Monday, June 25, 2018
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Vertical Processing Line Etches Fine PCB Features

Printed-circuit-board (PCB) producers are being asked for thinner circuit boards, with narrower line widths and spacings. Fortunately, the Vertical Developing/Etching/Stripping (DES) line of PCB production systems from Schmid can help meet these demands. These high-performance production solutions can handle panel thicknesses as fine as 25µm and form circuit line widths and spacings as tight as 10µm, to meet the ever-evolving microcircuitry needs of PCB manufacturers for high-density-interconnection (HDI) circuit boards and substrates.

The company has already delivered the first two vertical DES production systems of the 10 or more systems that have been ordered so far for 2013. In addition to these DES systems, Schmid's portfolio includes vertical stand-alone machines for developing, etching, and stripping as well as for flash etch processing, solder mask developing, and precleaning. The company also provides sophisticated horizontal etching machines with contact-free clamping transport well suited to handling thin flexible panels.

The systems are produced and refined by the company's development team at their Zhuhai Technology Center, building upon its long-term knowledge of wet processing and full inline automation. The DES systems rely on integrated contact-free inline clamping transport of PCB panels as thin as 25µm. The Zhuhai team can achieve high process quality and reliability with homogeneous process results by means of symmetric chemical treatment on both sides of a PCB panel. Vertical processing allows a double-sided symmetric chemistry treatment by identical process conditions on both sides of the substrate. Using a special chemistry that is absolutely homogeneous, the ?pudding? effect that can occur in horizontal etching is completely eliminated. Horizontal processing systems often employ elaborate intermittent spraying techniques in attempts to compensate for the "pudding" effect.

These Schmid DES production systems achieve high quality and consistency by using a vertical spraying system that is totally different than traditional spray manifolds typically in use by the PCB market. At the Zhuhai Technology Center and for on-site production systems, the company's engineers have fine-tuned the DES production setup for optimum results. The vertical systems have been capable of achieving even greater homogeneity of medium distribution by means of their vertical spraying system than even the most sophisticated horizontal etching methods with intermittent spraying, in terms of standard deviation and range over an entire circuit panel. For the same circuit parameter settings and chemistry, the etching speeds are much faster for the vertical etching systems than for the horizontal systems. In addition, the etch factor of the fine-line circuitry can be improved to a factor of 6. In a vertical process, excellent results are achieved on both sides of a panel since the fluid dynamics can be maintained with the same precision on the left and right sides, which is not always true for the top and bottom sides of a panel in a horizontal process.

These vertical DES production systems have adequate separation between their processing areas and their rear service areas, making them fully clean-room compatible. The rear service area provides access to pumps and filters as well as to the material transport system. When a vertical system is integrated into a separating wall, maintenance on the system can be performed without contaminating the clean room.

A typical vertical etching process line consists of main etching, water rinsing, and air drying modules. Schmid's vertical systems transport materials by means of contact-free clamping systems which have already been proven in the company's horizontal production lines. The clamping systems protect extremely fine circuit lines during the etching process. Standard horizontal conveyer approaches can damage fine circuit features because of minimum oscillation of the conveyer system or any roller contact. The contact-free clamping systems allow direct application of medium to the panels without interference of the spray nozzles and without any kind of roller mark that might affect medium treatment of the substrate.

The company has developed vertical and horizontal clamping systems for a wide range of panel sizes, with panel and clamping frame sizes limited only in width. Special frames are available for different process conditions, such as for chemical treatments or for solder masks and their high-temperature requirements. The company also offers transport solutions for reel-to-reel processing. The cleaning and drying processes incorporated into each production system are optimized to clean and dry both the panel and the clamping transport system with its fixing points. This ensures that the clamping transport is ready for use with the next incoming panel without drag-out of chemicals. To prevent chemical drag-in and drag-out during processing, special air knives powered by a central blower replace squeegee rollers normally found in standard transport systems. In contrast to the rollers, the air knives do not touch the panel surface, maintaining the concept of contact-free transport throughout the system.

Schmid offers fully automatic systems for loading and unloading its contact-free material clamping systems. Its production systems provide contact-free handling without human intervention to minimize operating errors, for less required workmanship and significant increases in yield. Since the company developed the technology, customers will have full access to future improvements, making the vertical production line with contact-free clamping a sustainable investment.

Contact: Schmid Group, Robert-Bosch-Str. 32-36, 72250 Freudenstadt, Germany +49 7441 538 0 E-mail: Web:  \par

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