Interlayer insulation resistance

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Since the invention of integrated circuits (ICs), polyimides as heat-resistant organic polymers have been applied to insulation materials in electronics devices such as flexible printed circuit boards (FPCs), interlayer dielectrics, buffer coatings, and tape automated bonding (TAB). A polyimide thin layer is easily... 

Data. reported in Table 3,12 shows resistivity as an exponential function of the degree of fluo-rination. The higher the degree of fluorination the more resistance is developed CF,, is an insulator. The increase in the resistivity of fluorinated carbon is due to a loss of resonating electrons and an increase in the interlayer spacing. 

High-temperature resists have been formulated from a group of polyesters based on styrylpyridine, which are thermally stable up to 450°C. Such resists have found applications as fine-line solder masks or when the polymer is intended as a permanent eomponent of the final deviee, he it as insulator, interlayer dielectric, or a-particle harrier. ... 

The main purpose of middle layers is to provide additional (thermal) insulation. Nowadays, these layers are often made of fleece materials with good air entrapment properties. Their thermal conductivity (typically 0.03-0.04 W/mK) is near from air (0.026 W/mK). The thermal resistance of such layers is directly correlated with their thickness, provided that no air movement occurs within the fabric. Thermal conductivity and air permeability also are generally dependent on the fabric density (Yip and Ng, 2008). Conduction has been shown to be the main heat transfer mechanism through textile layers as long as the fibre volume fraction is higher than 9% (Woo et al., 1994). However, materials with very low density (like spacer materials) allow radiant and convective heat transfer. This was demonstrated by Das et al. (2012) who compared a spacer fabric middle layer with two non-woven middle layers and showed that the contribution of this spacer fabric to the overall insulation was higher than the two other samples in a non-convective mode, while it was the lowest in a forced convective mode. The positive effect of metallised interlayers with low emissivity on the reduction of... 

It is noteworthy that each of these has an outer fabric containing meta- and para-aramid blends (see Chapter 8) for good fire protection and durability. However, a number of inner layers, whether joined to the outer or part of the Uner comprising breathable polyurethane or PTFE membranes, are also a common feature. Thirdly, the use of thermally insulative nonwoven interlayers and comfortable meta-aramid/FR viscose innermost linings are also present. It is the ordering and exact interlayer compositions that appear to be the major differences, while each design attempts to provide the common properties of fire resistance, thermal insulation, moisture transport, and comfort. 

Highly purified and high heat resistant PI for microelectronics was first developed in the early 1970s il). Purpose of the development was the application to the interlayer dielectric of dual metal semiconductor device. coating liquid PI precursor on a stepped first A1 wiring layer, flat PI insulating layer is obtained and step-free second A1 layer can be formed as shown in Fig. 1. As a result, reliability of the electrode, especially the second level electrode, is remarkabfy improved. 

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