Patent Application
20250092553
The present invention relates to an electrodeposited thick copper foil with a uniform matte surface. The present invention also relates to a method for manufacturing the present electrodeposited copper foils and articles made therefrom.
Electronic systems used in vehicles includes engine management systems, ignition systems, carputers, telematics, in-car entertainment systems, and others. Electronic systems have become an increasingly large component of the cost of an automobile. Consequently, the demand of automotive PCBs used in the above-mentioned electronic systems significantly increases.
Comparing to traditional consumer electronics, the automotive PCBs must meet high reliability and safety standards. More specifically, copper foils suitable for use in the automotive PCBs should have the following three features: (1) having sufficient thickness to bear high working current and allow good heat dissipation; (2) having a uniform matte surface to avoid poor etching during the manufacturing process and/or short circuit occurrence at work condition; and (3) allowing to be manufactured at industrial production rate.
The thickness of an electrodeposited copper foil (abbreviated as ED copper foil hereunder) is proportional to the electrodeposition duration at a specified current density. To have a thick ED copper foil without decreasing the production rate may be achieved by electrodepositing at a higher current density (i.e., higher than 30 A/dm2). However, the uniformity of the matte surface of the copper foil generally decreases as the current density increases. At high current density, the copper crystals may be unevenly deposited at certain locations to form abnormal protrusions (extraordinarily tall and large) on the deposited surface of the ED copper foil, and thus decreases the uniformity of the surface.
Generally, when the thickness of a copper foil is less than 30 μm, applying high current density during electrodeposition may not raise a serious uniformity problem on the matte surface (i.e., the deposited surface) of an ED copper foil since the electrodeposition duration is relatively short and no sufficient time to grow the abnormal protrusions. However, when the electrodeposition duration is lengthened to manufacture a thick copper foil, it is expected to form many abnormal protrusions on the matte surface of the ED foil. As a result, a PCB made from the thick copper foil having poor uniformity is likely to encounter poor etching during circuit forming stage, and potential problem in short circuit while at work later.
To minimize the above-mentioned abnormal protrusion formation on the matte surface of an ED copper foil, known solutions include: (1) decreasing the current density used for electrodeposition; and (2) adding large amounts of conventional additives in the electrolytic solution. The main drawback of the first solution is that as the current density decreases, the production rate of copper foil decreases. In addition, the first solution may suppress the size and numbers of the abnormal protrusions, but it cannot stop the formation of the abnormal protrusions.
The second solution is to add conventional additives to provide a uniform copper foil surface under high current density conditions. However, the large amounts of conventional additives in the electrodeposition cell decrease the service life of the electrolytic solution and will require an extra removal step when disposing the electrolytic solution as waste. Furthermore, it is difficult to control the quality of the copper foil during a continuous production process, i.e., by replenishing fresh electrolytic solution into an electrodeposition cell containing large amounts of conventional additives.
In view of the above, there exists a need to develop an electrodeposited copper foil with a uniform matte surface to bring overall benefits to the printed circuit board industry, especially for automotive PCBs.
To solve the aforementioned problems, the present invention provides an electrodeposited copper foil with a uniform matte surface and a method for manufacturing said electrodeposited copper foil.
According to the first aspect of the present invention, an electrodeposited copper foil with a uniform matte surface is provided.
The electrodeposited copper foil has an average thickness (TAve) of about 30 μm to about 400 μm; the electrodeposited copper foil has a matte surface and a shiny surface; the matte surface of the copper foil comprises a plurality of protrusions; and a number (PA50+) of the protrusions on the matte surface having flattened peaks after polishing with a surface area of 50 μm2 or more per 1 mm2 of the matte surface is 8.0 or less; wherein the average thickness is measured by a scanning electron microscope (SEM); peaks of some protrusions on the matte surface are flattened by: a) placing the electrodeposited copper foil on a glass substrate with the matte surface in contact with the glass substrate, and b) polishing off about 1 μm of the shiny surface of the electrodeposited copper foil by using a silicon carbide sandpaper with a grit size of 1200; the number and the surface area of the protrusions on the matte surface having flattened peaks after polishing is counted and measured by using an optical microscope having a magnifying power of 50 times or more and a resolution of at least 0.1 μm.
According to the second aspect of the present invention, a method for manufacturing the above-mentioned electrodeposited copper foil is provided. The method comprises:
wherein,
According to the third aspect of the present invention, a surface-treated electrodeposited copper foil comprises or is made from the electrodeposited copper foil of the present invention.
According to the fourth aspect of the present invention, an article comprises or is made from the electrodeposited copper foil of the present invention is provided.
In one embodiment, wherein the article includes negative electrode collectors of lithium-ion batteries, copper clad laminates, flexible copper clad laminates, heat dissipation plates, or printed circuit boards.
All publications, patent applications, patents and other references mentioned herein, if not otherwise indicated, are explicitly incorporated by reference herein in their entirety for all purposes as if fully set forth.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, will control.
Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.
As used herein, the term “produced from” is synonymous to “comprising”. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.
The transitional phrase “consisting of” excludes any element, step, or ingredient not specified. If in the claim, such a phrase would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase “consisting of” appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.
The transitional phrase “consisting essentially of” is used to define a composition, method or apparatus that includes materials, steps, features, components, or elements, in addition to those literally discussed, provided that these additional materials, steps features, components, or elements do not materially affect the basic and novel characteristic(s) of the claimed invention. The term “consisting essentially of” occupies a middle ground between “comprising” and “consisting of”.
The term “comprising” is intended to include embodiments encompassed by the terms “consisting essentially of” and “consisting of”. Similarly, the term “consisting essentially of” is intended to include embodiments encompassed by the term “consisting of”.
When an amount, concentration, or other value or parameter is given as either a range, preferred range or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of “1 to 5” is recited, the recited range should be construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 & 4-5”, “1-3 & 5”, and the like. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range.
When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to.
Further, unless expressly stated to the contrary, “or” refers to an inclusive “or” and not to an exclusive “or”. For example, a condition A “or” B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
As used herein, the term “hydrocarbon group” refers to an organic compound having at least one carbon atom and at least one hydrogen atom, optionally substituted with one or more substituents where indicated. “Alkyl group” refers to a straight or branched chain saturated hydrocarbon having the specified number of carbon atoms and having a valence of one, such as methyl, ethyl, n-propyl, i-propyl, or the different butyl, pentenyl and hexenyl isomers. “Alkylene group” refers to an alkyl group having a valence of two. “Cycloalkyl group” refers to a monovalent group having one or more saturated rings in which all ring members are carbon, such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl; “cycloalkylene group” refers to a cycloalkyl group having a valence of two. Examples of “cycloalkylene” include cyclopropylene, cyclobutylene, cyclopentylene and cyclohexylene. “Aryl group” refers to a monovalent aromatic monocyclic or polycyclic ring system where the ring member is constituted of carbon atoms and may include a group with an aromatic ring fused to at least one cycloalkyl or heterocycloalkyl ring, such as phenyl, biphenyl, triphenyl, naphthyl, and binaphthyl. “Arylene group” refers to an aryl group having a valence of two. The total number of carbon atoms in a substituent group is indicated by the “Ci-Cj” prefix.
The term “optionally substituted” is used interchangeably with the words “substituted or unsubstituted” or with the term “(un)substituted”. The expression “optionally substituted with 1 to 4 substituents” means that no substituent is present (i.e., unsubstituted), or 1, 2, 3, or 4 substituents are present (limited by available bond positions). Unless otherwise indicated, an optionally substituted group can have one substituent at each substitutable position of the group, and each substituent is independent selected. “Halide” refers to fluoride, chloride, bromide and iodide.
Embodiments of the invention as described in the Summary of the Invention include any other embodiments described herein, can be combined in any manner, and the descriptions of variables in the embodiments pertain not only to the composite laminate of the invention, but also to the articles made therefrom.
The invention is described in detail herein under.
The present invention relates to an electrodeposited copper foil with a uniform matte surface. The electrodeposited (ED) copper foils are manufactured by electrodeposition. Each ED copper foil has two surfaces; the surface facing the electrolytic solution during the manufacturing process is called the “deposited surface” and the opposite surface contacting the cathode drum/roller is called the “drum surface” or “roller surface”. Both surfaces of an ED copper foil have distinguishable appearance, thus, the deposited surface is also called a matte surface, and the drum surface is called a shiny surface. The matte surface of the ED copper foil comprises a plurality of protrusions when it's viewed with a microscope having high magnifying power. Some protrusions are abnormally taller and larger than other protrusions due to uneven copper deposition. In general, uniformity of the matte surface of an ED copper foil can be affected by the number and size of the abnormally taller and larger protrusions per unit area of the copper foil. As mentioned previously, the uneven copper deposition happens prominently when the electrodeposition is performed at high current density, such as at about 30 A/dm2 or higher. Consequently, ED copper foils produced conventionally at high current density are known to have poor uniformity on the matte surface.
The abnormally taller and larger protrusions on the matte surface of an ED copper foil may be revealed by: a) placing the electrodeposited copper foil on a glass substrate with the matte surface in contact with the glass substrate, and b) polishing off about 1 μm of the shiny surface of the electrodeposited copper foil by using a silicon carbide sandpaper with a grit size of 1200. The peaks of the abnormally taller and larger protrusions are flattened afterwards.
Surface area of each protrusion having a flatten peak after the above-mentioned polishing may be observed and measured by a scanning electron microscope (SEM). For example,
In general, the abnormally taller and larger protrusions having flatten peaks after polishing with a surface area of 50 μm2 or more are counted because these protrusions significantly affect the uniformity of the matte surface of an ED copper foil. An optical microscope having a magnifying power of 50 times or more and a resolution of at least 0.1 μm is used to observe and count the number of the protrusions having flatten peaks after polishing with a surface area of 50 μm2 or more, and the number is represented by PA50+. Because the observation window size of an optical microscope may vary from one instrument to another, number of the above-mentioned protrusions (PA50+) per 1 mm2 of the matte surface is used as one indicator for the uniformity of the matte surface of an ED copper foil.
Additionally, uniformity of the matte surface of an ED copper foil may be characterized by a uniformity factor (UF) which is calculated the equation 1:
wherein
The present electrodeposited copper foil with a uniform matte surface has the following features: (1) having an average thickness (TAve) of about 30 μm to about 400 μm; and (2) having a PA50+ per 1 mm2 of the matte surface is 8.0 or less.
The present electrodeposited copper foil further has the fourth feature that the matte surface of the electrodeposited copper foil has a uniformity factor (UF) of 5.5 μm or less.
In some embodiments of the present invention, the PA50+ per 1 mm2 of the matte surface is about 7.0 or less, about 6.0 or less, about 5.0 or less, or about 4.0 or less, 3.0 or less or about 2.0 or less.
In some embodiments of the present invention, the matte surface of the electrodeposited copper foil has a UF of 4.5 μm or less, or 3.5 μm or less, or 2.5 μm or less.
The second aspect of the present invention is to provide a method for manufacturing the above-mentioned electrodeposited copper foil with a uniform matte surface, comprising the following steps:
wherein
In the method of the present invention, the electrolytic solution comprises copper sulfate, sulfuric acid, chloride ion, and an additive. Copper sulfate is the source of copper ion and sulfuric acid is the electrolyte in the electrolytic solution Both copper sulfate and sulfuric acid are commercially available from a variety of sources and used without further purification.
In some embodiments of the present invention, the amount of copper sulfate in the electrolytic solution, based on the total volume of the electrolytic solution, is about 120 g/L to about 450 g/L; or about 180 g/L to about 400 g/L; or about 240 g/L to about 350 g/L.
In some embodiments of the present invention, the amount of sulfuric acid in the electrolytic solution, based on the total volume of the electrolytic solution, is about 30 g/L to about 140 g/L; or about 35 g/L to about 130 g/L; or about 40 g/L to about 120 g/L.
The source of the chloride ion may be copper chloride or hydrochloric acid. The source of chloride ion is commercially available and used without further purification.
In some embodiments of the present invention, the amount of chloride ion in the electrolytic solution, based on the total weight of the electrolytic solution, is about 0.1 ppm to about 60.0 ppm, or about 1.0 ppm to about 55.0 ppm, or about 2.5 ppm to about 50.0 ppm, or about 5.0 ppm to about 45.0 ppm, or about 10.0 ppm to about 40.0 ppm.
There is no specific limitation on the additive used in the present invention so long as the electrodeposited copper foil made by the present method has a uniform matte surface. Additives suitable for use in the electrolytic solution comprise gelatin, animal glue, cellulose, an organosulfonic acid or salts thereof, a nitrogen-containing cationic polymer, or mixtures thereof. Other additives, such as accelerators, inhibitors, leveling agents or crystal orientation modifier may also be added in combination of one or more kinds depending on the specific application of the ED copper foil.
In some embodiments of the present invention, the additive comprises gelatin, animal glue, cellulose, an organosulfonic acid or salts thereof, a nitrogen-containing cationic polymer, or mixtures thereof.
In the method for manufacturing the present electrodeposited copper foil, the amount of the additive in the electrolytic solution depends on the specific additive selected, the concentration of copper ion, the concentration of sulfuric acid in the electrolytic solution, and the current density applied.
Since the mass production operations of copper foils generally keeps recycling the electrolytic solution by replenishing needed ingredients (e.g., copper ion, sulfuric acid, chloride ion, etc.), then filtered through filter materials to remove impurities and degraded additive(s) prior to pumping into the electrolytic cell. When the total amount of the additive(s) is 50 ppm or less, based on the total weight of the electrolytic solution, it is beneficial to reduce the usage of the filtration materials such as activated carbon. Therefore, the method for manufacturing the present electrodeposited copper foil is beneficial for mass production and environmental protection.
In one embodiment of the present invention, the total amount of the additive(s) in the electrolytic solution is about 0.1 ppm to about 50.0 ppm, or about 0.5 ppm to about 40.0 ppm, or about 1.0 ppm to about 30.0 ppm.
Known organosulfonic acids or salts thereof suitable to use as a brightener or an accelerator in the electrolytic solution include bis(sodium sulfopropyl) disulfide (SPS), sodium 3-(benzthiazolyl-2-mercapto)-1-propane sulfonate (ZPS), 3-S-thiuronium propanesulfonate (UPS), sodium 3-mercapo-1-propanesulfonate (MPS), and the like. The amount of the organosulfonic acid or salts thereof in the electrolytic solution is generally in a range of 0.1 ppm to 20.0 ppm, or 0.5 ppm to 15.0 ppm, or 1.0 ppm to 10.0 ppm, based on the total weight of the electrolytic solution.
In one embodiment of the present invention, the additive is an organosulfonic acid or salts thereof.
In general, a nitrogen-containing cationic polymer (NCP) is a reaction product of an amine compound and an epoxide compound. Suitable amine compounds include, but not limited to, dialkylamine, trialkylamine, arylalkylamine, diarylamine, imidazole, triazole, tetrazole, benzimidazole, benzotriazole, piperidine, morpholine, piperazine, pyridine, oxazole, benzoxazole, pyrimidine, quinoline, isoquinoline, and the like. Preferably, the amine compounds include but not limited to a diamine of Formula (I) or an imidazole of Formula (II):
wherein
Examples of the diamine of Formula (I) include, but not limited to, ethylenediamine, tetrametyl-1,3-propanediamine, N1,N4-diethyl-1,4-butanediamine, tetramethyl-1,5-pentanediamine, N1,N6-dimethyl-1,6-hexanediamine, N,N,N′,N′-tetramethyl-1,6-hexanediamine, 1,4-diaminocyclohexane, 1,4-cyclohexane-bis(methylamine), N,N,N′,N′-tetramethyl-p-phenylenediamine, p-xylyenediamine, bis[2-(N,N-dimethylamino)ethyl]ether, bis(3-aminopropyl)ethane, 2,2′-[1,2-ethane-diylbis(oxy)]bis[N-methylethananmine, 1,1′-[1,2-ethanediylbis(oxy)]bis[2-propan-amine], 1,2-bis(3-aminopropoxy)ethane, 3,3′-[oxybis(ethyleneoxy)]bis[N,N-dimethylpropylamine] and 3,3′-[oxybis(propyleneoxy)]bis[N,N-dimethylpropylamine].
Examples of an imidazole of Formula (II) include, but not limited to, 2H-imidazole, 2-methyl-imidazole, 4-methylimidazole, 2-ethylimidazole, 2-isopropyl-imidazole, and 2,5-dimethyl-1H-imidazole.
Suitable epoxide compounds include those having one epoxide group, diepoxies having two epoxide groups joined together by a linkage, or polyepoxides having 3 or more epoxide groups. Preferably, the epoxide compounds include, but not limited to, an epoxide of Formula (III) or a diepoxide of Formula (IV):
wherein
Preferably, in the epoxide of Formula (III), X is chlorine or bromine, and more preferably chlorine. When Y is C1-C4 alkyl group, the alkyl group may be unsubstituted or substituted, i.e., one or more of its hydrogens may be replaced with another substituent group. Examples of compounds of formula (III) include, but are not limited to, epichlorohydrin and epibromohydrin.
Examples of the diepoxide of formula (IV) include, but are not limited to, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, 1,3-butandiol diglycidyl ether, glycerol 1,3-diglycidyl ether, neopentyl glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether poly(propyleneglycol)diglycidyl ether, 1,2-cyclohexanedimetanol diglycidyl ether, 1,4-cyclohexanedimetanol diglycidyl ether, poly(ethylene glycol) diglycidyl ether, and poly(polypropylene glycol) diglycidyl ether.
The preparation of the reaction products of amine compounds and epoxide compounds are well known, see, e.g., U.S. Pat. Nos. 8,268,158, 7,662,981, and 7,374,652, and 6,800,188. The reaction between the reaction product of the amine compounds and the epoxide compounds as described above can be carried out, for example, at a temperature of 30° C. to 90° C. for 45 minutes to 480 minutes. The reaction products typically have a molar ratio of amine compounds to epoxide compounds being from 10:1 to 1:4, and more typically from 2:1 to 1:2.
In one embodiment of the present invention, the additive comprises a nitrogen-containing cationic polymer.
In one embodiment of the present invention, the nitrogen-containing cationic polymer is a reaction product of a diamine of Formula (I) with an epoxide of Formula (III):
wherein
In another embodiment of the present invention, the nitrogen-containing cationic polymer is a reaction product of a diamine of Formula (I) with a diepoxide of Formula (IV):
wherein
In a further embodiment of the present invention, the nitrogen-containing cationic polymer is a polymerization product of an imidazole of formula (II) with an epoxide of formula (III):
wherein
In yet another embodiment of the present invention, the nitrogen-containing cationic polymer is a polymerization product of an imidazole of formula (II) with a diepoxide of Formula (IV):
wherein
In general, the reaction products of amine compounds and epoxide compounds may have a weight-average molecular weight (Mw) value in the range of 100 g/mole to 50,000 g/mole, typically from 500 g/mole to 30,000 g/mole, preferably from 1,000 g/mole to 10,000 g/mole, although other Mw values may be used.
In one embodiment of the present invention, the nitrogen-containing cationic polymer has a weight-average molecular weight (Mw) of about 1,000 g/mole to about 10,000 g/mole.
In general, the amount of the nitrogen-containing cationic polymer in the electrolytic solution is in a range of 0.1 ppm to 20.0 ppm, or 0.5 ppm to 15.0 ppm, or 1.0 ppm to 10.0 ppm, based on the total weight of the electrolytic solution.
In one embodiment of the present invention, the amount of the nitrogen-containing cationic polymer in the electrolytic solution is in a range of 0.1 ppm to 20.0 ppm, or 0.5 ppm to 15.0 ppm, or 1.0 ppm to 10.0 ppm, based on the total weight of the electrolytic solution.
The method for manufacturing the present electrodeposited copper foil can be operated at a wide range of temperature of the electrolytic solution. The temperature of the electrolytic solution is generally between about 20° C. and about 80° C., preferably between about 25° C. and about 75° C., and more preferably between 30° C. and about 70° C.
The method for manufacturing the present electrodeposited copper foil can also be operated by applying a wide range of electric current. The electrodeposition can be performed at a current density ranging from about 30 A/dm2 to about 100 A/dm2. When the electrodeposition is performed at a current density of higher than 60 A/dm2, the production rate of the electrodeposited copper foil may reach approximately at least 0.25 μm per second, which meets the standard industrial production rate.
The third aspect of the present invention is to provide a surface-treated electrodeposited copper foil comprises or is made from the electrodeposited copper foil of the present invention.
There are various types of surface treatment to impart desired properties to the copper foil depending on the specific application. The electrodeposited copper foil of the present invention can be subjected the conventional surface treatment steps, such as pickling, roughening (e.g., nodule plating), forming a heat-resistant layer, an antioxidation layer, and/or an adhesion promotion layer to obtain a surface-treated electrodeposited copper foil. The surface treatment steps described above may be applied to the matte surface, the shiny surface, or both surfaces of the electrodeposited copper foil.
Noted that none of the above-mentioned surface treatment steps is expected to deteriorate the uniformity of the matte surface of the basic ED copper foil. In other words, the UF value of the surface-treated copper foil of the present invention is expected to have the same UF value or even less than the UF value of the basic copper foil of the present invention.
For example, one may speculate that the surface treatment step such as roughening by electroplating nodules on the matte and/or shiny surface would form a nodule layer 4 having a thickness ranging from 100 nm to 1 μm. In addition, the nodules plated on the matte surface may be deposited to valleys more than that on the peaks, or vice versa, thus the average thickness of the ED copper foil may change after the roughening step.
Please refer to
It is worthy to note that when roughening on the matte surface of the copper foil according to one embodiment of the present invention as illustrated in
As previously described, PA50+ is counted and measured for surface area of the protrusions on the matte surface having flatten peaks with a surface area of 50 μm or more after polishing off about 1 μm of the shiny surface of the ED copper foil. After polishing, peaks of the abnormally larger and taller protrusions and the nodules deposited thereon are flattened as well. Therefore, Amax and PA50+ per 1 mm2 of the matte surface of a roughened copper foil are also expected to be approximately the same as that of the untreated basic foil 1. Consequently, the UF value of the present ED copper foil is expected to be approximately the same after the surface treatment steps.
The fourth aspect of the present invention is to provide articles that comprise or are made from the electrodeposited copper foils of the present invention. The articles include negative electrode collectors of lithium-ion batteries, copper clad laminates, flexible copper clad laminates, heat dissipation plates, or printed circuit boards.
Without further elaboration, it is believed that one skilled in the art using the preceding description can utilize the present invention to its fullest extent. The following examples are, therefore, to be construed as merely illustrative, and not limiting of the invention in any way whatsoever.
The abbreviation “E” stands for “example”, and “CE” stands for “comparative example”. The examples and the comparative examples were prepared in a similar manner except using different respective electrolytic solution. Performance tests of the examples and the comparative examples were carried out in the same or similar manner.
Gelatin was purchased from Jellice Pioneer Private Limited Taiwan Branch (Singapore) with model number FL-FCCO.
Bis(sodium sulfopropyl) disulfide (SPS) was purchased from HOPAX.
Hydroxyethyl cellulose (HEC) was purchased from DAICEL.
NCP-A: a reaction product of a diamine of Formula (I)
and a diepoxide of Formula (IV)
with a Mw of about 1,000-10,000 g/mol, sold by DuPont Electronics, Inc. Wilmington, DE, USA (referred as “DuPont Electronics” hereunder), under the trade name of Copper Gleam™, T1.
NCP-B: a reaction product of an imidazole of Formula (II)
with an epoxide of Formula (III)
with a Mw of about 1,000-10,000 g/mol, sold by DuPont Electronics, under the trade name of Copper Gleam™, T2.
NCP-C: a reaction product of an imidazole of Formula (II)
with and an diepoxide of Formula (IV)
with a Mw of about 1,000-10,000 g/mol, sold by DuPont Electronics, under the trade name of Copper Gleam™, T3.
Copper sulfate, sulfuric acid, hydrochloric acid, and compounds with unidentified commercial source were purchased from Sigma-Aldrich Company.
The ED copper foils of examples 1-13 and comparative examples 1-7 were prepared by the following steps.
First, the electrolytic solution of each example or comparative example was prepared by thoroughly mixing copper sulfate (260 g/L), sulfuric acid (105 g/L), chloride ion, and the additive(s) in the amounts as shown in Table 1. The electrodeposition was conducted in an instrument containing a titanium drum to be used as the negative electrode (cathode), and a dimensional stable anode (IrO2/Ti) to be used as the positive electrode. A DC power supply was used and the current density was set at 60 A/dm2. The space between the cathode and the anode was filled with the respective electrolytic solution, and the temperature of the electrolytic solution was maintained at 60° C. A copper foil of each example or comparative example was directly formed on the surface of the titanium drum with a plating duration as specified in Table 1. Lastly, the copper foil was removed from the titanium drum, and an electrodeposited copper foil was obtained. The copper foil specimens of E1-E13 and CE1-CE7 were basic copper foils that means they weren't subjected any surface treatment steps.
Uniformity of the copper foils of examples 1-13 and comparative examples 1-7 were measured by the following methods when applicable.
The copper foil obtained in each example or comparative example was cut into a specimen (size: 2 cm×1 cm) for thickness measurement by an SEM. For easy handling, each specimen was immersed in a room-temperature curable epoxy resin to obtain a clear epoxy coated Cu foil specimen. Noted that the epoxy coatings of the copper foil specimen was invisible or undetectable by SEM.
The scanning electron microscope (model: JEOL IT300HR, IT800SHL) was set with backscattered electron detector, enhanced contrast, reduced brightness and scanning speed longer than 40 s to obtain a high-quality electron channeling contrast image. Heights of 5 different peaks and 5 different valleys of each foil samples were recorded and averaged in the following Tables 2-1 and 2-2. The average thickness (TAve) is calculated by combining the averaged peak height and the averaged valley height, then divided by 2, and also listed in Table 2-2.
2. Maximum Surface Area (Amax) of Protrusions Having a Flatten Surface after Polishing and Numbers (P50+) of Protrusions Having a Flatten Surface after Polishing with a Surface Area of 50 μm2 or More on the Matte Side
A piece of copper foil specimen of each example or comparative example was cut into a square of 10 cm×10 cm. Then, the specimen was placed on a glass plate with the matte surface facing down and in contact with the glass plate. The shinny surface of the specimen was polished by using a SiC sandpaper, #P1200, manufactured by Buehler company. After polishing off about 1 μm of the shiny surface, flatten peaks of the taller/larger protrusions on the matte surface of the specimen appeared. A photograph of the matte surface of each specimen was taken by an optical microscope (OLYMPUS S™7-CS100) equipped with a 5 times objective lens and a 10 times ocular lens. The observation area of each photograph was 5,892,250 μm2.
The photograph of each copper foil specimen was analyzed by a software to measure the surface area of each protrusion having a flatten peak and counted the number of the flatten peaks with a surface area of 50 μm2 or more (PA50+) in the photograph. For easy comparison, the counted number of the above-mentioned protrusions per 5,892,250 μm2 of the observation matte surface area was divided by 5.892 to provide PA50+ per 1 mm2 (i.e., 1,000,000 μm2) of the matte surface.
As previously mentioned, the uniformity factor (UF) of the matte surface of each example and comparative example is calculated as follow:
The measured and calculated data of each copper foil specimen are listed in Table 3.
As shown in Table 1-3, the present electrodeposited copper foils of Examples 1-13 each has a uniform matte surface as judged by the UF value being 5.5 μm or less, and the PA50+ per 1 mm2 of the matte surface being 8.0 or less, respectively. Regardless the presence of gelatin or HEC, the addition of the nitrogen-containing cationic polymer including NCP-A, NCP-B and/or NCP-C in the electrolytic solution surprisingly enhanced the matte surface uniformity of the ED copper foils of E1-13 that had a thickness ranging from about 69 μm to about 374 μm.
In contrast, comparative examples 1-7 that were prepared by using only conventional additives such as gelatin and/or HEC in an amount similar to that of the nitrogen-containing cationic polymer in the respective electrolytic solution, and the resulting copper foils had poor uniformity as judged by the respective UF value (i.e., more than 5.5 μm). In addition, the matte surface of each copper foil specimen of CE1-7 had a PA50+ per 1 mm2 of the matte surface ranging from 9.0 to 25.6.
Therefore, the method of the present invention effectively suppresses the growth of abnormally taller and larger protrusions on the matte surface of ED copper foil during electrodeposition when the copper foil thickness is between about 30 μm and about 400 μm. PCBs made from the copper clad laminates or flexible copper clad laminates comprising the ED Cu foil of the present invention are expected to have improved safety and reliability, and less poor etching and/or short circuit problems.
While specific embodiments of the invention have been shown and described, further modifications and improvements will occur to those skilled in the art. It is desired that it be understood, therefore, that the invention is not limited to the particular form shown and it is intended in the appended claims which follow to cover all modifications which do not depart from the spirit and scope of the invention.
| Number | Date | Country | |
|---|---|---|---|
| 63578745 | Aug 2023 | US |
