Patent Grant
9472361
This application is substantially the same as provisional application Ser. No. 61/887,836 filed Oct. 7, 2013 by the same inventor-applicant bearing the same title “Improved Circuit Board Contacts Used to Implement Switch Contacts of Keyboards and Keypads” and the applicant hereby claims priority there from.
The problem with prior art Improved Circuit Board Contacts Used to Implement Switch Contacts of Keyboards and Keypads is that they are not reliable. This invention solves this problem with 4 layer contact switch as well as replacing gold with silver which is cheaper and better conductor of heat and electricity.
A formal preliminary prior art patentability and novelty search was neither conducted nor commissioned, but the inventor at the cutting edge of this technology is intimately familiar with the prior art. No prior art exists to match the functionality ergonomics and user friendliness of the present invention. Accordingly none of the prior art devices singly or even in combination provides all of the features and objectives established by the inventor for this system as enumerated below.
The main objective and benefit of the invention is that it makes possible high reliability switch contacts on a printed circuit board using primarily silver, in place of electrolytic gold, while simultaneously overcoming the difficulty of soldering components to the silver plated component pads of said printed circuit board, by having a thin layer, approximately three micro-inches, of gold plating over the silver. This electrolysis immersion process gold layer prevents the silver solder pads from oxidizing.
Other objectives, elegance of design, ease of manufacture, service and use and even aesthetics as will become apparent from the following brief description of the drawings and the detailed description of the concept embodiment.
The present invention describes a keyboard or keypad 10 of
In the preferred embodiment of
An alternate embodiment is shown in
In order to appreciate the novelty of the improvement in this invention, the following background of the prior art practice would focus on the improvement.
Keypad and keyboards implemented with conductive metal contacts plated onto printed circuit boards (PCBs) are well known in the art. In addition, key actuators made of elastomer with conductive pads attached thereto, that when pressed; electrically connect two aforementioned PCB contacts are also well known in the art.
There are many processes and materials that can be used in place of the metal contacts, such as, conductive inks and conductive polymers, additionally the printed circuit board can be fabricated with various rigid material, and in place of the elastomer, other materials such as polymers, or mechanical components can be used. The aforementioned substitutions are well known in the art.
For keypads and keyboards that require higher reliability and longer life, the typical configuration involves a traditional rigid printed circuit with copper conductors that are plated with gold to form switch contacts. These conductors might be in a pattern as shown in
There are well known processes for plating gold onto printed circuit board conductors. One is an electroplating chemical process based on Faraday's discovery which states that a given amount of material is deposited at an electrode by a given amount of electricity. Thus this method, which refers to electrolytic gold plating, can accurately control the thickness of the gold plating and is well suited for gold contacts, but it requires that an electrical connection which is used only for plating purposes be made to every part to be plated, this adds cost and complexity to the printed circuit board.
Another well-known process for plating gold onto printed circuit board conductors is an immersion process that does not need any electrical connections but instead uses a solution, typically an acid bath, containing the material to be deposited and relies on time, temperature, agitation and concentrations of materials and solutions to control the plating thickness. This is a lower cost process and does not require electrical connections to the surfaces to be plated, but it has several disadvantages. One of which is that all exposed surfaces are plated and the other is that it is limited in both controlling the thickness of the plating, as well as, the absolute plating thickness attainable. For these reasons, immersion gold plating is better suited for plating onto copper for the purpose of soldering components to the printed circuit board, such as for pads 30 and 32 of
Both electrolytic and electroless immersion gold plating are relatively expensive, but electrolytic gold is more costly in particular if a thicker switch contact is required. For these reasons the alternate element that can be used as a switch contact material, by plating onto a copper conductor on PCBs is silver and this is also well known in the art. These three metals, copper, silver and gold are the three metals in group IB of the periodic table of the elements, where the periodic table refers to the ordering of elements in a table by Mendeleev based on the concept that the properties of the elements are functions of their atomic numbers. These three metals are very ductile and malleable, and are also excellent conductors of heat and electricity. An additional metal, nickel, which has an atomic number of 28 and therefore is adjacent to copper in the periodic table of the elements, as copper has an atomic number of 29, can also be used in the plating process of printed circuit boards. Nickel is typically used as a barrier between copper and gold to prevent copper migration to the other layers and this is also well known in the art.
Additionally, of the three metals, copper, silver and gold commonly used for high reliability circuits and switch contacts on printed circuit boards, copper and silver when exposed to air form oxides, which oxides are still conductive but cannot be readily soldered to. In contrast to copper and silver, gold does not oxidize and this is well known in the art.
A great care has been taken to use words with their conventional dictionary definitions. Following definitions are included here for clarification.
3D=Three Dimensional
DIY=Do It Yourself
I/O=Input and Output
Integrated=Combination of two entities to act like one
Interface=Junction between two dissimilar entities
Keypad=A data entry device from an operator(s) to computer(s)
PCB=Printed Circuit Board
SPST=Keypad and Keyboard Key as Switches as SPST (Single pole single throw) 28×3=84 Total
Proportional=Ideal ratio under the design rules and circumstances.
Symmetrical=The shape of an object of integrated entity which can be divided into two along some axis through the object or the integrated entity such that the two halves form mirror image of each other.
1. The value and the tolerance of various electronic components may be modified.
2. The order of the process steps may be varied.
3. The keyboard and keypad keys may be built with prior art enhancements, such as membrane technology or with molded plastic keycaps or with alternate materials.
4. The PCB and its conductors can be made of different materials as they become available due to the technological progress in polymer chemistry
5. Additional complimentary and complementary functions and features may be added.
Other changes such as aesthetics and substitution of newer materials as they become available, which substantially perform the same function in substantially the same manner with substantially the same result without deviating from the spirit of the invention may be made.
While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention will be apparent to a person of average skill in the art upon reference to this description. It is therefore contemplated that the appended claim(s) cover any such modifications, embodiments as fall within the true scope of this invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4339644 | Aldinger | Jul 1982 | A |
| 5860513 | Suzuki | Jan 1999 | A |
| 7015406 | Ganz | Mar 2006 | B2 |
| 7215229 | Shen | May 2007 | B2 |
