JP6112658B2 - Circuit board characterized by a structure with thick copper on the hole and method for manufacturing the same - Google Patents

Description

  The present invention relates to a circuit board manufacturing method.

  In recent years, IC chips have been increased in speed and integration, and there has been a demand to use a hole such as a through hole of a circuit board used for connection between different layers in a circuit board as a connection part between the IC chip and the circuit board. It has come out.

In order to use the hole on the circuit board for connection with the IC chip, it is necessary to close the hole and provide a conductive layer thereon. However, the wire bonding method is used for the connection method between the IC chip and the circuit board. In this case, if the conductive layer on the conventional hole does not have a certain thickness or more, “connection peeling” tends to occur at the connection portion between the bonding wire and the conductive layer.
On the other hand, if copper plating is performed thickly to increase the thickness of the conductive layer above the hole, the copper plating layer is also thickened at portions other than the hole, and as a result, it is difficult to form a high-density circuit.

The said state is demonstrated with reference to FIG. 2 which shows the conventional manufacturing method (refer patent document 1, 2).
FIG. 2 is a process flow diagram based on a schematic cross-sectional view showing a conventional circuit board manufacturing method, FIG. 2a is a cross-sectional view of a copper-clad laminate to be used, and FIG. 2b is a cross-sectional view of a copper-clad laminate with a through hole, 2c is a cross-sectional view of a copper-clad laminate that is electrically conductive by copper plating, FIG. 2d is a cross-sectional view of a copper-clad laminate in which a non-through conductive through hole is formed with a filler, and FIG. Sectional drawing of the copper clad laminated board which provided the copper plating layer in the front and back which contains, FIG. 2f is sectional drawing of the produced circuit board.
In FIG. 2, 1 is a base material, 2 is a copper foil, 3 is a through hole, 3a is a through conduction through hole, 3b is a non-through conduction through hole embedded with a filler, 4 and 6 are copper plating layers, Fillers 10 are copper-clad laminates, 11 are copper-clad laminates with through-holes, and 20 is a circuit board.

First, when manufacturing a circuit board, the copper clad laminated board 10 which stuck the copper foil 2 to the base material 1 as shown to FIG. 2 a is used.
Here, although the copper clad laminated board 10 which stuck the 12-micrometer-thick copper foil 2 to the 0.2-mm-thick base material 1 was used, there is no restriction | limiting in the thickness of the base material 1 and the copper foil 2. FIG.

Next, as shown in FIG. 2 b, a hole is made in the copper clad laminate 10 to form a through hole 3. The drilling method is not particularly limited, but an NC drilling machine or the like is used. The shape of the hole is not limited to a round hole, but is selected according to the purpose, such as an elliptical hole, a square hole, or a deformed hole.
After forming the through hole, as shown in FIG. 2c, copper plating is performed on the entire surface of the copper-clad laminate 11 with through holes that has been subjected to drilling, or a necessary portion, to provide a copper plating layer 4, and through holes A through-conduction through hole 3a is formed by imparting front-back conduction to (FIG. 2b, reference numeral 3).

Next, as shown in FIG. 2d, a non-penetrating conductive through hole 3b that completely fills the inside of the through conductive through hole 3a is formed by burying the filler 5.
This filling operation can be performed by various methods such as a printing method, a roller method, a curtain coater method, and a dip method using a resin satisfying the following conditions as a filler.
There is no restriction on the type of resin to be used as long as the filler has viscosity during curing and is cured by heat, UV, light, etc., and epoxy, melanin, acrylic, etc. can be selected. However, a resin having high heat resistance and high rigidity is more desirable.
The filler 5 protruding from the non-penetrating conductive through hole 3 b is polished to have the same flat surface as the copper plating layer 4.

Next, as shown in FIG. 2e, a copper plating layer 6 is provided by performing copper plating on the entire surface or a necessary portion.
Although the thickness of the copper plating layer 6 is arbitrarily set, it needs to be thick enough to prevent the wire bond from peeling off, and is at least 25 μm or more.
In this case, the total thickness of the copper foil 2 and the copper plating layers 4 and 6 is 62 μm or more.

Next, as shown in FIG. 2f, unnecessary portions of the copper-clad laminate 10 and the copper-plated layers 4 and 6 of the copper-clad laminate 10 subjected to “drilling” and “copper plating processing” are removed by exposure and etching. As a result, a predetermined circuit board 20 is manufactured.
The surface of the outer copper plating layer 6 can be coated with a resist film where necessary, and other metal plating such as gold, silver, nickel, etc. can be performed as necessary. It is.

As described above, in the conventional method, when the copper plating for imparting conductivity to the hole is thin, it is difficult to mount the wire bond on the upper part of the hole due to insufficient hardness of the filler in the hole, so the copper plating layer has a thickness of 25 μm or more. Needed.
On the other hand, when a thick copper plating layer is provided in this way, the copper plating layer is thickened to the portion other than the hole, and as a result, the thickness of the conductive layer including the copper foil and the copper plating layer is increased. It becomes difficult to form a high-density circuit with an interval of 80 μm or less. For this reason, in the conventional method, it has been a problem to simultaneously increase both the thickness of the conductive layer on the hole and the formation of the high-density circuit in order to prevent the connection peeling.

JP 2002-76613 A JP 2002-57441 A

  Therefore, in such a situation, in the present invention, both the thickening of the conductive layer on the hole such as the through hole and the formation of the high-density circuit are simultaneously achieved without increasing the thickness of the copper plating layer other than the hole. The present invention provides a method for manufacturing a circuit board having a structure in which only the conductive layer on the hole is thick.

A first aspect of the present invention is a method for manufacturing a circuit board having a structure in which a conductive layer thickness immediately above a through hole is thicker than a conductive layer thickness on the outer periphery of the through hole. Forming a copper-clad laminate with a through hole by providing a hole; (2) providing a copper plating layer on the surface of the copper-clad laminate with a through hole and providing a copper plating layer on the side wall of the through hole; A step of forming a copper-clad laminate with conductive through-holes comprising conductive through-holes that conduct both sides of the copper-clad laminate with through-holes; (3) a non-through conductive through by filling the conductive through-holes with a filler; forming a hole process, (4) the by removing a portion of the surface layer to the filler surface in a non-through conducting through hole by irradiating a laser beam, the copper-clad laminate with non-through conducting through holes A step of making the surface of the non-penetrating conductive through-hole into a concave portion; (5) providing a copper plating layer on both sides of the copper clad laminate having the surface of the non-penetrating conductive through-hole as a concave portion; A process for producing a circuit board comprising the steps (1) to (5) of the step of flattening the portion in order.

The second aspect of the present invention, conductive layer provided on a straight upper surface of the filling layer provided in the through holes, have a thickness greater than the thickness of the conductive layer provided in the through hole periphery,
The circuit board is characterized in that a conductive layer provided directly on the top surface of the filling layer is electrically connected to a conductive layer provided on a bottom surface of the filling layer through a single copper plating layer .

A third aspect of the present invention, conductive layer provided on a straight upper surface of the first invention on a circuit board filling layer provided in the scan Ruhoru formed by the manufacturing method of the described, provided on the outer circumference of the through hole characterized in that have a thickness greater than the thickness of the conductive layer, and conductive layer provided on a straight upper surface of the filling layer is made conductive conductive layer provided immediately below surface of the filling layer through a layer of copper plating layer Is a circuit board.

According to the circuit board manufacturing method of the present invention, only the conductive layer on the hole can be thickened without increasing the thickness of the conductive layer on the portion other than on the hole, and the copper plating layer other than on the hole is made thick. Therefore, it is possible to easily provide a circuit board having a structure in which only the conductive layer on the hole is thick.
Further, by increasing the removal depth of the filler by the laser beam, it is possible to make the thickness of the conductive layer above the hole 25 μm or more without changing the thickness of the conductive layer on the surface.
Therefore, it is possible to prevent wire bond peeling and to form a high-density circuit at the same time, which is an industrially significant effect.

It is a manufacturing flowchart by the cross-sectional schematic diagram explaining embodiment of this invention. It is a manufacturing flow figure by the cross-sectional schematic diagram of the conventional wiring board.

Embodiments of the present invention will be described below with reference to the drawings and specific dimensions.
FIG. 1 is a manufacturing flow diagram according to a schematic cross-sectional view showing a method for manufacturing a circuit board according to the present invention. 1A is a copper-clad laminate, FIG. 1B is a cross-sectional view of a copper-clad laminate with through-holes, FIG. 1C is a cross-sectional view of a copper-clad laminate that is conductive on both sides by copper plating, and FIG. FIG. 1E is a cross-sectional view when the filler material on the surface layer of the non-through conductive through-hole is removed by the laser beam 21, and FIG. 1F is provided with the concave filler portion 5a. FIG. 1G is a cross-sectional view of a copper-clad laminate in which copper plating layers are provided on the front and back surfaces including the non-penetrating through-holes, and FIG. 1H is a cross-sectional view of the circuit board according to the present invention.
In FIG. 1, 1 is a base material, 2 is a copper foil, 3 is a through hole, 3a is a through conduction through hole, 4 and 6 are copper plating layers, 5 is a filler, 5a is a concave filler portion, and 6a is a through hole. Copper plating layer directly above the hole (also a conductive layer immediately above the through hole), 6b is a copper plating layer on the outer periphery of the through hole, 10 is a copper-clad laminate, 11 is a copper-clad laminate with through-holes, and 21 is a laser. It is a beam.

First, as in the conventional case, as shown in FIG. 1A, a copper clad laminate 10 in which a copper foil 2 is stuck to a base material 1 is used.
Here, in order to explain in more detail, the dimensions of specific materials, for example, the thickness of the base material 1, the copper foil 2, the copper plating, etc. will be described below.
First, the copper clad laminated board 10 which affixed the copper foil of thickness 12micrometer to the base material 1 of thickness 0.2mm was used.

Next, as shown in FIG. 1B, a hole is made in the copper-clad laminate to form a through hole 3 to produce a copper-clad laminate 11 with a through-through hole.
The drilling method is not particularly limited, but is performed using an NC drilling machine or the like. The shape of the hole is not limited to a round hole, but may be selected according to the purpose, such as an elliptical hole, a square hole, or a deformed hole.

  Next, as shown in FIG. 1C, copper plating is performed on the entire surface of the copper-clad laminate 11 with through-holes produced by drilling, or a necessary portion, to provide a copper plating layer 4. A through-conduction through hole 3a in which front and back conduction is imparted to the through hole 3 is formed.

Next, as shown in FIG. 1D, the through-conductive through hole 3a of FIG. 1C is completely filled with the filler 5 to form a non-through conductive through hole 3b, thereby producing a copper-clad laminate 12 with the non-through conductive through hole. To do.
This filling operation can be performed by various methods such as a printing method, a roller method, a curtain coater method, and a dip method using a resin satisfying the following conditions as a filler.
There is no limitation on the type of resin, and it can be selected from epoxy, melanin, acrylic, etc., as long as the filler has viscosity during the filling operation and has the property of being cured by heat, UV, light, etc. A resin having high heat resistance and high rigidity is more desirable.
The filler 5 protruding from the non-penetrating conductive through hole 3 b is polished to have the same flat surface as the copper plating 4.

  Thereafter, in order to reduce the thickness of the conductive layer, the copper plating layer 4 is subjected to a half etching process, and the filler formed as a protrusion by the half etching is removed by physical polishing.

Next, as shown in FIGS. 1E and 1F, the surface of the filler 5 is irradiated with a laser beam 21 (FIG. 1E) to remove a part of the surface layer of the filler 5 to form a concave filler portion 5a ( FIG. 1F).
The laser beam to be used is preferably one having a property that the filler can be removed but the copper plating portion is hardly affected. An example is a carbon dioxide gas laser having a wavelength of 9.2 μm.
The filling material removal depth can be arbitrarily adjusted according to needs such as mounting strength, but it is necessary that the depth be flattened by the copper plating layer 6 (see FIG. 1G). Further, the surface of the filler 5 removed by the laser beam 21 may be uneven as long as it can be planarized by the copper plating layer 6. Specifically, the depth is about 40 μm.

Next, as shown in FIG. 1G, copper plating is performed on the entire surface or a necessary portion to provide a copper plating layer 6.
As the copper plating layer 6, a layer having a property capable of flattening the recess of the concave filler portion 5 a removed by the laser beam by copper plating is used.
The copper plating layer 6 needs to be thick enough to flatten the concave portion of the filler 5 removed by the laser beam 21. Specifically, it is about 25 μm.

Next, as shown in FIG. 1H, the copper foil 2, the copper plating layers 4, 6 of the copper-clad laminate 12 with non-through conductive through-holes subjected to “drilling”, “laser beam”, “copper plating processing, etc.” The copper plating layer 6a, which is a conductive layer immediately above the through hole, is removed by exposure and etching to remove unnecessary portions of the conductive layer (the copper plating layer 6b, the copper plating layer 4 and the copper foil on the outer periphery of the through hole). The circuit board 20 having a thicker structure is manufactured.
The surface of the copper plating 6a, 6b, which is the outer layer, can be coated with a resist film where necessary, and other metal plating such as gold, silver, nickel or the like can be applied as necessary. It may be provided.

Hereinafter, the present invention will be described in more detail with reference to examples.
Using the manufacturing method of the present invention shown in FIG. 1 and the conventional manufacturing method shown in FIG. 2, a wiring circuit having the same thickness of the conductive layer immediately above the through hole is manufactured. The thickness of the outer conductive layer was compared.

In addition, Example 1 is a case where the surface layer is deleted by 25 μm by “half etching and physical polishing” in the step (3) so that the thickness of the conductive layer on the surface of the wiring circuit is reduced. This is a case where the thickness of the conductive layer on the wiring circuit surface is required as compared with Example 1.
The results are shown in Table 1. Each elemental technique (etching, copper plating, physical polishing) in the production of the wiring board was performed under the conditions shown in Table 2.

  As is apparent from Tables 1 and 2, the circuit board according to the manufacturing method of the present invention can make the thickness of the conductive layer immediately above the through hole larger than the thickness of the conductive layer on the surface of the circuit board. When wire bonding is performed, the problem of peeling of the connecting portion is greatly reduced.

DESCRIPTION OF SYMBOLS 1 Base material 2 Copper foil 3 Through-hole 3a Through-conduction through-hole 3b Non-through-conduction through-hole 4 Copper plating layer 5 Filler 5a Concave-shaped filler part 6 Copper plating layer 6a Copper plating layer (above through hole)
6b Copper plating layer (through hole outer periphery)
DESCRIPTION OF SYMBOLS 10 Copper-clad laminated board 11 Copper-clad laminated board 12 with a through-through hole Copper-clad laminated board 20 with a non-penetrating conduction through hole Circuit board 21 Laser beam

Claims (3)

A method for producing a circuit board having a structure in which a conductive layer thickness directly above a through hole is thicker than a conductive layer thickness on the outer periphery of the through hole,
The manufacturing method of the circuit board characterized by including the process of following (1)-(5) in order.
(1) A step of providing a through hole in a copper clad laminate to form a copper clad laminate with a through hole.
(2) A conductive through-hole that provides a copper-plated layer on the surface of the copper-clad laminate with through-holes and provides a copper-plated layer on the side wall of the through-hole to conduct both sides of the copper-clad laminate with through-holes. Forming a copper clad laminate with conductive through holes.
(3) A step of filling the conductive through hole with a filler to form a non-through conductive through hole.
(4) The surface of the non-penetrating conductive through-hole of the copper clad laminate with non-penetrating conductive through-hole by irradiating the filler surface layer in the non-penetrating conductive through-hole with a laser beam to remove a part of the surface layer The process which makes a concave shape part.
(5) The process of providing a copper plating layer on both surfaces of the copper clad laminated board which made the said through-penetration through-hole surface the concave shape part, and flatten the said concave shape part. Conductive layer provided on a straight upper surface of the filling layer provided in the through holes, have a thickness greater than the thickness of the conductive layer provided in the through hole periphery,
A circuit board, wherein a conductive layer provided directly on the top surface of the filling layer is electrically connected to a conductive layer provided on a bottom surface of the filling layer through a single copper plating layer . Conductive layer provided on a straight upper surface of the filling layer provided in claim 1 circuit scan Ruhoru formed by the manufacturing method of the substrate described, have a thickness greater than the thickness of the conductive layer provided in the outer periphery of the through hole, In addition, the circuit board is characterized in that the conductive layer provided directly on the top surface of the filling layer is electrically connected to the conductive layer provided on the bottom surface of the filling layer through a single copper plating layer .

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