JP3288290B2 - Multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a land for a plated through hole in a multilayer printed wiring board.

[0002]

2. Description of the Related Art A multilayer printed wiring board is formed by laminating a double-sided or single-sided copper-clad board or the like, a prepreg is interposed between the laminates, integrated by a hot press to obtain a laminated product, and a conductor circuit of each layer is connected. A hole was made in the laminated product, plating was performed to form a plated through hole, and a conductor was formed by a subtractive method or an additive method.

A land is formed in the plated through hole. The lands are usually formed concentrically from the inner wall of the plated through hole to the plated through hole.

At this time, when the number of laminated boards is increased or a soft laminated board mainly composed of Teflon or the like is used, the amount of expansion and contraction in the thickness direction of the multilayer printed wiring board due to a temperature change increases, and the land The stress of expansion and contraction concentrates on the inner peripheral portion, which may cause cracks. In other words, the plated through holes of the multilayer printed wiring board usually have a relatively small amount of expansion and contraction because the plating is uniformly applied inside the holes by copper plating, and a resin or the like is laminated on portions other than the plated through holes. Therefore, the amount of expansion and contraction is large (FIGS. 4 to 5).
reference). Therefore, when the multilayer printed wiring board repeats expansion and contraction, expansion and contraction stress mainly concentrates on the inner peripheral portion of the land.

In order to prevent this, the thickness of the plating is increased from the usual 25 μm to 50 μm or more to increase the strength of the plated portion to prevent cracks.

[0006]

However, increasing the thickness of plating requires extra plating metal and increases the time required for the plating process. In addition, since the thickness of the conductor to be removed to obtain the conductor increases, it becomes difficult to perform fine pattern processing.

Accordingly, the present invention solves the above-mentioned problems, reduces stress in through holes due to expansion and contraction in the thickness direction of the multilayer printed wiring board without increasing the plating thickness, and reduces cracks in the plating portion. It is an object of the present invention to provide a multilayer printed wiring board that can prevent such a problem.

[0008]

The multilayer printed wiring board according to the present invention has the following configuration to achieve the above object.

In other words, in the multilayer printed wiring board of the present invention, in the multilayer printed wiring board, a land notch in which a part of the inner peripheral portion of the land located on the surface of the multilayer printed wiring board of the plated through hole is formed of a non-plated portion. And a part of the inner wall of the plated through hole in the depth direction is formed as a through hole cut-out part continuous with the inner wall.

Further, in the above invention, the land notch may be configured to penetrate from the inner peripheral portion to the outer peripheral portion of the land located on the surface of the multilayer printed wiring board.

In the above invention, a plurality of land notches may be formed in one land located on the surface of the multilayer printed wiring board.

[0012]

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

FIGS. 1 and 2 are plan views showing one embodiment of the multilayer printed wiring board of the present invention. FIG. 3 is a sectional view showing one embodiment of the multilayer printed wiring board of the present invention. In the figure, 1 is a multilayer printed wiring board, 2 is a land, 3 is a cutout portion of a land, 4 is a plated through hole, 5 is an inner wall of a plated through hole, 6 is a conductor, and 7 is a cutout portion of a through hole.

In the multilayer printed wiring board 1 of the present invention, in the multilayer printed wiring board 1, a part of the inner peripheral portion of the land 2 located on the surface of the multilayer printed wiring board 1 in the plated through hole 4 is formed of a non-plated portion. In addition to the land notch 3, a part of the inner wall of the plated through hole 4 in the depth direction is a continuous through hole notch 7 (see FIGS. 1 to 3).

In order to obtain the multilayer printed wiring board 1 according to the present invention, the following is preferred.

A copper-clad laminate, a prepreg, a release film, etc., are stacked to make a reference hole, and only a copper-clad laminate having a copper-clad surface for an inner layer is taken out. After forming the inner layer wiring and subjecting it to a roughening treatment, a prepreg of appropriate performance and thickness is sandwiched between the inner layers, and a prepreg and a copper-clad laminate are successively stacked one above the other, and these components are heated. By sandwiching between the plates and applying heat and pressure, they adhere to each other to obtain a laminated product.
Further, even if the reference holes are not provided by overlapping the members in advance, a similar laminated product can be obtained by increasing the dimensional accuracy of the members.

As the insulating base material of the copper clad laminate, paper base phenol resin, paper base epoxy resin, synthetic fiber base epoxy resin, glass cloth / paper composite base epoxy resin, glass cloth / glass nonwoven composite There are a base epoxy resin, a glass cloth base epoxy resin and a glass cloth base Teflon resin.

Next, a through hole is provided in the laminated product. As a method of forming a through hole, there is a drilling method or the like.

Subsequently, a plated through hole 4 and a land 2 are formed.

Specifically, first, a plating layer of copper or the like is formed on both surfaces of the laminated product and the inner wall surfaces of the through holes by electroless plating or electrolytic plating.

Next, an etching resist layer is provided on a portion other than the land cutout 3 and the through-hole cutout 7, the plated through-hole 4, the conductor 6, and the like, on both sides of the laminated product which do not require etching. As the etching resist layer, a general etching resistant material may be used.

Next, portions of the plating layer that are not covered with the etching resist layer are removed by etching. To perform the etching removal, for example, an alkaline etching solution such as ammonium persulfate, ammonium, ammonium chloride or the like, or a cupric chloride, ferric chloride, chromic acid / sulfuric acid mixed solution,
It is preferable to use an acidic etching solution such as a mixed solution of aqueous hydrogen peroxide and sulfuric acid.

Next, the etching resist layer is peeled off.
In order to perform stripping, a stripping agent such as methylene chloride, glycol ether, a mixed solvent thereof, or an organic solvent such as a mixed solution thereof with an aqueous alkali solution such as sodium hydroxide or sodium carbonate may be used.
Alternatively, only an alkaline aqueous solution may be used as a release agent.

In this manner, the land notch 3 and the through-hole notch 7 made of the non-plated portion can be formed.

The land notch 3 is a land 2 located on the surface of the multilayer printed wiring board 1 in the plated through hole 4.
3 is provided so as to be located at a part of the inner peripheral portion of the inner wall 5 and a notch 7 is provided so that a part of the end of the inner wall 5 of the plated through hole is also continuous with the land notch 3 (the lower surface in FIG. 3). reference).

A land notch 3 may be provided from the inner peripheral portion of the land 2 to the outer peripheral portion (see FIGS. 1 and 3). Further, the land notch 3 may penetrate from the inner peripheral portion to the outer peripheral portion of the land 2 (see FIG. 2). Further, a plurality of land notches 3 may be provided in one land 2 (see FIG. 1).

Further, a plating resist layer may be used to form the land notch 3 and the through-hole notch 7.

That is, a plating resist layer is provided on portions of both sides of the laminate where plating is not required, portions where the land notches 3 are to be formed, and portions where the through-hole notches 7 are to be formed. As the plating resist layer, a plating-resistant material that does not deposit a plating layer thereon even after plating is used.

Next, a plating layer is formed on the inner wall surface of the through hole that is not covered with the plating resist layer by electroless plating or electrolytic plating.

In order to form the land notch 3 and the through-hole notch 7, the plating layer may be removed by a laser beam or the like.

The multilayer printed wiring board 1 thus obtained
Has a land notch 3 in a portion from the outermost plating through hole inner wall 5 of the plating through hole 4 to the outer peripheral portion of the land 2, and a part of an end of the plating through hole inner wall 5 is also formed in the land notch 3. By having the through-hole notch portion 7 so as to be continuous, stress is concentrated on the land notch portion 3 and the through-hole notch portion 7, and stress is applied to portions other than the land notch portion 3 and the through-hole notch portion 7. Can be prevented, and the occurrence of cracks can be prevented.

[0032]

EXAMPLE A 0.8 mm thick Teflon double-sided copper-clad board (copper 1)
A conductor is patterned on one side of 8 μm / copper 18 μm) by etching, and a Teflon single-sided copper-clad board (copper 18 μm) having a thickness of 0.7 mm is connected to a side having a double-sided copper-clad board and a conductor of a single-sided copper-clad board. 0.1 mm thick Teflon prepreg is sandwiched between the surface and the surface that does not have it, and laminated by heating press at 370 ° C. Then, a 0.8 mm diameter through hole is drilled by NC drill, and the thickness of through hole copper plating is increased. It was formed to a thickness of 25 μm, and both surfaces of the laminated outermost layer were etched.

At this time, the land width was 1.5 mm, and the radius of curvature was 0.7 mm around the inner wall surface of the through hole of the land.
Are provided at two places, and copper in this portion is removed by etching.

Thereafter, a solder resist was applied to necessary portions, and a nickel plating thickness of 3 μm and a gold plating thickness of 0.03 μm were formed on the other conductors to obtain a multilayer printed wiring board.

The multilayer printed wiring board thus obtained was subjected to a thermal shock test at 65 to 125 ° C. for 15 minutes for 100 minutes.
When the cycle was performed, no crack was generated around the land of the plated through hole.

[0036]

Since the present invention has the above-described structure, it has the following effects.

In the multilayer printed wiring board according to the present invention, a notch formed of a non-plated portion is provided on the inner peripheral portion of the land of the plated through hole, and a part of the inner wall of the plated through hole in the depth direction is continuous with the notch. Since the notch of the through hole is provided, stress of expansion and contraction is not mainly concentrated on the inner peripheral part of the land, and the inner wall of the plated through hole and the land can be connected without increasing the plating thickness of the plated through hole. No cracks occur at the connection.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a multilayer printed wiring board according to the present invention.

FIG. 2 is a plan view showing another embodiment of the multilayer printed wiring board of the present invention.

FIG. 3 is a sectional view showing one embodiment of the multilayer printed wiring board of the present invention.

FIG. 4 is a sectional view showing an example of a conventional multilayer printed wiring board.

FIG. 5 is a sectional view showing an example of a conventional multilayer printed wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Multilayer printed wiring board 2 Land 3 Land notch 4 Plating through hole 5 Plating through hole inner wall 6 Conductor 7 Through hole notch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-165094 (JP, A) JP-A-6-69660 (JP, A) JP-A-49-117970 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) H05K 3/46

Claims (3)

(57) [Claims] In a multilayer printed wiring board, a part of an inner peripheral portion of a land located on a surface of the multilayer printed wiring board in a plated through hole is formed as a land cutout portion made of a non-plated portion, and a plated through hole is formed. A part of the inner wall in a depth direction of the inner wall is formed as a cut-out portion that is continuous with the inner wall. 2. The multilayer printed wiring board according to claim 1, wherein the land notch penetrates from an inner peripheral portion to an outer peripheral portion of the land located on the surface of the multilayer printed wiring board. 3. The multilayer printed wiring board according to claim 1, wherein a plurality of land notches are formed in one land located on the surface of the multilayer printed wiring board.