As the electronic industry moves to lead-free assembly and finer-pitch circuits,widely used printed wiring board (PWB) finish,SnPb HASL,has been replaced with lead-free and coplanar PWB finishes such as OSP,ImAg,ENIG,and ImSn. While SnPb HASL offers excellent corrosion protection of the underlying copper due to its thick coating and inherent corrosion resistance,the lead-free board finishes provide reduced corrosion protection to the underlying copper due to their very thin coating. For ImAg,the coating material itself can also corrode in more aggressive environments. This is an issue for products deployed in environments with high levels of sulfur containing pollutants encountered in the current global market. In those corrosive environments,creep corrosion has been observed and led to product failures in very short service life (1-5 years). Creep corrosion failures within one year of product deployment have also been reported. This has prompted an industry-wide effort to understand creep corrosion although minimal progress has been made in this effort. This lack of progress has been primarily due to the inability of reproducing creep corrosion in the lab using realistic accelerated aging tests. In this paper,we will demonstrate that creep corrosion on a PWB is highly surface sensitive. Neither clean FR4 nor clean solder mask surfaces support the creep corrosion. In general,the board assembled with rosin wave soldering fluxes and solder paste containing rosin flux is also resistant to the creep corrosion. However,residue left on the solder mask surface by organic acid flux is highly active and supports the creep corrosion of copper sulfides. The proper choice of the assembly flux can eliminate product failure due to creep corrosion associated with the ImAg plated circuit boards deployed in highly corrosive global environments. Furthermore,mixed flowing gas testing (MFG) provides a realistic accelerated test for simulating the creep corrosion in the laboratory without requiring condensing conditions.

Although the advantages of Hot Air Solder Leveling (HASL) in providing the most robust solderable finish for printed circuit boards are well recognized,in the years leading up to the implementation of the EU RoHS Directive in July 2006 the conventional wisdom was that it would have no place in the new lead-free electronics manufacturing technology. The widely promoted view was that HASL,which had been the most popular printed circuit board finish in North America,Europe and most of Asia outside Japan during the tin-lead era,would be largely replaced in the lead-free era by Organic Solderability Protectants (OSP) and immersion silver with perhaps a minor role for immersion tin. This view was reinforced by some early trials of lead-free HASL in which the tin-silver-copper alloy,then promoted as the universal lead-free replacement for tin-lead,was used as the coating alloy. The aggressive dissolution of copper by that alloy and its non-eutectic behavior made it difficult to use and to get satisfactory results. In the meantime,however,in Europe a microalloyed tin-copper alloy with low copper dissolution and eutectic behavior was evaluated and found to yield promising results. A smooth mirror-bright finish could be achieved on existing equipment with process temperatures that existing laminate materials could accommodate. An unexpected advantage was that the thickness of the lead-free HASL finish was more uniform than typically obtained with tin-lead so that it could be used in applications previously excluded to tin-lead HASL because of concerns about coplanarity,e.g. pads for BGA,CSP and fine pitch QFP. By July 2006 there were nearly 200 lead-free HASL lines running in Europe and that number has continued to increase since then. In response to demand by European customers many Chinese printed circuit board shops have installed lead-free HASL and there are now lines operating in South East Asia,India and North America. As problems have been encountered with OSP and immersion silver finishes electronics manufacturers have looked to lead-free HASL as a solution. In the more than 5 years in which the lead-free HASL process has been used in commercial mass product much has been learned about the operation of the process on the optimization of results. In this paper the author will report on current best practice on the operation of lead-free HASL lines and the properties that can be expected of a properly applied lead-free HASL finish.

Within today’s Consumer Electronics Industry,a laboratory report listing elemental content is standard protocol. Understanding the information listed within a lab report can be difficult and understanding how that information was obtained is not common knowledge.
- Do you know what the Laboratory sample preparation techniques are?
- Is the Laboratory using the correct test methods?
- Does the Laboratory have the proper certifications?
- How interactive are you with the Laboratory?
Understanding the answers to these questions is imperative to showing compliance to the various global eco-compliance
directives and OEM “Green Programs” such as EU RoHS,China RoHS,REACH,Halogen Free,etc.
This paper will provide insight into laboratory protocols and practices. It will provide information on the appropriate
certifications a testing laboratory should have. It will also try to make clear how to interpret the information on a “lab report”
and explain terminology such as:
- MDLs
- PQLs
- Units of measure (mg/kg,ppm,etc…)
- LCS and LCS recoveries
- QC protocols
- Flags
- N.D. vs <
The paper will also discuss test methods specific to the various global eco-compliance directives as well as the different
instrumentation used for these types of analyses.
Lastly,this paper will discuss the importance of building a “partnership” between the laboratory and the Client. Due to the
diverse array of sample matrices as well as the various manufacturing procedures within the consumer electronics industry,
the need of a synergy between the Laboratory and the Client is a very important component of a company’s compliance strategy. It will also explain why sample preparation is more important than the actual testing of a sample and provide some examples of “issues” that are inherent to material testing.
The premise of this paper is to give a brief overview of laboratory protocols and practices,provide some answers to questions that you have and that we have been hearing,provide terminology/acronyms and their definitions,try to explain how to
interpret the information on a “lab report”,and try to increase your knowledge of what a Laboratory can provide. The topics we will cover are Accreditations,Acronyms/Terminology/Definitions,Lab Reports,Methods/Instrumentation,Sample Preparation,and criteria to consider when choosing a lab.

The following article is a series of “from the trenches” stories,taken both from the perspective of an electronics manufacturer and an environmental compliance consultancy. The accounts below provide a library of RoHS compliance scenarios that illustrate the extremes of building an RoHS compliant product and the pitfalls of assuming that a declaration of compliance is iron-clad.
Unlike most papers,portions of this one are written in first person. In order to preserve both the confidentiality of our sources and the integrity of this paper,all external stories provided to us have been copied into the paper and kept anonymous. This allows for a non-biased and often humorous accounting of RoHS.

Embedded passives,especially embedded resistors and capacitors have been a hot topic since the mid-to-late 1990s. It is easy to understand why they have generated so much interest. Technology continues to be driven by performance,space and cost. Embedded passives offer potential significant advantages in each of these areas.
Embedded passives have far less parasitic inductance than discrete components,which enables electrical performance advantages (noise and EMI reduction),especially in high speed digital applications. Embedding passives saves surface real estate,which allows for board size reductions which is critical in space constrained designs such as military/aerospace and portable products. The incremental cost of embedding additional passive components is typically negligible; this offers the potential for system cost reduction in designs with high passive component counts. Embedded passives also offer additional advantages such as improved reliability and weight reduction due to the elimination of vias and solder joints.
However,even with all of their potential advantages,high performance embedded passive materials remained a niche market
until the last couple of years. There were a number of reasons for this,including the typical fear of new technology,limited technical resources and funding,lack of successful case studies,lack of an experienced supply chain,lack of long term reliability data,very limited physical layout and simulation/modeling software tools,improvements in existing discrete passive products,the telecom bust,cost concerns and an insufficient knowledge of intellectual property and prior art.
After more than 10 years of large scale interest,high performance embedded resistors and capacitors have finally become mainstream technologies in many market segments. There are multiple suppliers of commercial thin film metal resistor materials and ultra thin embedded capacitor materials. A large number of PCB fabs across the globe have very significant experience in processing these materials in moderate to high volumes.
This paper will look at the above barriers to the implementation of high performance embedded passives,focusing on embedded capacitor laminate materials,and show how these barriers were overcome so that embedded passives could finally become a mainstream technology.

There are presently several techniques for forming a buried capacitor in the core of a multilayer board. For purposes of this discussion,attention will be directed toward a sheet capacitor; although most of what is presented below can be extended to the other techniques as well. A buried sheet capacitor is essentially a thin innerlayer. The core is composed of an organic material often reinforced with a woven glass structure. A classic example is FR-4. The laminate extends over the entire board and is essentially a very thin innerlayer. The copper weight is normally one ounce and the thickness of the dielectric is typically two mils or less. The innerlayer is biased top to bottom thus creating a large capacitor in the interior of the multilayer board. Except for through hole connecting pads and antipads the innerlay is normally not imaged. A cross-section is depicted below:
The purpose of this technology is to offer the designer a technique for EMI suppression and an alternative to the by-pass capacitors normally mounted on the surface of the board to minimize “voltage sag” in the power being supplied to the active devices. A more complete discussion of the electrical performance will follow later.

A new technology for MLB pressing has been developed by MBT and industry partners,called TOP,Temperature Optimised Process. The goal was to reduce energy consumption and to improve product quality by quicker and more even heat distribution throughout the book. This was achieved by using new materials and direct electrical heating of the tools. Tools are made using a 3- ply-material having a core of Aluminium and both sides clad with Stainless Steel. This gives 90% of the heat conductivity of Al combined with the thermal expansion and surface hardness of rolled Stainless Steel. Each part of the tools is heated by a specially developed ultra thin heating element having a connection capacity of only 3 kW/h. Build in sensors allow each heating element to be controlled separately so that only the actually needed energy is supplied. Each opening can be controlled separately. A third heating element is placed in the middle of the book,thus actually creating 2 books in one allowing for up to 50 mm MLB material to be in each book / opening. All connections for energy and sensors
built into the tool have their matching parts in the back of the press to have direct contact when putting the tool inside the press. Depending on the structure of the panels it takes 30 – 45 minutes from cold start to reach 200° C in book centre. Another important part of TOP is our patented Separator HTS 600. Having a thickness of only 0.5 mm HTS 600 has about 4 times better heat conductivity compared to Stainless Steel. Due to quick and even heat distribution no press pads are needed. Very tight thickness tolerances are achieved by even resin flow. Cooling is done by water circulation inside the top and bottom tool either under full pressure or controlled cooling/pressure ratio. This gives unequalled stability and extremely low shrink in X and Y axis. All above has been established by test runs with a number of German Customers and assistance by ISOLA Düren.

As PCB designs become ever more complex with more sequential build up layers,tighter annular ring designs and broader range of advanced materials,understanding the effect of material distortion is critical to maintaining yields. Determining the inner layer scale factors to compensate for various material movements is also becoming increasingly difficult and with the additional constraints of the “quick turn” market there is no longer the luxury of running scale factor test batches – the first batch made must be delivered to the customer.
Latest generation drilling and imaging equipment provides the ability to automatically scale the drill program or image to match each panel manufactured. These capabilities ensure accurate registration of the relevant processes,but if scale errors have already been made on the inner layers,these errors are being followed throughout the manufacturing process and will ultimately be delivered to the end customer. To provide products of nominal dimensions to the customer,the original inner layer scale factors must be accurate and an intelligent compensation system should be used at these processes to reduce or eliminate the effect of variations upon the product received by the customer.
This paper analyses the data from a variety of product designs and constructions made at numerous facilities worldwide and demonstrates the influence of this variety upon the required scale factors. By comparing production results over two years and additional experimentation by the author,this papers shows that the variations exhibited can not be accounted for by simple look up tables and a more complex model is required to accurately predict the correct scale factors for new product designs. The paper will also outline the concept of an intelligent compensation system and how this could be applied to the manufacturing processes.

This paper discusses a new technology to improve etching performance using shiny side surface treatment on copper foil. Until now,a lot of electro-deposited copper foils (ED foil) with very low profile on matte side have been introduced to the market to obtain fine line products such as HDI. In addition to copper foil thickness,roughness of matte side is thought to be a key factor to improve etching performance. However,our new technology is quite unique and different from other methods to obtain narrow traces. Using new technology,30 micron pitch circuits could be obtained using 9 micron copper foil.

The purpose of this study is to investigate the optimum plasma processing as a pre-treatment for the surface of Polyimide (PI) in order to increase adhesion strength of electroless copper (Cu) plating to PI directly. Two kinds of oxygen (O2) plasma processing were applied and compared in the experiment to investigate the optimum plasma processing. One method was surface wave plasma (SWP) processing generated by the microwave plasma reactor with the 2450MHz microwave power source. The other processing method was reactive ion etching processing generated by the capacitively coupled plasma reactor with the 13.56MHz radio frequency (RF) power source. The processing characteristic of microwave plasma which has comparatively higher electron density than that of RF plasma is anisotropic chemical etching processing without collision of electrically-accelerated atoms to processing objects. On the other hand,the processing feature of RF plasma is isotropic processing with ion bombardment and reactive etching to processing objects. The first part of this paper described the result of the surfaces roughness formed by two types of plasma processing under various processing time. The surface roughness was evaluated by atomic force microscope (AFM) measurement. The AFM measurement showed that the surface roughness formed by the SWP processing was much smaller than the surface roughness formed by the RF plasma processing. In the second part of the paper,chemical conditions of the PI surface measured by X-ray photoelectron spectroscopy (XPS) were investigated after SWP and RF plasma treatments. The measurements of XPS showed that large number of hydroxyl groups as well as the functional groups -C=O were observed on the surface of PI treated by SWP. In the case of RF plasma treatment,hydroxyl as well as the functional groups -COO was observed on the surface of PI. The functional groups -C=O was not observed on the surface of PI treated by RF plasma. The final part of this paper focused on the relationship between peel strength of electroless Cu based on treated PI measured by T-peel test. T-Peel adhesion strength measurement proved that PI surface treated by the SWP processing was greatly improved in adhesion strength without forming surface roughness or seed layers. On the other hand,electroless Cu adhesion strength after the RF plasma treatment was comparatively weak due to forming the excess surface roughness of PI due to oxygen ion bombardment and isotropic reactive etching.