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September, 2016
New Technology Platform Increases Functionality in
the Smallest of Spaces Continued from previous page
time now PCBs have been stacked or folded to achieve greater functionali- ty. Conventional technology will soon reach its limits here. Completely new manufacturing processes have to be scaled up from the laboratory and made suitable for mass production, which often takes years and a lot of cash. A solution here is the intelligent combination of common processes that are already able to serve mass production.
Panel and Pattern Plating Two of these technologies that
have already been used for many decades are the panel plating and pattern plating processes. Conven - tionally, this technology has only allowed switching circuits with con- ductor widths and distances of less than 50 µm to a limited extent. In addition, these processes do not sup- port all of the options for modern PCB technology. In pattern plating, a conductive
copper layer is attached to the board in a so-called strike plating step. Then, using photolithography, selec- tive plating takes place on the strip conductors, which are then covered with a metallic etching resist — usu- ally galvanic tin. After producing the circuit by alkaline etching, the etch- ing resist must be removed by strip- ping away the remaining tin. Although this aggressive stripping has little impact on the copper, it does have negative effect on the etched pattern. The smaller and more sensitive the structures, the more disturbing and noticeable this effect becomes. For panel plating or tenting, the
PCB is coated with all of the neces- sary copper and then a circuit dia- gram is created using photolithogra- phy. The process is simpler than pat- tern plating because it requires fewer process steps, is very reliable and does not require metal resist. But it has limitations when it comes to the smallest circuit and distance widths. A resolution of 25 µm and relevant distances can only be achieved with a very thin copper layer of around 8 µm with a photo resist of 10 µm in thickness. Due to the maximum total cop-
per thickness of 8 µm, no connections between layers using stacked via technology and small via-in-pad structures are possible — which are considered state-of-the-art. Even when using base materials with ultra-thin copper claddings, the thickness of the deposited galvanic copper layer is not sufficient to ade- quately fill blind holes with copper or to comply with the specifications.
Thin-Film Technology Using thin-film technology, in
recent years circuits have been implemented on organic substrates, such as polyimide or LCP films, as a classic semi-additive process using vacuum deposition, photolithography and electroplating, as well as chemi- cal and dry etching procedures. With this technology, it is possi-
ble to achieve circuit widths and dis- tances under 15 µm but since the size is limited to 232.2 cm2 (36 in2) the
price is simply too high. With new processes, it may be possible to scale up this technology, but at what cost? This would require new systems engineering. Process steps, and the handling of flexible films without copper lamination would have to be improved. In addition, the polyimide mate-
rials currently used are not available without copper lamination, which must be removed before processing
Using tracking technology, the company provides continuous traceability of components.
can start and also lack appropriate photoresist. Even if larger circuits were possible by this means, the high production costs would make manu- facturing unprofitable.
Further Miniaturization The disadvantages can be
avoided using an intelligent combi- nation of classical technologies. By developing its new DenciTec plat- form, Cicor follows the trend towards ever more intelligent PCB technology and offers users high functionality at reasonable production costs. With the technology, the company has cre- ated the option of producing switch- ing circuits with extremely high den- sity without the disadvantages of the methods stated above. The new tech- nology provides highly-reliable cir- cuits without restrictions on the design freedom. In addition, new base materials are available. The new technology enables the
functional structures of the PCB to be miniaturized further. The process allows down to 25 µm line widths and spacings, copper thicknesses of 20 µm, ±5 µm, on all layers, laser via diame- ters of 35 µm, annular rings of 30 µm on the inner layers and 20 µm on the outer layers, copper-filled blind vias with the option of via-stacking and vias in pads, ultra-thin circuits by using a 12.5 µm polyimide core mate- rial (four-layer flex circuits at a thick- ness below 120 µm), and does all of this with the highest reliability. With the miniaturization of the
circuit diagram that this permits, new functions can be integrated without expanding the size of the PCB, or in the best case scenario it is possible to save up to 70 percent of the area on average on all layers. High reliability is required in many industries, especially for medical devices. DenciTec achieves this, is very flexible, and the product output and yield are of a size common for PCB production. Contact: Cicor Americas, Inc.,
185 Alewife Brook Parkway, Suite 410, Cambridge, MA 02138 % 617-576-2005 E-mail:
info-americas@cicor.com Web:
www.cicor.com r
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