JPH04284690A - Copper foil for inner layer circuit of multilayer printed circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance adhesive properties with a prepreg, to scarcely cause a haloing and to further facilitate an optical inspection. CONSTITUTION:A copper foil for an inner layer circuit of a multilayer printed circuit board comprising a black metal-plated layer further provided at least on a rough surface as a front surface of the inner layer circuit board of the foil in which both side surfaces are previously roughed.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a copper foil for inner layer circuits of multilayer printed wiring boards that has excellent adhesion to prepreg, is less likely to cause the haloing phenomenon, and is easy to optically inspect, and a method for manufacturing the same. Regarding.

0002

[Prior Art] The conventional method for manufacturing multilayer printed wiring boards is to bond copper foil to an insulating base material to form a copper-clad laminate, and then remove unnecessary copper foil portions from the surface by etching to form inner layer circuits. Then, in order to further improve the adhesion with the prepreg, after roughening and oxidizing the copper surface of the inner layer circuit,
An outer layer material is laminated on this, a through hole is made in this outer layer material to connect the inner layer circuit and the outer layer circuit, and the through hole is formed.
After forming a copper layer in the hole using electroless plating or the like to obtain continuity, the outer layer circuit was formed by etching.

[0003] In the manufacturing process of such multilayer printed wiring boards, copper foil for inner layer circuits is exposed to various processing steps and harsh usage conditions after circuit board formation, and processing and usage conditions have become even more severe in recent years. In order to improve the adhesion between the inner layer circuit and the prepreg, the copper surface of the inner layer circuit has conventionally been subjected to the following treatments.

[0004] After forming an inner layer circuit using a conventional single-sided roughened copper foil, a chemical treatment solution containing an oxidizing agent is used to form brown or black copper oxide called brown oxide or black oxide on the copper surface. (2) The black oxide in (1) above is treated with a reducing agent such as formalin to form reduced copper (Japanese Patent Application Laid-Open No. 1-310595). ■
Use commercially available double-sided roughened copper foil.

[0005] However, the copper foil for inner layer circuits using black oxide described in (2) above has poor chemical resistance and is prone to haloing, while the copper foil for inner layer circuits using brown oxide has poor chemical resistance. It had the drawbacks of insufficient chemical properties and poor adhesion to the prepreg.

[0006] In addition, in the above-mentioned copper foil for inner layer circuits using reduced copper, after forming the inner layer circuits, the circuits are processed by, for example,
When performing automatic optical inspection using the VISION 206 AOI (manufactured by Optrotech), the color difference between the copper color of the circuit part and the insulating layer part is small, so there are many false alarms with the AOI, and it takes a lot of time to confirm them. Not only does this require additional time, but it also has the disadvantage of overlooking circuit defects, resulting in insufficient inspection efficiency and reliability.

[0007] In the copper foil for inner layer circuits using the double-sided roughened copper foil described in (2) above, the color difference between the copper color of the circuit part and the insulating layer part is small, as in the case (2) above, so the inspection efficiency and reliability are insufficient. Another drawback was that the copper parts would rust if left unattended after the circuit was formed.

Furthermore, in such conventional processing, as long as the substrate after pressing and etching is processed, a batch processing method in which the veneer is immersed in a processing tank must be adopted, which requires a large amount of equipment investment and processing time. The disadvantage was that it required In addition, the inner layer circuit part to be treated has unfinished circuits such as through-holes, and there are parts that are not electrically connected, so roughening treatment and so-called blackening are required to increase the adhesion with the prepreg. Chemical treatment had to be carried out using only chemicals, without mechanical treatment such as polishing or electricity.

[0009] For this reason, conventional treatments have disadvantages in that the treatment is insufficient and the treatment time is long compared to electrochemical treatment in which electricity is passed. In addition, copper foil blackened with copper sulfide has poor adhesion to the base of the copper foil, so it peels off due to thermal expansion or contraction, making it unreliable for printed wiring boards. was there.

0010

SUMMARY OF THE INVENTION It is an object of the present invention to have excellent adhesion and haloing resistance between an inner layer circuit and a prepreg, and high efficiency and reliability of AOI inspection.
It is an object of the present invention to provide a copper foil for inner layer circuits of a multilayer printed wiring board and a method for manufacturing the same, which can manufacture a multilayer board without undergoing roughening treatment or blackening treatment by a batch-type chemical treatment process.

[0011]

[Means for Solving the Problems] The present inventors discovered that the conventional method of blackening treatment after forming an inner layer circuit does not allow power to be supplied to the entire circuit surface, and therefore an electrochemical treatment method cannot be adopted.
Therefore, the blackening treatment process, which required a large amount of equipment and processing time and was insufficient, was carried out electrochemically using a specific metal at the copper foil manufacturing stage, which improved the adhesion between the inner layer circuit and the prepreg. and excellent haloing resistance, and A
The present invention was achieved by discovering that a copper foil for printed circuits with high OI inspection efficiency and reliability can be obtained.

[0012] The first aspect of the present invention is a multilayer printed wiring characterized in that a black metal plating layer is further provided on at least the rough surface of the copper foil, which is the surface of the inner layer circuit board, which has been roughened on both sides in advance. This is a copper foil for inner layer circuits.

The second aspect of the present invention is a method for producing a copper foil for inner layer circuits of a multilayer printed wiring board, which comprises roughening both sides of the copper foil and forming a black metal plating layer on the copper foil. be.

The present invention will be explained in detail below. The copper foil with roughened surfaces on both sides used in the present invention may be obtained by a known method, such as cathodic treatment in a sulfuric acid acidic copper sulfate bath to adhere roughening particles to the surface of the copper foil. (see Japanese Patent Publication No. 54-38053, Japanese Patent Publication No. 53-39327, Japanese Patent Publication No. 53-38700), copper foil surface roughened by etching by anodizing in an acid bath Publication No. 61-54592). Further, as the copper foil, an electrolytic copper foil or a rolled copper foil can be used.

The copper foil for a multilayer printed wiring board of the present invention has a black metal plating layer on at least the surface of the copper foil which is roughened on both sides and which becomes the surface of the inner layer circuit board. The black metal plating layer (hereinafter referred to as the black plating layer) used in the present invention is not particularly limited as long as it is a metal plated black, and the so-called discoloration layer that is obtained by treating the metal with a current density at or near the limiting current. It may be a plated layer or a plated layer treated at a current density lower than the limiting current density.

The black plating layer used in the present invention is preferably a plating layer containing one or more metals selected from the group consisting of nickel, cobalt, chromium, rhodium, and tin, and more preferably nickel, nickel·
It is a plating layer containing copper alloy, nickel-tin alloy, nickel-tin-copper alloy, tin, tin-cobalt alloy, chromium, and rhodium.

The black plating layer preferably has fine irregularities to the extent that visible light is not reflected, and has a thickness that maintains the irregular shape of the roughened surface of the base, and the thickness is 100 to 10
,000 angstroms, preferably 100-3.0 angstroms
00 angstroms. In addition, the black plating layer is
It is not necessary to completely cover the entire surface of the uneven portion of the roughened surface of the copper foil. For example, even if a portion of the uneven portion is covered, it is sufficient that the appearance appears black. Specifically, JIS
The black plating layer has a Yxy value defined in Z 8701 of 15% or less, preferably 14% or less, and more preferably 13% or less. When the Yxy value exceeds 15%, false alarms in the AOI increase, and inspection efficiency and reliability may decrease.

[0018] Regarding the content of the metal component in the black plating layer, for example, the black plating layer of nickel and nickel/copper alloy preferably has a nickel content of 2 to 20 mg/dm2. The black plating layer of tin-nickel alloy has a tin content of 5 to 30 mg/dm2 and a nickel content of 2 to 12 mg/dm2.
Preferably it is dm2.

The black plating layer of nickel-tin-copper alloy has a nickel content of 1 to 10 mg/dm2 and a tin content of 5 to 2.
It is preferable that the amount of copper is 5 mg/dm2 and the amount of copper is 0.1 to 2 mg/dm2. The black plating layer of tin-cobalt alloy is
The amount of tin is 5-15 mg/dm2, the amount of cobalt is 10-3
Preferably it is 0 mg/dm2.

[0020] When the amount of each metal in the black plating layer is less than the lower limit, it may not be possible to obtain a color difference from the insulating layer.
Even if the upper limit is exceeded, the color difference will not be improved much and the economic burden will increase, which may not be preferable.

The black chromium plating layer has a chromium content of 0.
It is preferably 2 to 5 mg/dm2, and 0.2 mg/dm2.
If it is less than dm2, no color difference with the insulating layer may be obtained, and if it exceeds 5 mg/dm2, the color difference will not be improved much and the economic burden will increase, which is not preferable.

[0022] The rhodium black plating layer preferably has a rhodium content of 5 to 15 mg/dm2, preferably 5 mg/dm2.
If it is less than m2, no color difference with the insulating layer may be obtained, and if it exceeds 15 mg/dm2, the color difference will not be improved much and the economic burden will increase, which is not preferable.

[0023] As a method for forming a discolored plating layer of nickel or nickel-copper alloy on copper foil, for example, the method disclosed in Japanese Patent Application Laid-Open No. 55-58502 can be adopted, and specifically, Bath composition (nickel sulfate...1 to 6 g/l as nickel, copper sulfate...0.
3-0.6g/l, ammonium sulfate...50-1
00g/l, boric acid...10-40g/l):p
H (2.5): Bath temperature (20-50°C): Current density (2
An example of this method is a method in which the amount of nickel is burnt-plated under conditions of 10 A/dm2), but the method is not limited thereto.

As a method for forming a black chromium plating layer on copper foil, for example, the bath composition (chromic anhydride...22
5-300g/l, acetic acid...210-218g/l
, barium acetate...5 to 10 g/l): Bath temperature (
A method of plating the amount of chromium at a current density (4 to 10 A/dm2) (32 to 46 DEG C.) can be mentioned, but the present invention is not limited thereto.

As a method for forming a black plating layer of tin-cobalt alloy on copper foil, for example, bath composition (stannous pyrophosphate...8 to 15 g/l, cobalt chloride...
25-30g/l, potassium pyrophosphate...275
~350g/l, Everoy SNC#1 [manufactured by Ebara Yugilite Co., Ltd.]...75-125ml/l, Evalloy SNC#3 [manufactured by Ebara Yugilite Co., Ltd.]...15~
25ml/l: Bath temperature (45-55°C): Current density (0
．． 5-2.0A/dm2): pH (8.5-8.8)
Examples include a method of plating the amounts of tin and cobalt under the following conditions, but the method is not limited thereto.

As a method for forming a black plating layer of a tin-nickel alloy on a copper foil, for example, the bath composition (stannous pyrophosphate...8 to 15 g/l, potassium pyrophosphate...150 to 280 g/l) is used. l, Everoy Nickel [manufactured by Ebara Yugilite Co., Ltd.]...160-240ml/
l, Everoy SNC #3 [manufactured by Ebara Yugilite Co., Ltd.]
...10-20ml/l: Bath temperature (45-55°C):
Current density (0.5-2.0A/dm2): pH (8.
Examples include a method of plating the amounts of tin and nickel under the conditions of 5 to 8.8), but are not limited thereto.

As a method for forming a black plating layer of tin-nickel-copper alloy on copper foil, for example, the bath composition (tin chloride...25 to 30 g/l, nickel chloride...28
~35g/l, potassium pyrophosphate...180~2
50g/l, copper sulfate...2-3g/l, glycine...18-25g/l, ammonia water...3-8
ml/l: Bath temperature (45-55°C): Current density (0.
A method of plating the amounts of tin, nickel and copper under conditions of pH (8.0 to 8.5) (1 to 1.0 A/dm2) may be mentioned, but is not limited thereto.

As a method for forming a rhodium black plating layer on copper foil, for example, the bath composition (rhodium sulfate...7
~15g/l, sulfuric acid...40~160g/l: Bath temperature (38~50°C): Current density (2.0~10A/d
Examples include a method of plating the amount of rhodium under the conditions of (m2), but are not limited thereto.

[0029]

[Example] Example 1 Electrolytic copper foil with a thickness of 35 μm was used as a cathode, and lead was placed on both sides as an anode. Bath composition: Copper sulfate...30 g as copper.
/l, Sulfuric acid...60g/l, Arsenous acid...1g/l as arsenic: Bath temperature 24°C: Current density 17A/dm
2: First stage treatment under conditions of treatment time: 12 seconds to make unevenness by adhering copper particles to the rough and shiny surfaces of the copper foil, followed by thorough washing with water, and then bath composition: copper sulfate. ...70g/l as copper, 60g/l as sulfuric acid: Bath temperature 49℃
: Current density: 21.5 A/dm2 : Processing time: A second stage treatment was performed under the conditions of 12 seconds to fix the copper particles.

Immediately after washing thoroughly with water, bath composition: nickel sulfate...4 g/l as nickel, copper sulfate...0.5 g/l as copper,
Ammonium sulfate...50g/l, boric acid...1
A nickel-copper alloy containing 5 mg/dm2 of nickel was tan-plated under the following conditions: 0 g/l: pH 2.5: bath temperature 25° C.: cathode current density 5.5 A/dm2, and washed with water.

Then, on the roughened side of the foil, bath composition: zinc sulfate heptahydrate...5 g/l as zinc, sodium hydroxide...70 g/l: bath temperature 25°C: cathode current density 0
．． 5A/dm2: Zinc plating was carried out under the condition that the processing time was 1 second. Next, after immediately washing it with water, bath composition: Sodium dichromate...25 g/l: pH 6:
After chromate treatment under the conditions of bath temperature: 45° C., cathode current density: 2 A/dm 2 and treatment time: 1 second, the copper foil was washed with water and dried to produce a copper foil for inner layer circuits of a multilayer printed wiring board.

The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated as follows. The results are shown in Tables 1 and 2. (1) Inner layer copper foil peeling test Compliant with JIS C 6481. (2) Required time for inner layer circuit inspection using AOI
Etched using iron solution, line width 80 μm, line spacing 16
After forming the 0μm inner layer circuit, Optrotech VI
500×50 using SION 206 AOI
The time required to inspect one 0 mm circuit board was determined. (3) Evaluation of haloing property Epoxy-impregnated prepreg was superimposed on the front and back sides of the inner layer circuit board prepared in the same manner as in (2) above, and heated at 180℃ for 50k
A four-layer board was produced by hot pressing at a pressure of g/cm2 for 120 minutes. A drill hole with a diameter of 0.4 mm was made in the four-layer board obtained, and the hole was immersed in 12% hydrochloric acid for 5 minutes, and the harrowing length was measured. (4) Yxy value measurement: Compliant with JIS Z 8701.

Example 2 After depositing and fixing copper particles on both sides of an electrolytic copper foil in the same manner as in Example 1, instead of the tan plating of nickel-copper alloy, the shiny side of the foil was coated with a bath composition: Chromic anhydride...250
g/l, acetic acid...215g/l, barium acetate...
7.5g/l: Bath temperature 40℃: Current density 15A/
dm2: A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that black chromium plating was performed under the conditions of a processing time of 60 seconds. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 3 Electrolytic copper foil with a thickness of 35 μm was used as a cathode, and lead was placed on both sides as an anode. Bath composition: copper sulfate pentahydrate...30 g/l as copper, sulfuric acid...80 g/l. l: Bath temperature 30℃
:Current density: 15A/dm2 :Processing time: Processed under the conditions of 10 seconds to create unevenness by adhering copper particles to the rough and glossy surfaces of the copper foil, and then washing thoroughly with water to reduce the amount of nickel to 3mg/dm.
A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that the nickel/copper alloy of No. 2 was plated with discoloration. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. Table 1 shows the results.
and shown in Table 2.

Example 4 A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that a rolled copper foil having a thickness of 35 μm was used in place of the electrolytic copper foil. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 5 A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that nickel/copper alloy discoloration plating was formed on both the glossy side and the rough side. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1 Copper particles were attached and fixed only to the rough surface of an electrolytic copper foil in the same manner as in Example 1, and then only this rough surface was coated without tanning plating with nickel-copper alloy. A copper clad board for an inner layer circuit board was prepared by galvanizing and chromate treatment in the same manner as in Example 1.

Next, this was etched using a ferric chloride solution to form an inner layer circuit with a line width of 80 μm and a line spacing of 160 μm, and then only the glossy side was etched with a bath composition of sodium hydroxide.
...15g/l, trisodium phosphate dodecahydrate...
・30g/l, sodium chlorite...90g/l
After black oxidation treatment under the following conditions: bath temperature: 85° C.: treatment time: 90 seconds, the inner layer circuit board was prepared by washing with water. The obtained inner layer circuit board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 2 Copper particles were adhered and fixed only to the rough surface of the electrolytic copper foil in the same manner as in Example 1, and then, instead of the faded plating of nickel-copper alloy, only the shiny surface was coated. Bath composition: Sodium hydroxide...15g/l, trisodium phosphate dodecahydrate...30g/l, sodium chlorite...90g
/l: A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that the black oxidation treatment was carried out under the conditions of bath temperature 85° C. and treatment time 90 seconds. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 3 The glossy side of the copper foil for the inner layer circuit of a multilayer printed wiring board produced in the same manner as in Comparative Example 2 was coated with a bath composition: Sodium borohydride...1 g/l: pH 12.5: Bath temperature 40℃:
After processing for 40 seconds and washing with water, bath composition: 36% formalin...4 g/l, sodium sulfate...71 g/l: pH 12.5: Bath temperature: 40°C:
Processing time: The potential of the copper surface is -1200 mV (silver -
The foil was treated with water to produce a reduced copper-forming treated foil. The obtained reduced copper-forming treated foil was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 4 A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that copper particles were not attached or fixed to the glossy side of the electrolytic copper foil. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 5 Both sides of the electrolytic copper foil were coated with bath composition: copper sulfate pentahydrate...30 g/l as copper, sulfuric acid...80 g/l, hydrochloric acid acidic antimony trioxide...0.0 g/l as antimony. 1g/l
, selenite...0.1 g/l as selenium: Bath temperature 30°C: Current density 15 A/dm2: Processing time: 10
The procedure was the same as that of Example 1, except that copper particles were applied to the rough and shiny surfaces of the copper foil to create irregularities, and then the copper foil was thoroughly washed with water and the nickel-copper alloy was not plated. In the same manner, a copper foil for an inner layer circuit of a multilayer printed wiring board was produced. Regarding the obtained copper foil for inner layer circuits of multilayer printed wiring boards,
Evaluation was made in the same manner as in Example 1. The results are shown in Tables 1 and 2. In addition, in the inner layer copper foil peeling test of this comparative example, a large amount of copper residue was observed.

Comparative Example 6 A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that the nickel-copper alloy was not plated with discoloration. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 7 In place of the tan plating treatment of nickel/copper alloy, Comparative Example 2
A copper foil for an inner layer circuit of a multilayer printed wiring board was produced in the same manner as in Example 1, except that the copper foil was treated with black copper oxide in the same manner as in Example 1. The obtained copper foil for inner layer circuits of a multilayer printed wiring board was evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Effects of the Invention] According to the copper foil for the inner layer circuit of a multilayer printed wiring board of the present invention, since both sides of the copper foil are roughened, the adhesion between the inner layer circuit and the prepreg is improved, and further,
Since a black metal plating layer is provided on the roughened surface, the haloing phenomenon does not occur, and the AOI test can be performed accurately in a short time.

Furthermore, according to the manufacturing method of the present invention, since both sides of the foil are roughened and the metal is black-plated when manufacturing copper foil, production efficiency is excellent, and furthermore, multilayer printed wiring boards can be manufactured easily. Since the batch-type chemical treatment process can be omitted in the process, it is possible to simultaneously improve the quality and productivity of multilayer printed wiring boards.

Claims (4)

[Claims] 1. Copper for inner layer circuit of a multilayer printed wiring board, characterized in that a black metal plating layer is further provided on at least the rough surface of the copper foil which has been roughened on both sides, which will become the surface of the inner layer circuit board. foil. 2. The copper foil for inner layer circuits of multilayer printed wiring boards according to claim 1, wherein the black metal plating layer contains one or more metals selected from the group consisting of nickel, cobalt, chromium, rhodium, and tin. . 3. The copper foil for internal layer circuits of a multilayer printed wiring board according to claim 1, which has a black plating layer having a Yxy value of 15% or less as defined in JIS Z 8701. 4. A method for manufacturing a copper foil for inner layer circuits of a multilayer printed wiring board, which comprises roughening both sides of the copper foil and forming a black metal plating layer on the copper foil.