JP2010251618A - Wiring board, wiring board assembly, and methods of manufacturing the wiring board and the wiring board assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board and an assembly of the wiring board, capable of suppressing formation of gas reservoirs at the bottom of a via hole without causing any large-scale investment in facilities. <P>SOLUTION: The wiring board includes a groove 6 for allowing the via hole 4 to communicate with the outside within a range of a land 5, where the groove guides gas residing in the via hole 4 to the outside of the via hole 4 when filling a conductor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wiring board or a wiring board joined body, and more particularly to a wiring board or a board wiring board joined body provided with a via hole having a feature in shape. The present invention also relates to a method for manufacturing such a wiring board or a wiring board assembly.

  In order to ensure electrical connection between the layers of a multilayered wiring board (hereinafter simply referred to as “multilayer board”), by providing interlayer through holes called via holes and filling the through holes with a conductor, It is common practice to ensure conduction between layers.

  As a method for filling the via hole with a conductor, a plating method for filling the via hole with a conductor using a plating technique has been widely used (for example, Patent Document 1). However, according to the plating method, if plating is performed on a via having an opening in the conductive layer on the surface of the substrate, such as a through-hole via or a blind via, plating is also performed on the periphery of the opening of the conductive layer. , The layer thickness of the conductive layer in such a portion is increased. Since it is difficult to remove the portion where the layer thickness is increased by normal etching, it is difficult to reduce the pitch between the via holes or between the via holes and another wiring more than a certain value. Therefore, when a conductor is filled by a plating method, a pitch of 40 to 50 μm is generally the limit. However, as the integration density of the wiring board increases, it is required to further reduce the pitch, that is, to make the pitch finer.

  Therefore, in a wiring board that requires fine pitch, it is considered to use a printing method in which via holes are filled with a conductive paste, which is a paste-like conductor, using a printing technique (for example, Patent Document 2). ). According to the printing method, the thickness of the copper plating layer does not increase in the process of forming the interlayer connection unlike the plating method, and it is easy to cope with the fine pitch compared with the plating method.

JP2008-103548 JP 2001-345555 A

  However, in the printing method, for example, in a wiring board provided with conductive layers 102 and 103 on both sides of a resin layer 101 as shown in FIG. 9, the conductive paste is filled by pressing the conductive paste from the opening of the via hole 104 under pressure. Therefore, there is a problem that gas tends to remain at the bottom of the via hole 104. If the gas remains in the via hole, for example, in the reflow process in which high heat of about 260 ° C. is applied to dissolve the solder, the residual gas may thermally expand, which may impair the connection quality. In order to solve such a problem, for example, a method of performing a printing method in a vacuum atmosphere is also conceivable. However, in order to perform such a process, a large-scale capital investment is required, and there is a problem that an initial cost is increased. .

  The present invention has been made to solve such a problem, and it is possible to suppress the formation of gas accumulation at the bottom of the via hole without involving a large-scale capital investment, and the bonding of the wiring substrate. To provide a body.

  A wiring board according to the present invention includes a plurality of conductive layers electrically isolated from each other by an insulating layer, a via hole for filling a conductor electrically connecting the plurality of conductive layers, and the conductor And a groove that communicates the via hole with the outside for guiding the gas remaining inside the via hole to the outside of the via hole.

  According to the above configuration, when the conductor is pushed into the via hole because the via hole and the groove communicating with the outside are provided to guide the gas remaining inside the via hole to the outside of the via hole when the conductor is filled, The gas is easily pushed out of the via hole via this groove. Therefore, the wiring board can suppress the gas from remaining in the via hole.

  The wiring board assembly according to the present invention is a wiring board assembly in which the conductive layers provided in each of the plurality of wiring boards are electrically connected to each other. In order to electrically connect the conductive layers to each other, a via hole for filling a conductor therein, and a gas remaining inside the via hole when the conductor is filled are guided outside the via hole. And a groove communicating the via hole and the outside.

  According to the above configuration, when the conductor is pushed into the via hole because the via hole and the groove communicating with the outside are provided to guide the gas remaining inside the via hole to the outside of the via hole when filling the electric body, Gas is pushed out of the via hole via this groove. Therefore, it is a wiring board joined body which can suppress that gas remains in a via hole.

In the wiring board or the wiring board assembly according to the present invention, it is preferable that a land is further formed in the peripheral portion of the via hole, and the groove is provided within the range of the land.
According to the above configuration, since the groove is provided in the range of the land, it is possible to prevent the conductor from oozing out of the land through the groove and conducting with other circuits. Here, the land is a concept indicating a conductive portion provided around the via hole in order to ensure electrical connection, and includes a land provided for soldering.

In the wiring board or the wiring board assembly according to the present invention, it is preferable that the groove is extended outward from the outer peripheral portion of the via hole.
According to the above configuration, since the groove extends outward from the outer peripheral portion of the via hole, when the conductor is pushed into the via hole, the gas is pushed outward from the outer peripheral portion of the via hole through the groove. It is. Accordingly, the gas is suppressed from remaining in the via hole.

  In the wiring board or the wiring board assembly according to the present invention, it is preferable that a plurality of the grooves are provided, and the plurality of the grooves are provided at positions facing each other across the via hole.

  According to the above configuration, since the plurality of grooves are provided at positions facing each other across the via hole, when the conductor is pushed into the via hole by the printing method, the printing position is shifted, so that the conductor 1 Even when one groove is filled, the other groove is not filled with the conductor, and the via hole can communicate with the outside. Therefore, the gas is pushed outward from the outer peripheral portion of the via hole through one of the grooves at the facing position. Accordingly, the gas is suppressed from remaining in the via hole.

The wiring board or the wiring board assembly according to the present invention is preferably provided with four grooves.
According to the above configuration, since the four grooves are provided, even when the conductor is pushed into the via hole by the printing method, even if one groove is filled with the conductor due to the shift of the printing position. The probability that the other grooves are filled with the conductor is further reduced. In other words, the number of grooves remaining without being filled increases regardless of the direction of printing misalignment. Therefore, the via hole can be communicated with the outside by the remaining groove. Therefore, the gas is pushed outward from the outer peripheral portion of the via hole through one of the grooves at the facing position. Accordingly, the gas is suppressed from remaining in the via hole.

In the wiring board or the wiring board assembly according to the present invention, it is preferable that the size of the minimum portion of the width of the groove is smaller than the size of the diameter of the minimum portion of the via hole.
According to the above configuration, since the size of the minimum part of the width of the groove is smaller than the size of the diameter of the minimum part of the via hole, the minimum part of the width of the groove is the smallest part of the via hole and the groove. Therefore, if gas remains in the via hole when the conductor is pushed into the via hole, the result is that pressure is most applied to the smallest part of the width of the groove, and the residual gas escapes from the smallest part of the width of the groove. Become. Therefore, the effect that the gas is pushed out of the via hole through the groove is further increased.

In the wiring board or wiring board assembly according to the present invention, it is preferable that the via hole and the groove are formed by a laser beam.
According to the above configuration, since the via hole and the groove are formed by the laser beam, it can be formed in a simple and accurate shape as compared with the case of forming by etching or the like.

  In the wiring board or wiring board assembly according to the present invention, it is also preferable that the laser beam is a laser beam previously formed in the shape of the via hole and the groove using a beam element.

  According to the above configuration, since the laser beam is a laser beam pre-formed in the shape of the via hole and the groove using the beam element, the shape of the via hole and the groove shape can be easily formed on the wiring board by irradiating the laser beam. Can be formed.

  According to the present invention, it is possible to provide a wiring board and a bonded body of the wiring board that can prevent gas accumulation at the bottom of the via hole without large-scale capital investment.

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows one Embodiment of the wiring board which actualized the wiring board concerning this invention, (a) is a top view, (b) is AA sectional drawing. It is drawing which shows one Embodiment of the wiring board which actualized the wiring board concerning this invention, and is drawing which shows 1 process in the manufacturing process. (A) is a top view, (b) is sectional drawing. It is drawing which shows one Embodiment of the wiring board which actualized the wiring board concerning this invention, and is drawing which shows 1 process in the manufacturing process. (A) is a top view, (b) is sectional drawing. It is drawing which shows one Embodiment of the wiring board which actualized the wiring board concerning this invention, and is drawing which shows 1 process in the manufacturing process. (A) is a top view, (b) is sectional drawing. It is drawing which shows one Embodiment of the wiring board which actualized the wiring board concerning this invention, and is drawing which shows 1 process in the manufacturing process. (A) is a top view, (b) is sectional drawing. It is drawing which shows one Embodiment of the wiring board which actualized the wiring board concerning this invention, and is drawing which shows 1 process in the manufacturing process. (A) is a top view, (b) is sectional drawing. It is drawing which shows one Embodiment of the wiring board which actualized the wiring board concerning this invention, and is sectional drawing which shows the connection state of a conductive layer. It is drawing which shows 2nd Embodiment of the wiring board assembly which actualized the wiring board assembly concerning this invention, and is sectional drawing which shows the connection state of a conductive layer. It is drawing which shows one Embodiment of the conventional wiring board, (a) is a top view, (b) is AA sectional drawing.

(First embodiment)
Hereinafter, an embodiment of a wiring board embodying the present invention will be described with reference to FIGS. The wiring board shown in FIGS. 1A and 1B is a multilayer wiring board having a conductive layer 2 and a conductive layer 3 on both surfaces of a resin layer 1 that is an insulating layer formed of a resin. The conductive layer 2 and the conductive layer 3 are electrically connected as necessary via the via hole 4 having a substantially circular cross section. A circular region called a land 5 is formed around the via hole 4 by the conductive layer 2 to improve the reliability of electrical connection. Note that a land refers to a region formed of a conductive layer for soldering in a narrow sense, but in this specification, a region formed of a conductive layer for the above-described purpose including such a region is widely used. Called.

  This wiring board is provided with a groove 6 in the range of the land 5 for communicating the via hole 4 and the outside for guiding the gas remaining inside the via hole 4 to the outside of the via hole 4 when the conductor is filled. Yes. Since the groove 6 extends outward from the outer peripheral portion 41 of the via hole 4, when the conductive paste as a conductor is pushed into the via hole 4, the outer peripheral portion of the via hole 4 passes through the groove 6. Gas is pushed out from the outside. Accordingly, the gas is suppressed from remaining in the via hole 4. Further, since the groove 6 is provided within the range of the land 5, it is possible to prevent the conductor from seeping out to the outside of the land 5 through the groove 6 and conducting with other circuits.

  Further, when the diameter of the via hole 4 is 100 μm, the groove 6 is formed with a constant width of 30 μm. Therefore, when the conductive paste is pushed into the via hole 4, if a gas remains in the via hole 4, a stronger pressure is applied to the groove 6 than the via hole 4. Therefore, the residual gas is pushed toward the groove 6 and the effect of being pushed out of the via hole 4 is further increased.

  Further, four grooves 6 are provided at equal intervals in the circumferential direction from the peripheral portion of the via hole 4 to the outside. Therefore, the grooves 6 are arranged at positions facing each other across the via hole 4. Since the printing position for inserting the conductive paste is shifted, even when one groove 6 is entirely filled with the conductive paste, a gap remains in the facing groove 6, so that residual gas remains. It is pushed toward the groove 6 and pushed out of the via hole 4. That is, the effect of suppressing the occurrence of gas accumulation in the via hole 4 can be maintained regardless of some printing position shift. Moreover, since it is extended in four directions, it is possible to show the same effect regardless of the direction of deviation.

A method of manufacturing a wiring board including the via hole 4 and the groove 6 will be described in detail below.
As shown in FIGS. 2A and 2B, the wiring board for forming the via hole is a multilayer board having conductive layers 2 and 3 on both surfaces of a resin layer 1 which is a non-conductive layer. Wiring is performed by partially removing the conductive layers 2 and 3 as necessary, and functions as a wiring board. In the following, for the sake of simplicity, the conductive layer 2 side in the figure is the front surface, and the conductive layer 3 side is the back surface.

  Next, as shown in FIGS. 3A and 3B, by removing a part of the surface and exposing the resin layer, the land 5 and the via hole 4 and the outer peripheral portion 41 of the via hole 4 are exposed outward. The part which becomes the groove | channel 6 extended in this is formed. Such treatment may be performed by ordinary etching or the like, but may be formed by laser beam irradiation.

  As shown in FIGS. 4A and 4B, portions of the resin layer 1 that become the via holes 4 and the grooves 6 are removed, and the via holes 4 and the grooves 6 reaching the conductive layer 3 on the back surface are formed. Such treatment may be performed by ordinary etching or the like, but may be formed by laser beam irradiation. Thereafter, the smear residue is removed and the surface of the conductive layer 3 exposed in the via hole 4 and the groove 6 is formed with a fine hole, and a desmear process is performed to improve the connection reliability of the conductive paste filled in a subsequent process.

  As shown in FIGS. 5A and 5B, the conductive layer 7 on the front side and the conductive layer 3 on the back side are electrically joined by filling the via hole 4 after the desmear treatment with the conductive paste 7. More specifically, a conductive paste containing a conductive filler and a binder resin such as an epoxy resin is used as the conductive paste 7, and the via hole 4 is filled by a known screen printing method. When the conductive paste 7 is pushed into the via hole 4, the gas remaining in the via hole 4 is pushed out through the groove 6. At this time, a part of the conductive paste 7 also enters the groove 6. However, since the groove 6 is provided in the land 5, the conductive paste leaks to the outside of the land 5 and is electrically connected to other wirings and the like. Contact does not occur. That is, the groove 6 prevents the conductive paste 7 from being in electrical contact with the wiring outside the via hole.

As shown in FIG. 6, a protective film 8 called a cover lay is attached to the front side and the back side through the adhesive layer 9 so that the conductive layer 2 and the conductive layer 3 are protected. The wiring board is heated and pressurized at 240 ° C. and 50 to 40 kg / cm ² . By such treatment, the conductive paste in the via hole 4 is compressed, and partly fused with the conductive layer 2 and the conductive layer 3, whereby the conductive layer 2 and the conductive layer 3 are electrically connected via the conductive paste 7. Is done. Further, since such overheating and compression are performed in a vacuum atmosphere, the gas remaining in the groove 6 is sucked and replaced with the adhesive layer 9.

According to the wiring board of the above embodiment, the following effects can be obtained.
(1) In the above embodiment, since the via hole 4 for guiding the gas remaining inside the via hole 4 when the conductive paste 7 is filled to the outside of the via hole 4 and the groove 6 communicating the outside are provided, the conductor is the via hole. When pushed in, the gas is easily pushed out of the via hole through this groove. Therefore, the wiring board can suppress the gas from remaining in the via hole.

(2) In the above embodiment, since the groove 6 is provided in the range of the land 5, it is possible to prevent the conductive paste 7 from seeping out of the land 5 through the groove 6 and conducting with other circuits. .
(3) In the above embodiment, since the groove 6 extends outward from the outer peripheral portion of the via hole 4, when the conductive paste 7 is pushed into the via hole 4, the via hole 4 passes through the groove 6. Gas is pushed outward from the outer periphery of the. Accordingly, the gas is suppressed from remaining in the via hole 4.

  (4) In the above embodiment, since the plurality of grooves 6 are provided at positions facing each other across the via hole, when the conductor is pushed into the via hole by a printing method, the printing position is shifted, Even when one groove 6 is filled with the conductor, the other groove 6 is not filled with the conductor, and the via hole can be communicated with the outside. Therefore, the gas is pushed outward from the outer peripheral portion of the via hole 4 through any one of the grooves 6 at the facing position. Accordingly, the gas is suppressed from remaining in the via hole.

  (5) In the above embodiment, the width of the groove 6 is a constant width of 30 μm, which is smaller than the diameter of the via hole 4 of 100 μm. Therefore, when the conductive paste 7 is pushed into the via hole 4, if the gas remains in the via hole 4, the result is that the groove 6 is most pressurized, and the residual reason gas is released from this portion. Therefore, the effect that the gas is pushed out of the via hole 4 via the groove 6 is further increased.

  (6) In the above embodiment, the via hole 4 and the groove 6 may be formed by a laser beam. When the groove 6 is formed by a laser beam, it can be formed in a simple and accurate shape as compared with the case where it is formed by etching or the like.

(Second Embodiment)
Next, an embodiment of a bonded assembly of wiring boards embodying the present invention will be described as a second embodiment with reference to FIGS. The first embodiment is an embodiment in a wiring board, whereas the second embodiment is an embodiment in a bonded body of a wiring board, and the basic configuration is the same, and therefore the same parts are not described. Detailed description thereof is omitted.

  As shown in FIG. 7, in the first embodiment, the conductive layers 2 and 3 in the wiring board are electrically connected. On the other hand, as shown in FIG. 8, the second embodiment is an embodiment in which the present invention is applied to a joined body of wiring boards in which a plurality of wiring boards are electrically connected. In FIG. 7 and FIG. 8, the coverlay is omitted for the sake of simplicity.

  Thus, also in the second embodiment, except that the via hole 4 and the groove 6 are formed in the wiring board assembly in which the conductive layers 2, 3, 2a, 3a of the wiring board are electrically connected to each other. Since it is the same as that of the case of 1st Embodiment, the effect similar to the case of 1st Embodiment can be acquired.

In addition, you may change the said embodiment as follows.
In the above embodiment, the via hole 4 and the groove 6 may be created by a laser beam, but a laser beam previously formed in the shape of the via hole and the groove using a beam shaping element may be used as the laser beam. In this case, the shape of the via hole 4 and the groove 6 can be formed on the wiring board simply by irradiating the laser beam. For example, DOE (Diffractive Optical Elements) is preferably used as the beam shaping element.

  In the above embodiment, four grooves 6 are formed, but other configurations may be used. For example, the number of the grooves 6 may be two or one as long as the printing accuracy is sufficiently high and it is not a problem that the grooves 6 are filled due to printing misalignment. By reducing the number of grooves 6, the manufacturing cost can be reduced.

  If the printing accuracy is not sufficient and there is a higher possibility that the groove 6 will be filled due to printing deviation, the number of the grooves 6 may be increased. In this case, the probability that all the grooves 6 are filled due to printing misalignment can be reduced, and the occurrence of gas accumulation can be suppressed more reliably.

  -Moreover, in the said embodiment, although the width | variety of the groove | channel 6 is formed with the fixed width | variety, another structure may be sufficient. For example, the groove width may be gradually reduced from the outer peripheral portion of the via hole 4 toward the outside. Further, it may be formed integrally with the via hole 4. For example, the combined shape of the via hole 4 and the groove 6 may be a star shape.

  In the above embodiment, the groove 6 is formed at a certain depth, but may have other configurations. For example, a shape in which the depth of the groove gradually decreases from the outer periphery of the via hole 4 toward the outside may be used. In short, it is only necessary that the gas that tends to remain at the bottom of the via hole 4 can be exhausted through the groove 6, and the shape of the groove is not particularly limited.

  -In the said embodiment, there is no restriction | limiting in particular in the material of a wiring board. For example, it may be difficult to deform such as a glass substrate or a hard resin substrate, or may be flexible such as a soft resin substrate.

  Similarly, in the wiring board assembly, there is no particular limitation on the material of the wiring board to be configured. For example, wiring substrates that are difficult to deform, such as glass substrates and hard resin substrates, may be joined together, or flexible wiring substrates, such as soft resin substrates, that are joined together. Also good. Moreover, what joined the wiring board which cannot change easily, and the flexible wiring board may be used.

In the above embodiment, the wiring board assembly is obtained by joining two wiring boards, but may have other configurations. That is, three or more wiring board assemblies may be used.
In the above embodiment, the wiring board is a three-layer board having the conductive layers 2 and 3 on the front side and the back side with the resin layer 1 interposed therebetween, but may be a multilayer board having three or more layers. In such a case, the depths of the via holes 4 and the grooves 6 also differ depending on the conductive layers to be electrically joined.

  Similarly, the wiring board constituting the wiring board assembly may be a wiring board having one conductive layer or a multilayer board having two or more layers. In the case of a multilayer substrate, the depths of the via holes 4 and the grooves 6 also differ depending on the conductive layer to be electrically connected.

  The present invention relates to a wiring board or a wiring board joined body, and more particularly to a wiring base or a board wiring board joined body provided with a via hole having a feature in shape. The present invention also relates to a method for manufacturing such a wiring board or a wiring board assembly. Therefore, it can be widely used for electric devices including a wiring board.

  DESCRIPTION OF SYMBOLS 1 ... Resin layer (insulating layer) 2, 2a, 3, 3a ... Conductive layer, 4 ... Via hole, 5 ... Land, 6 ... Groove, 7 ... Conductive paste (conductor), 8 ... Protective film, 9 ... Adhesion 41, outer periphery, 101 ... resin layer, 102, 103 ... conductive layer, 104 ... via hole.

Claims (9)

A plurality of conductive layers electrically isolated from each other by an insulating layer;
A via hole for filling the inside with a conductor electrically connecting the plurality of conductive layers;
A wiring board comprising: a groove that communicates the via hole and the outside for guiding a gas remaining inside the via hole to the outside of the via hole when the conductor is filled. The conductive layer provided in each of the plurality of wiring boards is a wiring board assembly electrically connected to each other,
In order to electrically connect the conductive layers to each other, a via hole for filling a conductor inside,
A wiring board joined body comprising a groove that communicates the via hole and the outside for guiding the gas remaining inside the via hole to the outside of the via hole when the conductor is filled. A land is further formed around the via hole,
The wiring board according to claim 1, or the wiring board assembly according to claim 2, wherein the groove is provided within the range of the land.   4. The wiring board or wiring board assembly according to claim 1, wherein the groove extends outward from an outer peripheral portion of the via hole. 5.   The wiring board or the wiring board assembly according to claim 1, wherein a plurality of the grooves are provided, and the plurality of grooves are provided at positions facing each other across the via hole.   The wiring board or wiring board assembly according to claim 5, wherein four grooves are provided.   7. The wiring board or wiring board assembly according to claim 1, wherein a size of a minimum part of the width of the groove is smaller than a size of a diameter of the minimum part of the via hole.   The method for manufacturing a wiring board or a wiring board assembly according to claim 1, wherein the via hole and the groove are formed by a laser beam.   9. The method for manufacturing a wiring board or a wiring board assembly according to claim 8, wherein the laser beam is a laser beam previously formed in the shape of the via hole and the groove.

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