JP2007220953A - Multilayer printed circuit board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent exfoliation of a soldered surface from a land while eliminating the need of increasing the size of the land. <P>SOLUTION: A multilayer printed circuit board 10 has a through-hole and land 20, and part of the land is covered with an insulating resin. Or the land is provided on an inner layer 1 of the printed circuit board to be connected to the through-hole in the inner layer 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multilayer printed circuit board and a manufacturing method thereof, and more particularly to a multilayer printed circuit board having lands suitable for use of lead-free solder and a manufacturing method thereof.

  Conventionally, there has been a problem that a land is peeled off in soldering a lead insertion part by lead-free solder. The land peeling will be described with reference to FIG.

  FIGS. 10A and 10B show through-hole cross sections. After inserting a lead terminal 801 of a component, soldering is performed with a solder jet apparatus. After confirming that the solder has wetted with respect to the lead terminal 801 and formed the solder fillet 803, the solder is rapidly solidified when the substrate is pulled up. Therefore, contraction stress acts in the direction shown in FIG. 10A due to solidification shrinkage of lead-free solder. As shown in FIG. 10B, the shrinkage stress causes land separation between the land 802 and the insulating resin 805 of the multilayer printed board 804, which causes a decrease in reliability.

  For example, Japanese Patent Application Laid-Open No. 2005-044990 discloses a technique for preventing land peeling. The technology prevents land peeling by providing a via hole in the land to increase the adhesion between the land and the insulating resin.

JP 2005-044990 A

However, according to the technique described in Japanese Patent Application Laid-Open No. 2005-044990, since it is necessary to provide via holes in the lands, the land size increases, which becomes a barrier to achieving high-density mounting and high-density wiring.
Accordingly, an object of the present invention is to prevent land peeling on the solder surface without increasing the size of the land.

  In order to achieve the above object, the multilayer printed board of the present invention has a through hole and a land, and the land is partially covered with an insulating resin.

  Since a part of the land is covered with the insulating resin, it is possible to prevent the solder surface from being peeled off without increasing the size of the land.

Next, the best embodiment of the present invention will be described.
(First embodiment)
A first embodiment of the present invention will be described with reference to FIG.

  FIG. 1 is a view showing a cross-section of a through hole according to a first embodiment of the present invention.

  Referring to FIG. 1, a multilayer printed board 10 according to the first embodiment of the present invention includes an inner layer land 1, an insulating resin 2, a lead terminal 3, a solder fillet 4, an outer layer land 5, a connection layer 6, and an opening 7. .

  The inner layer land 1 is a land provided in the inner layer of the multilayer printed board 10. The inner layer land 1 is an inner layer of the multilayer printed board 10 and is connected to the plating of the inner wall surface of the through hole 20. Here, the multilayer printed circuit board 10 may have any number of layers, and the inner layer land 1 may be provided in any one of the inner layers.

  By providing the inner layer land 1 in the layer closest to the solder surface of the multilayer printed board 10, the effect of improving the solder wet-up property into the through hole can be obtained. For example, in a multilayer printed board having four layers, when the fourth layer is a solder surface, an inner layer land may be provided in the third layer.

  Although the shape seen from the direction perpendicular | vertical with respect to the surface of the multilayer printed circuit board of the inner-layer land 1 is not specifically limited, Usually, it is comprised by circular shape. The land size of the inner layer land 1 is preferably smaller than the outer layer land 5 in consideration of the mounting density. However, it may be configured in the same size as the outer land 5.

  The inner land 1 is covered with the insulating resin 2 of the multilayer printed board 10 at the outer periphery. The multilayer printed board 10 is configured by laminating the insulating resin 2, but the inner land 1 is covered with an insulating resin of a specific layer of the insulating resin. The insulating resin 2 is made of a general material such as a glass epoxy material or polyimide, and is not limited to a specific material.

  Thus, since the insulating resin 2 has a structure that covers the outer peripheral portion of the inner layer land 1, it is possible to suppress the shrinkage stress of the solder fillet and to prevent the land peeling.

  A portion of the inner land 1 is exposed through the opening 7. A solder fillet 4 is formed on the exposed portion of the inner land 1 and is soldered to the lead terminal 3. Here, the necessary land exposure amount of the inner layer land 1 may be a minimum amount that can ensure solder wetting. As a specific example, the land exposure amount may be configured to be about the hole diameter of the through hole 20 +0.65 mm. However, the land exposure amount is not limited to this, and it may be configured to be the minimum amount that can ensure solder wetting.

  The lead terminal 3 is connected to the connection layer 6 through plating on the outer wall surface of the through hole 20 and is connected to the wiring on the inner layer of the multilayer printed board 10.

  The outer land 5 is a land provided on the component mounting surface. The shape of the outer land 5 seen from the direction perpendicular to the surface of the multilayer printed board is not particularly limited, but is usually configured in a circular shape.

  FIG. 2 shows a state in which the lead terminal 3 and the inner layer land 1 are soldered as seen from a direction perpendicular to the solder surface. As shown in FIG. 2, the outer peripheral portion of the inner layer land 1 is covered with an insulating resin 2 to prevent land peeling.

  As shown in FIG. 1B, the opening 7 is configured such that the cross-sectional shape in the direction perpendicular to the solder surface of the multilayer printed board 10 has a tapered shape extending from the inner land 1 to the solder surface. May be. By making the opening 7 have a tapered shape, it becomes easy for solder to enter the opening 7 and the inner land 1 and the lead wire 3 can be easily soldered.

  With reference to FIG. 3, the taper shape of the cross section of the opening part 7 is demonstrated.

FIG. 3 is a cross-sectional view in a direction perpendicular to the multilayer printed circuit board 10 and passing through the center of the inner layer land 1. The cross section of the inner land 1 in the direction parallel to the solder surface of the multilayer printed board 10 is circular.
The center points of the inner land 1, the opening 7, and the through hole 20 are all the same.

  The inner layer land diameter 91 indicates the diameter of the inner layer land 1.

  The opening diameter 92 indicates the diameter of the opening 7 on the solder surface of the multilayer printed circuit board 10.

  The inner layer land exposed diameter 93 indicates the diameter of the portion of the inner layer land 1 exposed by the opening 7.

  The inner land land diameter 91 and the opening diameter 92 are configured so that the inner land land diameter 91 ≧ the opening diameter 92. In addition, a line connecting the outer peripheral portion of the opening 7 on the solder surface and the outer peripheral portion of the exposed portion of the inner land 1 is configured to be tapered.

  By configuring the opening 7 in this manner, the cross-sectional shape of the opening 7 can be tapered while the size of the opening 7 is kept small. Therefore, the effect of increasing the mounting density of the multilayer printed circuit board 10 and facilitating soldering with the lead wire can be obtained, and the inner layer land 1 can be covered with the insulating resin 2 and the land peeling can be prevented. Can also be obtained.

  Next, a method for manufacturing a multilayer printed board according to the first embodiment will be described with reference to FIGS. 4 and 5.

  A multilayer printed circuit board 10 having the inner land 1 provided on the inner layer is formed (S1000 in FIG. 4A and FIG. 5). The inner layer land 1 is desirably provided in the inner layer closest to the solder surface in order to improve the solder wettability into the through hole. The shape (top view) of the inner layer land 1 viewed from a direction perpendicular to the multilayer printed board 10 is assumed to be circular.

  A through hole 20 is formed in the multilayer printed board 10 so as to penetrate the central portion of the inner layer land 1 (FIG. 4B, S1001 in FIG. 5). At this time, the top view of the inner land 1 has a shape with an open center as shown in FIG.

  The multilayer printed circuit board 10 including the inner wall surface of the through hole 20 is plated (FIG. 4C, S1002 in FIG. 5).

  Next, excess plating is removed, and outer layer lands 5 and wiring patterns (not shown) are formed (FIG. 4D, S1003 in FIG. 5).

  After the above steps, the outer land 5 and the insulating resin 2 are mechanically cut to form an opening 7 to expose a part of the inner land 1 (FIG. 4E, S1004 in FIG. 5). In cutting the insulating resin 2, cutting is performed so that the outer peripheral portion of the inner land 1 is covered with the insulating resin 2. By cutting so that the cross-sectional shape of the opening 7 in the direction perpendicular to the solder surface of the multilayer printed circuit board 10 becomes a tapered shape extending from the inner land 1 to the solder surface, the solder enters the opening 7. This makes it easier to solder the inner land 1 and the lead wire 3.

  Note that when the outer layer land 5 and the insulating resin 2 are mechanically cut, a drill 40 may be used as shown in FIG.

  Here, with reference to FIG. 7, the structure of the drill 40 is demonstrated in detail.

  FIG. 7A shows a cross-sectional view of a cross section that is parallel to the rotation axis 407 of the drill 40 and passes through the rotation axis 407.

  The drill 40 has a first cutting portion 404 and a second cutting portion 405, the first cutting portion 404 is provided with a first cutting surface 402, and the second cutting portion 405 has a second cutting portion. The cutting surface 403 is provided. The cross-sectional shapes of the first cutting portion 404 and the second cutting portion 405 that are perpendicular to the rotation shaft 407 are circular, although not particularly shown. Both the first cutting surface 402 and the second cutting surface 403 are configured to be perpendicular to the rotation shaft 407.

The first cutting surface 402 and the second cutting surface 403 are rough enough to cut the outer land 5 and the insulating resin 2. A portion of the insulating resin 2 and the outer layer land 5 is cut by the first cutting surface 402 of the first cutting portion 404 to form the opening 7 that exposes the inner layer land 1. Further, the outer layer land 5 remaining without being cut by the first cutting surface 402 is cut by the second cutting surface 403 of the second cutting portion 405.
What is necessary is just to comprise the diameter of the 1st cutting part 404 in a diameter required in order to ensure the required land exposure amount of the inner-layer land 1. Moreover, what is necessary is just to comprise the diameter of the 2nd cutting part 405 in the diameter sufficient to cut all the outer-layer lands 5. FIG.

  The first cutting portion depth 406 indicates the depth in the direction parallel to the rotation axis 7 of the first cutting portion 404. What is necessary is just to comprise the 1st cutting part depth 406 in the depth required in order to cut the insulating resin 2 and to expose the inner-layer land 1. Specifically, the inner resin layer 2 may be formed to a depth necessary for cutting the insulating resin 2 by the inner layer land depth 401 indicating the depth from the surface of the multilayer printed board 10 to the inner layer land 1.

  In addition, as shown in FIG.7 (b), it becomes possible to make the cross section of the opening part 7 into a taper-shape by making the cross-sectional shape of the 1st cutting part 404 into a taper shape. In this case, the tapered portion of the first cutting portion 404 is also configured to be a rough surface.

The multilayer printed circuit board in the first embodiment of the present invention is manufactured through the above steps.
(Effects of the first embodiment)
Since the outer peripheral portion of the land is covered with the insulating resin, it is possible to prevent the solder surface from being peeled off without increasing the size of the land.
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG.

  FIG. 8 is a view showing a cross-section of the through hole according to the second embodiment of the present invention.

  Referring to FIG. 8, the multilayer printed board 10 according to the second embodiment of the present invention includes an insulating resin 2, lead terminals 3, solder fillets 4, outer layer lands 5, openings 7, signal lines 9, and connection portions 50. Including.

  In the second embodiment of the present invention, the signal line 9 connected to the through hole 20 is provided in the layer closest to the solder surface of the multilayer printed circuit board 10 without providing the inner layer land as in the first embodiment. A connection portion 50 between the line 9 and the through hole 20 is provided.

  A part of the connection part 50 is exposed through the opening 7, and the solder fillet 4 is formed in the part, and the multilayer printed circuit board 10 and the lead terminal 3 are soldered.

  The connection part 50 has a structure in which a part thereof is covered with the insulating resin 2. With this structure, the shrinkage stress of the solder fillet can be suppressed, and land peeling can be prevented.

  The shape of the connection portion 50 viewed from the direction perpendicular to the solder surface of the multilayer printed board 10 is not particularly limited, but is usually configured in a circular shape.

  FIG. 9 shows a specific example of the shape of the connection portion 50 viewed from the direction perpendicular to the solder surface of the multilayer printed board 10. A part of the connection part 50 is covered with the insulating resin 2, a solder fillet 4 is formed in a part exposed by the opening 7, and the lead terminal 3 and the through hole 20 are soldered.

Note that the cross-sectional shape of the opening 7 in the direction perpendicular to the solder surface of the multilayer printed board 10 may be configured to be a taper shape extending from the inner land 1 to the solder surface. By adopting such a structure, as in the first embodiment, it becomes easy for solder to enter the opening 7 and the effect that the connecting portion 50 and the lead wire 3 are easily soldered can be obtained.
(Effect of 2nd Embodiment)
As described above, by soldering the connection portion 50 between the through hole 20 and the signal line 9, even if the inner land 1 is not provided on the multilayer printed board 10, a part of the connection portion 50 is insulated. Since it is covered with the resin 2, land peeling can be prevented. Thus, the effect that land peeling can be prevented is obtained while simplifying the manufacturing process of the multilayer printed circuit board 10.

It is sectional drawing of the through-hole part of the multilayer printed circuit board in this invention. It is a top view of the through-hole part of the multilayer printed circuit board in this invention. It is a figure which shows the cross-sectional shape of an opening part. It is a figure which shows the manufacturing process of the multilayer printed circuit board in this invention. It is a flowchart which shows the manufacturing process of the multilayer printed circuit board in this invention. It is a figure which shows the specific example of the formation process of an opening part. It is a figure which shows the cross-sectional shape of the drill for forming an opening part. It is sectional drawing of the through-hole part of the multilayer printed circuit board of 2nd Embodiment in this invention. It is a top view of the through-hole part of the multilayer printed circuit board of the 2nd Embodiment in this invention. It is a figure explaining land peeling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner layer land 2 Insulation resin 3 Lead terminal 4 Solder fillet 5 Outer layer land 6 Connection layer 7 Opening part 8 Plating 9 Signal line 10 Multilayer printed circuit board 20 Through-hole 40 Drill 401 Inner layer land depth 402 First cutting surface 403 Second Cutting surface 404 First cutting portion 405 Second cutting portion 406 First cutting portion depth 407 Rotating shaft 50 Connection portion 91 Inner layer land diameter 92 Opening portion diameter 93 Inner layer land exposed diameter

Claims (14)

In a multilayer printed board having a through hole and a land connected to the through hole,
A part of the land is covered with an insulating resin. The multilayer printed circuit board according to claim 1, wherein the land is provided in an inner layer of the multilayer printed circuit board, and is connected to the through hole in the inner layer. The multilayer printed circuit board according to claim 2, wherein the inner layer is a layer closest to a solder surface of the multilayer printed circuit board. 4. The land is partially exposed to the solder surface by an opening provided in a direction perpendicular to the solder surface of the multilayer printed board. The multilayer printed circuit board according to any one of claims. 5. The multilayer print according to claim 4, wherein the opening has a shape in which a cross-sectional shape in a direction perpendicular to a solder surface of the multilayer printed board expands from the land toward the solder surface. substrate. In a multilayer printed circuit board having a through hole,
A signal line connected to the through hole in the inner layer closest to the solder surface of the multilayer printed circuit board;
A connecting portion for connecting the signal line to the through hole;
An opening provided in a direction perpendicular to the solder surface of the multilayer printed board,
A part of the connection portion is exposed to the solder surface through the opening,
A part of the connection part is covered with an insulating resin. 7. The multilayer according to claim 6, wherein the opening has a shape in which a cross-sectional shape in a direction perpendicular to a solder surface of the multilayer printed board expands from the connection portion toward the solder surface. Printed board. An inner layer land forming step of forming lands on the inner layer of the multilayer printed circuit board;
A through hole forming step of forming a through hole in the multilayer printed circuit board so as to penetrate the center portion of the land;
A method of manufacturing a multilayer printed circuit board, comprising: cutting an insulating resin from a solder surface of the multilayer printed circuit board to form an opening and exposing a part of the land. The inner layer land forming step includes:
9. The method of manufacturing a multilayer printed circuit board according to claim 8, wherein the land is formed in an inner layer closest to the solder surface. The cutting process includes
The insulating resin is cut by a drill having a cutting surface perpendicular to the surface of the multilayer printed board and having a rough surface perpendicular to the rotation axis. The multilayer printed circuit board manufacturing method according to claim 8, wherein a part of the printed circuit board is exposed. The cutting process includes
Cutting the insulating resin from the solder surface so that a cross-sectional shape in a direction perpendicular to the solder surface of the multilayer printed circuit board in the opening is a shape extending from the land toward the solder surface; 11. The method for manufacturing a multilayer printed circuit board according to claim 8, wherein a part of the land is exposed. Forming a connection line in a layer closest to the solder surface of the multilayer printed board, and a connection part for connecting the through hole and the connection line;
Forming the through hole in the multilayer printed circuit board so as to penetrate the center of the connection part;
A method of manufacturing a multilayer printed circuit board, comprising: cutting an insulating resin from a solder surface of the multilayer printed circuit board to form an opening, and exposing a part of the connection part. The cutting process includes
The insulating resin is cut by a drill having a cutting surface perpendicular to the surface of the multilayer printed board and having a rough surface perpendicular to the rotation axis. The method for producing a multilayer printed circuit board according to claim 12, wherein a part of the printed circuit board is exposed. The cutting process includes
Cutting the insulating resin from the solder surface so that the cross-sectional shape in the direction perpendicular to the solder surface of the multilayer printed board in the opening is a shape that expands from the connection portion toward the solder surface, The multilayer printed circuit board manufacturing method according to claim 12, wherein the method is a step of exposing a part of the connection portion.

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