The data from the IPC Alternate Finishes Task Group Report “Time,Temperature and Humidity Stress for Final Finish Board Solderability” has been analyzed in a greater depth than in the actual report or a subsequent paper. Thermodynamically-based equations have been developed that are a better fit for the data than the intuitive ordering of the data in the report. Equations for the solderability results for the immersion silver,immersion tin,reflowed tin/lead,OSP and ENIG and the bare copper finishes studied in the IPC report are included here.

Organic Solderability Preservatives (OSP) continue to attract significant attention as circuit board final finishes. They have evolved from simple and thin benzotriazole coatings to thicker and more complex substituted imidazole and benzimidazole based films. The driver for these changes is the demand for better protection of the copper surface,which is strengthened further by the harsh demands of Pb-free processing. Better protection of the copper surface is effected by a more thermally robust active ingredient: the organic compound. The thermal properties of the organic compound,though,are not the only
characteristic of a good OSP coating. This paper attempts to describe the structure and composition of the organic film as well as the influence of the OSP coating process on achieving optimum performance in a Pb-free environment.

This paper analyzes the differences in plated through hole fill performance between the regular OSP and Pb-free OSP PCB surface finish chemistries in a Pb-free wave solder process. The variables studied include two board thicknesses - 93mil and 125mil,three hole sizes - pin plus 16,24 and 40mils,internal Cu layer connections - single and three plane layer connections,two pin shapes - circular and rectangular and two reflow atmospheric preconditions - Nitrogen and Air. A SnPb control was included for the 93mil thick test board. The bare PCBs were initially subjected to 220oC and 240oC peak reflow process twice for the SnPb and Pb-free wave soldering samples,respectively. This was followed by a wash process before wave soldering.
The Pb-free wave soldering results indicated that the Pb-free OSP performed better than the regular OSP chemistry by 15% under air and 40% under nitrogen reflow preconditioning. In Pb-free wave soldering,the air preconditioning resulted in better hole fill than nitrogen. Board to board variation of hole fill was much lower in the Pb-free OSP chemistry compared to regular OSP. Plated through hole size of 40mils and 16mils,larger than the pin diameter proved to be best and worst designs for the 125mil PCB,respectively. The SnPb control almost had greater than 92% average hole fill for every design variable in this experiment.
Overall,the results indicated that the regular OSP chemistry in Pb-free wave soldering failed to meet the 50% hole fill required per IPC-A-610,for all the conditions studied. The 125mil thick PCB using Pb-free OSP chemistry also failed to meet the IPC requirements for all the conditions evaluated. However,the 93mil thick PCB using Pb-free OSP chemistry was able to meet this 50% hole fill requirement(although not meeting the general 75% minimum requirement),except when the hole diameter is 16mils larger than the pin.

While glass fibers are commonly used to reinforce circuit board substrates,they have a high dielectric constant and loss. Cyclic olefin copolymer fibers have a lower dielectric constant and loss. By combining these fibers with glass fibers in
unique hybrid cloths,we have made circuit board substrate materials with a dielectric constant of 3.08 and loss of 0.013 using standard epoxy resins that are common in FR-4 glass reinforced substrates. The comparative glass materials had a dielectric constant of 4.49 and loss of 0.019. Substrates made from this fiber have passed Peel Strength,Solder Float,Water Uptake,and have a low coefficient of thermal expansion.

A new bifunctional low molecular weight polyphenylene ether (OPE oligophenylene ether) was obtained by the oxidative coupling of 2,2’,3,3’,5,5’-hexamethyl-[1,1’-biphenyl]-4,4’-diol (HMBP hexamethylbiphenol) and 2,6-dimethylphenol,and several thermosetting resins were synthesized from OPE by changing the end hydroxyl group into other reactive functional groups such as glycidyl ether group(OPE-2Gly) and vinylbenzyl ether group(OPE-2ST). These thermosetting resins keep such superior characteristics of high molecular weight polyphenylene ether(PPE) as low dielectric constant(Dk),low dielectric dissipation factor(Df),high glass transition temperature(Tg) and low water absorption rate,while formability in press and low solubility in organic solvents are desirably to be improved. A cured product of OPE-2ST had Tg :220°C(DMA),Dk(10GHz):2.46,Df(10GHz):0.0020. A curable resin composition containing OPE-2ST and
thermoplastic elastomer such as styrene-butadiene-styrene copolymer (SBS) and hydrogenated styrene-butadiene-styrene copolymer (SEBS) was able to form a curable film by solution casting method. Cured film obtained with aforementioned curable one containing OPE-2ST and SEBS kept high Tg of OPE-2ST because of micro phase separation. Characteristics of the film were Tg:200°C (TMA),Dk (10GHz) :2.29,Df(10GHz) :0.0011. The Df value of this film was close to that of polytetrafluoroethylene (PTFE). These resins are accordingly suitable for printed wiring board (PWB) base materials in
high-speed communication or telecommunication applications.

Increasing operating frequency of IO busses for computing has highlighted the importance of transmission line loss. For FR4 PCB mother boards computing at speeds above 1 GHz this is dominated by dielectric losses. FR4 dielectrics are epoxy based materials which absorb moisture and are subject to dielectric loss variation due to absorption of ambient moisture. Resonator measurements of the substrate alone are useful for modeling but they do not take into account PCB design variables that influence absorption rates. Transmission line loss data and analysis obtained from two PCB designs subjected to a program of drying and moisture absorption are presented. A model to predict absorption rates and transmission line loss is presented. FR4 materials will be compared and contrasted with a low-loss substrate material.

With the enactment of the European Union (EU) ROHS Directive 2002/95/EC (Ref.1),certain electrical and electronic products that are manufactured in or exported to the European Union have restrictions on the use of Lead,Mercury,
Cadmium,Hexavalent Chromium,Polybrominated Biphenyl (PBB) and Polybrominated Diphenyl Ethers (PBDE).
EDXRF (Energy Dispersive X-ray Fluorescence) is one of the methods that can be used for screening of RoHS materials. EDXRF has the advantage of simple or no sample preparation as well as being non-destructive with a relatively short testing
time. However,it has disadvantages such as matrix interference combined with the fact that for most electronic devices,it is difficult or impossible to perform the analysis on homogeneous areas without overlapping other materials on the device. Thus the ‘screening’ results need to be carefully analyzed or verified.
This paper describes the work done on the testing of European Union ROHS 5 of 6 (lead in solder exemption) and ROHS 6 of 6 components and solders with EDXRF equipment (both desktop and handheld). It identifies the various uses and
constraints of EDXRF equipment.

RoHS directives require screening and quantification of certain elements and compounds used in electronics components and parts.
X-ray Fluorescence (XRF) technology has emerged as an effective tool in the screening process of electronic components.
XRF analyzers,bench top and portable,can determine the presence of concerned elements,but not compounds,in a relatively short period of time.
XRF technology is an established analytical method for elemental analyses. However,there are certain technical aspects that directly impact the RoHS application that may require further understanding of XRF principles. The quantitative determination of elements for compliance with RoHS directives could be compromised under certain conditions if the fundamental principles of XRF technology are not well understood and adhered to for this application.
The most influencing factor in XRF application for RoHS compliance is the ability of an XRF system to excite and induce characteristic x-rays of concerned elements without any interference that may result in either false negative or a false positive indication. Any false indication causes operational difficulties and has financial consequences. This factor is more pronounced in electronic components which are often composed of complex matrices and contain elements that could interfere directly with the characteristic x-rays of RoHS-concerned elements.
This paper provides an overview of XRF technology as it is applied to electronic components,the effectiveness and limitations of XRF methods as a screening,and the contributing factors in obtaining accurate measurements.

Environmental compliance is becoming a global effort in the electrical and electronics industry. The Directive on “Restriction of Hazardous Substances” (RoHS) in Europe,is forcing the electronics industry to develop methods for analytical testing of its components and products for regulated substances. The use of lead (Pb),mercury (Hg),cadmium (Cd),hexavalent chromium (Cr VI),and some types of brominated flame retardants (like polybrominated biphenyls,PBB,polybrominated diphenyl ethers,PBDE) in products is being regulated. The industry is convinced of the importance to fulfill this requirement and has looked for confident testing methods to guarantee that banned substances contained in their products are within permitted limits. One of the more suitable analytical methods for the industry to screen and quantify the banned substances is
the Energy Dispersive X-Ray Fluorescence (XRF) because of its nondestructive,fast and result-efficient way of analysis. Analytical techniques are required to make accurate assessments. The purpose of this paper is to discuss how we evaluated the performance of XRF analytical equipment for RoHS application for the five XRF systems including Desktop and Handheld equipment. We use standard samples and production samples for the experiments:
There were four items studied with standard samples with 10,775 readings:
1. Cpk studies with 12 standard samples including PE,PVC,aluminum alloy,brass alloy,and solder alloy types.
2. Gage reproducibility & repeatability.
3. Stability test (five readings/day,and 10 days data collections).
4. Detection level versus acquisition time.
After testing numerous samples,we selected 11 samples with RoHS compliant,non-compliant,and inconclusive compositions to send to two outsourced laboratories. We studied the correlations between XRF and two test laboratories.
With this study,we are confident in the individual XRF capabilities and accurate test levels,capabilities and accurate test levels the individual XRF have. The results provided a good reference for us to review the production sample test results with XRF. The analytical methods will be discussed in the paper.

A perplexing challenge for RoHS compliance is adapting large,complex and thick,high-layer count multilayers to lead-free assembly. These are typically dense,complex assemblies with large BGAs and significant heat spreading features integrated into the design. Fine-pitch packages (QFPs and BGAs) and increasing pin count of packages further complicates the conversion to RoHS.
To provide RoHS robustness to an assembled multilayer that has a very high heat-sinking characteristic requires that the total layers be reduced,as well as its overall thickness. But how can this be accomplished? The answer is to increase signal routings per layer by 2X to 4X,and thus reduce overall signal layers and their referenced plane layers. The other new design feature is to change ‘topology’ so that a majority of vias are now ‘blind vias’,thus freeing up innerlayer space for this to be accomplished. HDI is the interconnect technology that has been developed to respond to these needs. Microvias are the principal feature of HDI,along with thinner dielectrics and smaller traces and spaces. The important feature is the “Design For Lower Layers Using HDI”. This paper covers the major design solutions from HDI that allows designers to implement fewer layers in a multilayer:
• Reduction in layer count for thickness control and RoHS compliance (Lead-Free Assembly)
• How to integrate high-I/O and fine-pitch devices without adding layers
• How to achieve higher component density and component I/Os without adding layers The resulting new multilayers are not only thinner and easier to design but are less expensive and suitable for lead-free
assembly. The resulting new multilayers are not only thinner,cheaper,and easier to design but are less costly and suitable for lead-free assembly.