Spontaneously forming tin whiskers,which emerge unpredictably from pure tin surfaces,have regained prevalence as a topic within the electronics research community. This has resulted from the ROHS-driven conversion to “lead-free” solderable finish processes. Intrinsic stresses (and/or gradients) in plated films are considered to be a primary driving force behind the growth of tin whiskers. This paper compares the formation of tin whiskers on nanocrystalline and conventional polycrystalline copper deposits. Nanocrystalline copper under-metal deposits were investigated,in terms of their ability to mitigate whisker formation,because of their fine grain size and reduced film stress. Pure tin films were deposited using matte and bright electroplating,electroless plating,and electron beam evaporation. The samples were then subjected to thermal cycling conditions in order to expedite whisker growth. The resultant surface morphologies and whisker formations were evaluated.

Over the last few years,there has been an increase in the Evaluation and use of halogen-free soldering materials. In addition,
there has been increased scrutiny into the level of halogens and refinement of the definition and testing of halogen-free
soldering materials. The challenge has been that there has been no common standard across the industry in terms of halogenfree
definitions and the corresponding test methods to determine these. This has created confusion in the industry as to what
end users want and what soldering materials suppliers can actually provide. This paper will review the status of both halogenfree
and halide-free in terms of definitions,test methods and the limitations and accuracy of test methods used to determine if
a soldering material is halogen/halide-free or not. For halogen-free and halide-free definitions,the paper will review the different industry standards which are currently available and those being drafted,and it will discuss any similarities and differences. It will also cover the origins of some of the definitions mentioned in the standards. The paper will include a review of the accuracy and limitations of several test methods and preparation techniques for halogen and halide determination.

As interest continues in the development of non-halogen flame retardants for printed circuit boards,the requirements for robust thermal stability and lead-free solder compatibility also continue. With respect to developing “greener” electronic materials,one option available to the formulator is to use compounds that are reactive so they will become part of the cross-linked laminate matrix when cured. A well-understood example for doing this is to develop laminate formulations for epoxy resin systems that incorporate the flame retardant tetrabromobisphenol A,since it is completely reacted into the system. The advantages of using a reactive system can also be achieved with certain non-halogen flame retardants,such as the curing agent discussed in this paper. These types of reactive systems also become part of the cross-linked laminate matrix. This new flame retardant material was developed as a reactive phosphorus-containing flame-retardant curing agent with very high thermal and hydrolytic stability. It is intended for use in conjunction with epoxy resin formulations in use today. This paper describes the development of this flame retardant and the performance in laminates with comparison to some existing non-halogen systems.

This paper reports on further developments for an innovative copper deposition technology that was presented two years ago at this conference. At that time,the innovative technology was described as a way to replace conventional sputtering and vacuum deposition techniques while achieving greater feature diversity,lower cost,and higher performance. The advancements reported here include the extension of the technology to deposit thin (depths of 0.1 to 10.0 microns) copper with good adhesion on the interior of via walls that have been pre-formed in the base material. This process extension has been demonstrated on vias as small as 25 microns in diameter and on thin (7.5 to 12.5 micron) polyimide base materials.

Metal plating of epoxy polymer has been widely applied for industrial products for a long time,especially in the field of Printed Circuit Boards (PCB’s). This technique is one of the most important technologies of electronics devices with high reliability and guaranteed quality. The authors are developing a new concept of PCB’s for next decade generations to improved the techniques of which including more fine line circuitries,higher densities and narrower spaced conductor lines. An essential part of subject for this technology is to improve the weak copper adhesion peel strength on epoxy insulation materials. To obtain the good adhesion property of copper plating,it is now widely used the Pd Colloid Solution method. In order to further improve more excellent adhesion for next decade generation PCB’s,we are investigating Super Critical Fluid (SCF) method. In this paper,an attempt has been made to impregnate some metal complexes into epoxy resin and then decomposed the complexes to produce free metal in the resin by reduction . Using the deposited metal is efficient electro-less Cu plating can be achieved. We will discuss the selection of the metal complexes and impregnation conditions on the complexes as well as peel strength of the plating.

Base on our experience,HiP defect comes in various shapes and
forms. Some of the HiP looks like an ordinary open joint,while others have an eclipse profile. The tough ones to detect are those that look like an absolutely good solder joint.
Although the HiP detection rate on the 5DX AXI averages about 70%,this system is currently by far the most efficient tool in the industry to screen for such defects. After the flagged joints are verified at the 5DX repair station,the remaining marginal or questionable joints are sent to a high resolution manual 2D x-ray machine for failure analysis.

-BA flux: Water soluble BA flux has a higher HiP risk relative to NC BA flux,likely due to higher surface oxidation risks.
-Deflux: Washing process using water or DIW in combination with other solutions
may make HiP risk higher when compared to leaving flux residue as received*.
-SMT paste: HIP improved models have higher performance than standard LF paste.

The reader may wonder why „PCB? in the title is between quotes. The original objective of the paper was to lay a firm base for people who are involved in printed circuit board (PCB) design for LED applications to understand and predict the thermal behavior of their design. However,after reading the paper the basic achievement will be the notion that such a designer cannot focus on the PCB alone,she has to take into account the rest of the world too (by way of speaking of course). Hence,the paper is equally well suited to serve all designers dealing with one or more aspects of the total LED application,be it the LED itself,the thermal interfaces,the heat sinks or the luminaire.
First of all,the paper will discuss the reasons why thermal management is important,and then treat the basics of heat transfer: conduction,convection and the concept of thermal resistance. How to perform back-of-the-envelope calculations is another topic that is covered,as well as the non-trivial concept of heat spreading,required in later stages of a design phase. Before jumping to conclusions,the paper discusses thermal interface materials and the associated wrong use of thermal impedance as their characterization.

Today,the metal core printed circuit board (MCPCB) business is booming thanks to the rising popularity of LED TV. The majority of MCPCB is single sided. However,the demand for multi-layer board is increasing since the interconnection density becomes higher. There are several approaches for this problem. One of them is to press resin coated foil (RCF) on the single side MCPCB. And even though there are many RCF products,RCF with high heat dissipation is rarely available. Therefore,the industry is looking for new thermal RCF material for multilayer MCPCB.
To meet this demand,a novel RCF material with high heat dissipation has been developed. Alumina fillers have been carefully selected,surface treated and highly loaded to the modified epoxy resin system. Only good dispersion with high power mixing can secure the material which has more than six times the thermal conductivity,1.5W/mK,than that of conventional RCF. It also shows a good thermal stability,withstanding longer than 10min at 288C,which makes it suitable for lead-free process. The other properties of this material,such as copper adhesion,dielectric properties and
laser via whole processibility will be presented.

To help address the environmental requirements driven by the European Union RoHS Directive,consumer applications have changed the solder alloys for the manufacturing of printed circuit board assemblies (PCBAs) by removing Pb from solder. Based on the anticipated end to various exemptions and other market forces,high end server applications are now following suit. In addition,as the server/computer industry evolves,the requirements for speed and memory storage continue to increase,causing a need for higher levels of signal integrity along with greater density/mass of components and wiring within PCBA’s. This change to more dense/higher thermal mass components on PCBA’s and going to a Pb Free solder at higher melting temperature than SnPb Eutectic Solder will aggravate the temperature gradients that occur during reflow,causing major limitations when using standard IR/Convection reflow. Excessive temperature gradients can damage less massive components and less dense laminate areas of the PCBA’s. Consequently,other techniques need to be investigated,and the leading alternative is Vapor Phase Reflow. Vapor Phase Reflow is a legacy soldering method that was popular before the 1990's. Vapor Phase Reflow has a processing advantage: its thermal blanket possesses a much greater heat density than convection or IR heating. This reduces the temperature gradients across the board assembly,preventing sensitive components from exceeding maximum temperature limitations. One of the many concerns for implementing Pb Free Vapor Phase Reflow is the effect on solderability. The objective of this publication is to compare the solder wetting between Vapor Phase Reflow and Convection Reflow using a specific Pb Free (SnAgCu) SAC solder paste. This study will compare the amount of area the solder wetted,solder heights,wetting angles,and voiding.