Effects of Cycling Parameters on the Thermal Fatigue Life of Mixed SnAgCu/SnPb Solder Joints

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
M. Meilunas ◽  
P. Borgesen
Keyword(s):  
Printed Circuit Boards ◽  
High Reliability ◽  
Lead Free ◽  
Solder Paste ◽  
Test Results ◽  
Circuit Boards ◽  
Sac305 Solder ◽  
Snpb Solder ◽  
Solder Balls ◽  
Eutectic Snpb

The mandated switch of the overwhelming part of microelectronics assembly to lead-free soldering has left the manufacturers of many high reliability products, which are still exempt from the requirement to change, with a choice between imperfect alternatives. One of these involves the inclusion of lead-free BGAs and CSPs in a eutectic SnPb solder paste based reflow process. In order to assess the consequences of this for reliability it is not enough to subject samples to common accelerated tests. Mixing of the alloys is almost certain to affect the acceleration factors so that comparisons of test results may not reflect relative performances under service conditions. This was illustrated with for a set of model BGA components with 20 mil (0.5 mm) diameter SAC305 solder balls, which were reflow soldered onto printed circuit boards using a eutectic SnPb solder paste and tested in thermal cycling together with controls soldered with a SAC305 paste. Mixed joints were found to outperform pure SAC305 in −40/125°C tests but not in 0/100°C, and general trends suggest that mixed joints may compare more poorly in service.

scholarly journals Evaluation of The Printability of Lead Versus Lead Free Solder Pastes

2021 ◽  
Author(s):  
Ala Al Robiaee
Keyword(s):  
Printed Circuit Boards ◽  
Lead Free ◽  
Solder Paste ◽  
Circuit Boards ◽  
Stencil Printing ◽  
Printed Circuit ◽  
Main Factors ◽  
Free Solder ◽  
Print Process ◽  
The Impact

As the global marketplaces consider mandating lead-free equipments, many questions arise about the impact and feasibility of replacing lead in printed circuit boards soldering applications. In this project, the results presented of a study on comparing the process of screening lead paste versus lead free paste parameters for regular stencil printing using standard manufacturing methods. The key process parameters studies were: squeegee speed, squeegee pressure, and screening yield for both types of pastes. Two solder paste formulations (lead paste and lead-free paste) were evaluated in this study. The analysis of the pastes deposit volumes showed that for normal manufacturing range of printer (screener) settings (speed and pressure) tested the two pastes performed the same. The results also showed that the squeegee speed has a greater effect on the printing process than the squeegee pressure. The tests clearly showed that the lead paste was affected more by setting changes compared to the lead free paste. Varying the print speed and pressure for type of pastes by observing the resulting printed paste volumes optimized screening parameters. This study confirms that a new stencil or stencil design is not needed for the lead free paste. However, this study recommends a change to the sitting of the screening print process. Stencil cleaning frequency is one of the main factors that impact the production rate in an SMT line. The project highlights new results that lead free paste throughput will be less compared to lead paste at the screening step. The number of rejected boards screened with lead free-paste exceeded normal manufacturing standards. As stencil cleaning is a must function, it was recommended to increase stencil wiping frequency when lead free paste [is] in use in order to obtain a consistent volume with less screening defect.

Reliability of an 1657CCGA (Ceramic Column Grid Array) Package With 95.5Sn3.9Ag0.6Cu Lead-Free Solder Paste on PCBs (Printed Circuit Boards)

2003 ◽  
Author(s):  
John Lau ◽  
Walter Dauksher
Keyword(s):  
Fatigue Life ◽  
Thermal Fatigue ◽  
Printed Circuit Boards ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Thermal Fatigue Life ◽  
Free Solder

In many applications such as computers and telecommunications, the IC chip sizes are very big, the on-chip frequency and power dissipation are very high, and the number of chip I/Os is very large. The CCGA (ceramic column grid array) package developed by IBM is one of the best candidates for housing these kinds of chips [1–7]. There are two parts in this study. One is to show that the 2-parameter Weibull life distribution is adequate for modeling the thermal-fatigue life of lead-free solder joints. This is demonstrated by comparing the 2-parameter and 3-parameter Weibull distributions with life test data of an 1657-pin CCGA package with the 95.5wt%Sn3.9wt%Ag0.6wt%Cu lead-free solder paste on lead-free PCBs (printed circuit boards) under thermal cycling conditions. The other part of this study is to determine the time-history creep strain energy density of the 1657-pin CCGA solder column with two different solder paste materials, namely, 95.5wt%Sn3.9wt%Ag0.6wt%Cu and 63wt%Sn37wt%Pb and under three different thermal cycling profiles, namely, 25 ↔ 75°C, 0 ↔ 100°C, and −25 ↔ 125°C. The effects of these solder pastes and temperature conditions on the thermal-fatigue life of the high-lead (10wt%Sn90wt%Pb) solder columns of the CCGA package are provided and discussed.

Study of Lead Free Solder Joints Subjected to Isothermal Mechanical Shear Cycling

2020 ◽  
Author(s):  
Mohd Aminul Hoque ◽  
Mohammad Ashraful Haq ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Printed Circuit Boards ◽  
Solder Joints ◽  
Polarized Light ◽  
Lead Free ◽  
Lead Free Solder ◽  
Circuit Boards ◽  
Sac305 Solder ◽  
Mechanical Cycling ◽  
Before And After ◽  
Free Solder

Abstract Electronic packages are usually subjected to varying temperature conditions, thus subjecting the package to thermal cyclic loadings. As the different components of the package are made up of materials of different Coefficients of Thermal Expansion (CTE), the thermal cyclic loading brings about fluctuating shear stress to arise within the package, ultimately leading to its failure. It has been seen in previous literature that the recrystallization assisted cracking is a major factor that leads to the failure of solder joints when subjected to thermomechanical cycles. In this study, the authors have tried to determine whether the mechanical shear cycling of aged and non-aged samples of SAC305 lead free solder joints undergo a recrystallization phase before its ultimate failure. Arrays (3 × 3) of SAC305 solder joints of roughly 750μm in diameter were reflowed in between two FR-4 printed circuit boards to create a sandwiched structural sample. The samples were then polished to expose the solder joints. A polarized light microscope was utilized to capture the images of the joints before and after the mechanical cycling and analyzed to observe any changes in the microstructure in the form of recrystallization of the tin grains.

Reliability of an 1657CCGA (Ceramic Column Grid Array) Package With 95.5SN3.9AG0.6CU Lead-Free Solder Paste on PCBS (Printed Circuit Boards)

2005 ◽  
Vol 127 (2) ◽  
pp. 96-105 ◽  
Author(s):  
John Lau ◽  
Walter Dauksher
Keyword(s):  
Fatigue Life ◽  
Printed Circuit Boards ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Circuit Boards ◽  
Printed Circuit ◽  
Thermal Fatigue Life ◽  
Free Solder ◽  
Two Parameter

In many applications such as computers and telecommunications, the IC chip sizes are very big, the on-chip frequency and power dissipation are very high, and the number of chip I/Os is very large. The CCGA (ceramic column grid array) package developed by IBM is one of the best candidates for housing these kinds of chips. There are two parts in this study. One is to show that the two-parameter Weibull life distribution is adequate for modeling the thermal-fatigue life of lead-free solder joints. This is demonstrated by comparing the two-parameter and three-parameter Weibull distributions with life test data of an 1657-pin CCGA package with the 95.5 wt %Sn3.9 wt %Ag0.6 wt %Cu lead-free solder paste on lead-free printed circuit boards under thermal cycling conditions. The other part of this study is to determine the time-history creep strain energy density of the 1657-pin CCGA solder column with two different solder paste materials, namely, 95.5 wt %Sn3.9 wt %Ag0.6 wt %Cu and 63 wt %Sn37 wt %Pb and under three different thermal cycling profiles, namely, 25↔75°C, 0↔100°C, and −25↔125°C. The effects of these solder pastes and temperature conditions on the thermal-fatigue life of the high-lead (10 wt %Sn90 wt %Pb) solder columns of the CCGA package are provided and discussed.

scholarly journals Evaluation of The Printability of Lead Versus Lead Free Solder Pastes

2021 ◽  
Author(s):  
Ala Al Robiaee
Keyword(s):  
Printed Circuit Boards ◽  
Lead Free ◽  
Solder Paste ◽  
Circuit Boards ◽  
Stencil Printing ◽  
Printed Circuit ◽  
Main Factors ◽  
Free Solder ◽  
Print Process ◽  
The Impact

As the global marketplaces consider mandating lead-free equipments, many questions arise about the impact and feasibility of replacing lead in printed circuit boards soldering applications. In this project, the results presented of a study on comparing the process of screening lead paste versus lead free paste parameters for regular stencil printing using standard manufacturing methods. The key process parameters studies were: squeegee speed, squeegee pressure, and screening yield for both types of pastes. Two solder paste formulations (lead paste and lead-free paste) were evaluated in this study. The analysis of the pastes deposit volumes showed that for normal manufacturing range of printer (screener) settings (speed and pressure) tested the two pastes performed the same. The results also showed that the squeegee speed has a greater effect on the printing process than the squeegee pressure. The tests clearly showed that the lead paste was affected more by setting changes compared to the lead free paste. Varying the print speed and pressure for type of pastes by observing the resulting printed paste volumes optimized screening parameters. This study confirms that a new stencil or stencil design is not needed for the lead free paste. However, this study recommends a change to the sitting of the screening print process. Stencil cleaning frequency is one of the main factors that impact the production rate in an SMT line. The project highlights new results that lead free paste throughput will be less compared to lead paste at the screening step. The number of rejected boards screened with lead free-paste exceeded normal manufacturing standards. As stencil cleaning is a must function, it was recommended to increase stencil wiping frequency when lead free paste [is] in use in order to obtain a consistent volume with less screening defect.

Conductive Filament Formation in Printed Circuit Boards – Effects of Reflow Conditions and Flame Retardants

2009 ◽  
Author(s):  
Bhanu Sood ◽  
Michael Pecht
Keyword(s):  
Flame Retardants ◽  
Printed Circuit Boards ◽  
Electrochemical Process ◽  
Lead Free ◽  
Circuit Boards ◽  
Filament Formation ◽  
Conductive Filament ◽  
Printed Circuit ◽  
Free Solder ◽  
Halogen Free

Abstract Failures in printed circuit boards account for a significant percentage of field returns in electronic products and systems. Conductive filament formation is an electrochemical process that requires the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. With the advent of lead-free initiatives, boards are being exposed to higher temperatures during lead-free solder processing. This can weaken the glass-fiber bonding, thus enhancing conductive filament formation. The effect of the inclusion of halogen-free flame retardants on conductive filament formation in printed circuit boards is also not completely understood. Previous studies, along with analysis and examinations conducted on printed circuit boards with failure sites that were due to conductive filament formation, have shown that the conductive path is typically formed along the delaminated fiber glass and epoxy resin interfaces. This paper is a result of a year-long study on the effects of reflow temperatures, halogen-free flame retardants, glass reinforcement weave style, and conductor spacing on times to failure due to conductive filament formation.

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