Metal fusion bonding – Process – Using high frequency vibratory energy
Patent
1997-09-19
2000-03-21
Heinrich, Samuel M.
Metal fusion bonding
Process
Using high frequency vibratory energy
22818021, 2281121, 219541, B23K 2010, B23K10318
Patent
active
06039238&
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming electrical connection and in particular to a method of forming an electrical connection with improved integrity and stability over a wide temperature range.
2. Description of the Prior Art
Various methods of forming electrical connections are known such as soldering, welding or the use of electrically conductive epoxy adhesives.
There are, however, problems in forming a suitable high integrity electrical connection between terminals and a terminal pad which is deposited on a substrate such as metal, steel or ceramic or a substrate comprising one or more metal, steel or ceramic components or layers. Most conventional methods and materials used for attaching terminals have an upper temperature limit beyond which the original characteristics no longer hold so that electrical connections so formed are incapable of maintaining their attachment integrity over a wide temperature range.
All known prior art methods of attaching terminals to terminal pads printed on substrates give electrical connections with limited integrity specifically as it approaches its upper operating temperature.
Such known methods include: consuming expensive and time consuming to 400.degree. C. but is very expensive and time consuming are very complicated, time consuming and have a limited operating life; in addition the integrity reduces with age welding, but these are not technically appropriate for terminal pads on a ceramic or ceramic based or coated substrate.
The present invention has been made from a consideration of these problem.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a method of securing a first terminal to a second terminal or to a terminal pad on a ceramic or metal substrate comprising holding the first terminal on the second terminal or terminal pad and applying friction at high frequency to the terminal and terminal pad to join said terminal and terminal pad together.
The connection of a terminal, for example, of copper, silver or alloys thereof to a terminal pad by the simultaneous application of pressure and high frequency friction is a known technique. However, this technique has not hitherto been applied to the connection of terminals to pads on a ceramic or metal substrate for use at high temperature.
Thus, using the method of the invention, an electrical connection can be formed which is capable of passing electrical current to heating elements that are deposited on metal and/or ceramic substrates using thick film techniques.
The method of the invention can be used, for example, for making connections to terminal pads for heating elements, the pads being printed on a ceramic/metal base The electrical connections thereby formed have been shown to function satisfactorily at both low temperatures such as room temperature and high temperatures above 700.degree. C. Further additional integrity and reliability can be achieved by making multiple contacts simultaneously to the same terminal pad. Statistically this gives added mechanical and electrical security against a percentage of connecting terminals becoming loose or detached for one reason or another.
Preferably, the friction at high frequency is achieved by means of ultrasound. It has been found that an electrical connection formed using the method of the invention has good mechanical and electrical integrity over a wide range of temperatures.
The present invention can be used for the attachment of electrical terminals of various composition and construction to terminals or terminal pads of various differing materials and/or construction on substrates including metal, steel and/or ceramic.
One of the terminals may comprise an electrical heating element or other associated passive or active component provided on the metal or steel substrates. The method provides good mechanical and electrical attachment that can tolerate both low and high temperatures and preferably the terminal means will have sufficient geometrical dimen
REFERENCES:
patent: 3650454 (1972-03-01), Coucoulas
patent: 3916518 (1975-11-01), Jones et al.
patent: 4119260 (1978-10-01), Stoeckel
patent: 5058800 (1991-10-01), Yoshizawa et al.
patent: 5118370 (1992-06-01), Ozawa
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