead-free solder. For the reliability of mechanical and electrical connection to external electric circuit boards that can effectively prevent mechanical destruction on the joint surface between the conductor bumps and the conductor bumps themselves over a long period of time. The object is to provide an excellent wiring board.

  The wiring board of the present invention is formed on the side surface of the insulating base on the outer peripheral portion of the lower surface of the insulating base, the insulating base formed by laminating a plurality of insulating layers, the wiring conductor formed inside the insulating base. A plurality of connection pads that are arranged to extend to the plurality of cutout portions and are electrically connected to the wiring conductor at the cutout portions, and a central portion of the lower surface of the insulating base. A conductive pad formed; a non-penetrating hole formed on a peripheral edge of the conductive pad on the lower surface of the insulating base; and a conductor layer formed on an inner surface of the non-penetrating hole. Features.

  The wiring board of the present invention is preferably characterized in that the hole has a circular or elliptical cross-sectional shape and is formed in plural at the same interval.

  According to the wiring board of the present invention, the conductive pad is formed at the center of the lower surface of the insulating base, and the non-penetrating hole is formed on the periphery of the conductive pad on the lower surface of the insulating base. Since the conductive layer is formed on the peripheral edge of the conductive pad, a solder pool is formed in the hole by the solder attached to the surface of the conductive layer on the inner surface of the non-through hole. The solder joint between the wiring conductor and the like can be effectively reinforced by the solder pool in the hole. As a result, the bonding between the conductive pad and the wiring conductor of the external electric circuit board, the bonding between the conductive pad and the solder can be maintained for a long time, and the connection between the wiring board and the external electric circuit board can be reinforced. Can do. Therefore, it is possible to reliably prevent mechanical damage on the joint surface between the connection pad and the conductor bump, the conductor bump itself, etc. over a long period of time. A wiring board having excellent connection reliability can be provided.

  In the wiring board of the present invention, the hole preferably has a circular or elliptical cross-sectional shape, and a plurality of holes are formed at the same interval, so that thermal stress does not concentrate on a part of the hole. Further, it can be reinforced with more uniform strength over the entire circumference of the conductive pad.

  Next, the wiring board of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1A is a cross-sectional view showing an example of an embodiment of a wiring board according to the present invention, and FIG. 1B is a plan view thereof. 1 (a) and 1 (b), 1 is an insulating substrate formed by laminating a plurality of insulating layers, 2 is a wiring conductor, 3 is a connection pad, 4 is a conductive pad, 5 is a non-through hole, and 6 is a non-through hole. It is a conductor layer formed on the inner surface of the through hole 5.

  The insulating substrate 1, the wiring conductor 2, the connection pad 3, the conductive pad 4, the hole 5 and the conductor layer 6 mainly constitute the wiring substrate 9 of the present invention.

  The insulating substrate 1 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, or a silicon carbide sintered body. Become.

  If the insulating substrate 1 is made of, for example, a glass ceramic sintered body, an appropriate organic binder and solvent are added to and mixed with a glass ceramic raw material powder such as silicon oxide and aluminum oxide to form a slurry, which is then treated as a doctor. A plurality of ceramic green sheets are obtained by adopting a blade method to form a sheet. After that, the ceramic green sheets are formed into an appropriate shape by cutting or punching, and a plurality of them are laminated. This laminated ceramic green sheet is manufactured by firing at a temperature of about 1000 ° C. in a reducing atmosphere.

  The insulating substrate 1 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 mounting and supporting a vibrator such as a quartz vibrator and other various electronic components (not shown), and faces its main surface (a main surface on which connection pads 3 described later are formed). Electronic components (not shown) are mounted on the main surface or the like.

  In the example of FIG. 1, the insulating base 1 has a shape in which a concave portion for housing and mounting an electronic component is formed on the upper surface, but may be a flat plate shape.

  A wiring conductor 2 is formed inside the insulating base 1, and a part of the wiring conductor 2 is exposed to a portion (hereinafter also referred to as a mounting portion) on the insulating base 1 where an electronic component is mounted. The other part is led out to the side surface of the insulating substrate 1.

  In addition, the outer peripheral portion of the lower surface of the insulating substrate 1 is arranged and formed so as to extend to a plurality of cutout portions formed on the side surface of the insulating substrate 1 and is electrically connected to the wiring conductor 2 at the cutout portions. A plurality of connected pads 3 are formed.

  The wiring conductor 2 and the connection pad 3 function as a conductive path for connecting an electronic component mounted on the mounting portion to an external electric circuit. Of the wiring conductor 2, an electrode of an electronic component is electrically connected to a portion exposed to the mounting portion via a bonding wire, solder, or the like, and the connection pad 3 is a conductor made of solder or the like to an external electric circuit (not shown). By connecting via a bump (not shown), the electrode of the electronic component is electrically connected to an external electric circuit.

  In addition, the notch 1a on the side surface of the insulating substrate 1 extends the connection pad 3 to the side surface of the insulating substrate 1 to increase the area and form a large meniscus of the conductor bump. It functions to make bonding stronger.

  The wiring conductor 2 and the connection pad 3 are made of a metal material such as copper, silver, palladium, gold, tungsten, molybdenum, or manganese. For example, when made of copper, copper powder is kneaded with an organic solvent and a binder. It is formed by printing the produced metal paste on a ceramic green sheet to be the insulating substrate 1.

  Further, the notch 1a on the side surface of the insulating substrate 1 is formed by subjecting the side surface of the ceramic green sheet to be the insulating substrate 1 to a groove-shaped notch, such as punching using a mold. In this case, the region to be the wiring substrate 9 is manufactured in a multi-cavity form (not shown) in which the region to be the wiring substrate 9 is arranged vertically and horizontally on the main surface of the large-area mother substrate. A wiring board having a notch 1a on the side surface is also formed by forming a through hole (not shown) so as to straddle the substrate and then dividing the mother board along the boundary of the region to be the wiring board 9 9 can be formed. The through hole is vertically divided into two along the dividing groove, and becomes a notch portion 1 a on the side surface of each wiring board 9. According to this method, a large number of wiring boards 9 having notches 1a can be formed in a lump, so that the productivity of the wiring board 9 can be ensured satisfactorily.

  And while mounting an electronic component on the upper surface of the insulation base | substrate 1, the electrode of an electronic component is electrically connected to the exposed part of the wiring conductor 2 via conductive connection materials, such as a solder and a bonding wire, and as needed An electronic device is completed by sealing the electronic component with a lid or a sealing resin.

  In this electronic device, the connection pad 3 is electrically and mechanically connected to the circuit wiring of the external electric circuit board via a conductor bump made of solder or the like, so that the electrode of the electronic component is connected to the wiring conductor 2 and the connection pad 3. And electrically connected to an external electric circuit through the conductor bump.

  In the wiring substrate 9 of the present invention, the conductive pad 4 is formed at the center of the lower surface of the insulating substrate 1.

  This conductive pad 4 functions to reinforce the connection when the connection pad 3 of the wiring board 9 (electronic device) is electrically and mechanically connected to the circuit wiring of the external electric circuit board. That is, the bonding between the wiring board 9 and the external electric circuit board is reinforced by bonding the conductive pads 4 to a dummy connection conductor or the like provided in advance on the external electric circuit board via solder or the like. Mechanical damage such as cracks is effectively prevented from occurring on the joint surface between the connection pad 3 and the conductor bump and the conductor bump itself, and the electrical and mechanical connection between the connection pad 3 and the circuit wiring can be maintained for a long time. Can be maintained.

  The conductive pad 4 has a non-penetrating hole 5 formed on the periphery thereof, and a conductor layer 6 is formed on the inner surface of the non-penetrating hole 5.

  According to the wiring substrate 9 of the present invention, a solder pool is formed in the hole 5 by the solder adhering to the surface of the conductor layer 6 on the inner side surface of the non-through hole 5 at the peripheral portion of the conductive pad 4 by the above configuration. Therefore, the solder joint between the conductive pad 4 and the wiring conductor of the external electric circuit board can be effectively reinforced by the solder pool in the hole 5. As a result, the bonding between the conductive pad 4 and the wiring conductor of the external electric circuit board, the bonding between the conductive pad 4 and the solder is maintained for a long time, and the connection between the wiring board 9 and the external electric circuit board is maintained. Can be reinforced. Accordingly, it is possible to reliably prevent mechanical damage on the joint surface between the connection pad 4 and the conductor bump, the conductor bump itself, and the like over a long period of time. It is possible to provide the wiring board 9 having excellent connection reliability.

  For example, the hole 5 is formed by punching a through hole on the periphery of the conductive pad 4 from the lowermost layer of the insulating layer, or from the lowermost layer to a plurality of layers upward from the lower layer. The insulating layer is laminated with an insulating layer in which no through hole is formed.

  In addition, the conductive pad 4 and the conductive layer 6 can be formed using the same metal material as that of the wiring conductor 2 and the connection pad 3. For example, if the conductive pad 4 and the conductive layer 6 are made of copper, copper powder is used as an organic solvent, binder. The metal paste prepared by kneading together is formed by printing on the central part of the lowermost part of the ceramic green sheet to be the insulating substrate 1 or the inner surface of the non-through hole 5 described above. .

  In the wiring board 9 of the present invention, it is preferable that the hole 5 has a circular or elliptical cross-sectional shape, and a plurality of holes 5 are formed at the same interval. Thereby, thermal stress does not concentrate on a part of the hole 5, and at the same time, it can be reinforced with more uniform strength over the entire circumference of the conductive pad 4. In addition, the bonding between the conductive pad 4 and the insulating base 1 or between the conductive pad 4 and the solder is more reliably maintained over a long period of time, and the connection between the wiring board 1 and the external electric circuit board is more effective. Can be reinforced. Further, the bonding between the conductive pad 4 and the wiring conductor of the external electric circuit board, the bonding between the conductive pad 4 and the solder is maintained for a long time, and the connection between the wiring board 9 and the external electric circuit board is reinforced. can do. Therefore, the mechanical and electrical connection to the external electric circuit board can be more reliably prevented over a long period of time from causing mechanical damage to the joint surface between the connection pad 3 and the conductor bump, the conductor bump itself, or the like. It is possible to provide a wiring board that is extremely excellent in reliability of general connection.

  For example, when the conductive pad 4 has a quadrangular shape, as shown in an example in FIG. 1B, a plurality of conductive pads 4 may be formed at the same interval on each side, or at the corners of the quadrangular shape. It may be formed.

  The depth of the non-through hole 5 is preferably set to 0.2 mm or more. If the thickness is less than 0.2 mm, the effect of reinforcing the bonding of solder or the like to the conductive pad 4 may be insufficient, and the electrical and mechanical connection between the connection pad 3 and the circuit wiring can be effectively performed over a long period of time. It tends to be difficult to reinforce.

  Further, the conductor layer 6 on the inner surface of the hole 5 is preferably arranged so that the lower end thereof is in contact with the peripheral edge of the conductive pad 4. If they are separated from each other, it becomes difficult for solder or the like bonded to the conductive pad 4 to be bonded to the surface of the conductor layer 6, and it becomes difficult to effectively reinforce the connection of the wiring board 9. is there.

  The conductor layer 6 may be formed not only on the portion of the hole 5 in contact with the conductive pad 4 but also on the entire inner surface. Further, it may be formed on the bottom surface of the hole 5.

  Further, when the thickness of the conductive pad 4 and the conductive layer 6 is less than 10 μm, the bonding strength such as solder tends to be insufficient, and when the thickness exceeds 35 μm, the bonding strength to the insulating layer tends to deteriorate due to internal stress. is there. Therefore, the conductive pad 4 and the conductor layer 6 are preferably 10 to 35 μm in thickness.

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

(A) is sectional drawing which shows an example of embodiment of the wiring board of this invention, (b) is a top view of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulation base | substrate 1a ... Notch part 2 ... Wiring conductor 3 ... Connection pad 4 ... Conductive pad 5 ... Non-through-hole 6 ... Conductor layer 9 ... Wiring substrate

Claims (2)

An insulating base formed by laminating a plurality of insulating layers, a wiring conductor formed inside the insulating base, and a plurality of notches formed on a side surface of the insulating base on the outer periphery of the lower surface of the insulating base And a plurality of connection pads electrically connected to the wiring conductor at the notch, and a conductive pad formed at the center of the lower surface of the insulating base, A wiring board comprising: a non-penetrating hole formed on a peripheral edge of the conductive pad on a lower surface of the insulating base; and a conductor layer formed on an inner surface of the non-penetrating hole. The wiring board according to claim 1, wherein a plurality of the holes have a circular cross section or an elliptical cross section and are formed at the same interval.

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