Guest Editorial -For Plateworld.com
Don Baudrand, Don Baudrand Consulting, e-mail:firstname.lastname@example.org
AN OLD ART TURNED INTO LEADING EDGE TECHNOLOGY
Early electroplating was used to produce statuettes and decorative art objects made from the electroplated copper, silver, and gold. These objects were made by plating very thick deposits of the pure metal onto a mold made of clay, wax or plaster like materials that was removed after the plating was completed. Today we call that method "electroforming". Electroforming is used to produce wave guides, aircraft components and plastic molds for thousands of different items such as rubber boots and glove molds, phonograph records, CD's, Prosthetics, auto dash boards, tail lights, dolls heads, holographs, etc.
Electroplating is known to the public as plated bumpers and jewelry items. These represent a small percentage of the plating industry. Electroplating is essential for most industries, providing surface properties unattainable by any other means. Corrosion protection and wear resistance are the most recognized uses. However, the electronics industry relies on plating for specific useful deposit characteristics such as Controlled resistance, high conductivity, (The specific resistivity of nickel, for example is about 7.4, Copper 1.7, gold 1.4, silver 1.1 micro Ohm cm. For comparison, tin-lead solder is about 11), magnetic properties, bonding abilities, such as solderability , wire bonding, die (computer chip) bonding, brazability, and many other useful characteristics.
Electrochemistry may be defined as the science that deals with the interconversion between electrical and chemical energy . This interaction may involve the use of an electric current to bring about a chemical reaction or a chemical reaction to generate and electric current. The branch of electrochemistry we will discuss is electrodeposition and "electroless deposition". Plating chemistry requires the knowledge of not only electrochemistry, but organic chemistry, physical chemistry, metallurgy, physics, ligand chemistry, chemical engineering, to name a few of the more important disciplines
Electrodeposition (plating) occurs from a solution containing metal ions called an electrolyte. (An electrolyte is a solution that can conduct electricity) The two electrodes are Anode, that may be made of the metal to be deposited, or in some cases an insoluble metal and a cathode onto which metal is deposited. When an electrical current (direct current, DC) is applied to the system metal is dissolved from the soluble anode and deposited onto the cathode. The cathode then is the object to be plated. It seems simple, but there are many special considerations which complicate the process. The electrical current can be from a battery (almost never used commercially) or from a rectifier which converts alternating current to direct current, of from a motor generator ( seldom used today). Plating is done with direct current.
To achieve good adhesion of plated deposits the metal item to be plated must be extremely clean and free from any films or oxides. The cleaning process steps are many. But properly done, adhesion can occur that exceeds the strength of the weakest metal. The chemistry of plating solutions is complex. For example, a simple acid copper plating solution would consist of copper sulfate and sulfuric acid. However the results would not be desirable inasmuch as the deposit would be somewhat and dull and possibly spongy. An addition of about 50 ppm (Parts per million) of chloride ion will result in a smooth deposit. The addition of organic compounds of very special nature will result in a deposit that is bright and will have leveling characteristics. This illustrates one of the simplest plating solutions.
When plating onto non-metals (non-conductors) the process becomes even more complicated. Each plastic and each grade of plastic requires a different preparation process. Plating onto hybrid circuits and other electronic devices require different processes. When plating silver, gold, copper, nickel, etc. onto rough or pitted objects the deposit will not be bright and smooth unless the basis metal is first prepared by polishing and/or buffing operations, cleaned in a many step process, acid treated to remove oxides, rinsed in clean water (deionized water) then plated in a plating solution containing organic compounds called brighteners. Some plating solutions utilize leveling agents in addition to brighteners.
In "electroless plating", electrons are supplied from within the solution. The chemical compounds that supply electrons are called reducing agents. Plating solutions are formulated so that plating only occurs on a surface that is catalytic to the chemical reduction reaction. (A catalyst is a material that causes a chemical reaction to take place, but is not usually consumed in the process). Only a few metals are catalytic, and only a few metals can be plated by what is known an autocatalytic deposition. Some examples of catalytic metals: iron alloys, nickel, aluminum, and palladium. There is electroless plating by chemical replacement, also known as immersion deposits, but the deposits are often non-adherent and usually too thin to have any functional use. There are some exceptions.
Chemicals used to prepare materials to be electroplated, and the plating solutions are often hazardous materials. The waste materials must be treated in approved ways so that there is no danger to persons or the environment. The plating industry has been leaders in the protection of the environment. It is also a target industry for OSHA, monitoring and control of air emissions, and waste water. The industries record has been exemplary. There have been a few incidence where violations, endangered people or the environment. Jail sentences and fines resulted. The industry is active in policing itself. There is a very high cost to meeting the requirements set forth by our government. Some of which have discharge limits to a sewer that are less than the daily intake requirements for good health. Sometimes our food contains higher levels of these chemicals than is allowed in the sewer. In addition too many large captive (incorporated with in a manufacturing facility for their own use) plating shops are being closed, about 20% have closed due the higher costs. (Note: the statistic is a few years old, the number is much higher now). The average plating shop in the U.S. employs less than 50 people.
Plating in electronics
Let us look at the Electronics Industry. Printed circuit boards, multi chip modules, hybrid circuits, individual components, and devices depend on plating for their existence. It would be impossible to make a computer without plating.
Consider a few examples where plating is used in computers. The 8088 Intel chip that powered the first IBM personal computer had 29000 transistors that could carry out 330,000 instructions in 1 second. The new P6 microprocessor used in the Pentium, and similar device used in the Power PC, has over 6 million transistors and can carry out over 300 million instructions a second.
The earliest microprocessors are still alive and active running microwave ovens, VCRs, car transmissions, cellular phones, and many other every day items.
Magnetic devices such as sensors and memory discs use plating for the properties of the deposit.
Albert Fert had an inkling that he was on to something big. The University of Paris Physicist knew that many metals exhibit a phenomenon called magneto resistance (MR) also known as magnetostriction. They show slight changes in electrical resistance when place in a magnetic field. Fert amplified the effect by designing materials made up of very thin layers of metals. (Plating is the best way one can produce very thin layers of metals). He made a sandwich of iron plated chromium and iron and found that it was 10 times better than standard metals. Many different metals and combinations provided even better characteristics.
Early applications include sensors which can tell when car wheel stop turning and start skidding, the key to antilock brakes (ABS). They can measure engine speed to help lower emissions or raise fuel economy. Hearing aids, weighing devices, memory chips that remember even when the power is turned off are some of the newer applications.
Memory chips called MRAM's (Magnetic Random-Access Memory) differ from DRAM (Dynamic Random- Access Memory) chips radically. The Magnetic RAM chips would retain information with out power. Not only does it cut power consumption, it allows computers store programs and data in their own rapidly accessible internal memory, rather than having to read it more slowly from hard discs. MR devices also could be better than other devices that "remember". They offer longer life than so-called "flash" memory chips.
Today, recording heads for your hard disc drives and for main frame computers use the technology to increase the capacity to amazing numbers. The plain MR drives on the market, made by IBM, pack about 564 megabits of information per square inch. The newest offerings will handle 10 gigabyts, 17 times more. At 10 gigabyts/sq.in. an entire movie, or encyclopedia could be stored on a disc. Today the capacity is much greater.
Memory discs have increased in capacity. For example, a floppy disc will hold about 250 typewritten pages of information. A similar size hard disc made by plating processes will hold over 25,000 pages of information. Now smaller discs hold even more. Information is stored on a disc by means of magnetic materials. The disc is made of Aluminum, polished to a high finish, plated with a nickel-phosphorus alloy which is hard and non-magnetic. Then either a magnetic cobalt-phosphorus alloy or a chromium-cobalt alloy is plated over the non magnetic coating. The nickel phosphorus and cobalt phosphorus alloys are laid down by a process called electroless plating where electrons are supplied in within the plating solution. The chromium-cobalt alloy is plated by vacuum process known as sputtering. The magnetic recording layer is 2-3 millionths of an inch thick. This produces tiny magnets laid end to end when the recording head passed over the surface. The magnets are oriented with magnetic polls one way or the other to form binary numbers or codes on the surface which are easily read by the pick up head. A floppy disc rotates at 300, while the hard disc (called a thin film plated disc) rotates at 3600 rpm. Therefore hard discs can store and retrieve information much faster than floppy discs. Vertical magnetization, requiring a slightly different plating process, can more than double the capacity of hard discs.
Plating plays an important role in several key aspects of manufacturing compact discs. The compact disc (CD) encompasses not only audio, but a wide number of variations. SDs (super -density discs) CD-Is, CD-Rs, mini-DISCS, and WORMS. Each optical memory storage device contains billions of bytes of information that has been digitally encoded and stored as a series of microscopic pits, about 1 micron or less in size. These discs are made by stamping these pits onto a plastic (polycarbonate). The stampers are made by electroplating pure nickel onto the original recording. The recording is made by a laser beam melting tiny holes in a metal surface (Tellurium) in the digital code form the sound or video signal. Since electroplating can precisely duplicate the surface, plating on the recording to a thickness of 300 +/- 3 microns, and separating the plated deposit form the original recording, results in tiny bumps exactly the size and shape of the pits. This becomes the stamper which can make 30,000-50,000 CDs before replacement is required. In actual precision the first plating becomes the pattern (father) for the second (mother, now with pits) the mother is plated to form the stamper. Many stampers are made from the mother, so that millions of CDs can be produced, each exactly alike, with nearly zero defects.
Where does the U.S. stand in the technology race? Why race? There is a European Consortium which includes Universities, Phillips. Seimens, Thompson, and many other large companies devoted to Giant Magnetic Resistance (GMR) devices for practical use on automobiles, military systems, and digital cassettes. In Japan, Hitachi Ltd. has a team of 30 researchers working on GMR- larger than any U.S. effort says Gary A. Printz, head of Magnetic Multilayer work at the Naval Research Laboratory in Washington.
Other work on advanced technology is lagging that of other countries. For the U.S. to be in a global market, which is essential for economic stability and growth, we need a great increase in students pursuing technical fields. The rewards are great in satisfaction. Knowing that one has made a significant contribution to the betterment of all mankind, and enhanced the standard of living for everyone is rewarding. Technical development is the key to our future. The "Pentium" ™ and "Power PC"TM Have over 6 million transistors and can carry over 300 million transactions per second. Note: This information is a few years old, the capacity is greater today.
You may download this article FREE in .pdf form, save it or share it with a colleague. Click here.