Since July 1st 2006,the 2002/95/EC RoHS European directive has forced the electronic industry to switch from Tin-Lead to lead-free soldering alloys for components assembly.
Exemption domains have been defined for highly failure sensitive applications with long service lifetimes like military and aerospace because of the lack of knowledge on long term solder joint reliability in harsh environment. Furthermore,the physical properties of lead-free solder alloys (such as SAC) greatly differ
from those of well known Tin-Lead so that well established accelerated tests can’t be replicated for lead-free to forecast lifetime. These tests are not yet defined and moreover,the statistics of failure mechanisms and rates from the field are not sufficient to manage the reliability risk for many kinds of THALES products.
However,component manufacturers have changed their package finish to comply with the RoHS directive without taking into account AHP equipment makers due to their low share in volume. As a consequence,AHP companies have to face this difficult situation: either manage the obsolescence by component storage
with the great difficulty to forecast the customer demands,or find a solution to use lead free package finishes with standard Tin-Lead alloy,particularly sensitive with all kinds of BGA.
Thales shared a cooperative and ambitious technological program with CELESTICA as a key partner in order to secure an industrial process solution called hereafter SnPb+ (mixed metal assembly).
This paper describes microstructures and thermal cycling performance of lead-free ball grid array and leaded components assembled with Sn-Pb solder using conventional SnPb reflow and reflow with temperature higher than 217°C to melt the lead-free ball and insure a full mixing (the SnPb+ process). The formation of
uniform and non-uniform microstructures as a result of Sn-Ag-Cu (SAC) solder ball dissolution in a molten Sn-Pb solder using a conventional SnPb reflow or melting is studied. The difference in mechanisms and performance of uniform fully mixed and non-uniform partially mixed joints as a response on thermal cycling
at -55°C to 125°C conditions is explored. Additional attention is paid to Sn-Bi finished QFPs and TSOPs. It is shown that Sn-Bi finish with 3 -5% Bi is not responsible for early failures if it is used with Sn-Pb solder.

Over these years,EU RoHS restriction and lead-free capability is the hottest environmental protection subject. In technology trend,signal integrity performance gets more critical upon today’s higher signal transmission speed demand in every field of applications such as computer CPU and GPU chipset levels,system operation frequency and a variety of communication bus and cable like PCI express,SATA II and AGP bus for computer system. Signal communication speed will shift from 1-5 Gbps range up to 5-10Gbps depending on applications. In order to meet lead-free ingredients and severe processes conditions with capable signal integrity performance,laminate material will play a more and more critical and sensitive role in the system.
From consumer products to high-end applications,they all need certain electrical and thermal performances; it is therefore essential to meet those requirements with cost effectiveness. As a base material supplier,we will hereby discuss material design and factors that influence signal integrity,including epoxy and hardener,resin chemical construction,laminate ply-up construction,amount of resin content,fabric weaving density,moisture pick-up and environment factors etc. for a massive mainstream application and low loss application under the hypothesis of lead-free capability.

We demonstrate here a novel CCL (Copper Clad Laminate) which exhibits an extremely low transmission loss at mm-wave band. The CCL which we developed is based on a new fluoropolymer with adhesive characteristics. In contrast to conventional PTFE,the adhesive fluoropolymer allows us to apply a wholly dry process for CCL fabrication,which contributes to environmental load reduction.
It is well known that the factor of transmission loss mainly consists of conductive loss and dielectric loss. However,in conventional CCL data sheets,only the loss tangent data at specific frequencies are disclosed. Neither the dielectric loss nor the whole transmission loss at the other frequencies is known. In order to minimize the transmission loss at mm-wave band,the quantitative analysis for those factors is essential.
We proposed the evaluation method which can clarify not only the dielectric loss but also the conductive loss of CCL up to 110GHz. Several transmission lines with different impedance were measured and analyzed; the two different losses were discriminated in straight forward manner. Besides the evaluation method,a highly accurate measurement technique for low loss transmission line was achieved.
Using several kinds of surface roughness of copper foil,we made CCL test samples and evaluated the transmission loss by the above-mentioned method. Since the results indicated that the surface roughness of copper foil remarkably influenced the transmission loss,profile free copper foil was used for developed CCL. Due to the adhesive characteristics of new fluoropolymer,enough peeling strength was obtained without extra surface treatment.
Finally we benchmarked our developed CCL to the Rogers RT/duroid 5880,world lowest loss characteristics,and the result showed improved loss characteristics compared to RT/duroid 5880.

The peel test will be reviewed,with special attention given to deposited adhesiveless copperclad laminates. A basic familiarity with the IPC test method will be assumed. The brief amount of time allotted permits focus on two general topics.
First,data will be presented to illustrate the influence of a number of variables on peel strength values,such as conductor thickness,conductor width,and copper treatment,as well as more subtle things such as surface finish and even simple choice of test method.
Second,a detailed comparison of adhesion performance between deposited materials and their cast and laminated cousins will be provided as well.

The Semiconductor industry is demanding more and more from today’s PWB manufacturers. This paper offers some insights to the needs,requirements,solutions and process verifications that R&D Circuits has spent years analyzing and perfecting for its customers in the industry.
The industry in question is known as the A.T.E. or Semiconductor test industry. The need is to electrically test or characterize a packaged device,prior to it being shipped to OEM’s for use in their electronic devices. The package size continues to decrease,while the test regimen gets tougher and tougher. The fine pitch of devices is pushing PWB manufacturing to the far limits of capability. Six mil diameter holes drilled and plated in 0.187 thick panels (30+:1 aspect ratios) is truly on the edge of that manufacturing capability.
New techniques in drilling holes,prepping them for the subsequent plating processes,of which DRPP has proven to be a crucial step for us,and finally solid verification of those steps is a fundamental requirement for any PWB manufacturer,looking to build PWB’s for this demanding industry.
Data is provided to validate the process techniques,utilizing the IST test methods,simply show that while the attributes are not those you would see in traditional PWB’s,reliable and repeatable A.T.E. boards can be produced.

The use of an insoluble anode in place of standard copper anodes (slab or titanium baskets filled with copper) improves the quality of plating,increases the productivity of the plating line,reduces cost and reduces waste.
The insoluble anode is used extensively in conveyorized acid copper plating equipment; however its use in standard acid copper plating tanks had a series of false starts that slowed its acceptance in the industry. Very high consumption of additives was the foremost reason that most attempts were abandoned. Difficulties in copper replenishment were also among the reasons why the system did not take off as expected.
This paper will highlight the advantages that the use of an insoluble anode brings to acid copper plating of PWB’s. It will report on how the consumption of additives was understood and contained. It will discuss replenishment methods that are both economical and implementable.
The paper will present the data from the implementation of insoluble anode at Electrotek Corporation. The data will show the quality and productivity improvements,as well as cost and waste reduction in acid copper plating.

As early as 2001,leading cellular phone manufacturers had established stable assembly processes that were RoHS compliant for their cellular phone products. Since this time,the products manufactured on these lines have demonstrated equal or better quality and reliability as compared to cellular phones assembled with tin-lead solder and non-RoHS compliant components. This success may have created the belief that there are few issues remaining in RoHS compliant assembly. This belief is far from the truth. Organizations that need to assemble a wide range of large,thick printed wiring boards (PWBs) continue to have considerable process challenges. These difficulties – combined with the need to assemble RoHS 5 (tin-lead solder paste and components with tin-lead finished leads,the remaining hardware being RoHS compliant),RoHS 5.5 (RoHS 5 with BGAs that have SAC or SACX solder balls) and RoHS 6 (fully compliant RoHS assembly) in one facility – create not only assembly technical challenges,but considerable material handling and logistics issues.
This paper is a review of the work done at one facility,to address these challenges. An overview of the process development work in stencil printing,component placement and reflow soldering that was required to develop optimized assembly processes for PWBs with dimensions exceeding 56 cm and thicknesses approaching 0.3 cm will be discussed. The methods developed to handle the logistics issues of having RoHS 5,RoHS 5.5 and RoHS 6 assembly in one facility will also be presented.
The paper will conclude with a review of several of the products currently being assembled with these processes and logistics.

This paper presents lead-free ball grid array (BGA) packages subjected to two ball removal and two ball attachment techniques. Solder attach strength is used as a metric to examine the reballing process. The impact of isothermal aging is also examined. In this study,lead-free (SAC305) 676 IO and 256 IO BGAs were reballed with eutectic tin-lead solder spheres. Two solder ball removal processes and two ball re-attachment processes were examined. For the 676 IO BGAs,the solder wick and low temperature solder wave removal process were examined. Ball re-attachment for this part was conducted with the perform method. For the 256 IO BGA,the low temperature solder wave removal process was applied followed by either perform or ball drop re-attach methods. Ball shear and the cold bump test results do not show a correlation with the reballing process. Further,isothermal aging does not appear to greatly influence the interconnect strength of tin-lead solder. Non-reballed lead-free solder balls were found to have greater strength and a wider strength distribution as compared to the reballed tin-lead solder samples. For the cold bump test,an increase in pull speed correlated to an increase in solder pull strength.

The recent use of lead free alloys has made the wave solder process more challenging in terms of achieving acceptable solder joints for both SMT and PTH components. It has been found that the Design for Manufacturability (DFM) guidelines,which were established for tin lead processes,in many cases do not result in the same level of quality joints when soldering with lead free alloy. Therefore,in order to improve the process yields and reduce manufacturing costs when converting to lead free,it is essential to establish DFM guidelines specifically for lead free soldering. The effect of pin to hole ratio,quantity of large copper planes connected to a pin through hole barrel,connection types for PTH and land patterns for glue and wave chip components are some of the main features which require further investigation for design optimization.
As there are a variety of lead free alloys available on the market today,each with differing properties,it is also important to determine if a set of DFM guidelines result in similar results among these various alloys.
This paper will discuss the outcome of a study of several DFM features incorporated on an internally designed test vehicle,which was created to evaluate alternative lead free alloys for Celestica. The DFM features included land pattern design and varying component spacing for chip components,pin to hole ratio and its interaction with the quantity of large copper planes connected to a PTH,quantity of large copper planes connected to a PTH and its interaction with the type of connection either solid or four spokes. The test vehicle was assembled with four Pb-free alloys (Sn-Cu-Ni,Sn-Ag-Cu-Bi,Sn-Cu-X & SAC405) and 63Sn-37Pb alloy as a baseline. The quality level of each of the described DFM features will be discussed. In addition to this,a detailed barrel fill analysis for the PTH components will be shown.

Over 3 years ago,Zestron initially addressed cleaning underneath 4 MIL standoff components. With the emergence of lead-free and even smaller components new challenges have now arisen to include components with less than 1MIL gaps.
This study set out to specifically investigate the impact of mechanical vs. chemical contributions during the removal of contamination under 1-2 MIL standoff components,respectively. To validate the results obtained,extensive studies were conducted,including actual user case-studies,specifically prepared test-assemblies,iterative experimentation,as well as new mechanical innovations that might help customers in future. The latter include but are not limited to various flow patterns as well as industry leading cleaning agents. As a result the authors will also include experimental data to address fluid flow mechanics,temperature and concentration related effects.
Initial results obtained indicate that clean-ability of residues under low standoff components has become a non-trivial issue. Not only are residues becoming harder to remove,but at the same token the penetration of the cleaning agent seems to be in direct relationship with the geometry and height of the components used. We will also illustrate surprising and unexpected results. For example,under specific conditions cleaning results under 1-2 MIL standoffs provided better cleanliness than under 4-5MIL standoffs!