JPS616297A - Surface treatment of copper foil and surface treated copper product - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the surface treatment of steel foils, and in particular to a process for rendering the surface of copper foils more adhesive, such as those used in printed circuits.

Prior Art and Problems The use of copper foils in applications requiring adhesion to non-metallic or resinous substrates is well known. For example, U.S. Patent No. 4,088,5 issued to Albertson
No. 47 discloses the use of steel foil with improved bond strength for the manufacture of thermal heat collectors. However, the most widespread use of adhesive steel foils is for the purpose of fabricating printed circuits by bonding the foils to suitable resin substrates. A number of patents are known that deal with treating the surface of copper foil to make it more adhesive to plastic. For example, U.S. Patent No. 3, issued to Conley et al.
No. 22O,897, U.S. Patent No. 3 to Rouse et al.
, 293,109 and 3,585,010, U.S. Pat. No. 3,799,84 to Vrashimirovna et al.
No. 7, U.S. Pat. No. 3,857, issued to Yotes et al.
No. 681, U.S. Patent No. 4,049,4, issued to Morisaki.
No. 81, reissued U.S. Patent No. 29, awarded to Konicef.
No. 82O, reissue US Pat. No. 30,180 to Walski et al. and WIPO Publication No. 8,2O2,991 to TODAY disclose such pretreatments.

The above-mentioned patents identify and disclose the difficulties encountered in the prior art when bonding copper to synthetic resin substrates.

In particular, to produce printed electronic circuits, copper foil is bonded to a polymeric substrate and portions of the copper foil are selectively removed to construct the actual electronic circuit.

Generally, acid etching is used to selectively remove portions of the foil to obtain the desired metal pattern. However, when forming a printed circuit, a part of the one-piece copper foil has poor adhesion to the resin substrate, which makes it impossible to sell the printed circuit board as a final product. A defect that sometimes occurs is a failure of the laminated part and the copper layer is damaged. In order to improve bonding properties, conventional techniques have applied new adhesives and pre-treated the bonding surfaces of steel foils to further improve bonding properties.

As disclosed in Reissue U.S. Pat. No. 30,180, a layer of "nodular" copper is deposited on the surface of a gold copper foil to increase surface type and surface roughness to improve copper bond strength. There is. This deposition is usually followed by a layer of pure copper, which locks the particulate copper or copper oxide onto the surface of the foil and prevents the powder from migrating. Many variations of these processes have been attempted, as disclosed in a number of the above-mentioned US patents, but none provide optimal bonding while being inexpensive to manufacture.

Therefore, initial efforts to increase bond strength involved depositing additional amounts of nodular copper, which created powder and oxide migration problems. Efforts to prevent such migration problems have included reducing the thickness of the nodular copper electrodeposit layer, but this has the drawback of reducing bond strength.

Of the numerous U.S. patents mentioned above, the most similar technology for processing steel foil is U.S. Patent No. 3,293,109 to Roose et al. This is No. 30°180. In each of these 49 U.S. locations, a first "roughening" process is performed, granular or "resinous" copper is added to the surface of the foil, and a second "locking process" is carried out to improve the bond strength of the copper. Alternatively, a "gilding" process is performed to electrodeposit a smooth layer of copper on the first roughened surface and attach this layer to the foil substrate. In the U.S. patent of Rouse et al., Utilizing baths of different compositions,
The bath in which the first surface roughening treatment is carried out must necessarily contain a higher amino protein of animal "glue", thereby controlling the properties of the coating of the first nodular layer. In a reissued U.S. patent granted to Wolski et al., copper and
A first layer is prepared from a bath containing additional arsenic to improve the bond strength of the deposit. The Wolski et al. technique provides a third surface treatment to produce another electrodeposited microcrystalline copper and arsenic containing layer.

Although the above-mentioned techniques were developed for the purpose of developing copper foil products of commercial value, they suffer from the drawbacks of being complex and expensive to implement. Further disadvantages include the need for separate treatment baths and the need to replenish relatively expensive components.

Also, transferring foil between separate processing baths can contaminate the tank and
To solve this problem, an additional step of cleaning the foil is required. Cleaning must solve water pollution.

Means of the Invention for Solving the Problem The first aspect of the present invention, which differs from the prior art, is that the copper foil is treated with a single treatment bath consisting essentially of copper sulfate and an aqueous solution of sulfuric acid; of treatment cycles and applying an electric current while the foil is immersed in the solution. Using a current magnitude and duration sufficient to deposit a first layer of nodules 2 on the surface of the copper foil, a second current smaller than the first current is applied to deposit a second layer on top of the copper foil. form a copper layer. The technique repeats many such treatment cycles and the final coating applied to the treated copper foil has significantly improved bonding properties 9 and does not exhibit undesirable treatment migration.

The above-mentioned technology of the present invention can be applied to 2&4 猽(
A bonding characteristic of 97.7 to 8.2 yen (17 to 18 bonds) per width (1 inch) can be achieved.

Preferred embodiments of the invention reduce overall processing time to achieve greater bond strength, thus reducing equipment and material costs.

More particularly, the method of the present invention essentially consists of immersing a copper foil in an aqueous solution of copper sulfate and sulfuric acid, and applying a current to the copper foil immersed in the aqueous solution by a plurality of pulse treatment cycles. The surface of the copper foil is treated to increase the bond strength by undergoing treatment. Each processing cycle essentially consists of a first peak current phase and a second base current phase.

Conduct a peak current phase with sufficient current density and duration to electrodeposit a completely adhesive nodular layer on the surface of the copper foil, but at the same time to bond said nodular layer to the surface of the foil. The peak current phase is carried out with insufficient current density and duration to produce a nodular electrodeposited layer that requires other coatings and creates process migration. This nodular layer essentially consists of copper. The base current phase is carried out at a current density that is smaller than the density of the peak current phase, and the density of this peak current phase prevents the formation of the nodular deposition layer that occurred during the previous peak current phase, so that nodular deposits formed at the present time are It is sufficient to place a thin, tightly adherent, smooth copper layer on the electrodeposit layer, but not enough to bond the nodular electrodeposit layer to the surface of the foil.

In one embodiment of the invention, the duration of the second applied current is υ shorter than the duration of the first applied current, and in an alternative embodiment the duration of the applied second or base current is υ shorter than the duration of the first applied current. of current or peak current. In still other embodiments, each successive treatment cycle is shorter than the previous cycle, and each application of current is similarly short.

In a particular embodiment of the invention, the copper is subjected to 2500 processing cycles to form a corresponding number of sequential nodular electrodeposited layers. Additionally, the time for each individual cycle may vary depending on the complexity of the process controller, with individual durations ranging from about 4 milliseconds to about 100 milliseconds (ms) or more. The current density available for each cycle can be varied widely up to a maximum of the order of 30 OASF (amps per square foot) or more, with currents for peak current phases of approximately 56 ASF
to about 8 OASF, and the current density of the base current phase can range from about 36 ASF to about 6 OASF, for example.
It can range up to science fiction. The above ranges are exemplary and are based on no active agitation of the processing bath and with the bath temperature maintained at approximately room temperature.

One gist of the invention is to employ a single treatment bath consisting essentially of an aqueous solution of sulfur rR steel (CuSO4*5H2O) and sulfuric acid. In particular, the concentrations in this treatment bath are kept the same during the application of both currents, for example copper as metals in an amount of 39 g per liter and sulfuric acid in an amount of 63.9 g per liter. The amounts mentioned above are exemplary and may vary. However, in optionally carrying out the method of the present invention, care should be taken to maintain the precise concentration of each component relatively constant.

The present invention also relates to a copper foil having a complex surface structure obtained by practicing the present invention, consisting of a plurality of electrodeposited layers, each layer consisting essentially of a nodular coating made of steel; The top surface supports the next layer of copper and prevents the formation of a nodular layer to prevent the formation of loose grained surfaces that would otherwise cause process migration.

Therefore, each nodular layer is self-adhesive and does not require special treatments such as "gilding" to attach it to the surface of the foil. Each smooth steel layer is sufficient to serve as a barrier against further nodularization, but insufficient to serve as a bonding means for the nodular pigeon nest.

The present invention produces a product with no treatment migration, the treated surface of which consists of an irregular and complex pattern, which provides excellent bonding when layered onto the resin base used in the production of printed circuit boards. This surface is suitable for forming parts. Copper foil treated according to the present invention has very good bond strength, with 25.4. , (1 inch) per width, j 11.31 kg (25 bond) or greater is achieved uniformly and regularly.

Adopts a single bath, with successive rapid alternations or "pulsations"
By employing an electric current of 100 mL, it does not use complex and expensive equipment and provides a relatively quick and inexpensive means of applying an electrodeposited copper coating.

OBJECTS OF THE INVENTION Accordingly, the main object of the present invention is to provide a method for treating copper foil that improves surface bonding strength.

Another object of the present invention is to provide a method for processing copper foil that is inexpensive and can be controlled more easily.

Another object of the present invention is to provide a method for treating copper foil that provides uniform and excellent surface bonding strength.

Another object of the invention is to obtain a copper foil of improved quality and low cost produced by the method of the invention.

Other objects and advantages will become apparent from the following detailed description.

Embodiments According to the present invention, the bondability of the steel foil is improved by applying a treatment method to the surface of the steel foil. This treatment method basically involves immersing the copper foil in a bath consisting of an aqueous solution of copper sulfate and sulfuric acid.
A continuous treatment of electrical current, essentially consisting of a plurality of pulsating treatment cycles, is applied to this tear to deposit an adhesive irregular surface with improved bonding properties on the surface of the sleeve.

Each of these pulsating treatment cycles essentially consists of a first peak current phase consisting essentially of the magnitude and duration of the applied current. The magnitude and duration of this current is sufficient to form a nodular layer that fully adheres to the copper surface, but insufficient to form a weak nodular electrodeposited layer. Such weak nodular electrodeposited layers result in processing migration and require other external means such as additional "gilding" to bond the nodular layer to the surface of the foil. A second base current phase is then used, which essentially consists of applying a current of a smaller magnitude than the peak current phase. The magnitude of this current is sufficient to electrodeposit a thin, tightly adherent layer of smooth copper onto the freshly formed nodular electrodeposit layer, as described above, and to interrupt the formation of the nodular electrodeposit layer that has already been applied. Although of sufficient size, it is insufficient to bond the nodular electrodeposited layer to the surface of the foil.

This general processing cycle of placing a first "nodular" layer on a copper surface and then adding a second "gilding" layer is generally disclosed in the prior art. The present invention differs from this conventional technology in a first gist and an important second gist.
There is. Thus, the first gist is that a single treatment bath consisting essentially of copper sulfate and sulfuric acid is used to correspondingly form all layers consisting essentially of copper, and the second gist is: There is no layer that can serve as a "guilding" layer.

It is characterized by the absence of additional components such as other metal salts, halide salts, amine proteins as disclosed in the prior art. This is essential in view of the significant improvement in bond strength obtained by the present invention. This is important, especially since conventional techniques require arsenic and animal "glues" to reduce process migration and improve the product.

The composition of this bath is also clearly distinguishable from conventional ones in that it is maintained at specific proportion levels during the practice of the process of the invention. For example, the bath contains about 399 grams per liter of copper as metal and 963 grams per liter of sulfuric acid. This bath can provide the necessary environment to form the improved nodular layer of the process of the present invention and does not require adjustment of the components or their violets. This ability to operate within a single, relatively constant bath composition is one of the distinguishing features of the process of the present invention.

Although the method of the present invention relates to surface treatment of steel foil, copper wire, copper wire, etc. can be similarly treated, and the present invention can be applied to all these copper products. Therefore, electrically formed, rolled or otherwise formed foils can be processed by this method, and foils of various thicknesses such as 1 oz or 2 oz can be processed as well. can do.

The continuous electrical treatment, which essentially consists of electrical pulsating cycles, according to the method of the invention is completely different from that of the prior art. Thus, by adjusting the magnitude and duration of the applied current, a change in the structure of the deposited layer is achieved. A first peak it flow phase is introduced at a suitable current density and duration, but of sufficient magnitude to form an electrically deposited dendritic or nodular coating, and the process transition It is insufficiently large to form a protective coating. The first mentioned prior art discloses dendritic coatings which provide the surface roughness and increased surface area necessary for improved bonding of copper foil to printed circuit boards. Generally, nodular or dendritic coatings formed by first applying an electric current consist essentially of copper.

In the prior art, the initial electrodeposition tends to be structurally imperfect, resulting in coating or treatment migration. This migration is undesirable because it can cause the metal particles to break or become detached from the deposited copper surface. In order to reduce or eliminate this undesirable migration behavior, it has traditionally been the practice to apply a second electrical current under treatment baths of different compositions or under different temperature or electrical conditions. That is, to rapidly form a second ``gilding'' or ``plating'' surface layer to bond the nodular layer to the surface of the steel foil. The present invention is based on this same principle, and the present inventors originally believed that it would be useful to apply the current disclosed herein to a second nodular coating to bond the first nodular coating. Further research by the inventors has shown that the above assumptions are incorrect.

The present invention, in all its embodiments, therefore involves the sequential electrodeposition of layered metal coatings, each layer comprising a structurally nodular bottom layer and a thin, adhesive, copper-containing smooth layer. It consists of a top layer and a top layer. Nodular layers are added to attach independently to the surface without the need for "locking" or "gilding" overplates, with a second smooth copper-containing layer present as a barrier between adjacent nodular layers and This second smooth copper content is not sufficient so that the nodular layer acts as a "gilding" layer.

In the present invention, the successive two-phase electrical treatments, each forming a nodular layer, consist of a first treatment and a second treatment, the first treatment being carried out at a peak current density, followed by the second treatment at a lower current density. Perform at base current density. In the present invention, this repetition of changing the current density is referred to as "pulse" or "pulsation". Each treatment cycle or "pulse" forms a particularly reinforced nodular layer.

The present invention is significantly different from the conventional technology in the following points. That is,
By continuously cycling the current density and the duration of the electrical treatment, a plurality of discrete self-adhesive nodular layers and an intermediate smooth copper-containing layer are produced, which results in Does not cause processing migration or structural defects.

The structural characteristics of the nodular layer according to the invention are considerably different from the properties of plated nodular layers of the prior art.

That is, by applying a second or pace current density, the formation of the previous nodular layer is prevented and only a thin, tightly adherent layer of smooth copper is formed. This layer serves as a barrier between successive nodular electrodeposited layers. It does not produce the "locking" or "gilding" layers that the prior art teaches and employs. Therefore, the duration of the base current phase and the current density do not result in a "gilding" layer in the method of the invention and do not affect the bonding of the formed nodular layer to the foil substrate. The method of the present invention therefore forms a nodular electrodeposited layer with slits, although the individual nodular layers are separated and thus limited, by the intervention of an intermediate smooth copper layer caused by rapid changes in current density. .

Therefore, a series of sequential treatment cycles is performed, which consists of applying a first peak current and applying a second pace current. The density of the applied current in each cycle can be 300 amps per square foot or more, and the duration can be up to 30-40 seconds;
Preferably it extends up to about 100 milliseconds. The extremely short duration possible for this treatment cycle is an important difference between the present invention and the prior art. The shortest processing time disclosed in Ruth et al. US Pat. No. 3,293,10'1 is 5 seconds, a difference of several orders of magnitude compared to the time parameters of the present invention. The fact that deposits with improved strength and bondability can be effectively formed by the method of the present invention is noteworthy given the prior art, which teaches that much greater minimum processing times are required than used herein. That's true. Also, the parameters that add the base current density phase are not sufficient to bond the nodular underlayer to the foil surface, which is reflected in the short duration of the base current density phase.

In a preferred embodiment of the invention, sequential processing cycles are performed continuously. Also, the first and second current densities applied sequentially during the treatment cycle can remain the same, the duration of the second current in each cycle can be varied, and the
The current can be made even longer.

Similarly, in other aspects of the invention, the duration of each cycle can be increased over the duration of the cycle that precedes it. For example, the first nodule layer can be applied by exposing the copper surface in a treatment bath to a current density of about 80 amperes per square foot for about 60 milliseconds. A second current is then applied for about 60 milliseconds at a current density of about 50 amps per square foot. The application of this peak current density of 11 ic can be repeated in the second treatment cycle, but the duration can be made even longer, for example by extending the duration of applying the base current density to 80 milliseconds.

Additionally, the initial treatment time can be a minimum of base current density time, such as 4 ms, and this duration is gradually increased to 70 ms while providing consistent "pulses" throughout. be able to. The processing schedule described above is merely exemplary) and serves as an illustration of the implementation of the present invention.

As mentioned at the outset, the present invention contemplates a large number of processing cycles, such as 2500 cycles. However, because of the relatively short duration, this multi-cycle process can be completed in 3 to 3.5 minutes. However, throughout the process, the treatment bath remains relatively constant with respect to its quantitative and qualitative composition, what changes are the current density and the duration of the treatment time. Unlike the present invention, conventional methods require between 120 and 140 or more separate processing tanks, an equal number of cleaning stations, and a number of successive layers of each component. A corresponding number of control devices are required to add In contrast, the present invention allows processing to be performed using a single tank and its associated controls.

The process of the invention can be carried out over a relatively wide temperature range, including operation at room temperature. Therefore, for example, if the indoor temperature is approximately 15.6°C (60c'F) or 26.7°C,
9C (80"F") There are no restrictions on the temperature range; the above temperature range is merely an example. Lower temperatures may be more suitable for the deposition of No. 2 layers. The method of the invention is somewhat temperature dependent, but provided that the temperature is maintained at a relatively constant level, i.e. within the specifically selected operating temperature plus or minus 2 degrees, preferably within the temperature ranges mentioned above. The practice of the invention is not affected.

FJ-prepared steel foils according to the invention are particularly suitable for use in the manufacture of printed circuit boards. Accordingly, various known substrates may be layered or bonded to the copper foil surface. Also, in particular, from TAM glass supports impregnated with epoxy resins, paper impregnated with carbolic acid resins, glass mats impregnated with polyester and other products known for use in combination in the production of flexible and non-flexible substrates. It may be bonded to a known specific material.

In this case, various adhesives are known for use in bonding the treated steel foil to the substrate, such as phenol nitrile adhesive, phenol petitral adhesive, acrylic adhesive,
All known adhesives are tried, such as fluorinated olefin copolymer adhesives, epoxy resin adhesives, etc. These materials are known to those skilled in the art and will not be discussed further.

The precise equipment for carrying out the process according to the invention need not be exact and may be any commercially available equipment employed in pulsating plating. Therefore, either an insoluble lead electrode or a copper electrode foil may be used. As far as parameters to be controlled in the process, such as current density and duration of current flow, known control devices can be used, including devices that can be programmably controlled using a microprocessor or the like.

For example, a normal pulse rectifier made at a time pace of 100 milliseconds and configured to output 411 current with low ripple DC 111
The current may be supplied by connecting to. It is understood that the foregoing description is by way of example only, and that the invention may be carried out entirely automatically by other specially configured equipment, or at a speed capable of performing a large number of processing cycles within a few minutes. Of course, it is a good thing to do.

The method of the invention may be carried out as a batch of steps or may be carried out continuously. The latter is commercially advantageous.

The batch process therefore immerses a finite length of foil into a treatment bath, holds the foil stationary during the treatment, and then removes the foil from the bath. Continuous processing involves passing an infinite length of foil through the bath and moving predetermined sections of the foil at predetermined speeds during treatment.

The term "continuous" herein differs from the meaning of the term used herein to describe the continuous performance of process cycles and currents described in this specification; Regardless of whether a continuous process or a continuous process is adopted, it means that the current is continuously applied, which is the gist of the present invention. Therefore, both batch and sequential steps are within the scope of the present invention.

The present invention also relates to copper foils and other copper products having an electrodeposited layer on the surface, the electrodeposited layer being basically a layer of several layers, each layer being self-adhesive to the bottom consisting essentially of copper. a nodular layer and a top thin, tightly adhering, smooth copper-containing layer, which serves as an intermediate layer and is not sufficient to prevent the successive deposition of two nodular layers; It may not be sufficient to bond the nodular layer to the surface of the copper product. Accordingly, each nodular layer formed in accordance with the present invention may be bonded independently to a copper foil or other surface, or may be bonded to each other by "locking" or "gilding" as used in the prior art. ” does not require external bonding means such as layers. It is therefore clear that this composite coating is layered from a series of alternating layers, yielding a structurally complete surface area with large multiple surfaces for improved bonding to non-gold-stripe substrates. .

The bonding strength of copper produced according to the present invention was tested as follows. The treated foil was laminated to several plies of Syntan Tiller Tilleron EF-527m epoxy impregnated glass fabric. This layering was accomplished by applying a pressure of 35 units/all (500 ps i ) for 45 minutes in a 10 x 12 inch platen press electrically heated to 350 inches (177 degrees Celsius).

Bond strength was tested by peeling a 1 inch width of foil at a speed of 2 inches per minute at a 90° angle to the lamination.

The invention and its advantages will be apparent from the following examples.

EXAMPLE 1 A 2 ounce quantity of steel foil was treated according to the invention by immersion in an aqueous treatment bath containing copper sulfate and sulfuric acid, designated as CuSO4.5H2O. The concentration of copper in this bath was approximately 39 grams per liter and the concentration of sulfuric acid was 63 grams per liter.

The copper is then subjected to two treatment cycles as shown in the first fit.

1st Table 1L meeting υ Current density (ASF') Peak current 35 8゜Pace current
10 70 beak electric a 1
6 80 base current 5
As can be seen from the table above, two cycles were performed within about one minute to add two layers of reinforced nodular copper coating to the surface of the foil.

The bond strength of this material was tested using the method described at the beginning and was tested on 2 oz. foil at 25.4 soi (1 inch) @7.
, 9 to 9 (17,5 Bond). Comparing this with the conventional technique, a process of at least 5 minutes and 15 seconds was required to obtain the same bonding strength. Therefore, the present invention can reduce processing time by about 79 seconds.

The above-described embodiment is illustrative of the first aspect of the invention, in which a number of treatment cycles or "pulse" cycles are performed in a single treatment tank of constant composition, varying the current density and treatment time to achieve a suitable bond. Formed a tough, rough surface coating. By carrying out further work according to the invention, further implementation variants have been developed which improve the joint strength and, in a surprisingly short time,
The number of deposited layers added to the surface of the foil can be increased.

The following example is illustrated.

Second Example A green strip of 2 oz. steel foil with a bond strength of 2.3 kg (5.0 bond) is immersed in a processing tank. The aqueous solution in this tank contains sulfuric acid and sulfuric acid having a composition and concentration corresponding to those of the first embodiment. A pulse rectifier manufactured by Ravid Electric Company rated for an average peak current output of 50 y at 50 volts DC was modified to reduce its base current "on time" to 4
~32 milliseconds to a range of 100 milliseconds. Connect this rectifier to a battery of approximately 6.3 volts.

The treatment was initiated with a series of treatment or "pulse" cycles. That is, first a current having a peak current density of 78 ASF is applied for a cant of about 10 millimeters, and then a current with a peak current density of about 49 ASF is applied.
A base current with a current density of . The setting for "Pace Adjust" is zero, "
"Voltage adjustment" and "Current adjustment" were 100 I. The entire processing time is 3 minutes and 2 minutes.
approximately 22.8°C (73'F) without stirring the bath.
A temperature range of 2 to 24.4°C (76°F) was maintained. 2 During this time, employ at least 2,500 pulse cycles, with each cycle lasting 70
<'J It was extended to 2nd. The peel strength of the resulting deposited copper foil product was tested using the method described above, and the peel strength was approximately 11
．． It turned out to be 3 kg (25 bonds).

Third Example An additional sample was prepared in the manner described in the second example above,
Tested. As well as peak current density and pace current density,
The composition of the processing tank was kept approximately the same. These parameters as varied from test to test are shown in Table 3 along with the peel strength results.

Table 3 22.2 72 3 10 60 2
1:1.7~22.871~733 10
6021:t, i~22.270~723 10
60 22O. 0~21.168-70 3
10 60 24:1.1-22.8
70-733 10 60 22.5:
1.7~23.371~74 3.5 10
60 2O. 5.1.7-23.371-743.
5 9 55 221.1~22.87
0-733.5 8 55 2O As is clear from the above table and examples, current density and duration or "on-time" parameters must be adjusted to achieve the coating and bond strengths obtained by the practice of the present invention. Care should be taken to make changes. Therefore, according to the first embodiment of the present invention, the base current density "on time" can be varied downward as shown in the first embodiment.

In the present invention, the base "on time" can be varied upwards, for example, the duration can be greater than 60 milliseconds. In this way, the improved bond strength obtained by the method of the present invention is achieved in a shorter time than in the conventional methods described above. The examples above demonstrate that adjustments to the duration of each treatment can themselves influence the properties of the resulting composite coating.

As mentioned at the outset, adjustments to processing time, current density, and temperature are possible within the above ranges and can vary the properties of the resulting coating to suit the particular end use of the product.

As can be seen from the foregoing, the composite multilayer electrodeposited products produced according to the present invention are structurally different from conventional processes. The present invention does not involve a series of alternating nodular-1- and "gilding" layers that limit the potential bond strength achieved with the present invention. It is carried out by using a continuous pulsating nodularization process that allows the formation of this composite nodular electrodeposition with a complexly textured surface.

In contrast to varying the performance of the method of the invention by gradually or continuously varying the duration of individual current treatment times, for example by varying the base current treatment time in steps, e.g. The maximum selected for
A first series of "pulses" or cycles may be applied, with the base "on time" set to be the duration of the "on time" emission. Second series of "pulses"
, the base "on time" can be set to a maximum "on time" ladle duration, and in the third and final processing phase the base "on time" can be maintained at its maximum value. .

By varying both the current vRI& and the duration, the peak current density and the base "on-time" current density can be varied together from a minimum value to a maximum value continuously and simultaneously. Accordingly, the first pulse cycle is performed at the minimum peak current density to form an acceptable nodular layer while simultaneously maintaining the base "on time" at its minimum acceptable value. Both parameters can be varied upward simultaneously in successive "pulse" cycles to the maximum possible value in the final cycle of the process. This description is intended by the inventors to fully disclose the scope of variations in the practice of the invention.

The invention may be carried out in other ways without departing from the scope of the invention. Therefore, what is disclosed herein is merely illustrative of the invention, and the claimed invention is not limited to the embodiments disclosed herein. Therefore, the present invention can be employed to treat metal foils other than steel, such as nickel foils, which undergo surface treatment. When processing nickel foil, the metal to be treated is transported to a bath containing a solution of a soluble salt of the same metal, namely nickel, mixed with a suitable acid, but the remaining other parameters of the process are It is the same as in the case of .

Patent Applicant Steven Jay, Kirwan Procedural Amendment June 11, 1985 Patent Application No. 88464 3, Relationship with the person making the amendment Patent Applicant Name (Name) Steven Jay Karhu/4 , Agent Showa Month, Day 6, Full text of the specification subject to amendment

Claims (1)

[Claims] 1. A method of treating the surface of a copper foil to improve bonding strength, comprising: A. immersing the steel foil in a bath consisting essentially of an aqueous solution of copper sulfate and sulfuric acid; B. A series of current treatments, each consisting essentially of a first peak current phase and a second base current phase, are applied to the bath along with the immersed copper foil to improve bonding strength. i) a current density sufficient to form a fully adhesive nodular layer consisting essentially of copper on at least one surface of the foil; operating said peak current phase with a duration of time to form a nodular layer which requires further processing to bond said nodular layer to said surface of said copper foil and which results in processing migration; ii) operating the base current phase at a current density smaller than the magnitude of the current density of the peak current phase to prevent formation of the nodular layer; a current density and duration sufficient to place a layer of smooth, adhesive smooth copper on the nodular layer, but insufficient to bond the nodular layer to the surface of the copper foil; iii) the total duration of each of the pulse treatment cycles is a few milliseconds. 2. The method of claim 1, wherein the duration of the base current phase is longer than the duration of the peak current phase. 3. The method of claim 1, wherein each successive base current phase is applied for a longer duration than the previous base current phase. 4. Claim 1, wherein each of the peak current phase and the base current phase is performed with the same current magnitude.
The method described in section. 5. Varying the magnitude of the peak current phase in current density from about 56 amps per square foot to about 80 amps per square foot, and varying the current density of the base current phase from about 40 amps per square foot to about 70 amps per square foot. A method according to claim 4. 6. The method according to claim 1, wherein the bath is essentially composed of an aqueous solution of CuSO_4.5H_2O and H_2SO_4. 7. The method of claim 6, wherein said bath comprises copper in an amount measured as metal of about 39 grams per liter and sulfuric acid in an amount of about 63 grams per liter. 8. The total time for each of the processing cycles is approximately 1
1. The method according to claim 1, wherein the time limit is up to 000 milliseconds. 9. The method of claim 1, wherein the peak current phase has a duration of about 8 milliseconds to about 10 milliseconds, and the base current phase has a duration of about 10 milliseconds to about 60 milliseconds. Method. 10. The method of claim 1, wherein the pulse treatment cycle has a total duration of from about 3 minutes to about 3.5 minutes. 11. The method of claim 1, wherein at least two pulse treatment cycles are performed. 12. The method of claim 1, wherein at least 60 pulse treatment cycles are performed. 13. Copper products selected from copper foil, copper rod, copper wire, and copper rod material having a surface electrodeposition layer that adheres tightly to improve bondability to nonmetallic substrates. 14. Copper products selected from copper foil, copper rods, copper wire, and copper rod materials that have a surface electrodeposition layer that closely adheres to nonmetallic substrates with improved bondability to nonmetallic substrates, The electrodeposited layer is comprised of a plurality of layers, each consisting essentially of a lower self-adhesive nodular layer, which is a copper-containing layer bonded together, and an upper, thin, tightly adhering smooth layer, which is a copper-containing layer. , the smooth layer is sufficient to act as an intermediate layer to prevent successive deposition of the nodular layer;
and is insufficient to bond the nodular layers to the surface of the copper article, such that each of the nodular layers so formed is bonded to each other without the use of external bonding means, and A copper product characterized in that the copper product is independently bonded to the surface of the copper product. 15. The copper article of claim 14, wherein said electrodeposited layer comprises up to about 2500 said layers. 16. The copper article of claim 14, wherein said electrodeposited layer comprises at least two said layers. 17. The copper article of claim 14, wherein said electrodeposited layer comprises at least 60 said layers.