Trace width

One last factor is the physical layout of the output stage when more than one output filter capacitor is used. The capacitors should be located radially symmetric from the output rectifier, and the printed circuit traces for the rectified voltage and the grounds should be of similar trace-widths and lengths. Any dissimilarity of these traces causes more series resistance and inductance to the... 

The so-called 1-oz board in the USA is actually equivalent to 1.4 mils (35 tm) copper thickness. Similarly the 2-oz board is twice that. For a moderate temperature rise (less than 30°C) and currents less than 5A, we can use a minimum llmils width of copper per amp for 1-oz board, and at least 7mils width of copper per amp for a 2-oz board. This rule of thumb is based on the DC resistance of the trace only. So to decrease its inductive impedance and AC resistance, higher trace widths may be required. 

We cannot see the data points because I have made the trace width for my plots thicker to make the screen captures easier to read. We will show how to change the properties of a trace, and in doing so, make the trace thinner so that we can see the data points. 

With planar coils of n concentric turns and constant interturn spacing and trace width, the S/N per unit volume is given by the following ... 

Table DC. The Effect of Trace Width on the Adhesion of Copper to Glass-HUed Polyetherimide.

The effect of heat-treatment time on adhesion and the impact of the metal trace width and filler content of the polymer is displayed in Table XI. The data show that for the lightly-filled polymers (20 and 30 % glass loading) that the peel strengths reached their ultimate values irrespective of line width within O.S hours. In contrast when the filler content was SO %, the O.S mm wide line approximated its final value within 0.5 hours while the 3.9 mm trace achieved only 53 % of its maximum value. A total heat-treatment time of 12.S hours was required in order to obtain the final peel strength for the 3.9 mm line and SO % glass loading sample. 

Heat treatment/environmental studies in air and argon revealed that an external source of oxygen is required for bond formation. Polymers containing less than 30 % filler displayed no dependence on line width, whereas those possessing SO % filler demonstrated a marked inhuence on the metal trace width. Narrow copper lines, e.g.,... 

The typical range of minimum trace widths, trace separations, printed through hole diameters, and maximum aspect ratios are shown in Table 11.2. The board cost for minimum widths, spacings, and PTH diameters, and small tolerances for the pad placements is high and reliability maybe less. 

FIGURE 13.4 Ti ace resistance vs. trace width and thickness. (Prepared by Ritch Tech.)... 

CAM tools are CAD systems tailored to the needs of the fabrication process.The output of the PCB design process is a set of CAD files that describes each artwork layer of a PCB, the sUk screen requirements, drilling requirements, and netlist information. This information must be modified before it can be used to build a PCB. For example, if a fabricator needs to build several copies of a PCB on a single panel, the fabricator will need to add specialized tooling patterns to the artwork and alter trace widths in order to compensate for etching. Initially, these operations were done manually with a high potential for error and significant labor costs. CAM stations or tools allow the fabricator to do all of these operations automatically and rapidly. 

To ensure compliance with manufacturing and transmission hne rules, the trace widths and trace spacings for each layer must be entered into the CAD system. This is typically done in tabular form. 

Chart Basics Known Current. When the current and the desired temperature rise are known, then the trace width can be calculated for various trace thicknesses. A 10°C rise is a common temperature rise for a design. The temperature rise should always be minimized. If the designer can manage a 1°C rise or less, then the contribution to board heating will be minimized. Increasing the size of a trace lowers the temperature rise, lowers the voltage drop, decreases component temperatures, and improves the reliability of the product. 

What is the required size trace that will have a 10°C rise if 6 amps is applied to it Starting with the top chart, follow the Une going across from 6 amps to the curve labeled 10°C. The 10°C curve represents the temperature rise that occurs for a specific size trace at that current level. Next, follow the line going down from the 10°C curve and look at where it intersects the axis labeled CROSS SECTION IN SQ MILS. The cross section is the cross-sectional area of the trace. The final step is to determine the trace width. 

The lower chart in Hg. 16.1 is used to determine the trace width for various copper thicknesses. For the same cross-sectional area, the width will be smaller for thick copper and wider for thin copper. Continuing with the example, follow the vertical fine down from 200 sq. mil. into the lower chart to the fine labeled (1 oz/fF ) 0.0014 see the discussion of copper thickness in Section 16.4.5. Following the Une across to the axis labeled CONDUCTOR WIDTH IN INCHES shows that the trace should be 0.15 in. wide for a copper trace that is 0.0014 in. thick. If 3 oz. copper were selected, the trace width wonld be approximately 0.05 in. wide rather than 0.15 in. wide for 1 oz. copper. 

A standardized process is not nsed to determine the amount of undercut resulting from the etching process that creates the traces from the layers of copper of a printed circuit board. Circuit board manufacturers have their own techniqnes for adjusting artwork to provide the desired trace size in a design. Variations exist from one manufacturer to another. The IPC Process Capability, Qnahty, and Relative Rehabihty (PCQR ) database is a source for determining the capabihty of a circnit board manufactnrer.Two of the pieces of data collected are trace width and thickness source. This database is a source for finding the cross-sectional area of a trace of a final prodnct compared to the initial artwork. Etch back is primarily a concern for small traces where the aspect ratio (the ratio of width to thickness) is small. 

Copper thickness is assumed 35.6 pm (0.0014 in.) thick for 1 oz. copper or possibly 34.3 pm (0.00135 in.). Two-ounce copper is considered twice those values and half the thickness for V2 oz. copper. IPC 2221 specifies the minimum acceptable copper thickness for an internal layer as shown in Table 16.4. The minimums are significantly less than what designers may think and should be considered when pushing current limits on small trace widths. For example, 1 oz. is... 

Trace width = the minimum trace width on the substrate Layers = the total number of layers in the substrate Annular ring = V2 the difference between the via land and the hole dia. 

P/N PCS SIZE Length Width (in.) (in.) Hole quantity Hole density Layers Thickness (mil.) Min. Trace width (mil.) Min. Annular ring (mil.) Min. Hole size (mil.) Aspect ratio Complexit xl... 

The wear, estimated from the measurement of the wear trace width, is not significant in the case of colloids, even at the end of the test. Figure 4.17 shows photonic micrographs and wear trace profiles (optical measurements) obtained on the worn surfaces after 2000 cycles in the presence of ZDDP, strontium and calcium octanoate dispersions in dodecane as lubricants. 

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