Printed wiring fabrication

Ferric chloride solutions are used as etchants for copper, copper alloys, Ni/Fe alloys, and steel in PC applications, electronics, photoengraving arts, and metal finishing. Current use of ferric chloride etchant in printed wiring fabrication is extremely limited in the United States because of costly disposal of the copper-containing etchant, and the much better commercial support for ammoniacal and cupric chloride etchants. There is still considerable use for alloy etching and photochemical machining applications. 

The following brief description of printed wiring fabrication will serve to acquaint the reader with some of the basic steps which are referred... 

Many of the fabrication processes for integrated circuits are similar or conceptually related to those used in the manufacture of printed wiring boards. However, because of the extremely fine device features, fabrication must be carried out in clean rooms having strictly controlled environments. Particulate and chemical contamination are minimized, and temperature, humidity, and even vibration are carefully controlled. 

The IC is fabricated by a series of lithographic processes similar to that described in the previous section. Each individual step constitutes a level in the device, the final level being a metalization pattern to interconnect the circuit elements that have been fiibricated in the surface of the silicon wafer. The completed wafer is then diced, a step that involves cutting the wafer, typically with a diamond saw, to separate the individual IC chips. The next step is to package the chips in some way, attach the devices along with other components to the printed wiring board (PWB), and interconnect them to produce the completed circuit board. 

Figure 1. Fabrication process of printed wiring boards using PTFE substrates.

On the other hand, our method constitutes only one step of laser irradiation for both surface modification and selective patterning. Moreover, the chemical modification with photolyzed hydrazine shows more reliable and stronger adhesion with a metal layer, compared with drastic chemical etching with a sodium solution. In conclusion, our processing provides a simple effective processing for fabrication of printed wiring boards with FTFE substrates. 

UL746 A B C D E Underwriters Laboratories. Pol5mieric materials Short term property evaluations Long term property evaluations Use in electrical equipment evaluations Fabricated parts Industrial laminates, filament wound tubing, vulcanised fibre, and materials used in printed wiring boards... 

NEMA standards include many variations for reinforcements, resins, and applications. Reinforcements include paper, fabrics, and glass mats. Resins include phenolic, melamine, silicone, epoxy, and polyester. Copper-clad laminates are covered with copper foil for use in printed wiring boards, whereas unclad laminates do not have a foil. Unclad laminates are used in many industrial applications, but NEMA s primary concern is when they are used as electrical insulation. 

Grade FR-4 This grade is the most common grade used in printed wiring applications. It is made with epoxy resin and glass fabric reinforcement and has properties similar to G-10 but with a flame resistance of V-0. Rods and roUed tubes are available. 

Amoco [7] reported several polyaryl ether-sulfones to be miscible with each other. The miscible blend comprises a 1,4-arylene unit separated by ether oxygen and another resin 1,4 arylene separated by an SO2 radical. The miscible blends showed a single glass transition temperature in between the constituent values. The blend was transparent. These can be used for printing wiring board structures, electrical connectors, and other fabricated articles that require high heat and chemical resistance and good dimensional and hydrolytic stability. 

Bringing the process back under control requires a methodology that involves planning the printed circuit layout process with predictive wiring density models. The other benefits include reducing printed circuit fabrication and assembly costs. 

A basic understanding of material performance is necessary for both the designer and fabricator of the printed wiring board (PWB). Understanding the materials available is one of the primary tasks for designing for manufacturability and performance. It is necessary to match the product end-use performance requirement as well as the environmental exposure the board experiences in the fabrication and circuit card assembly (CCA) processes with the capabilities of the material. It is common for boards to experience as many as five thermal excursions in CCA. 

H. Akaboshi, A New Fully Additive Fabrication Process for Printed Wiring Boards, IEEE Trans, on Comp., Hybrids and Mfg. Tech., Vol. CHMT-9, No. 2, June 1986. 

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