Electricity: electrical systems and devices – Miscellaneous
Patent
1990-10-22
1992-09-15
Griffin, Donald A.
Electricity: electrical systems and devices
Miscellaneous
174 685, 428546, H05K 104, C23C 302
Patent
active
051483556
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention is related to printed circuits for use in electrical and electronic equipment. In particular, it is an improved method of making printed-circuit boards and of producing printed circuits on surfaces other than conventional printed-circuit boards. This invention is also concerned with making printed circuits and is especially concerned with a method of making a printed circuit in which a layer is applied in a desired pattern to a substrate.
An element that is common to almost all electronic equipment is the printed circuit, typically in the form of a printed-circuit board (PCB). A PCB is generally made by laminating copper foil to a board. A desired pattern that includes conductors in the plane of at least one surface of the board is placed upon the board, and holes are drilled or punched for the mounting of components. This pattern is typically realized by placing a photosensitive resist on the board, exposing a photograph of the desired pattern on the resist, and developing the resist to produce a protective coating over the pattern. The remainder of the resist is treated to remove undeveloped resist from portions where it is desired to remove the copper. The board is then treated with a process that removes the exposed copper. When the remaining resist is then removed, the desired pattern remains in the copper. Mounting holes for components are drilled or punched at desired locations somewhere in the course of this process, either before or after the removal step.
The materials most commonly used for PCBs are either polymerized epoxy materials containing glass fibers or paper bound by impregnated synthetic resins such as phenolic materials. The latter group is often referred to generically as synthetic-resin-bonded paper (SRBP). Boards made of either of these types of materials are clad with copper on one side or both sides, with the heat and pressure of the cladding or laminating process helping to cure the resin. The material cost of an SRBP PCB is typically about half as much as that of an epoxy fiberglass board of the same surface area, so there is a potential cost advantage when the SRBP board can be used. There are various bases for the selection between epoxy fiberglass and SRBP material. For example, the epoxy fiberglass boards are generally higher in strength and are preferred for use in equipment that may be subject to vibration.
A particular problem of circuit design that leads to complication in PCBs is the fact that not all electronic circuits can be made with their connections in a single plane. It is sometimes necessary to make bridging connections between different portions of a circuit. A considerable amount of ingenuity goes into the design and layout of PCBs to minimize such bridging connections. However, sometimes it is impossible to avoid them. In such a case, it is possible to solder jumper wires between the portions of the circuit that are to be connected. This is especially undesirable for long runs, and it is better avoided even for short runs. A better solution is to use PCBs that have more than one conducting layer. The simplest of these is a two-sided PCB. This is a board that has copper laminated to both sides. Separate patterns are etched on the two sides to effect the desired circuit layout and cross-connections. However, in order to make such cross-connections, and to complete the connection between the two sides of the board, it is normally necessary to use epoxy fiberglass because of the necessity of plating holes through the board to connect the top layer to the bottom layer. Holes that are drilled in an SRBP board are adequate to support the leads of components that are placed in the board for soldering, but they are not normally clean enough when drilled or punched to permit satisfactory electroplating of connections between layers of the board. There is thus a long-felt need in the PCB industry for a way of making PCBs with crossover connections on single-sided SRBP boards without using soldered jumper wires.
The same consid
REFERENCES:
patent: 3644661 (1972-02-01), Asar et al.
patent: 4141055 (1979-02-01), Berry et al.
patent: 4245555 (1981-01-01), Alston
patent: 4522888 (1985-06-01), Eichelberger et al.
patent: 4800397 (1989-01-01), A-Ardakani et al.
patent: 4859807 (1989-08-01), Swiggett et al.
patent: 4921623 (1990-05-01), Yamaguchi et al.
Devonport Joseph
Lowe John M.
Griffin Donald A.
Technology Applications Company Limited
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