barcode reading using c#.net FIGURE 9.1 Comparison of laminates with standard (left) versus RTF (right) copper foils. in Software

Creator QR-Code in Software FIGURE 9.1 Comparison of laminates with standard (left) versus RTF (right) copper foils.

FIGURE 9.1 Comparison of laminates with standard (left) versus RTF (right) copper foils.
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Thin Copper Foils The capability to etch fine-line circuits is also improved through the use of thinner copper foils. Although electrical considerations can limit the use of very thin foils on innerlayer circuits,
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these thin foils can be used on external layers since the outerlayer process involves plating on top of the foil to the desired overall thickness. For dense, fine-line circuitry, 5.0 micron and 9.0 micron copper foils are sometimes used. Processes to use 3.0 micron copper foil have also been developed.
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9.3.4 Foils for High-Performance Resin Systems Many of the high-performance resin systems such as BT, polyimide, cyanate ester, and even some high-Tg epoxies exhibit lower peel strengths and resistance to undermining of the copper foil when exposed to aggressive chemistries. For these applications, foils with increased nodularization and coupling agents tailored to the resin system are often used. The increased nodularization results in more surface area for mechanical adhesion whereas the specific coupling agent aids in chemically bonding the foil to the resin system.
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Copper Roughness and Attenuation As circuit operating frequencies increase, more of the signal travels in the outermost part of the conductor.The skin depth that is, the region where much of the signal travels is shown in Fig. 9.2 as a function of frequency. As shown in this graph, the skin depth approaches the average roughness of 0.5 oz. copper foil above 1 GHz. Signal attenuation due to conductor losses related to the roughness of the foil becomes an important factor at these frequencies, and should be considered by the design engineer.
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Skin depth (ds) in copper
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Skin depth ( m)
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0.5 oz Commercial foil average roughness, Ra ( m) 5
0 0.01
1 Frequency (GHz)
FIGURE 9.2 Skin depth versus frequency.
A study of several different copper foil types correlated roughness and attenuation values.6 Figures 9.3 and 9.4 show pictures of the foils to highlight their relative roughness differences. Figure 9.5 shows the roughness distributions of these foils. Finally, in Fig. 9.6, the loss values associated with each of these foil types are graphed versus frequency. Up to about 1 GHz, there is very little difference in the observed loss across the several foil types. However, at higher frequencies, the difference becomes much greater, correlating to the roughness of the individual foil types; the greater the roughness, the greater the measured attenuation.
BASE MATERIALS PERFORMANCE ISSUES
RTCHP
JTCHP
Rolled
AMFN
50 m
FIGURE 9.3 Cross-sectional view of several copper foils.
RTCHP
ITCSHP
Rolled
AMFN
FIGURE 9.4 SEM views of several copper foils.
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Roughness Distribution. 3 2.5 Distribution 2 Rolled 1.5 1 0.5 0 0 2 RTC 1 Grade 3.3 RTC
oz Reverse and Matte Treat
AMFN RTCHP TCR JTCSHP
4 6 Roughness Rz ( m) RTC 2 Grade 3.4 VLP Grade 1.1
8 Grade 3.1 Grade 1.2
10 Grade 3.2
FIGURE 9.5 Roughness distributions for several foil types.
The roughness that results from the oxide/oxide alternative surface preparation process during printed circuit manufacturing is also important. Figures 9.7 and 9.8 compare the roughness obtained from two of these processes. The base copper foil and FR-4 resin system used were held constant. The test vehicles from which these cross sections were taken were also measured for attenuation. This measurement technique was used to calculate an effective dissipation factor, Df, for these material sets. The measured Df for the sample in Fig. 9.7, with the relatively smooth profile, was 0.021 at 1 GHz. The measured Df for the sample in Fig. 9.8, with the rougher profile, was 0.026. Obviously, the rougher profile created by the oxide alternative process in Fig. 9.8 resulted in a significantly higher loss value.
dB/inch
JTCSHP RTCHP AMFN RTC TCR Rolled
FIGURE 9.6
10 Frequency (GHz)
15 20 5 inch trace data
Loss versus frequency for several foil types.
BASE MATERIALS PERFORMANCE ISSUES
FIGURE 9.7
Copper profile obtained from process A.
FIGURE 9.8
Copper profile obtained from process B.
LAMINATE CONSTRUCTIONS
To satisfy requirements for impedance, layer count, and overall PCB thickness, a broad range of laminate dielectric thicknesses are needed. Table 9.2 shows many common laminate dielectric thicknesses, along with typical constructions and resin contents. Individual laminate suppliers may have preferred constructions, so not every construction shown in this section will be available from every laminate supplier. In addition, some of the high-performance resin systems will have slightly different constructions or resin contents in order to target certain performance characteristics, such as dielectric constant.
Single-Ply versus Multiple-Ply Constructions With dielectrics below 0.0040 in., there is often no choice but to use a single ply of fiberglass cloth to achieve the desired thickness. With dielectrics in the 0.0040 in. to 0.0080 in. range,
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