JP2005183799A - Multilayer print-circuit board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer print-circuit board in which a blind via having high reliability is formed, and a manufacturing method for the multilayer print-circuit board capable of easily forming the blind via having the high reliability. <P>SOLUTION: The multilayer print-circuit board is constituted so as to arrange cores 11a and 11b on the surface layer side. The multilayer print-circuit board is constituted so as to form the blind vias 13a and 13b and receiving lands 14a and 14b for the blind vias 13a and 13b to the cores 11a and 11b, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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) serving as wiring board base materials 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.

  In general, this type of multilayer printed wiring board has prepregs disposed on the surface layer side, and prepregs and cores are alternately laminated, and are laminated and integrated by applying temperature and pressure.

  At this time, there is a large difference in the finishing accuracy of the insulating layers of the core and the prepreg. The core has a higher finishing accuracy of the insulating layer than the prepreg. The reason for this is that the copper foil and the insulating layer are integrally formed in the core before the printed wiring board is manufactured, and the accuracy of the copper foil, the insulating layer and each flat surface is high. There is little variation in length. On the other hand, the prepreg has a role of filling the step difference of the inner layer pattern with an insulating resin. Therefore, the thickness of the insulating layer depends on the pattern density of the inner layer and also varies depending on the lamination conditions. For this reason, the variation in the thickness of the prepreg is large, and the center value and the degree of variation vary depending on the position in the plane. Also, the pattern shape and pattern density change each time the design of the printed wiring board changes. Accordingly, the thickness of the insulating layer using the prepreg is not constant and varies greatly, and the finishing accuracy is very poor compared to the core.

At this time, when providing a blind via by drilling in the wiring board body having the laminated structure as described above, the depth control of the hole by drilling greatly influences the normal blind via formation, and the prepreg was used. Since the finish of the blind via greatly depends on the finish accuracy of the insulating layer, there are problems in various aspects such as electrical reliability, manufacturability, and yield. In particular, in recent years, higher density and thinner thickness of multilayer printed wiring boards have been demanded, and the above problems have become more prominent.
Japanese Patent Laid-Open No. 8-32233

  As described above, in the conventional blind via machining technique, a drill is drilled in a core member, and the tip in the drilling direction is brought into contact with a land formed in the core member to form a blind via. The processing depth control has a great influence on the formation of normal blind vias, and there are problems in various aspects such as electrical reliability, manufacturability, 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 print comprising a wiring board body in which a core is arranged on the surface layer side, and cores and prepregs are alternately laminated and integrated, and a blind via provided in the core on the surface layer side of the wiring board body. Features a wiring board.

  The present invention also includes a step of manufacturing a wiring board body in which the core is arranged on the surface layer side, and the core and the prepreg are alternately laminated and integrated, and a blind via is formed in the core on the surface layer side of the wiring board body. The manufacturing method of a multilayer printed wiring board provided with the process to do.

  A multilayer printed wiring board provided with blind vias with high electrical reliability can be easily realized with high yield by drilling.

  Embodiments of the present invention will be described below with reference to the drawings. A multilayer printed wiring board according to an embodiment of the present invention has a laminated arrangement of base materials (prepregs and cores) constituting a printed wiring board, and a core that forms a blind via is arranged on the surface layer side in all multilayer structures. ing.

The structure of the multilayer printed wiring board according to the first embodiment of the present invention is shown in FIG.
The first embodiment shows a printed wiring board 10 having a four-layer structure. The printed wiring board 10 has four layers (L1 to L4) sandwiching an insulating layer (prepreg) 12a between two cores (copper-clad laminates) 11a and 11b.

  The cores 11a and 11b arranged on the surface layer side are provided with blind vias 13a and 13b and receiving lands 14a and 14b, respectively.

  The receiving lands 14a and 14b are formed at the same time corresponding to the positions where the blind vias 13a and 13b are formed when the wiring pattern on the inner layer side of the cores 11a and 11b is formed (in the etching process). The blind vias 13a and 13b have a predetermined diameter from a surface layer (L1, L4) side of the cores 11a and 11b to a depth in contact with the receiving lands 14a and 14b provided correspondingly via the insulating layers of the cores by drilling. It is formed by drilling a hole and applying predetermined plating to the inner wall of the hole. The blind via 13a connects the first layer (L1) and the second layer (L2) in a circuit, and the blind via 13b connects the fourth layer (L4) and a third layer (L3) in a circuit.

The structure of the multilayer printed wiring board according to the second embodiment of the present invention is shown in FIG.
This second embodiment shows a printed wiring board 20 having a six-layer structure. The printed wiring board 20 includes two cores 21a and 21b as a surface layer, and insulating layers (prepregs) 22a and 22b interposed between the three cores 21a, 21b, and 21c including the cores. Layers (L1 to L6) are formed.

  The cores 21a and 21b arranged on the surface layer side are provided with blind vias 23a and 23b and receiving lands 24a and 24b, respectively. Since the structures of the blind vias 23a and 23b received by the receiving lands 24a and 24b are the same as those in the first embodiment, the description thereof is omitted here. In the second embodiment, the first layer (L1) and the second layer (L2) are circuit-connected by the blind via 23a, and the sixth layer (L6) and the fifth layer (L5) are circuit-connected by the blind via 23b. Is done. Inner layer signal patterns 25 and 25 are provided in the third layer (L3) and the fourth layer (L4) formed by the core 21c provided in the inner layer, respectively.

The structure of the multilayer printed wiring board according to the third embodiment of the present invention is shown in FIG.
The third embodiment shows a printed wiring board 30 having an eight-layer structure. The printed wiring board 30 has two cores 21a and 21b as a surface layer, and insulating layers (prepregs) 32a, 32b, and 32c interposed between four cores 31a, 31b, 31c, and 31d including the cores, respectively. Thus, eight layers (L1 to L8) are formed.

  The cores 21a and 21b arranged on the surface layer side are provided with blind vias 33a and 33b and receiving lands 34a and 34b, respectively. Since the structure of the blind vias 33a and 33b received by the receiving lands 34a and 34b is the same as that of the first embodiment, the description thereof is omitted here. In the third embodiment, the first layer (L1) and the second layer (L2) are connected in circuit by the blind via 33a, and the eighth layer (L8) and the seventh layer (L7) are connected in circuit by the blind via 33b. Is done. The third to sixth layers (L3 to L6) formed by the cores 31c and 31d provided on the inner layer are provided with inner layer signal patterns 35 (3) to 35 (6), respectively.

The structure of the multilayer printed wiring board according to the fourth embodiment of the present invention is shown in FIG.
The fourth embodiment shows a printed wiring board 40 having a 10-layer structure. The printed wiring board 40 has two cores 41a and 421b as a surface layer, and insulating layers (prepregs) 42a, 42b, and 42c between five cores 41a, 41b, 41c, 41d, and 41e including the cores, respectively. , 42d are interposed to form 10 layers (L1 to L10).

  The cores 41a and 41b arranged on the surface layer side are provided with blind vias 43a and 43b and receiving lands 44a and 44b, respectively. Since the structures of the blind vias 43a and 43b received by the receiving lands 44a and 44b are the same as those in the first embodiment, the description thereof is omitted here. In the fourth embodiment, the first layer (L1) and the second layer (L2) are circuit-connected by the blind via 43a, and the tenth layer (L10) and the ninth layer (L9) are circuit-connected by the blind via 43b. Is done. The third to eighth layers (L3 to L8) formed by the cores 41c, 41d, and 41e provided on the inner layer are provided with inner layer signal patterns 45 (3) to 35 (8), respectively.

  As shown in each of the above-described embodiments, by using a laminated structure in which the core for forming the blind via is disposed on the surface layer side, the blind via by drilling can be easily performed with a stable structure with high electrical reliability and high yield. realizable.

Next, the embodiment of FIG. 5 of the present invention will be described with reference to FIGS.
In the fifth embodiment, in a multilayer printed wiring board in which a core for forming a blind via is disposed on the surface layer side, a hole having a predetermined diameter is formed by drilling in the core disposed on the surface layer side. When forming the blind via by bringing the tip in the drilling direction into contact with the land formed on the core, by forming the receiving land of the blind via formed on the core thicker than the thickness of the wiring pattern formed on the core, The tolerance of dimensional accuracy in the depth direction required for drilling can be expanded, and a sufficient joint area can be secured between the blind via and its receiving land, which ensures electrical reliability in a high yield state. High-quality blind vias can be easily formed.

  FIG. 5 shows a blind via structure of a multilayer printed wiring board according to the fifth embodiment of the present invention. In this multilayer printed wiring board, a core for forming a blind via is arranged on the surface layer side, and a core (copper-clad laminate) 50 and an insulating layer (prepreg) 58 are laminated by alternately applying temperature and pressure. It consists of layers. This multilayer printed wiring board having an n-layer structure includes through-holes 53 penetrating all layers, blind vias 51 penetrating only from the first layer (L1) to the second layer (L2), and wiring patterns of the surface layer and the inner layer 54-1, 54-2, 54-3, and so on.

  The multilayer printed wiring board shown in FIG. 5 is formed on the second layer (L2) and the (n-1) th layer (Ln-1) formed on the inner layer side surface of the cores 50, 50 arranged on the surface layer side. The receiving lands 52 and 52 of the blind vias 51 and 51 are provided, and the first layer (surface layer) and the second layer (L2), and the nth layer (surface layer) and the n-1th layer are provided by the blind vias 51 and 51. An example in which (Ln-1) is connected in a circuit is shown.

  Here, the receiving lands 52 and 52 of the blind vias 51 and 51 are formed thicker than the inner layer wiring pattern thickness of the same layer, as shown in the figure. For example, when the conductor thickness of the wiring pattern 54-2 of the second layer (L2) is Th1, the second conductor (L2) formed on the inner layer side surface of the cores 50, 50 arranged on the surface layer side includes the conductor A receiving land 52 having a conductor thickness Th2 thicker than the thickness Th1 is formed. A via receiving land 52 having a conductor thickness (Th2) similar to that of the second layer (L2) is also formed in the n-1th layer (Ln-1).

  A hole having a predetermined diameter is drilled in the core 50, 50 on the surface layer side provided with the receiving lands 52, 52 from the surface layer side to the depth contacting the receiving lands 52, 52 through the insulating layer of the core. By applying predetermined plating to the inner wall of the hole, blind vias 51 and 51 for circuit connection between the respective layers (between L1 and L2 and between Ln and Ln-1) are formed.

  As described above, by making the conductor thickness of the receiving lands 52 and 22 that receive the blind vias 51 and 51 larger than the conductor thickness of the wiring pattern 54 (TH1 <TH2), the dimension in the depth direction required for the drilling is described. Since the allowable range of accuracy can be expanded, a multilayer printed wiring board having a highly reliable blind via can be manufactured with a good yield at all times. Further, by making the conductor thickness of the receiving lands 52 and 52 thicker than the conductor thickness of the wiring pattern 14, the junction area of the receiving lands 52 and 52 in the blind vias 51 and 51 is increased, and stable blind vias with less electrical resistance are obtained. In addition, the circuit thickness of the wiring pattern can be reduced without being conscious of the conductor thickness of the via receiving land, thereby contributing to the reduction in thickness of the multilayer printed wiring board. 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. 6 shows an example of processing the via receiving lands 52 and 52 having a conductor thickness Th2 that is thicker than the conductor thickness Th1 of the wiring pattern described above.

  In the via receiving land processing step shown in FIG. 6, the copper foils 5a and 5b (see FIG. 6 (a)) on each surface of the core 50 arranged on the surface layer side where the blind via is formed are etched for each surface. In addition, the wiring patterns 5p, 5p,... Are formed for each surface, and the land 6p that is the basis of the receiving land 52 is simultaneously formed on the surface on the inner layer side (see FIG. 6B). Thereafter, the conductive paste 7p is printed on the land 6p by the squeegee 60 and cured (see FIG. 6C). By this process, as shown in FIG. 6 (d), a multilayer printed wiring board in which the core 50 arranged on the surface layer side where the blind via is formed is thickened only in the portion of the receiving land 52 that receives the blind via 51. Can be formed.

  According to the fifth embodiment, the receiving lands 52, 52 of the blind vias 51, 51 are formed thicker than the inner layer wiring pattern thickness of the same layer, so that the blind vias 51, 51 are formed. The allowable range of dimensional accuracy in the depth direction required for drilling can be expanded, and a multilayer printed wiring board having a highly reliable blind via can be manufactured with a good yield at all times. Furthermore, by making the conductor thickness of the via receiving lands 52 and 522 larger than the conductor thickness of the wiring pattern 54 (54-1, 54-2,...), The via receiving lands 52 and 52 are joined in the blind vias 51 and 51. Reduced multilayer printed wiring boards by increasing the area and forming a stable blind via circuit with low electrical resistance and reducing the conductor thickness of the wiring pattern without considering the conductor thickness of the via receiving land can do. Furthermore, since the blind via structure according to this embodiment forms the blind via by the hole drilled in the core member, the plated layer due to thermal stress caused by the difference in thermal expansion coefficient between the plated layer on the inner wall of the blind via and the insulating layer A highly reliable blind via can be formed without any risk of cracking.

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. Sectional drawing which shows the structure of the multilayer printed wiring board which concerns on 3rd Embodiment of this invention. Sectional drawing which shows the structure of the multilayer printed wiring board which concerns on 4th Embodiment of this invention. Sectional drawing which shows the structure of the multilayer printed wiring board which concerns on 5th Embodiment of this invention. Process drawing which shows the processing process of the via receiving land which concerns on 5th Embodiment of this invention.

Explanation of symbols

  10, 20, 30, 40 ... multilayer printed wiring board, 11a, 11b, 21a-21c, 31a-31d, 41a-41e, 50 ... core (copper-clad laminate), 12a, 22a, 22b, 32a-32c, 42a ... 42d, 58 ... Insulating layer (prepreg), 13a, 13b, 23a, 23b, 33a, 33b, 43a, 43b, 51 ... Blind via, 14a, 14b, 24a, 24b, 34a, 34b, 44a, 44b, 52 ... Receiving land.

Claims (6)

A wiring board body in which the core is arranged on the surface layer side, and the core and the prepreg are alternately laminated and integrated,
A multilayer printed wiring board, comprising: a blind via provided in a core on the surface layer side of the wiring board main body. A receiving land is provided on the inner layer surface of the core on the surface layer side corresponding to the position where the blind via is formed,
2. The multilayer printed wiring board according to claim 1, wherein the blind via is formed by drilling a hole reaching the receiving land from a surface layer surface of the surface layer side core and plating the inner wall of the hole. 3. .   The multilayer printed wiring board according to claim 2, wherein the receiving land provided on the inner layer surface of the core on the surface layer side is formed thicker than the other conductor pattern provided on the inner layer surface of the core on the surface layer side. A step of manufacturing a wiring board body in which the core is arranged on the surface layer side, and the core and the prepreg are alternately laminated and integrated;
And a step of forming a blind via in the core on the surface layer side of the wiring board main body. Prior to the lamination, a receiving land is provided on the inner layer surface of the core on the surface layer side corresponding to the formation position of the blind via,
The step of forming the blind via includes
Drilling a hole reaching the receiving land from the surface layer of the surface layer side core by drilling in the wiring board body;
The method for producing a multilayer printed wiring board according to claim 4, further comprising a step of plating the inner wall of the hole.   The receiving land that receives the blind via is formed by etching the inner layer pattern of the receiving land on the inner layer surface of the core on the surface layer side, and then printing and curing a conductive paste on the inner layer pattern surface of the receiving land. 6. The method of manufacturing a multilayer printed wiring board according to claim 5, wherein the conductor is formed to have a predetermined conductor thickness.

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