JPH05308192A - Board for multilayer printed wiring board - Google Patents

Abstract

PURPOSE:To provide a multilayer printed wiring board wherein it restrains a halo phenomenon around a through-hole plated part and it eliminates an interlayer exfoliation completely without lowering the bonding power of a printed wiring copper conductor to a prepreg resin. CONSTITUTION:In a board for multilayer printed wiring board one or more printed wiring boards for inner-layer are overlapped via prepregs while a board material for outer-layer is arranged at least on one surface and the whole assembly is heated, pressurized, laminated and united. The board for multilayer printed wiring board is constituted in the following manner: a copper oxide layer is formed on the surface of a printed wiring copper conductor for a printed wiring board for inner-layer the copper oxide layer is reduced; a reduced copper layer is formed; and the surface of the reduced copper layer is covered with a molybdenum compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a multilayer printed wiring board, and more particularly to modification of a printed wiring copper conductor surface of an inner layer printed wiring board used for a multilayer printed wiring board substrate.

[0002]

2. Description of the Related Art In general, a multilayer printed wiring board substrate has one or more inner layer printed wiring boards on which a printed wiring pattern is formed in advance through a prepreg and an outer layer substrate material disposed on at least one surface. It has a structure in which it is laminated and integrated by heating and pressing the whole.
By the way, for a copper clad laminate used as a starting material for a printed wiring board for an inner layer, an electrolytic copper foil excellent in quality and productivity is generally often used as a copper foil for the conductor. Due to the manufacturing method of this electrolytic copper foil, the surface (liquid surface side) is a matte rough surface and the back surface (electrode side surface) is a silky smooth surface. In order to improve the force, it is manufactured by arranging the matte rough surface of the electrolytic copper foil on the bonding surface side. Therefore, the surface of the printed wiring copper conductor of the printed wiring board for the inner layer is a silky smooth surface. For a multilayer printed wiring board obtained by arranging one or more of such inner layer printed wiring boards through at least one surface of the outer layer substrate material through a prepreg and superimposing them, and heating and pressing the whole to laminate and integrate them. Since the surface of the printed wiring copper conductor of the printed wiring board for the inner layer is a smooth surface, sufficient adhesion cannot be obtained. Therefore, by forming a layer of copper oxide chemically on the surface of the printed wiring copper conductor of the printed wiring board for the inner layer in advance, the surface is made uneven as a result of copper oxide, and the adhesion area is expanded and the anchor effect is achieved. It is possible to obtain extremely excellent adhesive strength. However, copper oxide easily dissolves in acid, and the printed wiring is removed by acids such as hydrochloric acid and sulfuric acid used in the through-hole plating process that passes through when finishing a multilayer printed wiring board substrate into a multilayer printed wiring board. When the copper conductor is eroded, a phenomenon (halo phenomenon) that causes corrosion traces of copper oxide from brown or black to pink of copper (halo phenomenon) occurs, the adhesive force at that portion disappears, and soldering of the multilayer printed wiring board There has been a problem that the layers may be separated during thermal shock during the process, which may lead to an accident when electricity is applied. As a solution to such a problem, after forming a layer of oxidized cupric on the printed wiring copper conductor surface of the printed wiring board for the inner layer, the surface of the oxidized cupric oxide film is oxidized by immersion treatment in an alkaline reducing agent solution. Proposal to reduce to a cuprous or metallic copper film (JP-A-56-
153797). However, this proposal requires that the proportion of metallic copper in the cupric oxide layer be small in order to exert excellent adhesive strength, but if the proportion of metallic copper is small, the acid resistance will be poor, and Conversely, if the proportion of metallic copper in the cupric oxide layer is increased to make it excellent in acid resistance, the adhesive strength will be inferior, and both acid resistance and adhesiveness will be satisfied at a high level at the same time. There is a problem that is difficult. The present invention has been made in view of such circumstances, and an object of the present invention is to suppress the halo phenomenon around through-hole plating without reducing the adhesive force between the printed wiring copper conductor and the prepreg resin. And to provide a multilayer printed wiring board with no delamination.

[0003]

In order to solve the above problems, the multilayer printed wiring board substrate of the present invention has a copper oxide layer formed on the surface of a printed wiring copper conductor of an inner layer printed wiring board. Then, this copper oxide layer was reduced to a reduced copper layer, and the surface of this reduced copper layer was coated with a molybdenum compound. The reason for forming the layer of copper oxide on the surface of the printed wiring copper conductor of the printed wiring board for the inner layer is to form an uneven surface due to the copper oxide to improve the adhesive force. A copper oxide layer can be formed on the surface of the printed wiring copper conductor by a chemical treatment, and for example, an alkaline sodium chlorite aqueous solution (sodium chlorite: 10 to 60 g / l, sodium hydroxide: 10). ~ 20 g / l, trisodium phosphate 5-1
A layer of copper oxide can be formed on the surface of the printed wiring copper conductor by immersing it in 0 g / l and a temperature of 80 to 100 ° C. for 2 to 5 minutes. Further, by immersing in an alkaline potassium persulfate aqueous solution (potassium persulfate 10 g / l, sodium hydroxide 50 g / l, temperature 80 to 100 ° C.) for 2 to 5 minutes, a copper oxide layer is formed on the printed wiring copper conductor surface. Can be formed. Furthermore, barium sulfide 2
4 g / l, ammonium chloride 24 g / l, copper acetate 30 g
It is also possible to form a layer of copper oxide on the surface of the printed wiring copper conductor by immersing in an aqueous solution of 1 / l, copper sulfate 24 g / l, and temperature of 40 to 50 ° C. for 2 to 5 minutes. The reason for forming the reduced copper layer on the surface of the copper oxide layer is that the copper oxide and the molybdenum compound having excellent acid resistance cannot be combined to form a film. This is because a molybdenum compound is combined as a copper layer to enable formation of a film. The surface of the copper oxide layer can be formed into a reduced copper layer by immersion treatment in an acidic reducing solution. For example, a copper oxide layer is prepared by adjusting an aqueous solution of 1 g / l to 50 g / l of dimethylamine borane to pH 3 to 7 with an acid such as acetic acid and immersing the solution in the temperature range of 10 to 80 ° C. for 1 to 30 minutes. Can be a layer of reduced copper. In the present invention, the coating of the molybdenum compound that coats the surface of the reduced copper layer is a molybdenum compound solution, for example, molybdic acid, ammonium molybdate, potassium molybdate, sodium molybdate,
A molybdenum compound solution obtained by dissolving calcium molybdate, lithium molybdate, etc. in a solvent such as water or alcohol to a concentration of 0.1% to 10% is immersed in a liquid temperature of 10 to 80 ° C for 10 seconds to 10 minutes, It can be formed by drying.

[0004]

Since the copper oxide layer is formed on the surface of the printed wiring copper conductor of the printed wiring board for the inner layer, the surface shape becomes an uneven surface due to the copper oxide. Since the copper oxide layer is a reduced copper layer to the extent that the uneven surface is not damaged, the surface of the reduced copper layer becomes an uneven surface which is almost the same as the uneven surface of the copper oxide layer surface. Since a molybdenum compound is bonded to the uneven surface of the reduced copper layer to form a film, the molybdenum compound film also has substantially the same uneven surface. Therefore, the uneven surface of the molybdenum compound coating has a smaller decrease in the adhesion area and the anchor effect less than the uneven surface of the copper oxide layer surface. Since it is covered with, the inner layer printed wiring pattern copper conductor will not come into contact with acid during the through hole plating process,
The halo phenomenon will not occur.

[0005]

Embodiment 1 A substrate for a multilayer printed wiring board according to the present invention is
It can be manufactured as follows. First, an inner layer printed wiring board on which a predetermined printed wiring is formed is prepared. A copper oxide layer, a reduced copper layer, and a molybdenum compound film are formed on this inner layer printed wiring board by the following procedures (1) to (3). (1) The inner layer printed wiring board was treated with an alkaline sodium chlorite aqueous solution (sodium chlorite 50 g / l, sodium hydroxide 15 g / l, trisodium phosphate 5 g / l,
Immersion in a temperature of 80 to 100 ° C. for 3 minutes to form a copper oxide layer on the surface of the printed wiring copper conductor. (2) The inner layer printed wiring board on which the copper oxide layer is formed is immersed for 5 minutes in an acidic reducing agent solution (dimethylamine borane 5 g / l aqueous solution adjusted to pH 6.0 with acetic acid, solution temperature 10 to 80 ° C.), It is washed with water and dried to form the copper oxide layer as a reduced copper layer. (3) The inner layer printed wiring board in which the reduced copper layer is formed on the surface of the copper oxide layer is immersed in a molybdenum compound solution (1% aqueous solution of ammonium molybdate, liquid temperature 20 ° C.) for 2 minutes,
After drying, a coating film of a molybdenum compound is formed on the surface of the reduced copper layer. Next, a copper oxide layer is formed on the surface of the printed wiring copper conductor thus obtained, a reduced copper layer is formed on the surface of this copper oxide layer, and molybdenum is formed on the surface of this reduced copper layer. At least one inner layer printed wiring board having a compound coating film formed thereon is placed on at least one surface of the inner layer printed wiring board via a prepreg and laminated, and the whole is laminated by heating and pressing to form a multilayer printed wiring board. A board substrate was obtained.

[0006]

Example 2 A multilayer printed wiring board substrate was obtained in the same manner as in Example 1 except that ammonium molybdate was changed to sodium molybdate.

[0007]

Comparative Example A multilayer printed wiring board substrate was manufactured in the same manner as in Example 1 except that the step of immersing in a solution of ammonium molybdate was omitted.

Throughholes of 0.4 mmφ are formed at predetermined positions on a total of three types of substrates for multilayer printed wiring boards of these 2nd Examples 1 and 2 and Comparative Example 1, and throughhole plating is carried out by a conventional method. Given the halo value,
Solder heat resistance and inner layer peel strength were measured, and the results are shown in Table 1.

[0009]

[Table 1]

In Table 1 above, the halo amount, inner layer peel strength, and solder heat resistance are measured under the following conditions. Halo amount: The inner layer copper surface is exposed and the maximum amount is measured. Inner layer peel strength: Based on JIS C-6481, the peel strength between the inner layer copper body surface and the prepreg resin adhesive surface is measured. Soldering heat resistance: 26 according to JIS C-6481
It is floated in a solder bath at 0 ° C. and the time for peeling between layers to occur is measured.

[0011]

EFFECTS OF THE INVENTION The substrate for a multilayer printed wiring board of the present invention has an effect that it is excellent in interlayer peel strength and has less halo.

Claims (1)

[Claims] 1. A multilayer printed wiring board in which one or more inner layer printed wiring boards are laminated on at least one surface of an outer layer substrate material through a prepreg, and the whole is laminated by heating and pressing. In the substrate, a layer of copper oxide is formed on the surface of the printed wiring copper conductor of the printed wiring board for the inner layer, and the copper oxide layer is treated as a reduced copper layer, and the surface of the reduced copper layer is coated with a molybdenum compound. A substrate for a multilayer printed wiring board characterized by being provided.