JPH03129794A - Treating method for circuit board substrate - Google Patents

Abstract

PURPOSE:To prevent a halo phenomenon for dissolving an oxide layer of copper in acid by oxidizing copper provided on the surface of a board, then reducing it and forming a zinc or zinc-copper alloy layer on the surface of the copper oxide layer in a specific amount of thickness. CONSTITUTION:Copper provided on the surface of a board is oxidized to form a copper oxide layer on the surface of copper, the copper oxide layer is then reduced, and a zinc or zinc-copper alloy layer is formed in the thickness of 0.001-1g/bm<2> on the surface of the reduced oxide layer. The oxide layer is coated with zinc, the zinc is so dissolved with acid or alkali. as to allow the layer of the zinc or the zinc-copper alloy to remain in the thickness of 0.001-1g/bm<2> to thereby reduce the copper oxide layer. An outer layer circuit board and other inner layer circuit board or a copper foil 3 are superposed on the board 1 through a prepreg 2, heated, pressurized and laminated.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for treating copper on the surface of a circuit board substrate used as an inner layer circuit board used in the manufacture of multilayer printed wiring boards.

[Conventional technology l] A multilayer printed wiring board is produced by overlapping an outer layer circuit board or copper foil via a prepreg on an inner layer circuit board with a circuit formed on one or both sides using copper foil, etc., and then forming this under heat and pressure. It is generally manufactured by laminating an inner layer circuit board and an outer layer circuit board or @foil. It is also necessary to ensure adhesion between the copper circuit formed on the inner layer circuit board and the resin of the prepreg on which the outer layer circuit board or copper foil is laminated. In particular, when forming circuits on inner layer circuit boards using electrolytic copper foil, one side of the copper foil is formed with a rough surface, while the other side is formed with a smooth surface. Because the copper foil is bonded to the inner layer circuit board, the surface of the copper circuit on the inner layer circuit board becomes a smooth surface of the copper foil, and the adhesion between the copper circuit and the prepreg resin is extremely low. Therefore, it is necessary to devise ways to increase the quality. Therefore, various methods have been studied to improve the adhesion between copper circuits and resins, and it is common practice to form an oxide layer on the surface of copper circuits to improve adhesion. When copper is oxidized, fine protrusions are formed on the surface of the oxide layer, and these protrusions can roughen the surface and improve adhesion. The oxide layer is generally formed on the surface of the copper circuit by treatment with an alkaline aqueous solution containing potassium persulfate or an alkaline aqueous solution containing sodium chlorite. By forming an oxide layer on the surface of copper in this way, sufficient adhesion between copper and resin can be ensured. However, copper oxide, especially cupric oxide (Cub), is easily dissolved in acids, so if it is immersed in a chemical plating solution when plating the through hole after drilling, it will cause the inner periphery of the through hole to The oxide layer on the exposed cross-section of the copper circuit dissolves in the acid (hydrochloric acid, etc.) of the plating solution, and the so-called halo phenomenon occurs in which the acid infiltrates the interface between the copper circuit and the resin from the inner periphery of the through-hole. This may easily occur, and the reliability of the multilayer printed wiring board may deteriorate. Therefore, as provided in Japanese Patent Application Laid-open No. 176192/1983, the surface of copper is oxidized and then reduced with an alkaline reducing solution such as dimethyl 7/poran, so that it dissolves in acid. Cupric oxide, which is easy to dissolve, is reduced to metallic copper, which is difficult to dissolve in acids, and the formation of a thick halo is prevented. [Problem to be solved by the invention] However, dimethylaminoborane When a copper oxide layer is reduced using, for example, a copper oxide layer, the surface becomes active metallic copper. There has been a problem in that copper is easily oxidized again, and this oxidized copper may dissolve in acid, leading to the formation of a large halo.The present invention has been made in view of the above points. The object of the present invention is to provide a method for processing circuit board substrates that can prevent the occurrence of the halo phenomenon while maintaining the effect of increasing the adhesion between copper and resin. Means for Processing] The method for processing a circuit board substrate according to the present invention includes oxidizing copper provided on the surface of the substrate to form a copper oxide layer on the copper surface, and then reducing the copper oxide layer. At the same time, a layer of zinc or zinc-copper alloy is added on the surface of the reduced copper oxide layer.
It is characterized in that it is formed with a thickness of oi to 1 g/bI12. Further, in the present invention, the surface of the copper oxide layer is coated with zinc so that the layer of zinc or an alloy of zinc and copper has a 0.
The copper oxide layer is preferably reduced by dissolving the zinc with acid or alkali so that it remains at a thickness of 001 to 18/bI02. The present invention will be explained in detail below. As a board, copper clad with copper foil can be used to create copper circuits on one or both sides by etching the copper foil such as lath epoxy Q (fat laminate, copper clad lath polyimide resin laminate, etc.). In addition, it is also possible to use a laminated board with copper circuits formed on one or both sides by chemical plating or electroplating.Then, first, the surface of this board is roughened. The surface roughening treatment can be carried out by buff polishing, chemical treatment such as soft etching, electrolytic treatment, liquid honing, etc. A copper foil with rough surfaces on both sides is used as the copper foil. In some cases, such surface roughening treatment can be omitted.Next, the copper surface of this substrate is oxidized.The oxidation treatment is performed using an alkaline aqueous solution containing potassium persulfate or sodium chlorite. This can be carried out by treatment using an alkaline aqueous solution containing an oxidizing agent, such as an aqueous alkaline solution containing an oxidizing agent.By performing the oxidation treatment in this way, a copper oxide layer can be formed on the surface of the copper. The copper oxide layer is mainly formed by cupric oxide (Cub).This oxidation treatment can roughen the surface of the copper.In this way, the oxide layer is formed on the copper surface of the substrate. After forming the copper oxide layer, the surface of the copper oxide layer is coated with metal zinc (Zn), which is more easily ionized than copper oxide (mainly Cub).This zinc can be used, for example, in the form of a powder. , wet the copper surface with water or solvent and then spray zinc powder on it, or apply a solution of zinc powder dispersed in water or solvent to the copper surface with a roll, or use this solution with zinc powder dispersed. The surface of the copper oxide layer can be coated with zinc powder by immersing the substrate in it.Ethylene glycol, polyethylene glycol, etc. can be used as the solvent.Of course, the method is not limited to these methods. Any method may be used as long as the surface of the copper oxide layer can be uniformly coated with zinc. After coating the surface of the copper oxide layer with metallic zinc as described above, the zinc is Alternatively, dissolve the oxide layer from the surface with an alkali.The acid or alkali that dissolves zinc can be used without particular limitation as long as it does not dissolve copper.In this way, zinc can be dissolved with an acid or an alkali. When dissolved, zinc is dissolved in the state of cations, and at this time, a reducing action acts on the copper oxide layer, converting CuO in the copper oxide to Cu20.
(cuprous oxide) or metal Cu. By reducing CuO in copper oxide in this way, it is possible to make the copper oxide layer difficult to dissolve in acid while maintaining the surface roughness. This makes it possible to prevent the halo phenomenon. In addition, when dissolving the zinc coated on the surface of the copper oxide layer, it is important to note that rather than dissolving the entire amount of zinc (or dissolving some of the zinc as a layer of zinc, or dissolving this zinc), By leaving the surface of the reduced copper oxide layer as a layer of zinc-copper alloy formed by migrating into the copper when or zinc-
It is coated with a layer of copper alloy. By coating with a layer of zinc or zinc-copper alloy in this way, the metallic copper that has been formed on the surface of the copper oxide layer during the reduction treatment is removed by treatment at high temperatures to dry and dehumidify the substrate. It is also possible to prevent oxidation, and it is possible to prevent the halo resistance from decreasing due to high-temperature treatment. This layer of zinc or zinc-copper alloy is 0.00
It is preferable to form the film with a thickness of 1 to ig/bm' (the thickness ranges from several tens to several thousand). If it is less than 0.001 g/1oo2, the thickness of the zinc or zinc-copper alloy layer will be insufficient, and the effect of preventing the oxidation of the metal copper during high-temperature treatment will be insufficient. If the
Copper remover (adhesion with fat may become insufficient. In addition, "blf12" in "g/b1112" above means "board export 2", and is a unit that includes both the front and back sides of the board. For example, if 1112 copper is formed on each of the front and back sides of the substrate, and a layer of zinc or zinc-copper alloy is formed in an amount of 1 g on the surface of the copper with the front and back sides of the substrate together, 1 g /bm2. Therefore, 1g
/bm2 is 1 g/2 m2= 0.5 g/l11
2 can be displayed. After performing the treatment to reduce the oxide layer on the surface of the copper as described above, it is immediately washed with water or hot water, heated and dried, and then used as an inner layer circuit board and carried out the normal process. Multilayer printed wiring boards can be manufactured using this method. In other words, the outer layer circuit board (
Alternatively, layers of copper foil (or circuit board for the inner layer of the pond) or copper foil are laminated by heating and pressurizing to form a multilayer prepreg as a bonding layer, and through-holes are formed by Y-rill processing and chemical plating, etc. A multilayer printed wiring board can be manufactured by performing through-hole plating using the method described above, and further processing such as etching to form an outer layer circuit.

【Example】

Next, the present invention will be explained by examples. LLLL ■ Thickness 1.0 formed by pasting 70μ thick copper foil on both sides.
Using a lath cloth-based epoxy resin laminate (Matsushita Electric Works Co., Ltd. product number 176G) of mm as a substrate, an inner layer circuit was created on copper foil, and the surface of the copper circuit was roughened by buffing. . ■ Next, K 2S , 08...13g/lNaO
H...-55g/I! A potassium persulfate bath having the composition was adjusted to 60° C., and the substrate was immersed in this oxidation treatment bath for 3 minutes to oxidize the surface of the copper circuit. ■ Next, metallic zinc powder with an average particle size of 3μ is dispersed in ethylene glycol in a blending amount of 11 parts I) 200 Fi,
By immersing the substrate in this zinc powder dispersion, the surface of the copper circuit was coated with zinc powder. ■ After coating with zinc powder in this way, the substrate is immersed for 30 seconds in an aqueous hydrochloric acid solution with a volume ratio of water:HCN of 1:1 to dissolve the zinc and to dissolve the copper. The copper oxide layer on the surface of the circuit was reduced. ■ After dissolving zinc with an aqueous hydrochloric acid solution in this way,
Immediately, the substrate was washed with running water and dried by heating at 130° C. for 60 minutes. In this board, there is no zinc on the surface of the copper circuit.
．． It remained as a layer of thickness in the amount of O1 g/m2. Then, the substrate 1 treated as described above was used as an inner layer circuit board, and as shown in FIG.
+a prepreg (1661JM manufactured by Matsushita Electric Works Co., Ltd.)
Layer 2 three sheets at a time, and add a layer of thickness 18 to the outside.
Copper foil 3 of μ is stacked and built up at 170℃ and 20kgf/cm2.1 in a reduced pressure atmosphere of 50Torr.
A multilayer board was obtained by secondary lamination molding for 20 minutes. A multilayer board was obtained in the same manner as in Example 1, except that the metal zinc powder formulation 1 in (2) was set to 1000 g per ethylene glycol 11. In this case, zinc was added to the surface of the copper circuit at 0.1 g/v on the board.
It remained as a layer of thickness r2. 11L After carrying out the treatments ① and ② in Example 1, 20% of trimethylamine borane was added to water. The substrate was immersed for 3 minutes in an alkaline reducing solution dissolved in an amount of /N, and then immediately washed with water and dried by heating at 80° C. for 60 minutes. A multilayer board was then obtained in the same manner as in Example 1 using this substrate. Comparative Example 2 A multilayer board was obtained in the same manner as in Comparative Example 1, except that the drying conditions were changed to 130° C. for 60 minutes. The multilayer plates obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were coated with 0
Through-hole processing was performed using a drill pit F of 4 mmφ under the conditions of a rotational speed of 80,000 rpm and a feed rate of 1.6 tn/win. Water this: HC1! is 1:
The sample was immersed in an acid solution having a volume ratio of 1 for 30 minutes, and the size of the halo was observed using a microscope and its maximum value was measured. In addition, the adhesion between the copper and prepreg resin in the multilayer board was measured as interlayer adhesion strength, and the multilayer board was placed in a solder bath at 288°C for 1 hour.
Soldering heat resistance was measured by immersion for 0 seconds. For solder heat resistance, those with no abnormality are marked with "○", and those with abnormalities such as 7 cracks are marked with "x1".These results are shown in barley.As seen in the previous table, copper circuit After oxidizing, zinc is coated and dissolved away to reduce the copper oxide layer of the copper circuit and to make the zinc or zinc-copper alloy layer the surface of the reduced copper oxide layer. In each example, no large halo was generated even when treated at a high temperature of 130°C for drying, but when reduction treatment was performed using noacylamine borane, 8
It is confirmed that when processed at a low temperature of about 0°C, ha-a does not increase as in Comparative Example 1, but when processed at a high temperature of 130°C, a large halo occurs as in Comparative Example 2.

【Effect of the invention】

As described above, in the present invention, the copper provided on the surface of the substrate is oxidized to form a copper oxide layer on the surface of the copper. By forming a layer, fine protrusions are formed on the surface of the copper circuit, and by roughening the surface, it is possible to improve the adhesion between the copper circuit and the resin.Also, by reducing this copper oxide layer, Since a layer of zinc or zinc-copper alloy was formed on the surface of the reduced copper oxide layer with a thickness of 0.001 to 1 g/bL112, #! The oxide layer can be made difficult to dissolve in acids, and the zinc or zinc-copper alloy layer can prevent the reduced copper oxide layer from being oxidized again by high-temperature treatment. This prevents the copper oxide layer from dissolving in acid during plating and causing a halo phenomenon. Also, by coating the surface of the oxide layer with zinc, the layer of zinc or an alloy of zinc and copper can be coated with 0.001 to 1 g/b.
If the copper oxide layer is reduced by dissolving zinc with acid or alkali so that it remains with a thickness of m2, the reduction treatment of the copper oxide layer and the reduction of the copper oxide layer Formation of the zinc or zinc-copper alloy layer can be performed simultaneously in one step, streamlining the work.

[Brief explanation of the drawing]

FIG. 1 is a schematic exploded view showing the laminated structure when forming a multilayer board, in which 1 is a substrate, 2 is a prepreg, and 3 is a copper foil.

Claims (2)

[Claims] (1) Copper provided on the surface of the substrate is oxidized to form a copper oxide layer on the surface of the copper, and then the copper oxide layer is subjected to reduction treatment, and zinc or zinc is added to the surface of the reduced copper oxide layer. −
A method for processing a circuit board substrate, comprising forming a copper alloy layer with a thickness of 0.001 to 1 g/bm^2. (2) Coating zinc on the surface of the copper oxide layer so that the layer of zinc or an alloy of zinc and copper is 0.001 to 1 g/b
2. The method of treating a circuit board substrate according to claim 1, wherein the copper oxide layer is reduced by dissolving zinc with acid or alkali so that the copper oxide layer remains with a thickness of m^2. .