Subtractive, processes

Most priated circuit board (PCB) production uses the subtractive process (41). In the simplest version, a thin copper foil is laminated to a nonconductor, holes are fabricated, and the unwanted copper etched off. These siagle-sided boards do not require plating. Known as ptint-and-etch, this version is used for the most simple priated circuit boards. 

There has been a continual increase in size and complexity of PCBs with a concurrent reduction in conductor and hole dimensions. Conductors can be less than 250 p.m wide some boards have conductors less than 75 pm wide. Multilayer boards greater than 2.5 mm thick having hole sizes less than 250 pm are being produced. This trend may, however, eventually cause the demise of the subtractive process. It is difficult to etch such fine lines using 35-pm copper foils, though foils as thin as 5 pm are now available. It is also difficult to electroplate holes having high aspect ratio. These factors may shift production to the semiadditive or fully additive processes. 

The cleaned and microetched boards are cataly2ed and activated in the same manner as for POP. The same coppers are used as for POP, but these are usually formulated to give greater deposition rates and thicknesses. Copper is typically deposited in 0.25—35 p.m thickness, depending on the process. Fully additive processing needs thicknesses of 25—35 p.m subtractive processing needs thicknesses of 0.25—2.5 p.m. 

Additive and semiadditive processing can give material savings and higher circuit densities, whereas subtractive processing is technologically easier. 

These oscillations are usually removed from the EXAFS, data during the background subtraction process according to eq 12, as previously they were... 

The ink jet printing of coloured images is a subtractive process and requires a YMC trichromat as in colour photography. Some of the properties required in the dyes are listed below. 

Substrate Treatment. When the desired image is developed in the resist, the pattern created provides a template for substrate modification. The various chemical and physical modifications currently used can be classified into additive and subtractive treatments. Examples of additive treatments include the insertion of dopants (by either diffusion or ion implantation) to alter the semiconductor characteristics and metal deposition (followed by lift-off or electroplating) to complete a conduction network. In most cases, however, the substrate material is etched by a subtractive process. 

Figure 5.14. LC-MS profiles of PEG formulation of compound that has undergone degradation (a) UV trace at 230-245 nm (b) TIC after PEG subtracting process (c) unprocessed TIC.

In Section 7.9, we saw how phase cycling can be used to remove the 13C coherence that comes from the original 13C z magnetization (Sz), so that only the coherence transferred from ll z magnetization (Iz) is observed. This is a subtraction process that requires more than one scan to accomplish. With gradients we can do it in one scan alone ... 

The above technique is called subtractive since patterns are created by "removing" material, i.e., blanket films are deposited and subsequently patterned. The consequence of this subtractive process is that numerous steps are required to create a single patterned film. This increases complexity of the process, and also increases capital expenditure, since appropriate tooling is required to realize these complex process flows. 

TFML interconnections are fabricated using a repetitional sequence of thin film processes to deposit and pattern the conductor and dielectric layers. A variety of individual processes and process sequences, including both additive and subtractive approaches, have been used. The subtractive process sequence shown in Figure 2 has been used at Honeywell for a variety of patterns (8 ) and is offered as an example. 

There are three main ways to create a rapid prototype. Formative techniques use machines to make raw materials into the desired shape. Subtractive processes start with a large solid, then remove material to make the shape desired. Additive processes rely on layering material over and over until the part or product reaches its final position and shape. 

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