JP2003013156A - Copper alloy foil for laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy foil with small surface roughness, and a high electroconductivity and strength, which has adequate adhesiveness to an adhesive containing an epoxy resin without being roughened, and can be laminated to be a copper-clad laminate, in a three-layer flexible substrate. SOLUTION: The copper alloy foil for laminate is characterized by employing a copper alloy containing specific elements, and making the thickness of a rust preventive film to be 3 nm or less from the surface, to give the surface adequate adhesiveness to the adhesive containing the epoxy resin, surface roughness of 2 μm or less by ten-points average surface roughness (Rz), and 180-degree peel strength of 8.0 N/cm or more when bonded to a substrate film with the adhesive containing the epoxy resin, without being roughened.

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate for printed wiring boards.
The present invention relates to a copper alloy foil used for a plate. [0002] 2. Description of the Related Art Printed wiring boards are used in electronic circuits of electronic equipment.
Is often used. Printed wiring board is the base resin
Depending on the type of hard laminated board (rigid board), flexible
And flexible laminates (flexible substrates). Flexi
The flexible substrate is characterized by having flexibility,
In addition to being used for wires,
Space saving wiring material.
It is also used. Also, is the substrate itself thin?
For semiconductor package interposer applications or
Also used as an IC tape carrier for liquid crystal displays
Have been. Flexible substrate is polyimide resin
Film or polyester resin film is used
However, at present, polyimide is often used because of its heat resistance.
ing. Is the conductive material of the flexible substrate a conductive point?
In general, copper is used. Printed wiring board is copper-clad
Various wiring patterns are formed by etching the copper foil of the laminate
Then, electronic components are connected by solder and mounted. [0003] A flexible substrate has a two-layer flexible structure due to its structure.
There are a kibble substrate and a three-layer flexible substrate. Double layer
Flexible substrate becomes conductive material with resin such as polyimide
It has a structure in which copper is directly bonded. Meanwhile, three layers
Flexible substrate is made of resin film such as polyimide.
Use copper foil as conductive material with epoxy resin or acrylic resin.
It is a structure bonded with an adhesive containing throat
However, it is widely used due to its good adhesiveness and low cost.
Has been. Because of this difference in structure,
The resin that is bonded to copper on
In contrast to polyimide, a three-layer flexible substrate
Is a resin contained in the adhesive. Adhesive used for three-layer flexible substrate
Needs properties such as heat resistance, durability, and flexibility
To adjust the strength and glass transition temperature by mixing various resins.
But generally based on epoxy resin
Is used. The adhesive for this application is epoxy resin
(For example, bisphenol A type glycidyl ether and
Curing amine etc. to (sidyl ester type epoxy resin)
Agents, nitrile rubbers and elastomers that provide flexibility.
Solvent-like or sheet-like materials are used. Copper clad
The method of manufacturing a laminated board is generally on a polyimide film.
Lay the copper foil where the solvent adhesive is applied and dried
Or sheet adhesive between polyimide film and copper foil
Between the rolls, roll press or flat
After temporary bonding with a hot press machine, it is several hundred minutes at 100-200 ° C
And heat-cured for several hours to adhere. [0005] Printed wiring boards connect electronic components with solder
When mounting, the thermal expansion coefficient of copper foil and resin
Thermal stress is applied due to the difference, so the adhesiveness between the copper foil and the resin
If it is bad, a problem of peeling occurs. For this reason, copper-clad laminates
The copper foil used is copper foil to improve the adhesion to the resin.
Roughening treatment to form copper particles on the surface by electroplating.
are doing. This is because irregularities are formed on the surface of the copper foil,
The copper foil is cut into the fat to obtain mechanical bonding strength.
The loose anchor effect improves the adhesion. on the other hand
With the recent trend toward smaller, lighter, and more sophisticated electronic devices,
Demand for high-density mounting on printed wiring boards
Fine pits with reduced wiring width and spacing between electronic circuits
Is becoming more common. Copper foil with large surface roughness
Using copper foil with irregularities formed by roughening treatment, etching
When the circuit is formed by using
Or uneven circuit width due to reduced etching linearity
Easy to be. Therefore, fine pitch electronic circuits
The surface roughness of the copper foil is
No. In electronic devices such as personal computers and mobile communications,
Although the air signal has a high frequency, the frequency of the electric signal is 1G
When the frequency is higher than Hz, the skin flows only on the surface of the conductor
The effect of the effect becomes remarkable, the transmission path changes due to surface irregularities
The effects of the change cannot be ignored. For this reason, high frequency characteristics
Attempts have been made to reduce the surface roughness of copper foils. [0006] The copper foil used as the conductive material of the printed wiring board is
It is classified into electrolytic copper foil and rolled copper foil according to the difference in manufacturing method.
You. Electrodeposited copper foil is generally removed from a sulfuric acid acidic copper sulfate plating bath.
Manufactured by electrolytic deposition of copper on a tin or stainless steel drum.
It is. Irregularities are formed on copper foil during electrolytic deposition and surface roughness
Becomes larger. Recently, additives have been added to the plating bath,
Copper foil with reduced surface roughness by adjusting electrolytic deposition conditions
Low-profile foils are being manufactured
Was. Rolled copper foil is produced by plastic working with rolling rolls.
The surface morphology of the rolling roll was transferred to the foil surface
A smooth surface is obtained. In addition, foil is generally 100μ
m means a thin plate having a thickness of not more than m. As described above, currently used for copper-clad laminates
Copper foil is roughened to improve the adhesion to the resin.
Treatment, but roughing treatment should not be performed for the above reasons.
A copper foil with a small surface roughness to a resin film
It is desirable to secure the adhesive strength without roughening
It is necessary to Also, with a three-layer flexible board
Has improved the bonding strength between copper foil, a metal, and adhesive, an organic substance.
Apply silane coupling agent etc. to copper foil to improve
Attempted, but not enough adhesion
No. [0008] Copper foil materials used as conductive materials include:
Pure copper or a copper alloy containing a small amount of additional elements is used. Electric
Copper foil, which is a conductor, has become thinner due to the finer pitch of the slave circuits.
And the circuit width is narrow, the copper foil
Low DC resistance loss and high conductivity
Is required. Copper is a material with excellent conductivity,
99.9% or more purity in the above fields where conductivity is important
Is generally used. But copper
When the purity is increased, the strength is reduced.
Since the handleability is poor, the copper foil
Is preferred. Under these circumstances, copper foil as a conductive material
Epoxy film without roughening
Attempt to bond using adhesive containing resin
Was. However, rolled copper foil of polyimide film and pure copper
Easily peels off, and the interface between the epoxy resin and copper easily peels off
Turned out to be. As a result, the copper foil, which is a conductive material, is roughened.
If used without any treatment, the main component of the adhesive, d
Peeling of the oxy-resin copper foil is likely to occur, resulting in disconnection
However, it has not been put to practical use. [0010] SUMMARY OF THE INVENTION Polyimide resin for base material
The film and the copper foil of the conductive material are
When manufacturing three-layer printed wiring boards bonded with adhesive
To improve the adhesion of the
Without the copper foil having a surface roughness (Rz) of 2 μm or less,
Adhesive strength of 8.0 N / cm or more at 0 ° peel strength
To provide a copper alloy foil for a laminated board to be manufactured. [0011] DISCLOSURE OF THE INVENTION The present inventors have proposed a polyimidizer.
Resin resin film and copper foil of conductive material contain epoxy resin
Consider the adhesiveness when bonding with adhesive
As a result, the adhesion is low based on pure copper, which has excellent conductivity.
Improvement by adding copper alloys
It was found that when the rust-preventive coating on the foil became thicker, it decreased.
Specifically, adhesion with adhesives containing epoxy resin
Of various additional elements on the corrosion, thickness and adhesion of anti-corrosion coating
As a result of repeated studies on the relationship of gender, the present invention provides (1)
  The Cr content of the additive element is 0.01 to 2.
0% by mass, and 0.01 to 1.0% by mass of Zr.
At least one of which is copper and the rest is copper and unavoidable impurities.
The thickness of the anti-corrosion film should be 3 nm or less from the surface.
The surface roughness was set to 10 μm average surface roughness (Rz) of 2 μm or less.
Lower, tensile strength 600 N / mm²As described above, the conductivity is 60%
It has characteristics higher than IACS, and does not require roughening treatment.
Epoxy when bonded to substrate resin with adhesive containing resin
180 ° peel strength between adhesive containing copper resin and copper alloy foil
Having a value of 8.0 N / cm or more.
For copper alloy foil. Is provided. Further, the present invention relates to Ag, Al, Be, C
o, Fe, Mg, Ni, P, Pb, Si, Sn, Ti
And Zn are both mainly solid solution strengthened copper alloys.
It has the effect of increasing the strength, so if necessary, one type
The above elements can be added. Its content is
If the amount is less than 0.005% by mass, the above effect is desired.
No effect is obtained, and when it exceeds 2.5% by mass, it becomes conductive.
A, since it greatly deteriorates the workability, solderability and workability.
g, Al, Be, Co, Fe, Mg, Ni, P, Pb,
The range of the contents of Si, Sn, Ti and Zn is the total amount.
It is possible at 0.005-2.5% by weight. [0013] BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, surface condition and alloy
The reasons for limiting the composition and the like to the above will be described. (1) Anti-corrosion coating: To prevent discoloration of pure copper and copper alloys, use Ben
Yes containing nitrogen such as zotriazole and imidazole
Using a machine, a chelate with copper is formed on the surface to prevent rust
It is widely used as a film. On the other hand,
The rust coating has water repellency and inhibits the binding of epoxy resin.
Has the effect of deteriorating adhesion. For this reason, the rust prevention coating
By limiting the thickness to 3 nm or less from the surface, epoxy
Copper alloy foil and polyimide fill using resin-containing adhesive
Can be firmly bonded to the system. Rust prevention
In order to reduce the thickness of the coating, for example,
Use benzotriazole as a rust inhibitor
If so, the concentration should be 3000 ppm or less.
Is preferred. The thickness from the surface of the rust prevention film is Auger
It can be quantified by measuring by electron spectroscopy.
  In other words, by Auger electron spectroscopy,
Analyzes and detects nitrogen, an element that constitutes the rust inhibitor,
Depth from surface until degree is equal to background
The SiO₂It is determined by measuring in conversion. (2) Cr, Zr: Cr and Zr are made of resin
During the production, it acts as a catalyst to promote polymerization.
It is known. Therefore, adding these to the copper
By using alloy foil, it is the main component of metal and adhesive
Promotes bonding with epoxy resin, strengthening interface bonding
It is considered that If the amount of these additives is too small,
Since it does not act sufficiently as a medium, the bond between metal and resin
Not sufficiently performed, and the effect of improving the adhesiveness is small. Pudding
180 ° peel strength for practical use as a wiring board
8.0 N / cm or more is required.
You. In order to obtain this characteristic, it is necessary to reduce the amount of Cr and Zr.
In both cases, the addition amount of one or more kinds is 0.01% by mass or more by weight ratio.
Turned out to be. On the other hand, the amount
As a result, coarse precipitates are generated due to segregation during casting.
become. Hot rolling of metallic materials containing coarse crystals
Cracks occur in the inside and hot workability deteriorates. Also electronic
As the pitch of circuits becomes finer, copper foil, which is a conductor, becomes thinner
And the narrow circuit width, the characteristics of copper foil
Low DC resistance loss and high conductivity
It has been demanded. In addition, the conductivity increases as the amount added increases.
It may go down. Cr and Cr which do not cause these problems
And the upper limit of the amount of Zr added is as follows.
% By mass, more preferably 0.4% by mass. Also Z
r is more than 1.0% by mass, more preferably 0.25% by mass.
You. This is because plastic working is easy. Therefore
As a copper alloy foil for laminates of printed wiring boards,
An appropriate range of the addition amount is that Cr is 0.01 to 2.
0 mass%, more preferably 0.01 to 0.4 mass%
is there. Zr is 0.01 to 1.0% by mass, more preferably.
More preferably, it is 0.01 to 0.25% by mass. (3) Surface roughness: The surface roughness of the copper foil is large
When the frequency of the electric signal is 1 GHz or more,
Impedance due to the skin effect flowing only on the surface of
It increases and affects transmission of high frequency signals. Therefore,
Surface roughness is small in conductive material applications for high frequency circuits
It is necessary to consider the relationship between surface roughness and high frequency characteristics
As a result, as a copper alloy foil for laminated boards of printed wiring boards,
The surface roughness is 2 μm or less in ten-point average surface roughness (Rz).
I knew it was fine. How to reduce surface roughness
Is to optimize the production conditions for rolled copper foil and electrolytic copper foil,
Hands such as chemical polishing or electrolytic polishing of the copper foil surface
There is a law. Generally, rolled copper foil easily reduces surface roughness
It is possible to make the surface roughness of the work roll of the rolling mill
Work roll to be transferred to copper foil.
The file can be made smaller. (4) Tensile strength and conductivity: Generally, strength and conductivity
Electrical conductivity is in opposition, and the higher the strength of a material, the more conductive it is.
Tends to decrease. Tensile strength is 600N / mm²Than
If small, wrinkles may occur during handling
When the conductivity is less than 60% IACS, the laminate
Is not preferable as a conductive material. High strength and handling
Conditions suitable for copper alloy foil for laminates with excellent
Tensile strength is 600N / mm ²As described above, the conductivity is 60% IAC
S and above. (5) 180 ° peel strength: 180 ° peel strength is small
If not, peeling may occur from the laminate.
An adhesive strength of 0 N / cm or more is required. The copper alloy foil of the present invention is limited to a manufacturing method.
There is not, for example, electrolytic copper foil by alloy plating method
Or rolled copper foil by melting and casting an alloy
It can be manufactured by The method by rolling is described below as an example.
You. A predetermined amount of alloying element is added to molten pure copper,
Cast into a mold to form an ingot. In the present invention, Cr,
Since an active element such as Zr is added, the generation of oxides
In a vacuum or in an inert gas atmosphere to suppress formation
It is desirable to do. The raw material has low oxygen content
It is desirable to use electrolytic copper or oxygen-free copper. I
Ngot was thinned to a certain thickness by hot rolling
After that, skinning is performed, and then cold rolling and annealing are repeated
Finally, cold rolling is performed to finish the foil. Rolling
Since the rolling material has rolling oil on it, acetone or petroleum
Degreasing with a system solvent. [0018] If an oxide layer is formed by annealing, trouble will occur in a subsequent process.
Annealing in a vacuum or inert gas atmosphere
It is necessary to perform or remove the oxide layer after annealing.
  For example, to remove the oxide layer by pickling, sulfuric acid + peroxide
Sulfuric acid, nitric acid + hydrogen peroxide, or sulfuric acid + hydrogen peroxide + fluoride
It is preferable to use a substance. [0019] Embodiments of the present invention will be described below. Copper alloy
Fabrication was performed in an Ar atmosphere using a high-frequency vacuum induction melting furnace.
Oxygen-free copper as the main material in a high-purity graphite crucible
However, copper chromium mother alloy and copper zirconium
Mother alloy, aluminum, silver, copper beryllium mother alloy,
Baltic, iron, magnesium, manganese, nickel, copper
Mother alloy, lead, copper silicon mother alloy, tin, titanium, zinc
After adding the additional element selected from the above, it is placed in a cast iron mold.
Cast. In this way, thickness 30mm, width 50mm, length
Obtain a copper alloy ingot of 150mm, weight about 2kg
Was. This ingot is heated to 900 ° C for hot rolling.
Rolled to a thickness of 8 mm to remove oxide scale
After that, cold rolling and various heat treatments were performed to obtain a 35 μm thick
A rolled copper alloy foil was obtained. The copper alloy having a thickness of 35 μm obtained by the above method
Gold foil has rolling oil, so immerse it in acetone
The oil was removed. This is sulfuric acid 10% by weight and peroxide
Immersion in an aqueous solution containing 1% by weight of hydrogen,
And the rust preventive film was removed. Investigate the effect of anti-rust coating thickness
To adjust the concentration of benzotriazole
Immersed in the solution and immediately dried. Other roughening treatment
And silane coupling treatment to improve the adhesion
No surface treatment has been performed. Made in this way
Polyimide film with copper alloy foil with adhesive containing epoxy resin
A copper-clad laminate was produced by bonding with a lum. Copper clad laminate
Fabrication is a solvent-type adhesive mixed with epoxy resin and hardener
The agent is placed on a 25 μm thick polyimide film with a gap
Apply with a 100μm applicator and put it in the dryer
After drying at 130 ° C for 4 minutes at
Overlap, using a flat heating press, temperature 170 ℃, pressure
30kgf / cm²Copper-clad laminate for 30 minutes
I got a board. Here, the thickness of the adhesive after drying is 20 μm.
there were. The copper alloy foil thus obtained was subjected to a “hot
Rollability, Surface roughness, Rust-proof coating thickness, Conductive
Rate, high frequency characteristics, tensile strength, and adhesive strength
"Degree" was evaluated by the following method. (1) Hot rollability: Hot rollability refers to hot-rolled material.
The material is penetrated and visually inspected for cracks in the material.
The presence or absence was evaluated. (2) Surface roughness: Surface roughness is measured using a stylus type surface roughness meter.
It was measured in a direction perpendicular to the rolling direction. Measurement conditions are JI
According to the method described in SB0601, a ten-point flat
It was evaluated by the average surface roughness (Rz). (3) Thickness of rust preventive film: As described above, Auger electron
Performs depth analysis of spectroscopic analysis to compose rust preventive
Detection intensity of elemental nitrogen is the same as background
The depth from the surface until₂Measured by conversion
Specified. (4) Conductivity: The conductivity is a direct current using a double bridge.
The electric resistance at 20 ° C. was determined by a four-terminal method. Measurement sample
Is a copper foil processed into a 35μm thick foil with a width of 12.7mm.
Cut. Measure the electrical resistance with a length of 50 mm between measurements.
The conductivity was determined. (5) High-frequency characteristics: High-frequency characteristics include high-frequency current
The impedance was evaluated at the time. Impedance is thick
A copper foil processed into a 35 μm foil is processed into a 1 mm
Voltage when a high-frequency current of 0 MHz and 20 mA is applied
The descent was measured and measured for a length of 100 mm. (6) Tensile strength: The tensile strength was measured at room temperature in a tensile test.
Tensile strength was measured. The measurement sample was processed to a thickness of 35 μm.
Copper foil is 12.7 mm wide and 1 long with a precision cutter
It was cut into 50 mm strips. This is the distance between scores 50
mm and at a pulling speed of 50 mm / min. (7) Adhesive strength: Adhesive strength is 180 ° peel strength by JI
Performed according to the method described in SC 5016.
Was. The measurement was performed with the stripped conductor width set to 5.0 mm and the
Fix the imide film side to the tensile tester side and
The copper alloy foil is bent in the 180 ° direction, and the tensile speed is 50 mm.
/ Min. Table 1 shows the composition of the copper alloy foil and Table 2 shows the copper alloy
The results of evaluating the properties of the foil are shown. Oxygen content is 10
ppm or less. Note that the parts indicated by “-” in the table
The minute indicates that the measurement was not performed. These are Zn
Alternatively, the copper alloy foil containing Pb is
Due to high volatility, the oxygen content could not be measured accurately
In any case, the oxygen content is 10 ppm or less.
It is estimated. Hot workability causes cracks to occur after hot rolling
Those that did not exist are indicated by ○, and those that cracked are indicated by X.
  The subsequent test was not carried out for the case where cracks occurred.
  No. of the embodiment. 1 to No. 14 is the copper alloy foil of the present invention.
This is an example. As shown in Table 1, the copper alloy foil of the present invention
Has a conductivity of 60% IACS or more and a tensile strength of 60
0N / mm²Above, when polyimide is bonded
The 180 ° peel strength was 8.0 N / cm or more.
Has excellent conductivity and handling properties, and high adhesion
It turns out that it has strength. In addition, all are hot
No cracks occurred during rolling. [0023] [Table 1] [0024] [Table 2]On the other hand, in Comparative Example No. 1 shown in Table 1, 15 is a book
It is a rolled copper foil to which the alloy component of the invention has not been added. Acid free
Ingot made by melting and casting elemental copper in Ar atmosphere
After processing, use the same adhesive
Adhered under the same conditions as LUM. Conductive because the material is pure copper
Is large, but the 180 ° peel strength is as small as 7.5 N / cm.
First, since sufficient adhesive strength is not obtained, print
Peeling may occur when used as a wiring board. No. of Comparative Example 16 and No. 17 is
Example with only one type added from Cr and Zr respectively
It processed into foil by the same method. Cr and Zr concentrations are weight ratio
Less than 0.01%, the effect of improving strength
Not enough, tensile strength is 600N / mm²Less than and less than
180 ° peel strength less than 8.0 N / cm
No. No. of Comparative Example 18 added Cr,
Because the concentration exceeded 2.0 mass% by weight ratio
In addition, coarse crystals of Cr are formed during casting,
Cracks occur during rolling, resulting in poor hot workability. N of Comparative Example
o. 19 added only Zr, but its concentration was
Since it exceeds 1.0% by mass, the same applies during hot rolling.
Cracks occurred. For this reason, No. 18 and no. 1
No. 9 could not carry out subsequent tests. No. of Comparative Example 20 added Fe,
Because the concentration exceeded 2.0 mass% by weight ratio
In addition, the conductivity is low, and as a conductive material for printed wiring boards,
Not suitable. No. of Comparative Example No. 21 is No. of the embodiment. 7
Using the alloy foil of Example 1, 6 using alloy foil
Gently scraping the surface with emery paper to roughen the surface
Processing was performed. As a result, when the surface roughness increases,
Impedance due to skin effect when energized by waves
It is not suitable for use as conductive material in high-frequency circuits.
No. No. of Comparative Example 22 is No. 22 of the embodiment. 7
Using benzotriazole as a rust inhibitor using an alloy foil of
In an aqueous solution whose concentration has been adjusted to 0.5% (5000 ppm)
Immersion treatment. High concentration of rust inhibitor
The thickness of the anti-corrosion film is as thick as 5 nm, and 180 ° peel
The strength is as small as 2.5 N / cm. [0031] The copper alloy foil of the present invention contains an epoxy resin.
The glue that is bonded to the polyimide resin film using an adhesive
When used for lint wiring board laminates, surface roughness is small.
Also has excellent adhesion to resin and high conductivity and strength
Have. As a result, electronic circuits that require fine wiring
It is suitable for use as a conductive material.

Continuation of front page    F term (reference) 4E351 AA04 BB01 BB30 DD04 GG02                 4F100 AK01A AK41 AK51G AS00D                       BA03 BA04 BA07 CA01B                       CB00 DE04B DJ01B EJ91D                       GB90 HB31B HB31C JA03A                       JJ02 JK11 JL02                 5E343 AA18 BB24 BB67 CC01 GG02                       GG11

Claims (1)

Claims: 1. A component of the additive element in which the content of Cr is 0.01 to 2.0% by mass and the content of Zr is 0.01 to 1.0% by mass. Including the above, the balance is made of copper and unavoidable impurities, and the thickness of the rust preventive film is 3 nm or less from the surface, so that the surface roughness is reduced to a ten-point average surface roughness (R
z) 2 μm or less, tensile strength 600 N / mm ² or more,
It has a conductivity of 60% IACS or more, does not require roughening treatment, and is made of an adhesive containing an epoxy resin and a copper alloy foil when bonded to a substrate resin with an adhesive containing an epoxy resin.
A copper alloy foil for a laminate, wherein the 0 ° peel strength is 8.0 N / cm or more.