Technical Library | 2017-10-16 15:03:32.0
The miniaturization and advancement of electronic devices have been the driving force of design, research and development, and manufacturing in the electronic industry. However, there are some issues occurred associated with the miniaturization, for examples, warpage and reliability issues. In order to resolve these issues, a lot of research and development have been conducted in the industry and university with the target of moderate melting temperature solder alloys such as m.p. 280°C. These moderate temperature alloys have not resolve these issues yet due to the various limitations. YINCAE has been working on research and development of the materials with lower temperature soldering for higher temperature application. To meet this demand, YINCAE has developed solder joint encapsulant paste to enhance solder joint strength resulting in improving drop and thermal cycling performance to eliminate underfilling, edge bonding or corner bonding process in the board level assembly process. This solder joint encapsulant paste can be used in typical lead-free profile and after reflow the application temperature can be up to over 300C, therefore it also eliminates red glue for double side reflow process. In this paper, we will discuss the reliability such as strength of solder joints, drop test performance and thermal cycling performance using this solder joint encapsulant paste in detail.
Technical Library | 2007-03-28 10:18:33.0
Legislation against the use of lead in electronics has been the driving force behind the use of lead-free solders, surface finishes, and component lead finishes. The major concern in using lead-free solders in the assembly and rework Chip Scale Packages (CSPs) is the relatively high temperatures that the components and the boards experience. Fine-pitch CSPs have very low standoff heights following assembly making inspection and rework of these components more difficult. One other concern pertinent to rework is the temperature of the neighboring components during rework. These issues, coupled with the limitations of rework equipment to handle lead-free reflow temperatures, make the task of reworking lead-free assemblies more challenging.
Technical Library | 2021-09-08 14:10:12.0
The Pb-Free Alloy Characterization Program sponsored by International Electronics Manufacturing Initiative (iNEMI) is conducting an extensive investigation using accelerated temperature cycling (ATC) to evaluate ball grid array (BGA) thermal fatigue performance of 12 commercial or developmental Sn based Pb-free solder alloys. This paper presents the initial findings from a specific subset of the temperature cycling test matrix. The focus is on comparing alloy performance for two of the most commonly specified temperature cycles, 0 to 100 °C and -40 to 125 °C.
Technical Library | 2015-02-12 16:57:56.0
Electronic systems are known to be affected by the environmental and mechanical conditions, such as humidity, temperature, thermal shocks and vibration. These adverse environmental operating conditions, with time, could degrade the mechanical efficiency of the system and might lead to catastrophic failures.The aim of this study is to investigate the mechanical integrity of lead-free ball grid array (BGA) solder joints subjected to isothermal ageing at 150°C for up to 1000 hours. Upon ageing at 150°C the Sn-3.5Ag solder alloy initially age-softened for up to 200 hours. This behaviour was linked to the coarsening of grains. When aged beyond 200 hours the shear strength was found to increase up to 400 hours. This age-hardening was correlated with precipitation of hard Ag3Sn particles in Sn matrix. Further ageing resulted in gradual decrease in shear strength. This can be explained as the combined effect of precipitation coarsening and growth of intermetallic layer. The fractured surfaces of the broken solder balls were also investigated under a Scanning Electron Microscope. The shear failures were generally due to ductile fractures in bulk solders irrespective of the ageing time.
Technical Library | 2009-03-27 22:22:40.0
The Sn-Ag-Cu (SAC) alloys have been considered promising replacements for the lead-containing solders for the microelectronics applications. However, due to the rigidity of the SAC alloys, compared with the Pb-containing alloys, more failures have been found in the drop and high impact applications for the portable electronic devices, such as the personal data assistant (PDA), cellular phone, notebook computer..etc
Technical Library | 2020-10-27 02:07:31.0
For companies that choose to take the Pb-free exemption under the European Union's RoHS Directive and continue to manufacture tin-lead (Sn-Pb) electronic products, there is a growing concern about the lack of Sn-Pb ball grid array (BGA) components. Many companies are compelled to use the Pb-free Sn-Ag-Cu (SAC) BGA components in a Sn-Pb process, for which the assembly process and solder joint reliability have not yet been fully characterized. A careful experimental investigation was undertaken to evaluate the reliability of solder joints of SAC BGA components formed using Sn-Pb solder paste. This evaluation specifically looked at the impact of package size, solder ball volume, printed circuit board (PCB) surface finish, time above liquidus and peak temperature on reliability. Four different BGA package sizes (ranging from 8 to 45 mm2) were selected with ball-to-ball pitch size ranging from 0.5mm to 1.27mm. Two different PCB finishes were used: electroless nickel immersion gold (ENIG) and organic solderability preservative (OSP) on copper. Four different profiles were developed with the maximum peak temperatures of 210oC and 215oC and time above liquidus ranging from 60 to 120 seconds using Sn-Pb paste. One profile was generated for a lead-free control. A total of 60 boards were assembled. Some of the boards were subjected to an as assembled analysis while others were subjected to an accelerated thermal cycling (ATC) test in the temperature range of -40oC to 125oC for a maximum of 3500 cycles in accordance with IPC 9701A standard. Weibull plots were created and failure analysis performed. Analysis of as-assembled solder joints revealed that for a time above liquidus of 120 seconds and below, the degree of mixing between the BGA SAC ball alloy and the Sn-Pb solder paste was less than 100 percent for packages with a ball pitch of 0.8mm or greater. Depending on package size, the peak reflow temperature was observed to have a significant impact on the solder joint microstructural homogeneity. The influence of reflow process parameters on solder joint reliability was clearly manifested in the Weibull plots. This paper provides a discussion of the impact of various profiles' characteristics on the extent of mixing between SAC and Sn-Pb solder alloys and the associated thermal cyclic fatigue performance.
Technical Library | 2011-08-25 17:47:23.0
While SnAgCu (SAC) alloys still dominate Pb-free selection in North America, especially Sn3.0Ag0.5Cu (SAC305), there are alternative material systems available. Any OEM that is concerned about the high reflow temperatures of SAC or relies on ODM, it is im
Technical Library | 2015-10-29 18:19:33.0
With the electronic industry moving towards lead-free assembly, traditional SnPb-compatible laminates need to be replaced with lead-free compatible laminates that can withstand the higher reflow temperature required by lead-free solders. Lead-free compatible laminates with improved heat resistance have been developed to meet this challenge but they are typically more brittle than SnPb laminates causing some to be more susceptible to pad cratering. In this paper, two novel approaches for minimizing pad cratering will be discussed. Preliminary results which validate the two approaches will also be presented.
Technical Library | 2014-01-30 18:08:04.0
As of today, the electronic industry is aware of the requirements for their products to be lead free. All components are typically available in lead free quality. This comprises packages like BGAs with BGA solder balls to PCB board finishes like HASL. The suppliers are providing everything that is needed. It is harder to get the old tin leaded (SnPb) components for new applications today, than lead free ones. So why has not everybody changed over fully yet and how can the challenges be overcome? A big concern in this transition process is reflow soldering. The process temperatures for lead free applications became much higher. Related with this is more stress for all the components. It affects the quality and reliability of the electronic units and products...
Technical Library | 2018-02-14 22:58:54.0
This document describes general guidelines and attention points for PCB design regarding selective soldering. The guidelines can be applied for Select Wave and/or Multi Wave soldering process in both leaded and leadfree alloy. When a PCB is designed according to these guidelines, a stable and solid solder-process can be guaranteed.
