This paper explores the behaviour of a copper test vehicle with multiple reflowed solder joints,which has direct relevance to ball grid arrays (BGA) and high density interconnect structures. The paper explores the relative stress conditions on the distributed joints and the sensitivity to ball joint shape. The joints were exposed to isothermal fatigue,which was produced by a mechanical load that induced a cyclic shear stress across all the joints. The same structures were modelled using finite element analysis. The loading response distribution profile through the joints was analysed. The regions of likely failure were identified to be along the shear band and at the stress concentration areas in the corners of the joints. Failure of the individual joints was analysed by quantifying the accumulated creep strain per cycle. Solder joint models of three different shapes were investigated: rectangular,convex and concave shapes. This analysis has shown that less damage is found in concave shaped joints,indicating that BGAs would have more damage than the rectangular joints tested here. Results have also shown that more damage occurs in the outer joints as a vertical component appears due to a turning moment on the copper test vehicle. This behaviour could affect the external joints of large components,where the same vertical stress component may arise due to the differential CTE of the PCB and BGA component.

Board-level drop test performance was evaluated and compared for the following four different solder combinations in
BGA/CSP assembly: 1) SnPb paste with SnPb balls,2) SnPb paste with SAC105Ti balls,3) SAC305 paste with SAC105Ti
balls,and 4) SAC305 paste with SAC105 balls. The presence of Ti improved the drop test performance significantly,despite
the voiding side effect caused by its oxidation tendency. It is anticipated that the voiding can be prevented with the
development of a more oxidation resistant flux. The consistently poor drop test performance of 105Ti/SnPb is caused by the
wide pasty range resulting from mixing SAC105Ti with Sn63 solder paste. The effect of Ti in this system is overshadowed
by the high voiding outcome due to this wide pasty range material. In view of this,the use of a SAC105 BGA with an SnPb
solder paste is not recommended,with or without the Ti addition. High reflow temperatures drove the fracture to shift to the
interface at the package side,presumably through building up the IMC thickness beyond the threshold value. A lower reflow
temperature is recommended. The electrical response is consistent with the complete fracture data,but the complete fracture
trend is inconsistent with that of the partial fracture trend,and neither data can provide a full understanding about the failure
mode. By integrating the complete fracture and the partial fracture into a “Virtual Fracture”,the failure mechanism becomes
obvious and data sets become consistent with each other.

Developing low-cost alternatives to near-eutectic SAC alloys for Pb-free assembly is crucial to continue producing affordable electronics products. Metals prices,especially silver,have been on the rise,and will likely stay at their near historic high levels. Solder alloys with lower silver content have been considered,with trade-offs in performance,but are there alternatives?
There are many reasons to consider alternative Pb-free alloys to SAC305. Several new alloys have been recently introduced,while others,which had little popularity in the past,are showing more potential due to changes in the industry. The question is: how much do subtle variations in alloy composition affect the performance and process requirements of PCB assembly? This paper will compare some of these alloys side-by-side and discuss whether existing processes need to be modified for alternative alloys.

In response to a growing concern within the Electronic Industry to the transition to Halogen-Free laminates (HFR-Free)
within the Client Market space (Desktop and Notebook computers) iNEMI initiated a HFR-Free Leadership Workgroup to
evaluate the readiness of the Industry to make this transition. The HFR-Free Leadership WG concluded that the electronic
industry is ready for the transition and that the key electrical and thermo-mechanical properties of the new HFR-Free
laminates can meet the required criteria. The HFR-Free Leadership WG verified that the laminate suppliers can meet the
capacity demands for these new HFR-Free laminates and developed a “Test Suite Methodology” (TSM) that can facilitate the
comparison and choice of the right laminate to replace brominated FR4 in the Client space.

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Recent environmental concerns over the safety of the halogenated flame retardants (HFR) used in commonplace FR4 printed
circuit boards (PCB) have prompted market demand for HFR-free computer systems. Unfortunately,the critical electrical
properties of most HFR-free dielectrics on the market in 2009 made high-speed bus designs such as DDR3 & PCIe3
problematic without increasing the cost of the system. The iNEMI HFR-Free Signal Integrity Working Group was
established in early 2009 with membership from 16 OEM,ODM and laminate supplier companies to address these industry
concerns. This effort has helped pave the way for member companies to produce “green” HFR-free product lines by: 1)
Uniting a large portion of the industry on the problems associated with high-speed bus design on HFR-free PCB’s,2)
Defining a common approach to mitigate the signal integrity challenges and 3) Communicating a unified set of desired
electrical properties to the major laminate manufacturers to produce higher volumes and lower cost HFR-free dielectric
materials suitable for high-speed bus design.

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The market for high-layer-count printed circuit boards (PCB) containing blind and buried vias was once relatively small,and
focused on specialized applications in the military and high end computing. The demand for these types of PCBs today is being driven by an increasing number of commercial applications in the telecommunications and semiconductor test market segments. These applications typically require high-aspect-ratio plated-through-holes (PTHs) and blind and buried vias in order to meet the applications interconnect density requirements. Blind and buried vias and high aspect ratio PTHs continue to present manufacturing challenges and frequently are the limiting features to achieving high fabrication yield. Multiple lamination cycles,the indeterminate yield of sub-cores,backdrilling and extended plating times add to the overall poor yield of high layer count PCBs. An attractive solution to the high-aspect-ratio PTH dilemma is to break the high-layer-count PCB into a number of subassemblies that can be 100% inspected and then be interconnected. Conductive paste-based interconnects are an attractive interconnect technology option,but passively loaded copper or silver filled pastes do not demonstrate the requisite performance and reliability. Sintering conductive pastes,which metallurgically bond directly to the copper pads of the PCB during a standard lamination cycle,do meet the requirements of these high-layer-count PCBs and at substantially lower cost than conventional manufacturing methods.

This paper presents systematic investigations on complete Through Hole filling for cores by a Cu electroplating process as an alternative to the common paste plugging process. This electro plating process consists of two steps,a first process to merge both centers of the through hole walls (X- plating) followed by filling up the resulting Blind Micro Vias. Processes and manufacturing technology are described as well as current limitations and requirements. Complete filling of through holes is achieved by Reversed Pulse Plating,RPP. This Through Hole filling technology is targeting both at HDI production and also at the packaging level.
Through Hole filling by RPP offers a viable alternative to the standard paste plugging for core processing in substrate manufacturing. Current core manufacturing requires a paste plugging process for through holes so that subsequent build up layers can be produced by sequential lamination,the flat core surface is essential for stacked via and also via in pad technology.
This paste plugging process requires additional process steps,each of which has its own limitations and contributes to the overall cost. Filling the core through vias by electroplating can eliminate the plugging process and significantly reduces the number of overall process steps which will also reduce costs. Moreover,it offers certain advantages such as potentially higher reliability in accelerated aging tests and an improved thermal management as the thermal conductivity of a completely copper filled through via is significantly higher than a paste plugged through via.
Today’s challenges in the so called Through Hole Filling process are represented by through holes with a high aspect ratio. Voids after X-Plating occur easily for smaller through hole diameter and higher board thickness. In addition,depending on designs,different pitches on one board increase the difficulty to achieve an acceptable plating uniformity. This paper presents systemic variations of some key parameters and concentrates on the performances of the second plating step,the blind micro vias filling. Main focus is laid on recess distribution. Parameters as reverse pulse parameters,inorganic concentrations (Cu,Fe,and sulfuric acid),organic concentrations,electrolyte flow and temperature have been systematically varied and their influence on the filling performance are described.

Miniaturization and increased functionality demands of electronics have substantially decreased the sizes of electronic features that need to be plated. The circuit density of printed circuit designs has been increasing accordingly. Copper is the most preferable metal used in electronic industry for filling small features due to its electrical and thermal conductivity properties and the possibility of electroplating. New technologies started to develop in order to completely fill through vias in build-up core layers in HDI and IC with solid copper. This has been associated with improved thermal and mechanical properties as well as with increased reliability. In this paper the effect of the chemical composition and the processing parameters on the hole filling characteristics of copper electroplating has been studied. It was established that a preliminary treatment in a chemical solution was the most significant factor for void free filling of blind micro vias. Copper concentration was also significant factor,while the leveler concentration was only significant in some cases. The brightener concentration was not a significant factor for the responses tested,which included the fill ratio,dimple,planarization,and surface copper thickness. The optimum conditions of a DC process for filling up a wide range of via sizes and plating simultaneously though holes were determined. The results obtained allow for enhancing via plating capabilities and increasing the reliability. The second part of this paper shows a novel process for filling through vias in core layers up to 400 mkm thick. This process includes two subsequent steps,being PPR or DC plating depending on the substrate thickness and hole diameters. The through vias were completely filled by using a modified process for acid copper electroplating. The chemical and plating parameters are discussed in the paper. Data enclosed demonstrate through vias in build-up core filled without any voids and defects. This innovative technology is at an early stage being at the process of further optimization to enable a variety of HDI and IC substrate package designs.