JPS6152240B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to surface treatment of the surface to be bonded which is conventionally used for copper foil used in copper-clad laminates used for printed circuit boards, etc., and in particular, secondary electrodeposition which is carried out using the copper foil as a cathode. The present invention relates to treated copper foil and its manufacturing method. Conventionally, the above-mentioned electrodeposition addition processing method includes so-called powdery plating, which simply belongs to burnt plating, or a two-stage processing method in which so-called smooth plating with a current density below the critical current density is further superimposed on this to prevent it from breaking off. Also, in order to improve adhesion, a synthetic resin suspension may be added in place of the burnt plating, or a colored metal salt such as arsenic, antimony, or bismuth may be added to the copper plating solution to give a finely roughened surface. , some related modification methods have been proposed. In addition to these methods for imparting lamination adhesion, copper-clad laminates are also subjected to an etching process, which is an essential circuit pattern used as a printed circuit.
Occurs often. In order to avoid defects caused by the physical or complex chemical transfer of copper to organic materials of the substrate, such as lamination stains, transfers, and stains, in addition to the above-mentioned adhesion treatment, the adhesive side of the copper foil is Another method has also been proposed in which an alloy layer mainly consisting of a brass layer is electrodeposited. However, in recent years, the uses of printed circuit boards have become wider.
As high performance is required, in addition to flame resistance, there is also a demand for less deterioration in peel strength after prolonged heating. According to the world-renowned Underwriters Laboratory, so-called UL standards, the peel strength after long-term heating at 153°C for 56 days is 2 lbs.
It requires that at least an inch remains. The residual peel strength after long-term heating is of course largely dependent on the properties of the organic material used in the laminated base material, but after minimizing the inevitable thermal deterioration of the organic material, In this case, it is necessary to treat the surface of the copper foil to be adhered. As a result of various experiments regarding this problem, the inventors have determined that the residual peel strength after long-term heating can be determined by thermal tests that have been adopted in conventional standard tests for copper-clad laminates.
For example, solder heat resistance (solder blister test),
It was confirmed that this is a separate property that cannot be measured by peel strength after heat resistance in a solder bath for 5 to 20 seconds or several hours. For example, in the laminates obtained by using the prior art as described above, there are some problems with respect to the initial peel strength, the solder heat resistance, which is a heat test of several tens of seconds at 260°C, and the solder bath resistance. Peel strength after heat resistance of 5 to 20 seconds has been very commonly required in this field for single-sided or double-sided copper-clad laminates. Many products meet the adhesion between the copper foil and the adhesive organic base layer as well as the peel strength after a heat cycle of seconds to minutes, but in the UL standard mentioned above, for example, in the heat resistance test at 153°C for 56 days, It has been found that many of these products, not only have a residual peel strength of 2 pounds/inch (0.357 Kg/cm), but also lose most of their residual peel strength within about two weeks. Furthermore, in recent years, methods for producing laminates that require performance as indicated by this property in actual processes have come into widespread use. That is, it is a multilayer copper-clad laminate. Later, the inner layer double-sided board is laminated (by heat pressing) and subjected to various circuit processing (e.g. circuit formation, hole drilling, through hole plating, etc.), and then the outer layer material is further layered on top and heat pressed. be exposed. When multiple layers are laminated two or three times, hot pressure is applied to the copper foil for several hours. This takes the form of pressurization and cycle tests at temperatures within the UL test range, and the required properties are completely different from the conventional open atmosphere test of 260° for several tens of seconds. In the production of these multilayer laminates, in addition to maintaining adhesion with the laminated organic substrate, in the surface electrodeposition treatment of copper foil by multiple electrodeposition, there are often The close adhesion between metal layers, such as copper foil and secondary electrodeposited layer, each copper layer, and between alloy layers, has often become a problem. In investigating copper foil processing methods to keep up with these recent laminated circuit board manufacturing technologies, the present inventors have determined that the thermal stability of the metal interface will solve the above two problems, namely the secondary voltage. Knowing that this leads to long-term thermal stability between each laminated layer and the adhesive organic substrate, from this point of view, long-term heating (approximately 170℃-1 during press lamination)
Actively suppress the physical and complex chemical migration of copper from the copper foil to the base organic matter during the 56 days of UL), and the copper and copper-based alloy layer. For the former, tin and zinc were added as a copper migration barrier on the surface to be adhered to the organic substrate. The ternary alloy layer consisting of the permeated alloy layer is extremely effective for long-term thermal stability.For the second point, in copper electrorefining, it has long been necessary to use a surface layer that is rough or thermally difficult to handle. By proactively using arsenic, which is shunned for giving We researched the possibility of creating a copper foil that can be adhesively laminated onto printed circuit boards that retains its peel strength even after long-term heating.
In addition to the desired effect, a synergistic effect between the two was demonstrated,
We have now established a copper foil and a method for producing the same that can withstand the harsh long-term conditions and processing methods mentioned above. The present invention exhibits extremely remarkable effects when two or more layers are successively deposited in multiple stages on the surface to be treated of the copper foil, that is, the surface that will be bonded to an organic substrate or adhesive later. That is, when applied to a specific surface increasing electrodeposition process in which multiple electrodeposited copper layers are deposited in a superimposed manner, the tightness between the electrodeposited layers is strengthened by the trace arsenic content interposed between them. Furthermore, during lamination, the secondary electrodeposited copper layer, which is active and has a large specific surface area, is bonded directly to the organic material of the laminated substrate by thermocompression, resulting in staining during the production of printed circuits, which is caused by physical and complex chemical transfer of copper. In order to suppress lamination stains such as stains and transfers, for example, a secondary alloy electrodeposited layer is applied to copper foil as shown in Japanese Patent Application Laid-open No. 74537/1983, which was previously proposed by the present applicant, and a secondary alloy electrodeposited layer is applied to the copper foil by subsequent heating. It can be applied in combination with the technique for forming the original alloy layer and the technique proposed in JP-A-52-111428. Furthermore, without impairing the effects obtained by combining these technologies in the slightest, we were able to maintain peel strength after long-term heating, which could not always be achieved stably by combining these technologies alone, and the application field of copper-clad laminates has been improved. For example, the reliability can be improved when applied to heat-resistant substrates or when used as an inner layer copper foil of a multilayer (multiple circuit) laminate. The present invention will be specifically described below with reference to the drawings. The drawings are explanatory diagrams of one embodiment of the present invention.
is the first stage electrodeposition tank, in which the copper foil 1 supplied is
is negatively charged by the power supply contact roll 2, and the metal surface is cleaned by the pickling bath 3. 4 is an anode, and the copper foil passes through the electrolytic solution with the electrodeposited surface facing the anode 4. The anode 4 is connected to a separate power supply system for each tank. In this stage, the material is generally processed at a current density near or above the critical current density, giving it a fine grain texture and increasing its specific surface area. For example, in an acidic copper sulfate bath, the following conditions can be selected. CuSO ₄ (as copper content) 12-20g/H ₂ SO ₄ 45-120g/Liquid temperature 22-35℃ Current density (cathode surface average conversion) 6-18A/dm ² Current application time 8-25sec 1st stage electrodeposition The copper foil 1 that has passed through the tank passes through a squeezing roll 5 and enters the second stage electrodeposition tank while maintaining a minimum thickness liquid film to prevent oxidation. The treatment in this bath is used to cover and smooth plating to prevent the layer added to increase the specific surface area in the first stage electrodeposition bath from falling off when the copper foil is handled in subsequent processing steps. It is. The bath composition and plating conditions are CuSO ₄ (as copper content) 40-85g/H ₂ SO ₄ 40-120g/Liquid temperature 36°-55°C Current density (converted to cathode area average) 12-30A/dm ² Passage time 10-25 seconds. In the first stage, the amount of electrodeposition is greatly affected by the current efficiency, so care must be taken to prevent trace amounts of transitional impurities such as iron, chromium, arsenic, and antimony, as well as the bath composition and electrodeposition conditions. It is necessary to use the second
The steps are fairly flowy, and if electrodeposition is applied below the critical current density to give a smooth plating on the plane, then the process of the invention will proceed to bring the layers closer together. In order to prevent the copper foil from leaving the second stage bath from causing large fluctuations in the bath composition in the next stage, excess liquid is removed from the second stage by a squeezing roll 5 that prevents the liquid from being brought in to the extent that the liquid film does not break. Return to the bath and enter the third stage electrodeposition tank. In the third stage electrodeposition bath, an arsenic-containing copper layer is applied to improve the adhesion between the copper foil and various electrodeposited layers. For this purpose, first prepare an arsenic-containing additive solution. For example, as an arsenic source, arsenous acid is used as an aqueous solution dissolved in caustic soda so as not to generate harmful arsine gas (hydrogen arsenide AsH ₃ ). The bath composition and electrodeposition conditions for the third stage are as follows: CuSO ₄ (as Cu) 7-10 g / H ₂ SO ₄ 20-70 g / Arsenic additive liquid (as AS) 0.05-0.5 g / Liquid temperature 18-22°C It is possible to select and set the current density (as an average of the cathode surface) from 4 to 6 A/dm ² and the passage time from 5 seconds to 20 seconds. The amount of arsenic in the arsenic-containing layer, which corresponds to the third layer, is not necessarily a simple proportional amount even if the bath conditions and electrodeposition conditions are specified in the above range. There is a slight deviation depending on the surface condition of the copper layer or copper foil, and the value shown by the analysis of the arsenic-containing copper precipitate electrodeposited by a beaker test of only this electrodeposited layer is quite different. It differs. In addition, depending on the conditions, the color of the arsenic-containing layer may change from being almost the same as an electrodeposited layer made only of copper to becoming so protrusive that needles can break off, making it appear black. Although it can be varied in various ways, it is not necessary to allow the copper to grow to the point where it breaks off, and the purpose of the invention can be sufficiently achieved by keeping the copper color within the range of considerably different grayish brown to light thiokolate color. In addition to having both the first and second secondary electrodeposited layers, depending on the intended type of circuit board, the first layer or both the first and second layers may be added for the sole purpose of maintaining peel strength after long-term heating. It is also possible to omit this step, but in this case, it is desirable to produce an arsenic-containing layer with a light cyokolate color, which has the effect of improving the adhesion between the raw copper foil and the subsequent alloy layer. Significant. The copper foil that has come out of the third stage electrodeposition tank is washed on both sides with a sufficient amount of water in the washing tank 6 to prevent the arsenic solution from getting mixed into the reducing metal bath in the next stage, and then the washing nozzle 8 After washing both sides with (in the presence of an arsenic source, there is a risk of arsine gas generation in an acidic reducing atmosphere), the product enters the fourth stage electrodeposition tank. The fourth stage electrodeposition tank is used for drying the copper foil that follows, coating and drying the adhesive, and for the purpose of permeation alloying to form a ternary alloy, in a narrow sense, bronze, during lamination press bonding, etc. This is an electrodeposition bath for making a tin hybrid alloy coating layer. When discussing the process in the fourth stage electrodeposition bath, we will roughly divide the process into two methods based on the above two technical ideas, taking into account the compatibility of the copper foil with the corresponding laminate due to minute nuances in use. Conceivable. The first method is to electrodeposit an alloy layer to a thickness that can be visually determined, with the main aim of completely preventing copper migration. For example, as a bath composition, add K ₄ P ₂ O ₇・3H ₂ O 20 to 40 g/ to ZnSO ₄ (as Zn) 0.8 to 2.0 g/Sn(SO ₄ ) ₂ (as Sn) 0.05 to 1.0 g/. , adjust the PH to within the range of 10.7-11.5. Incidentally, the objects and effects of the present invention are not hindered even if stannous sulfate is used in place of stannic sulfate, and zinc and tin are used as pyrophosphates. As for electrodeposition conditions, the bath temperature should preferably be high, 40 to 48℃.
Select a current density (corresponding cathode surface average) of 0.5 to 5.5 A/ ^dm2 and a passage time of 10 to 25 seconds. The second method is to apply a thin alloy layer as a rust prevention method (on both sides of the copper foil), and the bath composition is ZnSO ₄ (as Zn) 0 to 2.5 g/SnSO ₄ (as Sn) 0.1 to 2.5 g/ Add 15-50 g of K ₄ P ₂ O ₇ to the solution to adjust the pH within the range of 10.5-11.7. The above-mentioned alternative use of zinc salt and tin salt is exactly the same as in the previous section. The bath temperature was 40° to 48°C as above, and the current density was
0.3 to 3 A/dm ² on the copper foil treated side, and 0.3 to 3 A/dm 2 on the glossy side.
At 0.05 to 2 A/dm ² and a passing time of 1 to 10 seconds, the specific surface area of both sides, the total amount of electricity given, and
The selection can be determined by the appearance of Zn-Sn infiltration into the copper surface in the subsequent process. Note that the anode 7 provided at the center of the fourth stage electrolytic cell shown in the drawings is used in the second method described above, that is, when applying a thin electrodeposition treatment to both sides for rust prevention. Rust prevention is essential for copper foil to prevent oxidation and discoloration during the subsequent essential processes such as adhesive coating and lamination to become a printed circuit board, as well as during the stock period between processes. Except for the second method in the fourth stage, conventional methods such as organic oxidation inhibitors (triazole-based, pyrazolone-based, imidazole-based, silane coupling-based) methods can be used, and preferably, the above-mentioned method Continuing from the 4th layer, when the superimposed rust prevention method using chromate is combined in the 5th stage treatment tank, a synergistic rust prevention effect between the residual Zn/Sn and chromate occurs, resulting in extremely effective rust prevention ability. I can do it. That is, after washing the copper foil treated in the fourth stage with water to sufficiently prevent impurities from being brought in,
Chromate rust prevention treatment is performed in the fifth stage treatment tank. As a specific example, in a method that involves only immersion in chromic anhydride, it is also possible to immerse the solution in a solution containing 0.3 to 3 g of chromic anhydride for 10 to 20 seconds; g/, counter electrode current density 0.02 to 0.2 A/dm ² per side, passing time 5
Even if both sides of the copper foil are subjected to cathode treatment for ~15 seconds, the rust prevention effect of the fourth layer treatment can be achieved. The final process for copper foil is washing, draining, and drying, and the final washing water is preferably deionized water, especially water from which chlorine ions have been removed. Air knife 9 to save energy in the drying process
Alternatively, use the squeeze roll 5 and then dry it. As for the drying method, it is desirable to use hot air using purified air. In particular, it is better to dry the copper foil for at least 30 seconds at a temperature above 60°C and below 120°C, and in this process, the fourth layer of zinc and tin electrodeposited layer has already begun to undergo some penetrating alloying, making it easier to carry out subsequent storage and processing. Stable results are obtained. 10 is a heater, 11 is a cooling fan, and 12 is a winding roll. In carrying out the present invention, the present invention is not limited to the above-mentioned five-layer treatment, but an arsenic-containing copper layer may be electrodeposited directly on the surface of the copper foil or on a surface that has undergone one or more layers of copper layer electrodeposition treatment. and then at least one of zinc and tin.
Copper foil having multiple additional electrodeposited layers obtained by electrodepositing a coating layer consisting of a seed or an alloy of copper and at least one of the metals mentioned above, and which is obtained by electrodepositing a coating layer made of an alloy of copper and at least one of the above-mentioned metals, and as a result of being left in nature or heated, at least a copper layer is formed. If the arsenic-containing layer is interposed between the copper-based alloy layer and the arsenic-containing layer, the tightness between these various metal layers can be maintained and the object of the present invention can be achieved. Examples of the present invention will be shown below. Example 1 Width 1.1 m, nominal thickness 1 oz/in2 (35
Using a continuous surface treatment device that supplies copper foil with a thickness of .mu.) from a coil, the first to fifth stages of treatment were sequentially performed. The processing conditions are as follows. First stage bath composition CuSO ₄ (as Cu) 14g / H ₂ SO ₄ 65g / Bath temperature 26 ± 1°C, cathode surface average current density 12A/dm ² , passed through the electrodeposition bath for about 13 seconds. send to Second stage bath composition CuSO ₄ (as Cu) 50 g / H ₂ SO ₄ 70 g / bath temperature 48 ± 1°C, cathode surface average current density 15 A / dm ² , passed through the electrodeposition bath for about 17 seconds, and squeezed roll. Pass through and send to the third stage. In the third stage electrodeposition bath, three conditions shown in Table 1 were used.

[Table] The copper foil that came out of the third-stage electrodeposition tank was passed through a light squeezing roll, and then sent to the fourth-stage electrodeposition tank after passing through a shower wash, a water washing tank, and a shower wash. As comparative examples, 1-A-(0), 1-B-(0), 1-
It was set as C-(0). The others were treated under the same conditions from the fourth layer onwards. The fourth stage bath composition conditions are: ZnSO ₄ (as Zn) 1.5g / Sn (SO ₄ ) ₂ (as Sn) 0.6g / K ₄ P ₂ O ₇ 34g / bath temperature 46℃±1℃ using a PH meter. When measured, the pH was 10.9. Electrodeposition was carried out at an average cathode current density of 4.5 A/dm ² for 13 seconds. As a result, an amount of electrodeposition (estimated at 0.05 to 0.15 μm immediately after coating) is obtained that clearly indicates the presence of this layer. This fourth
After stage treatment, after rinsing with immersion shower in the rinsing tank, rust prevention was applied to both sides. 5th stage treatment layer bath composition Chromic anhydride 2.5g/bath temperature 20°C±1°C 4th stage treated surface Current 0 Glossy surface Chromate treatment was carried out at a cathode current density of 0.03A/ ^dm2 . After passing through a squeeze roll, it is introduced into a washing zone, and after one stage of washing with city water, both sides are thoroughly washed with deionized water, drained using a squeeze roll, and then cut up and sent to a drying zone.
After draining, the residual moisture is further blown off using a hot air knife at 60 to 65°C, and the air is completely dried by passing through an infrared heater and forced convection drying zone for 1 minute and 20 seconds at an ambient temperature of 100°C. It was cooled with a fan and wound into a coil. Separately, as a comparative example, one in which only the third stage of electrodeposition was omitted was designated as 1-(0). Each of the copper foils obtained above was heated at 170°C for 1 hour at 17Kg/cm ² using a commercially available impregnated glass cloth for glass epoxy substrates, grade FR-4.
Copper-clad laminates were created by press crimping, and evaluation tests were conducted. Initial peel strength of each, 260℃
Table 2 shows the peel strength after 20 seconds of soldering bath, the transfer at the time of initial peel strength measurement, the stain status after etching, and the change in peel strength every two weeks at 153° C. for 56 days. The performance that is generally required by the standard for copper-clad laminates can be achieved at almost the same level even if the steps of the present invention are omitted, but the peel strength remaining after long-term heating is different from that of the present invention. This shows that the company is unrivaled. Example 2 A treated copper foil was obtained from the same sample as in Example 1 under the same conditions, except that only the fourth stage electrodeposition conditions were the bath composition and electrodeposition conditions shown below. That is, the bath composition in the fourth stage was 1.0 g of ZnSO ₄ (as Zn) / 0.9 g of Sn (SO ₄ ) ₂ (as Sn) / 21 g of K ₄ P ₂ O ₇ / adjusted to pH 11.2 at a bath temperature of 42°C. . this

【table】

[Table] Introducing a copper foil that has been washed after the third stage (shower and soaking) into the bath, the current density (cathode surface average) is 1.1A/d.
m ² /one side A rust-preventing Sn-Zn layer was electrodeposited on the treated and glossy surfaces in a counter electrode passage time of approximately 3 seconds. The samples thus obtained were designated as 2-A, 2-B, and 2-C, respectively, corresponding to the third stage treatment conditions. Separately, as a comparative example, a sample obtained by omitting only the third stage electrodeposition treatment was designated as 2-(0). Each copper foil obtained by the above method was laminated on the same laminated base material as in Example 1, and the same test was conducted. The results are shown in Table 3. As is clear from Table 3, the effects of the present invention do not depend on the thickness of the fourth layer, but are due to the synergistic effect of the third arsenic-containing layer and the fourth coating layer. Example 3 Electrodeposited copper foil (thickness: 35μ, average width: 1.1m) was unwound from a coil, passed through a power supply roll, and then pickled after being energized.
Using the rough surface (matte surface) as a cathode, electrodeposition was performed using the following bath composition. 9 g of CuSO ₄ (as Cu) / 19 g of H ₂ SO ₄ / 0.3 g of arsenic additive solution (as As) was passed through the counter electrode for 13 seconds at a bath temperature of 18° C. and an anticathode current density of 4.3 A/dm ² . This copper foil was passed through a squeezing roll, thoroughly rinsed with water to remove traces of As, and then passed through a tin-zinc alloy electrodeposition bath. The electrodeposition bath for the fourth coating layer contained ZnSO ₄ (as Zn) 2.2g/Sn(SO ₄ ) ₂ (as Sn) 0.9g/bath temperature 45±2℃, anticathode current density 1.3A/dm ² counter electrode It was electrodeposited on both sides in a passing time of about 7 seconds to serve as a rust preventive layer. Next, excess Zn is removed using a washing tank and a washing shower.
After washing away salt, etc. (electrodeposited metal tin does not dissolve while eluting Zn), drain with an air knife, pass through a forced convection drying zone at 110℃ using a regular infrared heater for 1 minute and 30 seconds, and cool with cold air. I wound it into a coil. This copper foil is designated as 3-A. 3-B is one in which 2.5 g/anhydrous chromic acid is added to the washing tank, and chromate rust prevention is further applied. Comparative sample (3) was prepared by simply electrodepositing the arsenic-containing copper layer, omitting the coating layer, and immediately immersing it in a 1% solution of benzotriazole, which is well-known as a discoloration inhibitor for copper, for 15 seconds, washing with water, and drying. . Comparative sample (4) was treated with the same chromate rust inhibitor used in 3-B instead of the triazole rust inhibitor in sample (3). The copper foils thus obtained were coated with commercially available adhesives from companies M and E that were most suitable, respectively, and dried to form adhesive-coated copper foils, which were then laminated with FR-2 and FR-3 prepregs, respectively. Tests similar to those in Example 1 were conducted and the results are shown in Table 4. As is clear from Table 4, the present invention has sufficient effects even when applied directly to the surface of untreated electrolytic copper foil.

【table】

【table】

【table】

【table】 [Brief explanation of the drawing]

The drawings are explanatory diagrams of one embodiment of the present invention. In the drawing, 1 is a copper foil, 2 is a power supply contact roll, 4 and 7 are anodes, 1 is a first stage electrodeposition bath, and 2 is a second electrodeposition tank.
The stage electrodeposition tank is a third stage electrodeposition tank, is a fourth stage electrodeposition tank, and is a fifth stage treatment tank.

Claims (1)

[Scope of Claims] 1. On the arsenic-containing copper layer electrodeposited on the surface of the copper foil to be coated, at least one of zinc, tin, or an alloy of at least one of the above metals and copper is formed. A copper foil for printed circuits having a composition in which metals constituting each layer of multiple additional electrodeposited layers formed by electrodepositing a covering layer interpenetrate with each other. 2. The copper foil for printed circuits according to claim 1, wherein the coating layer comprises 10 to 100% by weight of tin and the balance zinc. 3. The treated surface of the copper foil is a two-stage treated surface formed by superimposing and coating a thin smooth copper electrodeposited layer on the electrodeposited surface of fine granular copper, as described in claim 1 or 2. Copper foil for printed circuits. 4. A copper foil for printed circuits as set forth in claim 1, 2, or 3, which has a chromate antirust treatment layer as the outermost layer. 5 Electrodeposit an arsenic-containing copper layer on the surface of the copper foil to be coated using an electrolytic solution containing a trace amount of arsenic, and then apply zinc,
At least one type of tin or at least one of the above metals
A method for producing copper foil for printed circuits, which comprises electrodepositing a coating layer made of seeds, copper, and an alloy, and then allowing the coating layer and the metal constituting the arsenic-containing layer to penetrate into each other. 6. The method for manufacturing a copper foil for a printed circuit according to claim 5, wherein the coating layer is heated to 100° C. or higher to infiltrate the arsenic-containing layer. 7. The method for manufacturing a copper foil for printed circuits as set forth in claim 5 or 6, wherein after electrodepositing the coating layer, antirust treatment is performed using chromate or an organic oxidation inhibitor.