JP2005166764A - Multilayer printed wiring board and method for producing multilayer printed wiring board - Google Patents

Abstract

It is an object of the present invention to provide a multilayer printed wiring board provided with a highly reliable blind via and a method for manufacturing a multilayer printed wiring board capable of easily forming a highly reliable blind via.
A via receiving land having a conductor thickness Th2 that is thicker than a conductor thickness Th1 of a wiring pattern 14 is formed in a third layer (L3) of the core member 10, and the core member 10 provided with the via receiving land 12 is provided. Then, by drilling, a hole with a predetermined diameter is drilled from the surface direction facing the via receiving land 12 through the insulating layer 18 to a depth in contact with the via receiving land 12, and predetermined plating is applied to the inner wall of the hole As a result, the blind via 11 for connecting the circuits between L1 and L3 is formed.
[Selection] Figure 1

Description

  The present invention relates to a multilayer printed wiring board applied to various electronic circuits and a method for manufacturing the multilayer printed wiring board.

  In various small electronic devices including information processing devices, multilayer printed wiring boards in which insulating layers (prepregs) and cores (copper-clad laminates) are alternately laminated are widely used. In this type of multilayer printed wiring board, in addition to the wiring pattern, a through hole that penetrates the laminated wiring board, a blind via hole that does not penetrate the wiring board, and the like are provided.

  As a technique for forming blind vias in multilayer printed wiring boards, conventionally, via holes are drilled in the insulating layer toward the core member, and the tip of each hole is brought into contact with an inner land formed in the core member to blind blind vias. In order to reduce cracks in the plating layer due to thermal stress due to the difference in thermal expansion coefficient between the plating layer on the inner wall of the blind via and the insulating layer, the conductor layer is formed on the via formation peripheral part (hole formation peripheral part). There is a technique for thinning the insulating layer in the periphery of the via formation. As described above, in the prior art, the thickness of the insulating layer is reduced with respect to the blind via formed by drilling the insulating layer toward the core member. The crack of the plating layer due to the thermal stress caused by the difference in thermal expansion coefficient is reduced.

  However, conventionally, a blind via processing technique in which a hole having a predetermined diameter is formed in a core member by drilling, and a tip of the hole in the drilling direction is brought into contact with a land formed in the core member to form a blind via. There was no effective technique to improve the yield.

In particular, in recent years, signal patterns on printed wiring boards tend to become thinner and thinner due to high density wiring. In order to form a thin signal pattern (wiring pattern), it is desirable in terms of pattern formation and yield to reduce the thickness of the wiring pattern (conductor thickness). Usually, the blind via receiving land is formed simultaneously with the wiring pattern of the same layer by pattern etching or the like. Therefore, if the thickness of the wiring pattern is reduced, the conductor land of the blind via receiving land is also reduced. When the conductor thickness of the blind via receiving land is reduced, the blind via is formed in the core member by drilling as described above and the tip in the drilling direction is brought into contact with the land formed in the core member. In this processing technology, drilling depth control greatly affects the formation of normal blind vias, resulting in yield problems. Specifically, when the hole formed in the core member is shallow, a defect due to unconnected circuit is caused, and when the hole is deep, a defect due to circuit connection with another layer at the tip of the drilling direction is caused. Occurs. Further, at this time, a laminated structure with the insulating layer as a surface layer is common, and the dimensional accuracy in the thickness direction of the insulating layer is inferior to the dimensional accuracy in the thickness direction of the core. Become prominent.
Japanese Patent Laid-Open No. 8-32233

  As described above, conventionally, in the blind via machining technique in which a drill is drilled in a core member and a blind via is formed by abutting a tip formed in the drilling direction on a land formed in the core member. Control of the processing depth has a great influence on the formation of normal blind vias, and there are problems in terms of ease of blind via processing and yield.

  The present invention has been made in view of the above circumstances, and provides a multilayer printed wiring board provided with a highly reliable blind via and a method for manufacturing a multilayer printed wiring board capable of easily forming a highly reliable blind via. With the goal.

  The present invention relates to a multilayer printed wiring board in which a drill is drilled in a core member and a blind via is formed by contacting a tip formed in the drilling direction with a land formed in the core member. The formed wiring pattern, the receiving land of the blind via formed in the core in a direction protruding from the surface of the wiring pattern, and the core are formed from the surface facing the receiving land, And a blind via formed at its front end in contact with the receiving land.

  In the present invention, a land and a wiring pattern for receiving a blind via are formed in the core portion, a hole having a predetermined diameter is drilled from a surface of the core portion facing the land forming surface, and the drilled hole is formed. In the method of manufacturing a printed wiring board, in which a blind via is formed on the core portion through an insulating layer by plating the inner wall of the substrate and the land surface in contact with the hole, the tip end portion of the blind via in the drilling direction The land receiving the via via is provided with a conductor thickness larger than that of the wiring pattern in the same layer.

  A highly reliable blind in a multilayer printed wiring board in which a drill hole is drilled to a predetermined diameter in the core member, and a blind via is formed by contacting the tip of the hole in the drilling direction with a land formed in the core member. A multilayer printed wiring board provided with vias can be easily realized with a high yield.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the present invention, a hole having a predetermined diameter is drilled in a core member by drilling, and a blind via is formed in the core member when a tip in the drilling direction is brought into contact with a land formed in the core member. By forming the land (the receiving land of the blind via) thicker than the thickness of the wiring pattern formed on the core member, it is possible to expand the allowable range of dimensional accuracy in the depth direction required for drilling, A sufficient bonding area can be ensured between the blind via and its receiving land, so that a highly reliable blind via can be easily formed in a high yield state.

  FIG. 1 shows a blind via structure of a multilayer printed wiring board 1A according to the first embodiment of the present invention. This multilayer printed wiring board 1A is composed of n layers in which insulating layers (prepregs) 18 and core members (copper-clad laminates) 10 are alternately laminated by applying temperature and pressure. The n-layer multilayer printed wiring board 1A includes a through hole 13 that penetrates all layers, a blind via 11 that penetrates only to a predetermined layer, and a wiring pattern 14 (inner wiring patterns 14-1, 14-2, ...).

  A multilayer printed wiring board 1A shown in FIG. 1 includes a third layer (L3) and a (n-1) th layer (Ln-1) of the core member 10 provided in the second layer (L2) and the third layer (L3). Receiving lands 12 and 12 for the blind vias 11 and 11 are provided in the n-2th layer (Ln-2) of the core member 10 provided in the n-2th layer (Ln-2). , 11 shows an example in which the first layer (surface layer) and the third layer (L3), and the n-th layer (surface layer) and the n-2th layer (Ln-2) are connected to each other.

  Here, the receiving lands (hereinafter referred to as via receiving lands) 12 and 12 of the blind vias 11 and 11 are formed thicker than the inner layer wiring pattern thickness of the same layer as shown in the figure. For example, if the conductor thickness of the wiring pattern 14-3 on the third layer (L3) is Th1, the via receiving land 12 having a conductor thickness Th2 that is thicker than the conductor thickness Th1 is formed on the third layer (L3) of the core member 10. Is done. Via receiving lands 12 having the same conductor thickness (Th2) as the third layer (L3) are also formed in the n-2th layer (Ln-2).

  The core members 10 and 10 provided with the via receiving lands 12 and 12 are drilled to the via receiving lands 12 and 12 from the surface direction facing the via receiving lands 12 and 12 through the insulating layers 18 and 18. Blind vias 11 for connecting circuits between the layers (between L1 and L3 and between Ln and Ln-2) by drilling holes with a predetermined diameter to a depth in contact with each other and applying predetermined plating to the inner walls of the holes , 11 are formed. The drilling process and the plating process at this time are illustrated in FIGS. 4 (a) and 4 (b).

  As described above, by making the conductor thickness of the via receiving lands 12 and 12 larger than the conductor thickness of the wiring pattern 14 (TH1 <TH2), the allowable range of the dimensional accuracy in the depth direction required for the drilling process is expanded. Therefore, it is possible to manufacture a multilayer printed wiring board having blind vias with high reliability at a high yield. Furthermore, by making the conductor thickness of the via receiving lands 12 and 12 thicker than the conductor thickness of the wiring pattern 14, the junction area of the via receiving lands 12 and 12 in the blind vias 11 and 11 is increased, and the electrical resistance is stable and less. A circuit of a blind via can be configured, and the conductor thickness of the wiring pattern can be reduced without being aware of the conductor thickness of the via receiving land, which can contribute to the thinning of the multilayer printed wiring board 1A. Further, in the blind via structure according to this embodiment, since the blind via is formed in the hole drilled in the core member, the difference in thermal expansion coefficient between the plated layer and the insulating layer of the inner wall of the blind via as described above. Thus, a highly reliable blind via can be configured without the risk of causing cracks in the plating layer due to thermal stress caused by the above.

  FIG. 3 shows a processing example of the via receiving lands 12 and 12 when forming the via receiving lands 12 having the conductor thickness Th2 which is thicker than the conductor thickness Th1 of the wiring pattern described above. The process shown in FIG. 3 shows an example in which the above-described thick via receiving lands are formed on both surfaces of the copper-clad laminate 30 serving as the core member 10.

  The via receiving land processing step shown in FIG. 3 is performed by first etching the copper stays 31 on each surface of the copper clad laminate 30 serving as the core member 10 for each surface (see FIG. 3A). Each of the wiring patterns 31-1, 31-1,..., 31-2, 31-2,... And the lands 32-1 and 32-2 that form the basis of the via receiving land 12 are simultaneously formed (see FIG. 3 (b)). Thereafter, the conductive pastes 41-1 and 41-2 are printed on the lands 32-1 and 32-2, respectively, by the squeegee 40 and cured (see FIGS. 3C to 3E). With this process, the conductor thickness can be increased only in the via receiving lands 12 and 12 that receive the blind vias 11 and 11.

  FIG. 2 shows a blind via structure of the multilayer printed wiring board 1B according to the second embodiment of the present invention. Unlike the above-described first embodiment, the multilayer printed wiring board 1 </ b> B forms a surface layer by the core member 20, and forms an n layer by alternately stacking the insulating layers 28 and the core member 20. In this multilayer printed wiring board 1B having an n-layer structure, through holes 23 penetrating all layers, blind vias 21 provided in the core member 20 on which the surface layer is formed, and wiring patterns 24 (24-1, 24-2). ,...

  A multilayer printed wiring board 1B shown in FIG. 2 includes a first layer (L1) serving as a surface layer, a second layer (L2) of the core member 20 provided on the second layer (L2), and an nth layer (Ln) serving as a surface layer. ) And the n-1 layer (Ln-1) of the core member 20 provided in the n-1 layer (Ln-1) are provided with receiving lands 22 and 22 for the blind vias 21 and 21, respectively. 21 and 21 show an example in which the first layer (surface layer) and the second layer (L2), and the n-th layer (surface layer) and the n-1th layer (Ln-1) are connected to each other.

  In the second embodiment, as in the first embodiment, the receiving lands 22 and 22 of the blind vias 21 and 21 are formed thicker than the inner wiring pattern thickness of the same layer. As a result, the tolerance range of the dimensional accuracy in the depth direction required for drilling when forming the blind vias 21 and 21 can be expanded, and a multilayer having a highly reliable blind via always in a good yield state. A printed wiring board can be manufactured. Furthermore, by making the conductor thickness of the via receiving lands 22 and 22 thicker than the conductor thickness of the wiring pattern 24, the junction area of the via receiving lands 22 and 22 in the blind vias 21 and 21 is increased, and the electrical resistance is stable and less. The circuit of the blind via can be configured, and the thickness of the wiring pattern conductor can be reduced without being aware of the conductor thickness of the via receiving land, so that the multilayer printed wiring board 1B can be reduced in thickness. Furthermore, since the blind via structure according to this embodiment forms the blind via by the hole drilled in the core member, the difference in the thermal expansion coefficient between the plating layer and the insulating layer of the inner wall of the blind via as described above. A highly reliable blind via that does not cause a crack of the plating layer due to the resulting thermal stress can be configured.

Sectional drawing which shows the structure of the multilayer printed wiring board which concerns on 1st Embodiment of this invention. Sectional drawing which shows the structure of the multilayer printed wiring board which concerns on 2nd Embodiment of this invention. Process drawing which shows the processing process of the via receiving land which concerns on embodiment of this invention. Process drawing which shows the drill process and plating process of the via receiving land which concern on embodiment of this invention.

Explanation of symbols

  1A, 1B ... multilayer printed wiring board, 10, 20 ... core member (copper-clad laminate), 11, 21 ... blind via, 12, 22 ... via receiving land, 13, 23 ... through hole, 14-1, 14- 2, 24-1, 24-2, 24-3 ... wiring pattern, 18, 28 ... insulating layer (prepreg), TH1 ... conductor thickness of wiring pattern, TH2 ... conductor thickness of via receiving land.

Claims (6)

The core,
A wiring pattern formed on the core, and a land thicker than the wiring pattern;
A multilayer printed wiring board, comprising: a blind via formed in the core in a surface direction opposite to the land, the tip of the drilling direction being in contact with the land.   2. The multilayer print according to claim 1, wherein the blind via is formed by drilling a hole reaching the land from a surface facing the land forming surface of the core and plating the inner wall of the hole. Wiring board.   3. The multilayer print according to claim 2, wherein the blind via is formed by plating an inner wall of a hole extending from a surface layer formed of an insulating layer to a land provided in the inner layer core through an inner layer core provided with the land. Wiring board.   The multilayer printed wiring board according to claim 2, wherein the blind via is formed by plating an inner wall of a hole extending from a surface layer formed by the core to a land provided in the core via the core. A land and a wiring pattern for receiving blind vias are formed in the core portion, a hole having a predetermined diameter is drilled from a surface direction of the core portion facing the land forming surface, and an inner wall of the drilled hole and its inner wall In the method of manufacturing a printed wiring board in which the land surface in contact with the hole is plated and a blind via is formed in the core portion without an insulating layer or an insulating layer.
A method of manufacturing a multilayer printed wiring board, wherein a conductor thickness of a land that receives the blind via provided at a front end portion of the blind via is made thicker than the wiring pattern of the same layer.   The land that receives the blind via is formed by etching an inner layer pattern on the core portion, and then printed and cured with a conductive paste on the surface of the inner layer pattern portion that corresponds to the land that receives the blind via. The method for producing a multilayer printed wiring board according to claim 5, wherein the multilayer printed wiring board is formed.

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