JP6181455B2 - Wiring board - Google Patents

Description

  The present invention relates to a wiring board having a connection pad for electrical connection with the outside.

  As a wiring board on which electronic components such as a semiconductor element, a capacitive element, and a piezoelectric vibrator are mounted, an insulating board such as a square plate formed by laminating a plurality of insulating layers made of aluminum oxide or glass ceramic sintered body; In many cases, an insulating substrate is provided with a connection pad provided on the main surface of the insulating substrate using a metal material such as copper or silver.

  The connection pad is a portion that is electrically connected to, for example, an electrode of an electronic component or an external electric circuit via solder or the like. The connection pad is usually a conductor layer for a signal (signal) that transmits an electrical signal provided inside the insulating substrate, a conductor layer for a power source (power) that supplies current to operate the electronic circuit, or a reference for the electronic circuit It is electrically connected to a grounding conductor layer that becomes a potential.

Japanese Patent Laid-Open No. 11-260957 JP 2000-349192 A JP 2009-182238 A

  In recent years, for example, with the increase in the speed of digital signals and the like used in the above-described electronic devices, it has become necessary to transmit high-frequency signals in the tens of GHz band, for example.

  As the signal speed increases, countermeasures against noise such as crosstalk noise between signals and electromagnetic noise are required. In response to this, by increasing the area of the conductor layer for power supply, grounding, etc., or by increasing the thickness of the conductor layer and lowering the impedance, the electromagnetic field distribution is stabilized and the power supply, grounding conductor layer It is effective to prevent mixing of noise.

  However, if the conductor layer provided on the main surface of the insulating substrate on which the connection pad is provided is widened or thickened, for example, a temperature cycle is added due to the difference in thermal expansion coefficient between the insulating substrate and the conductor layer. However, the wiring board may be warped. In addition, when the insulating substrate is made of ceramic, the wiring substrate may be warped due to a difference in shrinkage between the ceramic green sheet that becomes the insulating substrate and the metal paste that becomes the conductor layer when firing. there were.

  In order to solve such a problem, it can be considered that the thickness of the conductor layer provided on the main surface of the insulating substrate is made thinner than the thickness of the conventional connection pad, for example. However, since a part of this conductor layer functions as a connection pad, there is a possibility that a new problem of lowering connection reliability in the connection pad is induced. For example, it is difficult to reduce the thermal stress caused by the difference in thermal expansion coefficient between the insulating substrate and the external circuit substrate with a relatively thin connection pad. In particular, when the insulating substrate is enlarged, the thermal stress applied to the connection pad is increased. Further, when the area of the connection pad is reduced, the bonding area between the connection pad and the insulating substrate is reduced. Therefore, especially in such a case, there is a high possibility that a crack occurs in the connection pad or the insulating substrate.

A wiring board according to an aspect of the present invention covers an insulating substrate having a main surface, a conductor layer provided on the main surface of the insulating substrate, the main surface of the insulating substrate, and the entire conductor layer. And an insulating layer having a plurality of openings in which a part of the conductor layer is exposed, wherein the part of the conductor layer exposed in the plurality of openings forms a plurality of connection pads. The part of the conductor layer that overlaps each of the plurality of openings of the insulating layer is thicker than the part that overlaps the surrounding insulating layer, and the conductor layer is the opening of the insulating layer. In the part exposed at the portion, a portion formed of a first metal layer and a second metal layer sequentially provided on the main surface of the insulating substrate, and a portion extending outward in a part of the outer peripheral portion in the thickness direction is , Between the first metal layer and the second metal layer Has an auxiliary insulating layer sandwiched, the insulating substrate and the conductive layer and the glass in the insulating layer are contained, the in the part forming the connecting pads of said conductor layer The glass content is larger on the insulating substrate side than on the side opposite to the insulating substrate side .

  According to the wiring board according to one aspect of the present invention, the conductor layer having the above-described configuration is insulated at the portion where the thickness of the conductor layer provided on the main surface of the insulating substrate is exposed at each of the plurality of openings of the insulating layer. Since it is larger than the portion covered with the layer, it is possible to provide a wiring board that can easily improve the connection strength of the connection pads. That is, the thickness of the conductor layer exposed at the opening of the insulating layer serving as the connection pad is relatively thick, so that the thermal stress is effectively relieved.

  In addition, the thickness of the conductor layer of the conductor layer that is covered with the insulating layer is relatively thin, which is caused by either or both of the difference in thermal expansion coefficient and the shrinkage rate between the conductor layer and the insulating substrate. Thus, the thermal stress itself generated is reduced, and the warping of the wiring board due to the thermal stress can be reduced.

(A) is a bottom view which shows the wiring board of the 1st Embodiment of this invention, (b) is sectional drawing in the AA of (a). It is a principal part expanded sectional view which shows the principal part in the wiring board of the 1st Embodiment of this invention. (A) is a bottom view showing an insulating layer on the bottom surface of the wiring board shown in FIG. 1, and (b) is a bottom perspective view showing a conductor layer on the bottom surface of the wiring board shown in FIG. 3A is a bottom perspective view in which FIGS. 3A and 3B are superimposed, and FIG. 3B is a bottom perspective view in which a through conductor is superimposed on FIG. (A) is a bottom view which shows the wiring board of the 2nd Embodiment of this invention, (b) is a principal part expanded sectional view in the BB line of (a). (A) is a bottom view showing the insulating layer on the bottom surface of the wiring board shown in FIG. 5, and (b) is a bottom perspective view showing the conductor layer on the bottom surface of the wiring board shown in FIG. FIG. 7 is a bottom perspective view in which FIGS. 6 (a) and (b) are superimposed. It is sectional drawing which shows the modification of the wiring board shown in FIG. (A) is a principal part expanded sectional view which shows the modification of FIG. 2, (b) is a principal part expanded sectional view which shows the other modification of FIG.

(First embodiment)
A wiring board of the present invention will be described with reference to the accompanying drawings. FIG. 1A is a bottom view showing a wiring board according to the first embodiment of the present invention, and FIG. 1B is a cross-sectional view of FIG. FIG. 2 is an enlarged cross-sectional view showing a main part of the wiring board according to the first embodiment of the present invention.

  In the example shown in FIGS. 1 and 2, the wiring substrate 10 is basically composed of an insulating substrate 1, a conductor layer 2 provided on the main surface of the insulating substrate 1, and an insulating layer 3 covering the conductor layer 2. Is formed. The insulating layer 3 has a plurality of openings 4. A part of the conductor layer 2 is exposed in each of the openings 4. The conductor layer 2 exposed in the opening 4 forms a connection pad 5 for external connection of the wiring board.

  The conductor layer 2 and the insulating layer 3 are shown in an exploded manner in FIGS. 3A is a bottom view showing the insulating layer 3 and the opening 4 on the lower surface of the wiring board shown in FIG. 1, and FIG. 3B is a conductor layer on the lower surface of the wiring board shown in FIG. It is a bottom view which shows the main surface of the insulated substrate 1 in which 2 and the conductor layer 2 are formed. 4 is a bottom perspective view showing a state in which the insulating layer 3 in FIG. 3A is superimposed on the conductor layer 2 in FIG. FIG. 3B can also be regarded as a perspective view of FIG. Further, FIG. 3B is a bottom perspective view in which a through conductor 8 is further added to FIG. Details of the through conductor 8 will be described later.

  In other words, the conductor layer 2 is provided in a relatively wide area on the main surface of the insulating substrate 1, and a part of the conductor layer 2 serves as the connection pad 5. The conductor layer 2 may be one or plural. When there is one conductor layer 2, a plurality of openings are provided in the insulating layer 3 for the one conductor layer 2, and a plurality of connection pads 5 electrically connected to each other are formed on the main surface of the insulating substrate 1. Will be provided.

  When there are a plurality of conductor layers 2, one or a plurality of openings 4 are provided in the insulating layer 3 for each conductor layer 2. When a plurality of openings are provided for one conductor layer 2 among the plurality of conductor layers 2, as in the case where one conductor layer 2 is provided on the main surface of the insulating substrate 1 as described above, A plurality of connection pads 5 electrically connected to each other are provided. Further, when a plurality of conductor layers 2 are provided, one or a plurality of connection pads 5 having the same potential are provided for each conductor layer 2, and different potentials ( A plurality of connection pads 5 (for example, a power source and a ground) are provided. In the example shown in FIGS. 1 and 2, a plurality of conductor layers 2 are provided, and a plurality of connection pads 5 including a grounding pad 5a, a power supply pad 5b, and a signal pad 5c are arranged vertically and horizontally. .

  These connection pads 5 are externally connected to electrodes of an electronic component (not shown) or an external electric circuit (not shown) mounted on the insulating substrate 1. The connection pad 5 is externally connected through a conductive connection material (not shown) including a solder such as tin-silver solder, a metal material such as gold, or an organic material such as a conductive adhesive. .

The insulating substrate 1 is formed by laminating a plurality of insulating material layers (no symbol) made of, for example, a glass ceramic sintered body or an aluminum oxide sintered body. The glass-ceramic sintered body that forms the insulating substrate 1 can be manufactured, for example, as follows. First, ceramic filler powder is prepared. Examples of the ceramic filler powder include aluminum oxide, chromium oxide, copper oxide, zirconium oxide, spinel and quartz. Moreover, a glass powder is prepared. Examples of the glass powder include SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —Al ₂ O ₃ —MgO—CaO—BaO—SrO-based glass. An appropriate organic binder and organic solvent are added to and mixed with the raw material powder containing these ceramic filler powder and glass powder to prepare a slurry. Next, a plurality of ceramic green sheets are produced by forming this slurry into a sheet by employing a sheet forming technique such as a doctor blade method or a lip coater method. Thereafter, the ceramic green sheet is made into an appropriate shape by a processing method selected from cutting and punching and the like, and a plurality of them are laminated. Finally, the laminated ceramic green sheets are heated to about 900 to 1000 ° C. in a reducing atmosphere. It can be manufactured by firing at a temperature.

The insulating substrate 1 has, for example, a quadrangular shape (square plate shape or the like) in a plan view, an electronic component (not shown) is mounted on the upper surface, and the lower surface is mounted to face an external circuit substrate (not shown). . Note that, as in the example shown in FIG. 1, so-called chamfering may be performed at a portion where a crack such as a corner portion of the insulating substrate 1 is likely to occur to increase the angle of the corner portion of the insulating substrate 1. Further, unevenness (so-called castellation) for forming a conductor layer may be provided on the side surface of the insulating substrate 1.

  Electronic components include semiconductor integrated circuit elements such as IC and LSI, semiconductor elements including optical semiconductor elements such as LED (light emitting diode), PD (photodiode), and CCD (charge coupled device), surface acoustic wave elements, and crystals. Various electronic components such as a piezoelectric element such as a vibrator, a capacitive element, a resistor, and a micromachine (so-called MEMS element) in which a minute electromechanical mechanism is formed on the surface of a semiconductor substrate can be given.

  On one main surface (upper surface) of the insulating substrate 1, for example, a central portion thereof includes a mounting portion (range not shown) on which the above-described various electronic components are mounted. Connection pads 5 are provided on the mounting portion or the periphery thereof. An electronic component is mounted on the mounting portion, and an electrode of the electronic component is electrically connected to the connection pad 5 via a conductive connecting material such as a bonding wire or solder.

  On the upper surface of the insulating substrate 1, the connection pads 5 provided in the mounting portion or the periphery thereof are connected to the insulating substrate via an internal conductor such as a wiring layer (not indicated) provided in the insulating substrate 1 and the through conductor 8. 1 is electrically led to the other main surface (lower surface) opposite to the one main surface. A connection pad 5 that is electrically connected to an external electric circuit is provided on the lower surface of the insulating substrate 1. The connection pad 5 on the upper surface of the insulating substrate 1 and the connection pad 5 on the lower surface are electrically connected to each other through the internal conductor.

  The connection pads 5 on the upper and lower surfaces of the insulating substrate 1 are formed by the conductor layers 2 provided on the upper and lower surfaces of the insulating substrate 1, respectively. Specifically, as described above, the conductor layer 2 is covered with the insulating layer 3 having the opening 4, and the conductor layer 2 exposed in the opening 4 of the insulating layer 3 serves as the connection pad 5.

  With respect to these connection pads 5, the thickness of the conductor layer 2 forming each connection pad 5 is larger at the portion exposed at the plurality of openings 4 of the insulating layer 3 than at the portion covered with the insulating layer 3. Includes things. In the first embodiment, the connection pads 5 provided on the lower surface of the insulating substrate 1 are formed by such relatively thick portions of the conductor layer 2. In the following description, the connection pads 5 provided on the lower surface of the insulating substrate 1 are mainly taken as an example.

  The thickness of the conductor layer 2 provided on the main surface (lower surface) of the insulating substrate 1 is larger at the portion exposed at each of the plurality of openings 4 of the insulating layer 3 than at the portion covered with the insulating layer 3. The connection strength of the connection pad 5 can be easily improved.

  That is, since the thickness of the conductor layer 2 exposed at the opening 4 of the insulating layer 3 serving as the connection pad 5 is relatively thick, the thermal stress generated between the wiring board 10 and the external electric circuit is effectively relieved. Is done. Therefore, it is possible to provide a wiring board having high external connection strength and reliability in the connection pad 5.

  In addition, since the thickness of the conductor layer 2 of the conductor layer 2 covered with the insulating layer 4 is relatively thin, either the difference in thermal expansion coefficient between the conductor layer 2 and the insulating substrate 1 or the difference in contraction rate is selected. It is also possible to reduce warpage of the wiring substrate 10 (particularly warpage of the insulating substrate 1) due to stress caused by one or both. The shrinkage rate means that when the ceramic green sheet is fired, the volume of the ceramic green sheet or metal paste is small because the space between the metal particles or between the ceramic particles becomes small due to bonding between the particles. It means the ratio of the amount of shrinkage.

  In addition, the portion of the conductor layer 2 covered with the insulating layer 4 is electrically connected to, for example, a power source or a ground potential, so that the wiring substrate 10 (such as the internal conductor or the electronic component mounted on the mounting portion) and the outside are electrically connected. It can also function as an electromagnetic noise shielding layer. In this case, a portion of the conductor layer 2 that is the connection pad 5 (a portion exposed at the opening 4 of the insulating layer 3), a portion that functions as a noise shielding layer (a portion covered with the insulating layer 3), and Are the same conductor layer 2 and are electrically connected to each other. Therefore, for example, the conduction resistance in the supply of the power supply or ground potential to the conductor layer 2 as the shielding layer from the connection pad 5 for power supply or ground is effectively reduced, and the potential of the power supply or ground (or both power supply and ground) is reduced. Can be more stable.

  The conductor layer 2 is made of a metal material such as copper, silver, palladium, gold, platinum, tungsten, molybdenum or manganese, or a mixed material or alloy material containing a plurality of these metal materials. The conductor layer 2 is formed on the insulating substrate 1 in the form of a metallized layer, a plating layer, a vapor deposition layer, or the like.

  If the conductor layer 2 is made of, for example, a copper metallized layer, a metal paste produced by adding an organic solvent and a binder to copper powder is printed on the surface of the ceramic green sheet to be the insulating substrate 1, The printed ceramic green sheet can be formed by laminating and firing a plurality of ceramic green sheets so that the surface of the ceramic green sheet becomes the lowermost surface.

  The internal conductor can also be formed by the same method using the same material as the conductor layer 2. The metal paste serving as the inner conductor is printed on the surface of the ceramic green sheet that becomes the inner layer when laminated. The through conductor 8 among the internal conductors can be formed by providing a through hole in a ceramic green sheet in advance, filling the through hole with the above metal paste, and firing it. The through hole can be formed by punching the ceramic green sheet by a method such as mechanical punching or laser processing.

  The insulating layer 3 is made of, for example, the same ceramic material as the insulating substrate 1 and is formed by simultaneous firing with the insulating substrate 1. If the insulating layer 3 is made of a glass ceramic sintered body similar to that of the insulating substrate 1, first, a glass ceramic material similar to that of the insulating substrate 1 is kneaded with an organic solvent and a binder to produce a ceramic paste. Next, this ceramic paste is printed by a screen printing method or the like so as to cover a ceramic green sheet to be the insulating substrate 1 and a metal paste printed on the ceramic green sheet, and then fired. The insulating layer 3 can be formed by the above steps.

  The opening 4 of the insulating layer 3 can be formed by providing a non-printing part in a part of a printing pattern such as a screen printing plate when printing a ceramic paste to be the insulating layer 3. Alternatively, a ceramic green sheet may be prepared, and a through hole may be provided in a portion to be the opening 4 of the insulating layer 3 and laminated on the surface of the conductor layer 2.

  The insulating layer 3 is not necessarily made of the same material as that of the insulating substrate 1. For example, the insulating layer 3 may be made of a ceramic material that is different from the insulating substrate 1 in the type or content of the glass component. It may consist of.

  In order to make the thickness of a part of the conductor layer 2 exposed at the opening 4 of the insulating layer 3 thicker than that of the other part, for example, after the insulating layer 3 is formed on the conductor layer 2, The thickness of the conductor layer 2 below the insulating layer 3 may be reduced by applying pressure. When the pressure is applied, the conductor layer 2 spreads in the plane direction. Therefore, it is possible to prevent an electrical short circuit by increasing the distance (clearance) between the conductor layers 2 having different potentials in advance. .

  Moreover, what is necessary is just to make the printing thickness of the metal paste used as the conductor layer 2 thicker than the other part in the part corresponding to the opening part 4 of the insulating layer 3. FIG. In order to make the printing thickness partially different in this way, for example, the number of times of printing may be increased in the portion where the printing thickness is relatively thicker than in other portions.

  For example, in the example of FIGS. 1B and 2, the conductor layer 2 on the lower surface of the insulating substrate 1 is sequentially provided on the main surface of the insulating substrate 1 in a part exposed at the opening 4 of the insulating layer 3. The first metal layer 6 and the second metal layer 7 are formed. This is a result of the metal paste that becomes the first metal layer 6 and the metal paste that becomes the second metal layer 7 being sequentially printed on the ceramic green sheet that becomes the mother substrate 1 and fired. That is, the number of times of printing of the metal paste in the portion corresponding to the opening 4 of the insulating layer 3 is greater than the number of times of printing of the metal paste in other portions.

The first and second metal layers 6 and 7 preferably have a thickness of about 25 μm or more in order to ensure the strength as the connection pad 5. Further, in order to suppress deformation such as warping of the wiring board, each thickness is preferably about 100 μm or less. Also,
The total thickness of the first and second metal layers 6, 7, that is, the thickness of the conductor layer 2 as the connection pad 5 is desirably about 50 μm or more, and is about about for suppressing deformation such as warping of the wiring board. It is desirable that it is 150 μm or less.

  Further, the mesh opening diameter of the plate making used for screen printing may be increased in the portion exposed at the opening 4 of the insulating layer 3. In this case, productivity is high because there is no need to increase the number of times of printing.

  As described above, by providing a portion where the thickness of the conductor layer 2 is reduced, it is possible to prevent the ceramic green sheet from being deformed when printed on the ceramic green sheet. That is, when the ceramic green sheet is thin, as the conductor layer 2 is thinner, deformation due to stress applied during printing and deformation due to the weight of the metal paste can be reduced.

  For example, as shown in FIG. 2, when a plurality of openings 4 are provided in the insulating layer 3 for one conductor layer 2, each of the plurality of openings 4 and the openings 4 and The thickness of the conductor layer 2 in the overlapping portion is thicker than the thickness of the conductor layer 2 overlapping the surrounding insulating layer 3. That is, the conductor layer 2 is thicker than the surrounding portions for each of the portions serving as the plurality of connection pads 5 (5a). Thus, since the range of the relatively thick portion of the conductor layer 2 is limited to the range necessary for improving the connection strength and the like as the connection pad 5, the entire thickness of the conductor layer 2 is unnecessary. Thickening is suppressed. Therefore, deformation such as warping as a wiring board including the insulating substrate 1 is effectively suppressed.

  In addition, since the conductor layer 2 is thicker than the other portions for each of the plurality of connection pads 5, the bonding surface between the conductor layer 2 and the insulating layer 3 is a longitudinal section at the outer peripheral portion of each connection pad 5. Since the shape is curved as viewed, it is possible to obtain an effect of improving connection reliability against thermal stress acting in the horizontal direction on the outer peripheral portion.

  Further, in the example of FIG. 1B and FIG. 2, the outer periphery of the second metal layer 7 is located outside the opening 4 of the insulating layer 3 in a plan view. Since the second metal layer 7 spreads outward from the opening 4, for example, the area of the conductor layer 2 that becomes a potential such as a power supply or ground on the lower surface of the insulating substrate 1 is increased, and the internal conductor of the wiring substrate 10 is increased. Alternatively, electromagnetic shielding (noise reduction) between the electronic component mounted on the wiring board 10 and the external electric circuit is more effectively performed.

  Further, the portion of the conductor layer 2 where only the second metal layer 7 spreads is thicker than the two-layer portion of the first and second metal layers 6 and 7 (portion serving as the connection pad 5). small. Therefore, it is easy to suppress a stress such as a thermal stress generated between the insulating substrate 1 and the conductor layer 2 to be small, and the deformation of the insulating substrate 1 due to this stress can be more effectively suppressed. Therefore, in this case, it is possible to provide a wiring substrate in which the external connection reliability in the connection pad 2 is high and the deformation of the insulating substrate 1 is suppressed.

  Moreover, in the example of FIG.1 (b) and FIG. 2, although the 2nd metal layer 7 was extended outside the opening part 4, the 1st metal layer 6 was extended outside the outer periphery of the opening part, The second metal layer 7 may be accommodated in the opening 4 in plan view. In this case, the first metal layer 6 enhances the electromagnetic shielding effect between the wiring board and the external electric circuit. Further, deformation of the insulating substrate 1 is also suppressed. That is, when the conductor layer 2 includes the first metal layer 6 and the second metal layer 7, either the first metal layer 6 or the second metal layer 7 may extend outward from the opening 4.

  In order to further increase the reliability of the external connection in the connection pad 2, the configuration in which the second metal layer 7 extends outward from the outer periphery of the opening 4 (examples of FIGS. 1 and 2) is better. There is a high possibility that a higher effect will be obtained. That is, when the second metal layer 7 extends outward from the outer periphery of the opening 4, the thermal stress generated between the wiring board and the external circuit board is dispersed in the relatively wide second metal layer 7. Is alleviated. Therefore, mechanical destruction of the bonding interface between the connection pad 5 and the insulating substrate 1 and the connection pad 5 near the interface or the insulating substrate 1 due to thermal stress is more effectively suppressed.

  Further, in the wiring board 10 of the present embodiment, the second metal layer 7 includes the one extending so as to be connected to each other between the adjacent connection pads 5. The connection pads 5 connected to each other via the second metal layer 7 are portions having the same potential as each other, for example, the connection pads 5 for power supply or ground.

  As in this example, a plurality of connection pads 5 for power supply or grounding are connected to each other via a second metal layer 7 constituting a part of each connection pad 5, thereby providing a power supply. Alternatively, the ground potential becomes more stable, and noise reduction between the wiring board and the external electric circuit becomes more effective. Moreover, since the thickness of the second metal layer 7 that connects the connection pads 5 is relatively small, deformation of the insulating substrate 1 is also effectively suppressed. Further, since the connection pads 5 are connected to each other, the thermal stress applied in the plane direction can be more efficiently reduced.

  When the connection pads 5 are connected to each other, the conductor layer 2 is arranged on the main surface of the insulating substrate 1 in a balanced manner (for example, in a point-symmetric pattern with respect to the center of the lower surface of the insulating substrate 1). It is possible to further reduce the warpage of the wiring substrate 10 (particularly the warpage of the insulating substrate 1) due to the stress caused by one or both of the difference in thermal expansion coefficient between the layer 2 and the insulating substrate 1 and / or the difference in shrinkage rate. it can.

  The plurality of connection pads 5 provided on the lower surface of the insulating substrate 1 include a grounding pad 5a, a power supply pad 5b, and a signal pad 5c. A power supply pad 5b and a ground pad 5a are located around the signal pad 5c. The signal pad 5c is surrounded by a portion extending outward from the outer periphery of the opening 4 of the second metal layer 7 constituting a part of the power supply pad 5b or the ground pad 5a. Thereby, the effect of noise reduction for the signal passing through the signal pad 5c is improved.

In the example shown in FIG. 4B, the through conductor 8 connected to the signal pad 5c is surrounded by a plurality of through conductors 8 connected to the ground pad 5a when seen from below. This is a so-called pseudo coaxial through conductor (via) structure, and this through conductor 8 is connected to the lowermost conductor layer 2 of the insulating substrate 1, so that a high-frequency signal passing through the signal through conductor 8 and the signal pad 5c. Reflection is reduced. Therefore, it is possible to suppress the characteristic impedance from changing in the vicinity of the signal pad 5c. Further, the through conductor 8 can also be connected to a portion extending so that the ground pads 5a are connected to each other (in the example of the present embodiment, a portion covered with the insulating layer 3 in the second metal layer 7). Since this is possible, the degree of freedom of arrangement of the through conductors 8 is improved.

  Further, in order to improve the connection strength of the connection pad 5 to the insulating substrate 1, it is preferable that the end portion of the through conductor 8 and the connection pad 5 overlap each other when viewed from below. That is, in such a case, the thermal stress generated in the connection pad 5 by the metal material forming the through conductor 8 can be reduced. When the areas of the respective end portions are different between the plurality of through conductors 8, a higher effect can be expected when a larger area is connected to the connection pad 5.

  However, as shown in FIG. 4B, when the second metal layer 7 forming a part of the connection pad 5 extends so as to be connected to each other between the adjacent connection pads 5. The through conductor 8 and the connection pad 5 are not necessarily connected. This is because the connection strength of the connection pad 5 to the insulating substrate 1 is enhanced by the metal layer (second metal layer 7 or the like) extending so as to be connected.

  Further, when an electronic component with a high calorific value is mounted on the wiring board 10, a heat radiating through conductor 8 may be provided in addition to the through conductor 8 as a part of the internal conductor. In the case of such a heat radiating through conductor 8, if the connecting portion between the end portion and the conductor layer 2 is a portion where the thickness of the conductor layer 2 is relatively thick, the heat dissipation can be further improved. It is.

In the case where the plurality of connection pads 5 are arranged vertically and horizontally on the main surface of the insulating substrate 1, among the plurality of connection pads 5 , those located at the corners of the rows and columns are the positions where the thermal stress is maximized. It is. Therefore, the first metal layer 6 and the second metal layer 7 may overlap at least with respect to the connection pad located at the corner portion. In this case, as in the first embodiment, a part of the connection pads 5 (for example, the second metal layer 7) extends so as to be connected to each other between the adjacent connection pads 5 . Is preferred. In this example, the connection pads 5 of the corner portion of the sequence of horizontal and vertical is a non-formed, in this case, the position of the connection pad 5 the connection pad 5 is adjacent to the corner portion which is a non-formed at the corner portion It is considered to be.

  Since the signal pad 5c normally transmits a different signal for each signal pad 5c, the connection pads (signal pads) 5 are connected to the power pad 5b and the grounding pad 5a. High reliability is required. Therefore, when the signal pads 5c are included in the plurality of connection pads 5, it is desirable that at least the signal pads 5c have a higher external connection reliability. That is, it is preferable that at least the signal pad 5c is composed of the first metal layer 6 and the second metal layer 7, and the connection pad 5 is relatively thick.

(Second Embodiment)
FIG. 5A is a bottom view showing a wiring board according to a second embodiment of the present invention, and FIG. 5B is an enlarged cross-sectional view of a main part taken along line BB in FIG. The wiring board of the second embodiment is different from the wiring board 10 of the first embodiment in the arrangement form of the conductor layer 2 and the insulating layer 3 on the lower surface of the insulating board 1, and the other points are the first embodiment. This is the same as the wiring board 10 of FIG. A description of the same points as in the first embodiment will be omitted.

  In the example shown in FIG. 5, a plurality of rectangular conductor layers 2 are provided on the outer peripheral portion of the lower surface of the insulating substrate 1. The plurality of conductor layers 2 are arranged in the center of the side portion of the outer periphery of the lower surface of the insulating substrate 1 having a quadrangular shape. Further, in a portion other than the plurality of conductor layers 2, one conductor layer 2 having a relatively large area is provided from the central portion of the lower surface of the insulating substrate 1 to the corner portion of the outer periphery.

  Similar to the description of the first embodiment, the conductor layer 2 and the insulating layer 3 are shown in an exploded manner in FIGS. 6 and 7. 6A is a bottom view showing the insulating layer 3 on the bottom surface of the wiring board shown in FIG. 5, and FIG. 6B is a bottom view showing the conductor layer 2 on the bottom surface of the wiring board shown in FIG. It is. FIG. 7 is a bottom perspective view showing a state in which the insulating layer 3 in FIG. 6A is superimposed on the conductor layer 2 in FIG. 6B. FIG. 6B can also be regarded as a perspective view of FIG.

  As shown in FIGS. 5 to 7, each of the conductor layers 2 is covered with one insulating layer 3. The insulating layer 3 is provided with a plurality of openings 4. A plurality of openings 4 are provided for one relatively large conductor layer 2. One or two openings 4 are provided for a plurality of relatively small conductor layers 2. The conductor layer 2 exposed in the plurality of openings 4 forms a plurality of ground pads 5a. The conductor layer 2 exposed in the two openings 4 forms a power supply pad 5b. The conductor layer 2 exposed in one opening 4 forms a signal pad 5c.

  Each conductor layer 2 includes a first metal layer 6 and a second metal layer 7. The first metal layer 6 has a shape and size that can be accommodated in the opening 4, and the second metal layer 7 connects the connection pads 5 (the ground pads 5a and the power pads 5b) having the same potential. It extends to. Thereby, as in the case of the first embodiment, the strength and reliability of bonding of each connection pad 5 to the insulating substrate 1 is improved. Therefore, a wiring board with high reliability of external connection can be provided.

  In the wiring board of the second embodiment, a plurality of ground pads 5a connected to each other by the relatively large conductor layer 2 are formed, so that a stable ground potential can be supplied. Further, since the two power supply pads 5b are connected to each other, the potential of the power supply is more stable. Further, since these grounding pad 5a and power supply pad 5b are arranged around the signal pad 5c, the effect of noise shielding on the signal pad 5c is enhanced.

  In the wiring substrate according to the second embodiment, a part of the conductor layer 2 having a relatively large area is formed at a corner portion where the thermal stress generated between the insulating substrate 1 (wiring substrate) and the external electric circuit (substrate 9) is large. Since a certain grounding pad 5a is arranged, the reliability of electrical connection between the wiring board 10 and the external electric circuit due to thermal stress is enhanced.

  The wiring board of the present invention is not limited to the examples of the first and second embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, the conductor layer 2 may also contain glass as with the insulating substrate 1 and the insulating layer 3. This glass component can further increase the bonding strength between the conductor layer 2 and the insulating substrate 1 and insulating layer 3.

  In this case, the glass content in a part of the conductor layer 2 forming the connection pad 5 is more on the side of the insulating substrate 1 than on the side opposite to the side of the insulating substrate 1, particularly on the surface of the connection pad 5. Larger is preferred. Thereby, while ensuring high electrical conductivity in the external connection of the conductor layer 2, the bonding strength with the insulating substrate 1 can be increased, and the plating adherence and solder wettability of the surface of the connection pad 5 can be improved.

  Regarding the portion of the conductor layer 2 where the connection pad 5 is formed (first and second metal layers 6 and 7), if the second metal layer 7 in the first metal layer 6 has a higher glass component content, The structure in which the glass content in a part of the conductor layer 2 forming the connection pad 5 is larger on the insulating substrate 1 side than on the opposite side can be easily realized. In this case, as shown in FIG. 8, the first metal layer 6 may extend outward from the opening 4 of the insulating layer 3. The wettability of the solder in the second metal layer 7 exposed in the opening 4 and having a relatively small glass component content is ensured, and the bonding strength of the connection pad 5 to the insulating substrate 1 is enhanced by the first metal layer 6. Has been enhanced. FIG. 8 is a cross-sectional view showing a modification of the wiring board shown in FIG. In FIG. 8, the same parts as those in FIG.

  In addition, as a glass component contained in the conductor layer 2, the material (silicon oxide, aluminum oxide, etc.) similar to the glass component contained in the insulated substrate 1 or the insulating layer 3, for example is mentioned. The content rate of the glass component in the conductor layer 2 should just be set, for example to about 5-20 mass% on the insulated substrate 1 side, and may be set to about 0-5 mass% on the opposite side.

  In the above description, the connection pads 5 (conductor layer 2) for external connection provided on the lower surface of the insulating substrate 1 have been mainly described. However, for connecting electronic components provided on the upper surface of the insulating substrate 1, etc. The same configuration as described above may be applied to the connection pad 5 (conductor layer 2).

  Further, as shown in FIGS. 9A and 9B, in the configuration in which the conductor layer 2 includes the first and second metal layers 6 and 7, in the portion where the insulating layer 3 covers the conductor layer 4, An auxiliary insulating layer 3 </ b> A that overlaps at least part of the insulating layer 3 in plan view may be provided between the adjacent first metal layers 6. 9A is an enlarged cross-sectional view of a main part showing a modification of FIG. 2, and FIG. 9B is an enlarged cross-sectional view of the main part showing another modification of FIG. 9, parts similar to those in FIGS. 1 and 2 are denoted by the same reference numerals.

Auxiliary insulating layer 3A in the example of these extends outwardly in part the outer peripheral portion of the thickness direction. This extended portion (not shown) is sandwiched between the upper and lower first and second metal layers 6 and 7. In this case, the joining interface between the insulating layer 3 and the conductor layer 2 is intricately shaped, the joining area of each other becomes larger, and a part of the joining surface intersects the direction in which the thermal stress acts. Become. Therefore, it is possible to provide a wiring board or the like with higher connection reliability of the connection pads 5 to the insulating substrate 1.

  In the example shown in FIG. 9A, the outer periphery of the first metal layer 6 is located outside the outer periphery of the second metal layer 7. Therefore, it is possible to increase the thickness of the conductor layer 2 in the outer peripheral portion of the connection pad 5a to which a large thermal stress is applied, and to reduce the thermal stress more effectively.

  In the example shown in FIG. 9B, the outer peripheral portion of the first metal layer 6 is embedded in the insulating substrate 1. Therefore, a so-called anchor effect is further increased between the first metal layer 6 and the insulating substrate 1. Therefore, the bonding strength of the connection pad to the insulating substrate 1 can be further improved.

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... Conductor layer 3 ... Insulating layer 4 ... Opening 5 ... Connection pad 5a ... Ground pad 5b ... Power supply pad 5c ... Signal pad 6 ..First metal layer 7 ... second metal layer 8 ... penetrating conductor
10 ... wiring board

Claims (6)

An insulating substrate having a main surface;
A conductor layer provided on the main surface of the insulating substrate;
The conductor layer covers the main surface of the insulating substrate and the entire conductor layer, and has a plurality of openings in which a part of the conductor layer is exposed, and the conductor layer exposed in the plurality of openings. And an insulating layer, a part of which forms a plurality of connection pads,
The portion of the conductor layer that overlaps each of the plurality of openings of the insulating layer is thicker than a portion that overlaps the surrounding insulating layer,
The conductor layer is composed of a first metal layer and a second metal layer sequentially provided on the main surface of the insulating substrate in the part exposed at the opening of the insulating layer,
A portion extending outward in a part of the outer peripheral portion in the thickness direction has an auxiliary insulating layer sandwiched between the first metal layer and the second metal layer ,
The insulating substrate and the conductor layer and the insulating layer contain glass,
The wiring board according to claim 1, wherein the glass content in the part of the conductor layer forming the connection pad is larger on the insulating substrate side than on the side opposite to the insulating substrate side . In the flat surface fluoroscopy, the wiring board according to claim 1, being located outside the said opening of one of the outer periphery of the first metal layer and the second metal layer is the insulating layer . The wiring board according to claim 2, wherein an outer periphery of the second metal layer is located outside the opening of the insulating layer in a plan view. 4. The wiring board according to claim 3, wherein the second metal layer extends so as to be connected to each other between the adjacent connection pads. The connection pads include a ground pad, a power pad and a signal pad,
The wiring board according to claim 2, wherein at least the signal pad includes the first metal layer and the second metal layer. The plurality of connection pads are arranged vertically and horizontally on the main surface of the insulating substrate, and the plurality of connection pads positioned at corner portions of the rows and columns are the first metal layer and the first metal layer. The wiring board according to claim 2, comprising two metal layers.

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