Research Proposals

This page contains new proposals for Membership review. Proposals are formatted in accordance with the NEW PROJECT PROPOSAL process.

New Project Proposal Process
TB2013 Design Overview

Author: Micheal Meilunas
As part of many of our studies for 2013 a new Test Board has been designed to provide test vehicles for surface finishes, underfills, conformal coating, etc. For this reason we have prepared a short report describing the various coupons on the test board. The Gerber files for this board can be downloaded at the following link.

MAT1A: 2013 Underfill Studies

Author: Pericles Kondos
Universal instruments will study a limited number of new materials, the exact number and nature to be decided based on expressed members’ interests. The evaluation will include:

  • Flow characteristics (including ease of dispensing)
  • Compatibility with no-clean flux residues (wetting, voids etc.) from fluxes either directly applied (e.g. by dipping) or as part of solder paste and for various pad finishes (e.g. ENEPIG, lead-free HASL, OSP (ENTEK OM), Pallaguard).
  • Reliability in thermal cycling

The specifics and the exact type of tests will depend on the type of underfill material – for example, no-flow underfills act themselves as fluxes, therefore compatibility with assembly flux residues is not an issue. Reworkable underfills will be included in the study list if enough interest is expressed by members.

MAT2B: Effect of Aging on Reliability of Packages in Thermal Cycling Test

Author: Babak Arfaei
Evaluate degradation in product life due to aging. The degradation of board, component and assembly due to aging and resulting effect on the thermal cycling reliability test will be examined separately. The goal is to better understand the failure mechanism and parameters affecting it, such as precipitate coarsening and recrystallization, in thermal cycling test and correlate it with stiffness of assembly. The resulting knowledge will help to come up with more accurate damage function that can predict the fatigue life time of packages.

MAT3A: 2013 Pad Finishes Proposal

Author: Pericles Kondos
There are many surface finishes available in the electronics industry, some of them older, some newer, and all differing in properties, solderability, performance and cost. Even ignoring the last factor (as if one could), which finish is “the best” depends on the particular application and requirements, as each has some advantages and some disadvantages compared to the others. The AREA Consortium has used most if not all of common finishes in past projects and is familiar with their characteristics. The proposed project will aim at a systematic comparison among several newer finishes of interest by using boards otherwise identical but with different finishes. The boards will contain several components of various types each, as well as areas design for other tests, e.g. wetting balance testing (J-STD-003) and resistance to corrosion (flowers of sulfur testing). The finishes to be tested will include most or all of ENEPIG, lead-free HASL, OSP (ENTEK OM), Pallaguard, but others of interest to the Consortium’s members could be added, depending on availability and cost.

MAT4A: Component Leveling Characterization of Gap Pad Materials

Author: Harry Schoeller
This study seeks to build upon the consortium’s knowledge base leveraging previous studies to characterize ten thermal interface materials using a Thermal Test Vehicle (TTV) provided by a consortium member. The thermal performance will be measured after heat sink assembly. A specially designed fixture will apply a uniform load across the TIM interface to measure thermal resistance as a function of pressure. Reliability of gap pads will be tested by measuring the thermal performance after thermal cycling and after aging. The fixture was constructed such that pressure can be applied during thermal cycling and aging. Results garnered from this work will provide a component level test methodology for determining the thermal resistance of gap pad materials as a function of pressure.

MAT6A: Effect of Surface Finish on the Reliability of HMP Passive Interconnects

Author: Harry Schoeller
92.5Pb-5Sn-2.5Ag solder is widely used in high temperature electronics. However there are many options for component surface finish, which not only change the composition of the interfacial IMC, but of the solder joint itself. Previous studies have shown both IMC and solder microstructure play an important role in determining the mechanical behavior of the solder joint. Further, in high temperature environments, solder joints can experience excessive interfacial IMC growth limiting the reliability of the solder joint. To date, there are no published studies looking at the effect of component surface finish on the reliability of HMP solder joints.

MAT6C: Second Level Process Development and Material Evaluation for HMP

Author: Harry Schoeller
92.5Pb-5Sn-2.5Ag solder is widely used in high temperature electronics. There are many options for component finish which not only change the composition of the interfacial IMC, but of the solder joint itself. One popular finish for downhole electronics is Sn. During reflow Sn dissolves into the solder changing the composition of the resultant joint. Previous consortium research has shown Sn from the component surface finish can drastically reduce the liquidus temperature of the alloy and change the microstructure and IMC growth kinetics. This study seeks to build upon previous work by measuring the strength and reliability of HMP joints with varying Sn concentrations.

MAT7A: New Lead-Free Solder Alloy Evaluations & Microstructure

Author: Babak Arfaei
There have been lots of efforts to find more suitable alloys to replace SAC 105 and SAC 305, which have currently extensively been used in electronic industry. Generally high Ag solder alloys show better thermal fatigue performance, and lower Ag content alloys seem to outperform in the high strain rate tests such as drop and vibration. However, Ag is an expensive element and there is a general tendency to replace it with lower/no Ag alloys. The failure mechanism in low strain rate tests such as thermal fatigue is very different than in high strain rate tests. The reason is that Sn based solder alloys are very strain rate sensitive, which means that at low strain rates the solder is weaker than IMC at the interface; thus, failure in thermal fatigue tests usually happens in the bulk solder. Our previous results and published data in the literature show that crack propagation occurs in intergranually across the network of newly formed grain i.e. recrystallized region. However, in the high strain rate tests such as drop and vibration, the solder becomes harder than the IMC and thus the failure mostly occurs in the intermetallic compounds at the interface. The above argument clearly shows that by modifying different aspects of microstructure, it is possible to improve the life time of the product. For example, some published data by our member company showed that addition of Mn and Ti can change the thickness and morphology of IMCs and improve the drop test performance of package. Our previous works have also shown that the size of solder balls and small addition of various elements from under bump metallization layers can alter the solidification temperature and results in different Sn grain morphology, i.e. interlaced twinning, which has more fatigue resistance. Changes associated with the microstructures of the solder and the intermetallic bonds to the contact surfaces/pads will eventually have consequences for design, material selection, and process optimization. This work tries to explore the effect of minor alloying on various aspects of microstructure and correlate it with reliability results using these alloys.

MAT8A: Impact of Conformal Coating on Thermal Cycling Reliability of SMT Components

Author: Martin Anselm
This research intends to evaluate the change in lifetime due to the application of conformal coatings using accelerated thermal cycle (ATC) testing using LF solders. Various coatings (acrylic, epoxy, polyurethane, silicone, polyparaxylene (ParyleneTM)) are used in the electronics industry for environmental insulation in order to limit corrosion. For that reason qualification test methods like those described by MIL-I-46058 and IPC-CC-830B specify material physical characterization, appearance, humidity and thermal performance. However, the effect of the conformal coat on the long-term reliability of an assembly is not part of the qualification process. It is well established that certain classes of materials such as Parylene offer superior environmental protection, chemical resistance and minimum impact on thermal cycling reliability (due to thin coating thickness). However, Parylene is a costly material and expensive to process. Other materials, such as acrylics (solvent or water based) are both low cost and reworkable. Urethanes, although cost effective and providing excellent environmental protection and chemical resistance; can be more difficult to process and are hazardous to operator health. Epoxies and silicones are least popular due to difficult rework-ability and known CTE mismatch issues with components. Silicones are also known for poor hydrogen sulfide resistance.

REL1A: Impact of Partial Pad Cratering on PCB Reliability

Author: Michael Meilunas
This research intends to evaluate the degradation in product life due to induced partial PCB pad cratering compared to as-received samples (i.e. cratering not induced) using the following tests:

  • Accelerated thermal cycling
  • Mechanical drop/shock
  • Cyclic bend
  • Vibration (optional / to be determined)

Ultimately, can we determine which stress inducers are the worst accelerators of partial pad cratering at the PCB level?

REL3A: Vibration testing method and FE analysis for circuit board solder joint reliability

Author: Prof. Quand Su and Prof. James Pitarresi
This project will explore circuit board vibration testing methods for high cycle solder joint reliability studies that account for changes in circuit board vibration response during testing. A control system will be identified and implemented to vibrate the circuit board at the first resonant frequency. If needed, the control system will adjust the driving frequency and excitation level to maintain the circuit board first mode deflection shape and vibration level during the harmonic test.

Finite element models of the circuit board with electronic components will be developed so that the stress in the solder joints due to vibration can be computed. These models also allow the prediction of vibration natural frequencies and mode shapes. Experimental modal analysis will be performed on the circuit boards for verification of the finite element models, and for fine tuning of the parameters in the models.

The purpose of this effort is to develop methods for reducing scatter in solder joint high cycle fatigue S-N curves by improved control and repeatability, removing variability between tests. SN data acquired with these methods will then be used in life predictions for various loading conditions (e.g. Gaussian random vibration with different power spectral densities, non-Gaussian signals with different kurtosis levels, etc.). We will be able to measure and predict the operating deflection shape for a given specified vibration input, predict the stresses in the solder joints, estimate accumulated damage, and predict the fatigue life.

REL4A: 2013 Creep Corrosion Studies

Author: Pericles Kondos
This research intends to continue the study of Creep Corrosion using a Flower of Sulfur (FoS) chamber to create a corrosiveenvironment. In 2013, more pad finishes will be tested with an effort to quantify differences among finishes by having boards identical in other respects except pad finish. The efforts to develop an improved understanding of the migration of Cu2S, and the rate limiting factors as well as to help develop effective testing and mitigation strategies will also continue.

Creep corrosion, or corrosion creepage, is the migration of corrosion products on the surface of electronic components or PCBs in corrosive environment without bias. The lateral growth of corrosion products, mostly Cu sulfide (Cu2S), could lead to premature product failure by shorting. There are significant interests of effective testing and mitigation methods for creep corrosion. However, a complete understanding of the lateral growth (creepage) mechanism is currently lacking, in terms of ionic transportation and compound formation processes.

REL6A: BGA Reliability vs. Solder Paste Print Variability

Author: Babak Arfaei
The primary objective of this project is to determine if the occasional, low volume or high volume paste deposit affects the yield and/or reliability of a BGA device.

REL10A: Drop Test Proposal

Author: Michael Meilunas
Evaluate the new JEDEC drop test board design. Results to be presented to JEDEC for consideration before the new standard is implemented. Note that this work is being performed in conjunction with an AREA member who is working with the JEDEC committee.

REL11A: Effect of TIM Compression Loads on Solder Joint Reliability

Author: Harry Schoeller
The thermal performance of certain types of thermal interface materials (TIMs) is pressure sensitive. Previous consortium research has shown the thermal resistance for gap pads decreases with increased pressure. The rule of thumb is 30% TIM compression is a good tradeoff between increased thermal performance and acceptable component reliability. However the relationship between TIM compression pressure and BGA reliability is not fully understood and warrants further study.

This project will investigate the effect of TIM compression loads on BGA reliability. A test vehicle containing 9 BGAs with simulated heat sinks has been designed for this study. The component is a bare die flip chip BGA. Pressure will be applied through a simulated heat sink by spring captured bolts.

APD2A: Fine Pitch Project Proposal

Author: Michael Meilunas
The primary objectives of this project are to

  1. Determine optimum design and processing parameters for successful 0.3mm pitch assembly and reliability.
  2. Evaluate the effect of plated vs. non-plated via-in-pad features using reliability tests.
  3. Study thin die components.

Universal Instruments will design four test boards based upon, but not fully conforming to, the JESD22-B111 (drop test) standard utilizing surface mount packages which will be supplied by Ericsson, Rockwell Automation and Celestica (via Matrix). Board fabrication will be performed by Multek.

Design A: Includes SMR, QFN, CSP, WLCSP (non plated vias)
Design B: Identical to A, except vias will be plated
Design C: Includes 0.3mm pitch WLCSP 16×16 array (plated vias)
Design D: Includes 0.3mm pitch WLCSP 8×8 array (plated vias)

Assembly, test and failure analysis will be performed at Universal Instruments. Our focus is on solder joint integrity, we hope to avoid board issues such as pad cratering.

APD4A: Comparison of Vapor Phase and Conventional Rework Processes for Large BGAs

Author: Harry Schoeller
The objective of this project is to compare vapor phase desoldering to a conventional desoldering process for large BGAs.  Processes will be compared in terms of process variables such as time and temperature, and in terms of drop/shock reliability after the rework process and reassembly.

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