A new versatile laser technology is available that is capable of working with both rigid and flexible boards using only one laser source. This system is based on a THG-UV laser (355 nm) and vector data software. This system can be used for drilling,cutting and structuring. Small and medium board manufacturers will be able to enter the HDI market with a minimum investment and a guaranty of high yields for each technology step. Various materials and combinations including glass fiber reinforced substrates can be drilled,cut and structured with the same equipment. This paper will introduce special applications in the area of micro via formation (minimum diameter of 30?m at 250
holes per second),laser direct structuring (minimum line widths of 0.8mil at 13.8 inches per second) and routing (compounds of various materials ) and will discuss the technological benefits.

Because of environmental concerns,elimination of lead from electronic components has been recently encouraged,and as a result,lead-free solders are frequently adopted for solder mounting. The OSP and HASL treatments have been primarily used for the majority of final surface treatments for PWB’s used for electronic components,while conventional electroless Ni/Au plating process has been used for the remainder. Lead-free solder mounting can lead to poor solderability in the case of some OSP-treated PWBs. The problems associated with HASL for the latest generation PWBs and packages is already well documented. Under the present conditions in which manufacturers are switching from conventional solders to lead-free solders and are beginning mass-production,this problem is being highlighted. Consequently,it is urgently required to establish a treatment method that can replace OSP treatment. This paper compares the solderability of immersion Ag,immersion Sn,and immersion Au plating that is treated directly on copper,and electroless Ni-P/Au plating,all of which are now attracting industry wide attentions as alternative surface treatments for PWB’s. The paper makes recommendations regarding the treatment method that supports future lead-free solder mounting.

The market for optical communication equipment and components has grown significantly since the early 1980s with growth rates exceeding 50% annually in the late 1990s. Although demand has dropped significantly since 2000,the underlying drivers for demand are still operating. This paper discusses the drivers for optoelectronic devices and optical PWBs,the major differences between IC packaging and optoelectronic device packaging,the emerging evolution of optical printed circuit board,and some of the opportunities for assembly and materials suppliers in these areas.

An optical interconnection technology for multi-layer printed circuit boards is presented. The application of this technology enables onboard data rates of several Gbps whereas at the same time a significant improvement on the electromagnetic compatibility (EMC) can be achieved. After an introduction,the most important properties of electrical interconnects are compared with those of optical interconnects. Moreover,requirements are derived which are essential to be met for an industrial use of optical interconnection technology on the printed circuit board level. The most important one of these requirements is to ensure compatibility with the existing design,manufacturing,and assembly processes. In the second part the current state of the art of this new technology,which takes into account the different demands and requirements,is presented. Technologies for the manufacturing of optical layers,their integration into the printed circuit board,as well as coupling concepts enabling furthermore the pick & place process are presented and discussed. As an efficient employment of this new technology requires also an enhanced and efficient design process,the necessary extensions are introduced. This includes an overview on modeling and simulation techniques for the active and passive components whereas again compatibility with the existing printed circuit board design tools is essential.

The rapid developments of IT equipment are placing increased demands on printed wiring boards (PWBs) in terms of high efficiency,high-density and lightweight. Industry experience has proven that glass fiber base materials are essential for highly reliable PWBs,in particular to obtain such characteristics as heat resistance,dimensional stability,and mechanical strength and insulation reliability. There can be some difficulties in the processing of traditional PWB laminating in terms of accuracy and cost performance applications are focused on fine glass fiber fabric developments. Resin coated copper foil (RCC) is used widely as layer material for build-up (sequential) processing technology as a solution to these accuracy issues. However,in RCCs increasing use,much higher reliability such as no warp and crack and correspondingly improved dimensional stability and high cost performance are being demanded. We are investigating new glass base materials to overcome these deficiencies in both systems by developing improved spinning and binder technology in a novel,non-woven glass fiber fabric (FF sheet). This novel base material for microvias is able to bring high reliability,good processing and also high productivity as an improved
RCC alternative.

The next generation of surface finish coatings to replace HASL are now being installed by various PWB manufacturers and have been implemented by many OEMs. Coating thickness requirements are part of the OEMs’ specification given to the board manufacturer. Clearly from previous and existing final finish coating performances,thickness has shown to have a major impact on the performance of the surface finish during soldering. OEMs have traditionally specified wide thickness specifications,to meet production variations by PWB producers. This paper investigates the current methodologies / alternatives used to determine accurately and consistently the thickness of these new immersion silver & tin coatings,and how this variation may impact solderability performance under various pre-conditioned states.

Dry film photoresist to produce highly integrated and advanced PWBs has been developed to meet more demanding
fine line requirements.
Advantages for volume production of fine features below 50?m with high yield are now available with newly
developed dry film photoresist that is designed to have specific features. In order to develop such a highly reliable
dry film photoresist,Quality Function Deployment (QFD) helped significantly to well interpret 'Voice-Of-the-
Customer' (VOC) into specific requirement of dry film photoresist performance and how it can be achieved by
formulation design. The developed dry film photoresist resulted in L/S resolution and isolated adhesion better than
1:1 aspect ratio to thickness,with very wide exposure range,and with wide developing latitude.

We will present a new positive working dry film resist system that is suitable for high accuracy use. The new positive working dry film resist is composed of base polymers with active hydrogen functionality,and a
multifunctional vinyl ether compound plus a photo acid generator,and makes use of a chemical amplification method to allow imaging at low exposure levels of UV light. At the pre-bake stage,a ketal structure is formed by an additive reaction between the active hydrogen functional
groups and the vinyl ether. Consequently,the base resin is cross-linked and the resist becomes insoluble in an alkaline developer.
At the UV exposure stage,the photo acid generator forms a strong acid and the area of exposure becomes soluble in alkaline developer via an hydrolysis reaction. This new chemistry makes it possible to form a high reliability image with high contrast in comparison with conventional positive- and negative-acting systems. The new positive working dry film resist achieves on the order of 10?m Line/Space patterns plus the ability to tent 5mm diameter through holes with a resist as thin as 10?m.

Prepregs used in the PCB industry possess various properties and need to be handled with care to maintain
identical chemo -rheological properties to yield dimensionally stable laminates. A prepreg is a viscoelastic polymeric material which losses some portion of energy exerted on it. The characteristic viscoelasticity property depends on the chemical reaction and rheological flow path. To heat the prepreg more uniformly,a new method is invented,utilizing a metal separator as an electrical heating medium (Heated Electrical Separator -HES). The HES technology has been tested to demonstrate the improvement in temperature uniformity among the boards in daylight. A mathematical squeeze flow model is used to stress the consequences of different heating histories on the pressed
laminate thickness.

Polyimides have proven their performance in electronic applications demanding high strength,increased durability,
broader temperature ranges and exceptional chemical resistance. They serve as the material of choice for fabricating
flex circuitry due to their excellent properties and demonstrated capabilities. Typical polyimides require the use of
an adhesive to assemble multilayer circuits,which results in additional material thickness for the overall package.
Several concerns related to the adhesives currently used involve CTE mismatch,wrinkling,voids and delamination
of the layers that can ultimately lead to circuit failure. The recent trend is toward adhesiveless materials; reducing
the total package thickness without compromising the performance,capacity or cost of the final product.
One material,which has been investigated in an effort to meet the demands of the electronics industry,is an
advanced polyimide developed by researchers at NASA Langley Research Center. SI (Soluble Imide) is a
thermoplastic that extends the possibilities for polyimides in flex circuits. SI can be used as a substrate material by
laminating or casting directly onto metal foil such as copper or aluminum yet is versatile enough to be used as the
adhesive in fabricating flex circuits thereby producing an ultra-thin adhesiveless,monolithic flex circuit. Eliminating
the adhesive results in a reduction in materials and processing costs,lighter end weight circuits,increased flexibility,
and circuits with smaller z-axis expansion.