An accelerated thermal cycle experiment comparing similarly constructed area array devices representing Land Grid Array
(LGA) and Ball Grid Array (BGA) technology with 0.254,0.30,and 0.40mm diameter SAC305 solder balls was performed. The devices were subjected to three thermal cycle conditions in order to promote 2nd level solder fatigue. Failure data was compared using Weibull analyses. The results show that time to failure is highly influenced by the package pitch and thermal cycle temperatures in a manner predicted by simple mechanics. However,there were instances in which the effect of solder ball size did not fit the traditional solder joint reliability model in which increasing solder joint standoff height improves reliability (i.e. more cycles to failure). A theory is proposed that substantial differences in SAC305 solder joint Sn grain morphology may explain,at least partially,the discrepancies and evidence to support this theory is presented.

Based on the trend for new technology in the automotive market including high power modules for e-mobility,and a combination of logic and power which will be developed for the future market with economic,safety and reliability effects. One of the most important challenges are electrical systems and the realization of complete energy management. The connection between sensor,logic and control units,as well as power transmission for electrical vehicles,is the assembling technology for electronics (eAVT). This paper will discuss and show results of reliability with soft soldering alloys (based on lead free) for higher temperature (>125°C - 175°C) as well as possibilities for different applications. Therefore,it will present the basis of the material and the realization for processes for the e.AVT. Furthermore alternatives and development stages for temperature more than 200°C will be discussed.

Lead Free Technology has brought new materials and different quality concerns to the Electronics Industry. For that,the creation of new methods to determine the quality of materials is needed and preferred. Intermetallic compounds for example can grow faster in lead-free metallization and decrease the possibility to form good joints. For that,a new method to measure IMC layer thickness is presented. This new method uses a combination of X-Ray Fluorescence Method (XRFM) and Coulometric Stripping Method (CSM). XRFM is capable to measure percentage of elements and correlate the values to their layer thickness. This procedure makes XRFM not so suitable to measure intermetallic thickness when it is growing because the elements only combine each other and are not removed; therefore XRFM gives similar values in thin metallization layers of tin-copper with thick or thin IMC layer,for example. On the other hand,CSM removes pure element layer using an electrochemical depletion. The combination of both methods allows evaluating the IMC layer thickness in a more precise form. For validation of the method,SEM/EDX and Auger microanalyses were made to compare values. Besides,several experiments were carried over in several temperatures and reflow profiles to measure IMC growth in Chemical Tin PCB’s. The results were used to develop a more precise equation to predict the IMC growing. The new equation uses the Activation Energy depending on the IMC thickness.

•Transition to Pb-free soldering is incomplete for high reliability or high temperature applications
•For those not fully converted into Pb-free,mixed system is common due to lack of some Pb-containing components
•Mixed system encountered voiding problem,particularly for BGA applications
•Miniaturization aggravate vulnerability of device toward voiding
•Unravel voiding mechanism of mixed system critical for DFR for solder joints

Conclusions:
•Tin/Lead BGAs: The location of the void within the solder joint was the primary root cause for the loss of solder joint integrity.
•Lead-free BGAs: The statistical analysis and the metallographic cross-sectional analysis results revealed that the presence or size of the solder joint voids did not correlate to the loss of lead-free solder joint integrity.
•A single set of BGA solder joint void process control limits is applicable for both tin/lead and lead-free BGA solder joints

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- Nanosolder on multi-segment nanowires have been successfully fabricated by electrodeposition method;
- Flux assisted environment enhanced reflow result and micron scale solder spheroids formed on non-wetting Si substrate;
- Nanosolder reflow performance on reactive Cu substrate was studied;
- 1-D interdiffusion on Cu-Sn two-segment nanowire were observed through the thermal heating and e-beam irradiation;
- Nanojoints formed between nanowires and a network was constructed through quasi-reflow process in liquid.

•What is a halogen?
•Impact on the environment
•Halides and halogens
•Halides in electronics
•Halogens in electronics
•Definition of halogen free
•Technical challenges to remove halogen
•Current ‘State of the Art’

There has been a rapid increase in the use of selective soldering equipment for PCB assembly
–Lower equipment costs
–Smaller equipment footprint
–Lower solder “inventory” cost (smaller pots)
–Decrease use of through hole devices
–Some technical challenges
•Tighter component spacing
•More complex board designs
•Increased desire to control flux spread
The selective soldering process is much different than wave soldering so there are different liquid flux considerations

Looking back twenty-five years ago,the solder pastes residues had to be cleaned after reflow due to their corrosive nature: two ways of cleaning were possible,either with solvent or by using water,with or without detergent. Now the assembly world is mainly no-clean: paste formulation is safer in terms of chemical reliability and process costs are reduced without cleaning. However,some applications,i.e. military,aerospace,high frequency,semiconductor require a perfect elimination of the residue after reflow. There are several options to achieve this result: the use of a no-clean paste which residue can be removed with the most suitable cleaning method or the use of a paste designed to be cleaned,as a water-soluble solder paste.
The water-soluble solder pastes generally show great wettability because of their strong activation but they are also known to have shorter stencil life and to be more sensitive to working conditions as temperature and humidity,compared to the no-clean pastes. Additionally,with the components stand-off getting smaller and smaller,washing residues with water only is more and more challenging due to its high surface tension: the addition of detergent becomes often necessary.
The purpose of this paper is to highlight the differences between these two families of solder pastes to guide users in their choice. This will be achieved through the comparison of several recent water-soluble and no-clean formulations as far as reliability is concerned. First the printing quality will be evaluated (viscosity,tack,cold slump,printing speed according to pressure,stencil life,idle time,printing consistency). Then the reflow properties will be compared (hot slump,solderballing,reflow process window,wetting ability on different finishes). Finally the residue cleanability will be assessed. The IPC SIR test (method IPC TM 650 2.6.3.7) will be also done to conclude the study. Both standardized tests and production tests will be used to evaluate the performance of these two kinds of solder pastes.