The conductive paste - a substance, viscous consistency, conducting electric current. Today, agents of this class is at least two applications: the production of printed circuit boards and contacts grease. With the conductive paste is often confused thermal grease for CPU coolers.
The conductive paste for reducing the contact resistance emerged at the beginning of the second half of the XX century. The patent states that the detachable connections conductivity decreases due to the presence of gaps and voids reduced area of contact between the conductors. The conductive paste was designed to correct this drawback.
Later, a conductive paste was used in the form of lubrication. For example, for removal of electrostatic potential to the movable part of the bearing. It is known that other types of wax and grease do not conduct current. It is possible to build up of static charge that is sometimes dangerous. For example, in the oil industry, any spark could lead to a fire. Natural gas, in addition electrified. It is clear the desire of people to get rid of the charge. One type of conductive paste is considered to be silicone oil, which has referred to the benefits of:
- Low resistance. Semi-liquid phase is easy to fill all the gaps, increasing the conductivity of the contact. A side effect is considered to decrease heat generated by flowing electric current under the law Joule.
- Incredibly thin layer. Silicone grease on the surface is ground to a thickness of 8 microns. That can handle the exact mechanisms and devices that contain moving parts.
- Versatility is manifested in the ease of use, ease of upgrade waste layer.
- Low price. Silicon is cheap element, which ensures the high popularity of solid-state electronics.
- Reliability. Silicone lubricant is uniquely superior to organic material made from natural minerals and oils.
- The new generation of silicone grease is not discharged to the outside forces of centrifugal forces and vibrations. Consistency is such that the layer remains in place, which suffered.
- A good manufacturer will boast durability of their own products. For example, thermal grease Wakefield demonstrates retention of properties even after six months of operation.
In 1955 began the process povalny production of synthetic lubricants. Simultaneously several firms working today, joined the struggle for the market, providing the highest level of competition. Each manufacturer's own secrets. Among the advertising of chips called the absence of solvents, toxic substances or incredible conductivity. Pastes are produced together with gels, compounds, greases made based on an identical, but different features of the application.
Called thermo conductive paste is not far from the truth. Metal and semiconductor switching bad conductors of heat. The meaning of the application of thermal paste former - to fill tiny gaps between the heater and cooler. Readers may have a similar composition was applied to a processor system unit from a special gun. What is different from the compound paste, gel, grease:
- The compound is a viscous substance serving sometimes to retain parts. It is used to fill a par with the resin in electronics. Most compounds have pronounced barrier properties, but periodically required to achieve a particular effect. Among other substances, the compound is considered to be the most viscous.
- Lubrication is intended for application to the rubbing surface. Expected resistance to mechanical stress and frictional forces.
- Pasta is usually used to fill a relatively large cavities, at rest. For example, thermal grease CPU cooler.
- The gel shows a thin consistency and is used to fill the tiny pores, but it is assumed that the surface is not too much shifted relative to each other.
In addition to the above products may be available to meet the cement of a similar kind.
Today, the conductive pastes used in different industries. Athletes known belt for weight loss, and computer scientists are aware that compositions improve cooling of the processor.
opening the era of electromagnetism
Pioneer invited to call Sir Humphrey Davy. His tireless experiments in the field of electrolysis convinced that not only solids conduct electricity. Of the first known structures containing moving parts contact with the liquid, called the installation of Wollaston, a copy of which made Michael Faraday, the world's first electric motor.
Experience Faraday immediately and successfully repeated Ampere. Although the report before heard the words that the installation unusable. A movable contact served as mercury. It was poured into a cup where revolved around the permanent magnet end of the wire, the supply electric potential. Then such technical solutions have been used frequently. One example is called Barlow wheel (1822). Mercury was used until the end of the XIX century, and some technical curiosities full strokes entered the XX. Assume counter of electric energy.
By the beginning of World War II, the increasing use of electricity has put humanity before the task of finding new technical solutions.
One of the first patents for the conductive grease with grit considered US 2,244,436. Chester Tetig of Covington writes that his invention relates to lubricated conductive contacts. It turns out that patent a general idea without specifying. Under the protection of copyright metals fall any formation with pores and irregularities, filled with fire-resistant grease. Chester specifies that the paste is able to burn in the flames, but does not itself support combustion.
The lubricant is solid, liquid, fluid, viscous. Made of wax, tar, oil, synthetic materials. Inventor intentionally limits the metal alloy contacts then popular (1939) bronze, but says any composition. Specifically provides that the "porosity" is not necessarily visible to the naked eye, but is able to be viewed under a microscope only. The cover the entire range of irregularities alleged contacts. It bypasses Chester and composite materials, such as ferrites used for shortwave antennas.
The patent says that conductive grease is able to simultaneously solve the problem of wetting the surfaces to reduce the frictional forces to evaporate, forming a specific atmosphere in the enclosed space. The author briefly describes lubricant compositions tested in personally:
- "From the non-natural lubricants I prefer alcohols - glycerol and glycol as variation thereof may be applied ethylene or propylene, reaching marketed under the trademark of Preston. "Substances and are now used as the basis for a conductive lubricant, for example, in the belts for weight loss.
- "Glycerol and glycol can be used in pure form, slightly diluted with water to 25% by weight. To increase the conducting means may add a little powdered graphite or suspension. "This solution leads directly to self-regulating heating cable. Graphite substance produced while in Huron, Michigan company Acheson.
- Type of grease may contain 25 - 50% of the engine oil. The remaining components are described above.
- As a semi-solid lubricant is permissible to use naphthalene company Galovaks. Chester praises the products under the code number 2025. It is considered appropriate in 1000, 1013, 1014. Finally, the semi-phase of the above characterized naphthalen 1000.
Chester says plainly that his patent is applicable to electrical installations, having movable contacts. For low-voltage circuits better suited glycerine lubricant, in other cases, preferably oily and Tar bases.
The conductive paste
US Patent No. 2702756 of February 22, 1955 introduces the concept of a conductive paste. Five years is the text before the Commission, perhaps because of the similarity to the previous. In addition, there were no suitable electrical installations for a broad application, which is considered an important condition for the adoption and approval of the patent.
At the time of filing of the patent have been widely used to provide electrical contact junctions, welding, carbon substance, silver paint. Simultaneously brazing magnesium alloys can not be joined with carbon electrodes directly by said methods. Referred to other technological highlights that are exercisable solely under management. Carbon lubricant have too much resistance, and paint needs time to dry. Solvents that are part of these mixtures are corrosive surfaces.
The conductive paste on a plan designer, provides a viscous at room temperature, with easily obliged to melt when heated, to give it the desired shape. The approximate composition of the conductive paste:
- Silver crumb grain size 2 - 100 micrometers, a density of from 4 to 1.5 g / cc. cm - 80%.
- Blacking - 20%.
The base serves as a grouting composition for conductive metal. Apply: ozotserit, paraffin, ceresin, beeswax, oil Euphorbus Antisifilitika (Mexican variety milkweed), carnuba (Brazilian) from palm wax.
January 1, 2002 Noriko Sukuni, Koji Yoshizaki, Heroshi Komiyya patented bearing grease (US 6,335,310 B1). The substance allows the moving part to ground, to discharge any static electricity. Base - a synthetic oil, for example, dioctyl sebacate, resistant to high temperatures without evaporating, cheap and harmless to metals.
The conductive substance by mass is 0.5 - 5% by weight. Antistatic additive eliminates electrification proper lubrication. The resulting material was used in drives hard disks, increasing capacity. Among the most suitable oils for lubrication fundamentals call:
- Polyalkylene glycol.
The oils have a low coefficient of thermal expansion, which can effectively maintain the desired pressure axis to eliminate backlash. viscosity regardless of external conditions and high resistance to heat complement several advantages. Various additives prolong the life of the lubricant and reduce friction forces torsional drive. With such a unique bearing head does not jump across the surface, it becomes possible to increase the recording density, or increase the diameter of the information carrier.
The approximate composition of the lubricant:
- 0.1 - 5% of conductive substance. Fewer makes conductivity so high that the material no longer perform its function, and the upper ceiling is taken from non-resistance considerations lubricant bases properties.
- Antistatic is 0.5 - 2% by weight.
Other assigned a conductive oil, which amounts to 97.5% by weight. For example, dioctyl sebacate.