JP2006152329A - Surface treatment method for copper layer, and laminate and wiring board including copper layer subjected to the treatment - Google Patents

Abstract

The present invention provides a surface treatment method for a copper layer capable of ensuring sufficient adhesion for integrating a copper layer and a resin insulating layer.
The surface of the copper layer is subjected to etching-type chemical roughening so that the height from the valley to the peak includes unevenness exceeding 5 μm, and the treated surface is further subjected to blackening reduction treatment. The etching type chemical roughening treatment is preferably performed so that the height from the valley to the peak includes unevenness exceeding 8 μm, more preferably including unevenness exceeding 12 μm. Further, a coupling agent treatment may be added after the blackening reduction treatment. The treatment method is applied to, for example, a rolled copper foil having a thickness of 100 μm or more, and the treatment surface is overlapped with the prepreg layer and integrated by heating and pressing to obtain a laminated plate.
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Description

  The present invention relates to a surface treatment method for a copper layer. Moreover, it is related with the laminated board and wiring board containing the copper layer which performed the said process. The wiring board is suitable for applications in which a large current is passed.

  A wiring board mounted on an electronic device is required to have a technology for fine wiring and high-density mounting in accordance with a reduction in the thickness and size of the electronic device, and a technology for high heat dissipation corresponding to heat generation is also required. In particular, in electronic circuits such as automobiles that use a large current for various controls and operations, heat generation due to the resistance of the conductive circuit and heat generation from the power element are very large, and the heat dissipation characteristics of the wiring board may be high. It has become essential. As a countermeasure, it has been proposed to increase the thermal conductivity by increasing the copper layer constituting the conductive circuit of the wiring board and to promote heat dissipation.

In the production of the wiring board, a laminated board in which a copper layer is integrated with a resin insulating layer by heating and pressing is used, and the copper layer of the laminated board is processed into a conductive circuit to form a wiring board. Usually, the copper layer is selected from electrolytic copper foil or rolled copper foil, but if a thin copper layer is acceptable, electrolytic copper foil by electrodeposition is selected, and a thick copper layer that is difficult to manufacture by electrodeposition is required. In this case, a rolled copper foil is selected.
Since one surface of the electrolytic copper foil is a rough surface resulting from electrodeposition, the rough surface is brought into contact with the resin insulating layer and the above-mentioned heat-press molding is performed, and the convex portions constituting the rough surface are made of resin. The insulating layer is bitten and the anchoring effect increases the adhesion between the resin insulating layer and the copper layer. On the other hand, since both sides of the rolled copper foil are smooth surfaces in the manufacturing process, in integrating the copper layer into the resin insulation layer, the contact surface of the copper layer to the resin insulation layer is A separate roughening treatment is required.

  Common roughening treatment methods for copper layers include blackening treatment and blackening reduction treatment, but sufficient heat resistance in the integration of copper layer and resin insulation layer (copper layer and resin insulation even after heat treatment) It is known that it is not possible to ensure properties that do not reduce the adhesion of the layers. Moreover, as a roughening method of the rolled copper foil, there is a method (for example, Patent Document 1) in which fine particles collide with the surface of the copper layer at high speed to give fine irregularities on the surface. However, even with such a treated copper layer, sufficient adhesion and heat resistance with the resin insulating layer have not been secured.

JP 2002-79466 A

  The problem to be solved by the present invention is to provide a surface treatment method of a copper layer that can secure a sufficient adhesion force when the copper layer and the resin insulating layer are integrated. Moreover, it is providing the laminated board and wiring board which integrated the copper layer and resin insulating layer which processed the said process.

  The surface treatment method for the copper layer is preferably applied to a rolled copper foil having a smooth surface, and aims to ensure adhesion between the copper layer and the insulating resin layer.

In order to achieve the above object, the surface treatment method for a copper layer according to the present invention includes an etching-type chemical roughening treatment on the surface of the copper layer so that the height from the valley to the mountain includes irregularities exceeding 5 μm. Further, the processing surface is subjected to blackening reduction processing (claim 1). In the above, the etching-type chemical roughening treatment is preferably performed so as to include an unevenness having a height from a valley to a peak exceeding 8 μm (Claim 2), more preferably an unevenness exceeding 12 μm (Claim 3). .
The copper layer is, for example, a rolled copper foil having a thickness of 100 μm or more (Claim 4).

  Here, the blackening reduction treatment is an operation of producing fine acicular cuprous oxide or cupric oxide on the surface of the copper layer, and thereafter reducing this.

  The surface of the copper layer roughened by the method according to the present invention is provided with micron-order irregularities by etching-type chemical roughening treatment, and further sub-micron-order irregularities by blackening reduction treatment are provided thereon. Is done. As a result, the copper layer exhibits fine and complicated surface properties.

  The laminated board in which the copper layer having the above-described surface property is integrated by heating and pressing while the roughened surface is brought into contact with the resin insulating layer is formed by the fine and complicated surface property of the copper layer. Throwing effect on the insulating layer is increased.

  In the method according to the present invention, a coupling agent treatment may be further performed after the blackening reduction treatment (Claim 5). In this case, the integration of the copper layer and the resin insulating layer is not only an adhesion force due to the anchoring effect but also a chemical bonding force.

  According to the surface treatment method for a copper layer according to the present invention (Claims 1 to 3), the copper layer can be provided with fine and complicated irregularities, and the copper layer is integrated with the resin insulating layer by heat and pressure molding. In the laminated board (Claim 6) and the wiring board (Claim 7) processed from the same, the adhesion between the copper layer and the resin insulating layer is excellent due to the large anchoring effect of the copper layer on the resin insulating layer. Can be.

  A copper layer having a thickness of 100 μm or more becomes increasingly difficult to produce by the electrodeposition method, and is produced by rolling. In this case, since the surface of the copper layer is smooth and has no irregularities, a high adhesion between the copper layer and the resin insulating layer is ensured if the surface treatment is performed by the method according to claim 4 and the laminate is manufactured. Convenient to. This contributes to the provision of a wiring board having a thick conductive circuit, and the reliability is improved by applying it to a wiring board for automobile equipment and large machines through which a large current flows. Since the conductive circuit is thick, heat dissipation is good.

  If the copper layer processed by the method according to claim 5 is used, the integration of the copper layer and the resin insulating layer is performed by adding not only adhesion due to anchoring effect but also chemical bonding force. As a result, the laminated board and the wiring board can also improve the characteristic (hereinafter referred to as “heat resistance”) that does not reduce the adhesion between the copper layer and the resin insulating layer even after the heat treatment.

  An embodiment of the invention will be described for the case of using a rolled copper foil as the copper layer. The rolled copper foil usually has a thickness of 100 μm or more.

  First, the etching-type chemical roughening treatment for the rolled copper foil can be performed using a sulfuric acid-hydrogen peroxide-based chemical roughening solution or an organic acid-based chemical roughening solution. This roughening process is performed so as to include the irregularities having a height from the valley to the mountain exceeding 5 μm. In this case, the amount of copper foil removed by the roughening treatment (hereinafter referred to as “roughening amount”) is set to an amount corresponding to a thickness of 4 μm or more in terms of the thickness of the copper foil.

  The inclusion of irregularities exceeding 5 μm is necessary for obtaining sufficient adhesion between the copper foil and the resin insulating layer. In order to further increase the adhesion, the etching type chemical roughening treatment is performed so as to include irregularities exceeding 8 μm, more preferably irregularities exceeding 12 μm. In this case, the roughening amount is set to 8 μm or more and 20 μm or more, respectively, in terms of the thickness of the copper foil.

  Thereafter, the roughening treatment surface is subjected to blackening reduction treatment to form smaller sub-micron irregularities on the roughening surface of the roughening treatment. As a result, the surface properties of fine and complicated irregularities are exhibited. For the blackening treatment, a roughening solution mainly composed of an aqueous sodium chlorite solution can be used, and this treatment produces fine acicular cuprous oxide or cupric oxide on the copper foil surface. Let In the subsequent reduction treatment, both organic and inorganic reducing agents can be used. By this treatment, the cuprous oxide or cupric oxide is reduced to copper. For the blackening treatment and the reduction treatment, treatments generally used in the manufacturing process of the multilayer printed wiring board can be applied.

  After the above blackening reduction treatment, a coupling agent treatment is preferably performed. The coupling agent is a silane coupling agent or a titanate coupling agent.

  The roughened surface of the rolled copper foil subjected to the above treatment is brought into contact with the resin insulating layer and integrated by heating and pressing to obtain a laminated plate. The resin insulation layer does not include a prepreg or a sheet-like fiber base material that is semi-cured by impregnating a sheet-like fiber base material (a woven or non-woven fabric of inorganic or organic fibers) with a thermosetting resin such as an epoxy resin. It is a resin insulating layer (BT resin or the like). In the prepreg, the resin is cured by heating and pressing to form a resin insulating layer. A metal oxide or hydroxide, inorganic ceramics, and other fillers can be blended in the resin insulating layer. Even when such a filler is blended, good adhesion between the copper layer and the resin insulating layer can be secured.

  The laminated plate may be integrated with the ceramic substrate via a resin insulating layer. The laminated board becomes a wiring board by processing the copper layer into a conductor circuit, and the treatment method according to the present invention is applied to the surface of the conductor circuit, and the copper layer is integrated on the resin insulating layer thereon. And a multilayer wiring board configuration can be obtained.

  Hereinafter, examples according to the present invention will be described in detail together with comparative examples. In addition, this invention is not limited to a present Example, unless it deviates from the summary.

Example 1
After degreasing a rolled copper foil (JIS C1201P) having a thickness of 100 μm, it is immersed in a sulfuric acid-hydrogen peroxide-based etching type chemical roughening treatment solution and subjected to a roughening treatment for 120 seconds. Concavities and convexities with a thickness of 2 to 8 μm were applied. The roughening amount of the copper foil at this time was adjusted to 4 μm in terms of the thickness of the copper foil.
Then, the blackening reduction process was implemented in order of the degreasing process, the acid process, the oxidation process, and the reduction process. At this time, sulfuric acid was used for the acid treatment, a mixed aqueous solution of sodium chlorite, sodium phosphate and sodium hydroxide was used for the oxidation treatment, and a mixed aqueous solution of dimethylaminoborane and sodium hydroxide was used for the reduction treatment. .
On the roughened surface of the rolled copper foil subjected to the above roughening treatment, a layer composed of five high heat resistant FR-4 grade prepregs was stacked, and heated and pressed for 90 minutes under the conditions of a temperature of 175 ° C. and a pressure of 4 MPa. To obtain a laminated plate having a thickness of 1.2 mm.

Example 2
In Example 1, after the blackening reduction treatment and drying, a treatment of immersing in an aqueous solution of a silane coupling agent was performed. Thereafter, a laminate having a thickness of 1.2 mm was obtained in the same manner as in Example 1.

Example 3
In Example 2, the roughening time by the sulfuric acid-hydrogen peroxide etching chemical roughening treatment liquid was 180 seconds, and unevenness having a height from the valley to the mountain of 5 to 12 μm was imparted. The roughening amount of the copper foil at this time was adjusted to 8 μm in terms of the thickness of the copper foil. Thereafter, a laminated plate having a thickness of 1.2 mm was obtained in the same manner as in Example 2.

Example 4
In Example 2, the roughening time by the sulfuric acid-hydrogen peroxide etching chemical roughening treatment solution was 600 seconds, and unevenness having a height from the valley to the mountain of 10 to 25 μm was imparted. The roughening amount of the copper foil at this time was adjusted to 20 μm in terms of the thickness of the copper foil. Thereafter, a laminated plate having a thickness of 1.2 mm was obtained in the same manner as in Example 2.

Comparative Example 1
In Example 1, the blackening reduction treatment was performed without performing the sulfuric acid-hydrogen peroxide-based etching type chemical roughening treatment, and a 1.2 mm thick laminate was obtained in the same manner as in Example 1.

Comparative Example 2
In Example 2, a blackboard reduction treatment was not performed, and a laminate having a thickness of 1.2 mm was obtained in the same manner as in Example 2 except for that.

Comparative Example 3
The surface of the rolled copper foil used in Example 1 was blasted using a suction type air blasting device using air pressure. This is a process of spraying particles mainly composed of alumina having an average particle diameter of 70 μm on the surface of the copper foil at a discharge pressure of 0.4 MPa for 40 seconds.
On the roughened surface of the rolled copper foil subjected to the above roughening treatment, a layer consisting of five prepregs was stacked in the same manner as in Example 1, and a laminated plate having a thickness of 1.2 mm was integrated by heating and pressing. Obtained.

Comparative Example 4
In Example 2, the roughening treatment time with the sulfuric acid-hydrogen peroxide etching chemical roughening treatment liquid was set to 60 seconds, and irregularities with a height from the valley to the mountain of 1 to 3 μm were imparted. The roughening amount of the copper foil at this time was adjusted to 2 μm in terms of the thickness of the copper foil. Thereafter, a laminated plate having a thickness of 1.2 mm was obtained in the same manner as in Example 2.

Comparative Example 5
In Example 2, the roughening time with the sulfuric acid-hydrogen peroxide based etching type chemical roughening treatment liquid was 90 seconds, and unevenness with a height from the valley to the mountain of 2 to 5 μm was imparted. The roughening amount of the copper foil at this time was adjusted to 3 μm in terms of the thickness of the copper foil. Thereafter, a laminated plate having a thickness of 1.2 mm was obtained in the same manner as in Example 2.

A test piece of 25 mm × 100 mm was cut out from the laminate of each of the above examples, and the copper foil peeling strength after aging at 177 ° C. for 240 hours was measured (measured at room temperature using a shopper). The results are shown in Table 1. Indicated.
The copper foil peel strength in the normal state is shown as a relative index with reference to Example 1. Moreover, the peeling strength after aging was expressed as 50% or more: 、, 20% to less than 50%: ◯, less than 20%: x with respect to the peeling strength in a normal state.

  As is clear from the above table, the laminated board in which the copper layer treated by the method according to the present invention is integrated with the resin insulating layer by heat and pressure molding has good peel strength in a normal state and good heat resistance. Can be understood (contrast of Example and Comparative Example). It is understood from the comparison between Example 2 and Comparative Examples 4 and 5 that it is necessary to perform treatment so that the height from the uneven valleys to the peaks provided by the etching type chemical roughening treatment exceeds 5 μm. it can.

  If the height from the valleys to the peaks of the unevenness includes more than 8 μm, and further includes more than 12 μm, the peel strength is further increased (Examples 2 and 3, 4 contrast).

  It can also be understood that heat resistance can be improved by adding a treatment with a coupling agent (contrast of Example 1 and Example 2).

Claims (7)

  A copper layer characterized by subjecting the surface of the copper layer to an etching-type chemical roughening treatment so that the height from the valley to the mountain includes unevenness exceeding 5 μm, and further subjecting the treated surface to a blackening reduction treatment Surface treatment method.   2. The surface treatment method for a copper layer according to claim 1, wherein the etching type chemical roughening treatment is carried out so as to include the irregularities having a height from the valley to the mountain exceeding 8 [mu] m.   2. The surface treatment method for a copper layer according to claim 1, wherein the etching-type chemical roughening treatment is performed so as to include the unevenness having a height from the valley to the mountain exceeding 12 [mu] m.   The copper layer surface treatment method according to claim 1, wherein the copper layer is a rolled copper foil having a thickness of 100 μm or more.   The copper layer surface treatment method according to any one of claims 1 to 4, further comprising a coupling agent treatment after the blackening reduction treatment.   The laminated board which integrated the roughening process surface into the resin insulating layer by heat-press molding using the copper layer processed by the method in any one of Claims 1-5.   The wiring board by which the copper layer of the laminated board of Claim 6 was processed into the conductive circuit.