The signal channels that link high speed processors to memory and various other peripherals,are limited by the inherent characteristics of the printed circuit board. These are what ultimately connect information to the outside world. One limiting factor is the effect of non-uniformity of the glass fiber distribution in the printed circuit substrate material,also known as fiber weave effect (FWE). FWE introduces signal skew and timing errors which place an upper limit on bit rate and trace length.
Using unique fabrication techniques and a proprietary low dielectric constant glass composition,a revolutionary glass fabric
is presented that is essentially free of fiber weave effect while demonstrating inherently improved resistance to conductive
anodic filament (CAF) formation. Improved laminate performance is demonstrated with finite element modeling and HyperLynx simulations,and corroborated with dielectric property measurements on prototype substrates.
A printed circuit board using this material demonstrates superior signal integrity performance over the traditional glass-based
solution. By uniformly distributing glass fibers the maximum surface area becomes available to bond with the resin,which is
enhanced by direct application of a finish to provide a high quality interface between glass and resin. Two high profile performance issues,fiber weave effect and CAF,are addressed by a unique laminate reinforcement.

The ever-increasing use of high frequency in high density interconnect (HDI) assemblies,combined with the worldwide move towards lead-free manufacturing,has initiated a closer assessment of effective flux removal processes. Since adequate climatic operating conditions can’t always be assured,system signal integrity maybe vulnerable to failure through induced capacitive effects of hygroscopic activator residues. Furthermore,such contamination is no longer detectable by ionequivalent
measurements alone.
Most failures of electronic components in humid environment are caused by electrochemical migration and corrosion induced
leakage currents. In this paper,the origins and effects of such failure mechanisms are examined. In addition,we are also discussing the influence of alloy types with particular reference to lead-free formulations. The critical importance of contamination free surfaces in high frequency circuits is outlined and put into context with the quality of conformal coating.
Finally,we will describe different methods to determine climatic reliability as well as introduce a new and innovative test method.

Specialty high frequency circuit materials have been used in the PCB industry for decades and for many different reasons. There are several attributes of these materials that are very unique when comparing to the more traditional PCB materials. When these attributes are well understood,the PCB fabricator and the OEM can benefit greatly from improved electrical performance. And there are many other non-electrical improvements that can be achieved of which the general public in the PCB industry may not be aware. In order to realize the full potential of the benefits these materials offer,the PCB fabrication issues must be well understood.

This presentation will examine materials declaration from a practical point of view,identify the role of materials declaration in the product lifecycle analysis and thus hone in on the practical implications of presenting and exchanging various pieces of data in a materials declaration. A certain emphasis will be placed on current and evolving regulatory needs,such as being able to meet upstream and downstream communications requirements,for example,on product safety data sheets,safe use training multimedia material,authorized uses and test data in a practical,efficient and sufficient manner. Emerging needs for product footprint development will also be briefly addressed.

Industry associations,such as IPC,were quick to develop standards to help the electronics industry deal with emerging environmental regulations; however,for regulatory compliance,smooth international trade and international supply chains,we rely heavily on International Standards Organizations such as ISO and IEC. In 2004,the International Electrotechnical Commission (IEC) launched TC111 on Environmental Standardization.
IEC/TC111 has a comprehensive work program developing international standards and guidelines for Environmentally Conscious Design,analytical test methods,materials declaration,and guidance for evaluating products with respect to restricted substances,and recycling and reuse.
IEC recently published IEC 62321 on Analytical test methods; IEC/PAS 62596 with guidelines for sampling procedures; and IEC 62430 on Environmentally Conscious Design. The IEC62321 standard was considered crucial for International trade to ensure that manufacturers and authorities are using the same test methods for assessing conformity to RoHS. Obtaining accurate substance concentration levels near the legal thresholds is difficult and requires the use of the right extraction and test methods.
The ECD standard (IEC62430) specifies requirements and procedures to integrate environmental aspects into design and development processes. It provides a framework of ECD requirements and provides a level of alignment with emerging international regulations that will require an ECD process.

Restrictions on the use of chemicals in began 30 years ago in the US with the passage of the Toxic Substances Control Act. Over the last five years we have seen a logarithmic increase in product and
substance legislation globally with China,the EU,Korea,Argentina,Australia,Canada,and Mexico to name a few. These regulations ban the use of chemicals in everything from baby bottles and batteries to electronics,children’s toys and medical devices.
During the next 2 to 5 years,the chemical industry,consumer product companies and manufacturers will face increasing regulatory pressures and burdens globally,as more substances will be restricted,banned or otherwise regulated. Increased substance regulation is coming; the only real question remaining is how fast. Green products will not offer a marketing advantage as much as being table stakes to remaining the game.
The successful organization will see this as a strategic opportunity by investing the time in developing the expertise,people and systems that result in a full suite of compliant products that anticipate the next change.
Successful individuals will see this as an opportunity to get involved in the standards setting process and regulatory process adding another skill in their portfolio to bring added value to the organization and the customer.

The formation during the soldering process of the layer of intermetallic compound Cu6Sn5 at the solder substrate interface
provides the essential evidence that a metallurgical bond that is the basis of a solder joint has been established. Although the
importance of this interfacial intermetallic was long recognized in tin-lead solders the implications of the change to lead-free solders on this layer and its impact on solder joint reliability are yet to be fully understood. An obvious and important difference is that the copper required to form that intermetallic that for tin-lead solder joints could come only from the substrate is now a constituent of all of the commonly used lead-free solders. It has recently been found that the allotropic transformation of the Cu6Sn5 from the hexagonal close packed form to the monoclinic form as the temperature falls below 186°C appears to have implications in lead-free solders that it did not have in tin-lead solders. This paper reports the discovery that the inclusion of a specific level of nickel in the formulation of a tin-copper solder has the effect of stabilizing
the hexagonal close packed form of the intermetallic at normal operating temperatures. The consequences of this stabilization
on the mechanical integrity and three-dimensional structure of the intermetallic layer will be described and the implications for solder joint reliability reviewed.

With increasing use of portable appliances such as PDA and cellular phone,changing environment of application requires higher solder joint reliability. The Cu-OSP process has been widely used for portable devices due to its benefits including good surface planarity,cheapest finish and higher drop reliability than others.
This study is about reliability according to solder materials on package with OSP finished,and is evaluated the various Ag,Cu contents and adding few special dopants.
The Inter-Metallic Compound between pad and solder material after reflow has the scallop type and is composed Cu6Sn5 by using EDS.
Investigated the 3 types fracture mode after drop strength: The first is the crack propagating along IMC layer which composed of Cu6Sn5 (interfacial fracture mode),the second is the crack propagating along solder side (bulk fracture mode); the final is the crack propagating along the above IMC layer between IMC and solder.
The unstable interface exists through IMC,pad material and solder bulk by the lattice mismatch,so that the thermal and physical stress due to the continuous exterior impact is transferred to the IMC interface.
Therefore,it is strongly requested to control solder morphology,IMC shape and thickness to improve the solder reliability. In case of increasing the Cu contents,IMC shape changed scallop type to spike type,and IMC had larger toughness by using nano-indenter.
Accelerated stress propagated along the weaken surface between solder and IMC,this phenomenon is caused to increasing drop performance.
Moreover,as the special dopants were added,the relatively weak thermal shock strength could be improved.

Electroless nickel immersion gold (ENIG) has captured the major share of the lead free final finish market globally even though it’s not the least expensive. ENIG not only provides a robust metallic
coating required for assembly with lead free alloys,but also,an effective barrier to virtually stop copper migration into the attachment surface of the PCB. This provides a true surface with long term,low contact resistance with long shelf life and good solderability. So why make any changes to ENIG?
Three reasons;
• Improved window on lead free soldering
• Improved robustness for touch contacts.
• Wire bonding of fine features
Lead Free Soldering: After years of testing,discussions,failures and success,lead free soldering has completed the transition from the lab to production. Lead while bad for the environment,was great for soldering and had a tremendous operating window. When compared to eutectic tin lead,liquidous time and spreadability of lead free alloys is less making the final finish on the PCB more critical. As far as ENIG,imperfections in the ENIG deposit,which were not critical with eutectic tin lead,can become an issue because the operating window on Pb-free soldering processes are tighter.
Soldering actually occurs on the electroless nickel as the immersion gold is dissolved into the solder joint. Oxides or intermetallics on the electroless nickel decrease the solderability of the electroless
nickel surface causing poor solder wetting or weak solder joints. The oxides and intermetallics are actually corrosion products from the deposition of immersion gold on the electroless nickel. With
eutectic tin lead this was called black pad and as suppliers we have learned to reduce the aggressiveness of the immersion gold by shorter times or chemical changes and to increase the chemical resistance of the electroless nickel by increasing the phosphorus content and selection of stabilizers. Classic black pad was a major issue with eutectic solder,but minor amounts of corrosion products typically soldered fine. Now with reduced wetting from lead free soldering,the amount of corrosion products that can be
tolerated is reduced.
These corrosion products can be observed under the immersion gold by stripping the gold and evaluating the surface below. A few things become evident in the location and formation of the
corrosion products. They almost always initiate around the electroless nickel grain boundaries and or in areas where the electroless nickel coverage is not complete,like around micro-pits or edges of traces or around pads. When cross-sectioned,if due to imperfections in the electroless nickel deposit,large corrosion spikes can be seen at relatively low power. These areas while extremely small would still solder completely with eutectic tin lead and with most lead free soldering processes. The exception is a
lead free process with extremely short liquidious time. This provides less wetting time to penetrate the corrosion products.

Excessive moisture entrapped/absorbed within printed board laminates can expand during soldering operations,causing delamination or other damage. While moisture absorption data is available for some materials used in PB construction,little information has been made available for finished PBs,where not
only the laminate material is important in moisture gain or loss,but also the board thickness,copper content,details of the construction,and assembly process conditions. This study measures moisture absorption and desorption rates within various representative rigid multilayer PB structures,under varying conditions of temperature and humidity,including shop ambient environments and baking operations. Weight gain or loss attributable to moisture was measured using an analytical balance. The effectiveness and response times of humidity indicator cards used in PB packaging was also assessed. This information may be used to develop process controls for PB fabrication or PB assembly operations,dry storage practices,or baking procedures.