Technical Library | 2010-04-29 21:40:37.0
The purpose of this paper is to investigate the effects of reflow time, reflow peak temperature, thermal shock and thermal aging on the intermetallic compound (IMC) thickness for Sn3.0Ag0.5Cu (SAC305) soldered joints.
Technical Library | 2014-06-23 14:50:52.0
It was unusual to see chip terminations change colors when tin lead solders were used but with the introduction of lead free reflow soldering and the corresponding increases in reflow temperatures terminations are now changing colors. Two conditions are present when reflow temperatures are increased for lead free solder alloys that leads to discoloration. Reflow temperatures are above the melting point of tin (Sn MP is 232oC). Air temperatures commonly used in forced convection reflow systems are high enough to both melt the tin plating on the termination allowing it to be pulled into the solder joint due to solder joint liquid solder surface tension leaving behind the exposed nickel barrier. Now those metal oxide colors will be visible due to high air temperatures during reflow.
Technical Library | 2024-09-02 18:48:58.0
The conversion to higher temperature "Lead Free" assembly reflow conditions has created an increased awareness that entrapped or absorbed moisture is a frequent root cause of thermally induced delamination at assembly reflow. There are two connected failure modes from entrapped moisture; incomplete resin cross-linking resulting in premature resin decomposition and also severe Z axis expansion from "explosive vaporization of the entrapped moisture at elevated temperatures at assembly reflow". Ultimately, both result in delamination failure. Other papers have shown the negative effects of entrapped moisture before lamination including delamination, red color, reduced thermal reliability and increased high speed signal loss. In this paper, various materials were tested for moisture sensitivity during lamination. Tests were performed at varying lamination conditions including a pre-vacuum step and "kiss" step. Pressure and cure temperature parameters were evaluated for minimizing or eliminating the effect of trapped moisture. Also included are the results of inner layer moisture removal baking conditions and their effect on peel strength and thermal reliability.
Technical Library | 2019-04-10 22:08:31.0
The stimulating impact of the automotive industry has sharpened focus on immersion tin (i-Sn) more than ever before. Immersion tin with its associated attributes, is well placed to fulfill the requirements of such a demanding application. In an environment dominated by reliability, the automotive market not only has very stringent specifications but also demands thorough qualification protocols. Qualification is ultimately a costly exercise. The good news is that i-Sn is already qualified by many tier one OSATs. The focus of this paper is to generate awareness of the key factors attributed to soldering i-Sn. Immersion tin is not suitable for wire bonding but ultimately suited for multiple soldering applications. The dominant topics of this paper will be IMC formations in relation to reflow cycles and the associated solderability performance. Under contamination free conditions, i-Sn can provide a solderable finish even after multiple reflow cycles. The reflow conditions employed in this paper are typical for lead free soldering environments and the i-Sn thicknesses are approximately 1 μm.
Technical Library | 2014-06-12 16:40:19.0
Occurrence of popcorn in IC packages while assembling them onto the PCB is a well known moisture sensitive reliability issues, especially for surface mount packages. Commonly reflow soldering simulation process is conducted to assess the impact of assembling IC package onto PCB. A strain gauge-based instrumentation is developed to investigate the popcorn effect in surface mount packages during reflow soldering process. The instrument is capable of providing real-time quantitative information of the occurrence popcorn phenomenon in IC packages. It is found that the popcorn occur temperatures between 218 to 241°C depending on moisture soak condition, but not at the peak temperature of the reflow process. The presence of popcorn and delamination are further confirmed by scanning acoustic tomography as a failure analysis.
WASET - World Academy of Science, Engineering and Technology
Technical Library | 2010-07-08 19:56:15.0
As technology becomes increasingly reliant on electronics, understanding the reliability of lead-free solder also becomes increasingly important. This research project focused on phase transformation kinetics with the lead-free solder SAC 305. Today in the electronics industry, SAC 305 is the most widely used solder, making it a high priority to understand its long-term stability and performance in a variety of service conditions. Recent evidence has shifted the focus from thermal aging to reflow temperature and time above liquidus values during initial solder melting.
Technical Library | 2019-08-14 22:20:55.0
Cleanliness is a product of design, including component density, standoff height and the cleaning equipment’s ability to deliver the cleaning agent to the source of residue. The presence of manufacturing process soil, such as flux residue, incompletely activated flux, incompletely cured solder masks, debris from handling and processing fixtures, and incomplete removal of cleaning fluids can hinder the functional lifetime of the product. Contaminates trapped under a component are more problematic to failure. Advanced test methods are needed to obtain "objective evidence" for removing flux residues under leadless components.Cleaning process performance is a function of cleaning capacity and defined cleanliness. Cleaning performance can be influenced by the PCB design, cleaning material, cleaning machine, reflow conditions and a wide range of process parameters.This research project is designed to study visual flux residues trapped under the bottom termination of leadless components. This paper will research a non-destructive visual method that can be used to study the cleanability of solder pastes, cleaning material effectiveness for the soil, cleaning machine effectiveness and process parameters needed to render a clean part.
Technical Library | 2014-08-19 15:39:13.0
Understanding warpage of package attach locations on PCBs under reflow temperature conditions is critical in surface mount technology. A new industry standard, IPC 9641, addresses this topic directly for the first time as an international standard.This paper begins by summarizing the sections of the IPC 9641 standard, including, measurement equipment selection, test setup and methodology, and accuracy verification. The paper goes further to discuss practical implementation of the IPC 9641 standards. Key advantages and disadvantages between available warpage measurement methods are highlighted. Choosing the correct measurement technique depends on requirements for warpage resolution, data density, measurement volume, and data correlation. From industry experience, best practice recommendations are made on warpage management of PCB land areas, covering how to setup, run, analyze, and report on local area PCB warpage.The release of IPC 9641 shows that flatness over temperature of the package land area on the PCB is critical to the SMT industry. Furthermore, compatibility of shapes between attaching surfaces in SMT, like a package and PCB, will be critical to product yield and quality in years to come.
Technical Library | 2018-11-20 21:33:57.0
There are several industry-accepted methods for determining the reliability of flux residues after assembly. The recommended methods of test sample preparation do not always closely mimic the thermal cycle experienced by an assembly. Therefore, extraction from actual assemblies has become a popular method of process control to assess consistency of post-reflow cleanliness. Every method of post-reflow flux residue characterization will depend on the reflow process followed to prepare the coupon.This investigation will focus on the effect of thermal conditions on the remainder of active ingredients in flux residues after assembly with no-clean solder pastes.
Technical Library | 2007-05-31 19:05:55.0
This paper discusses solder paste printing and flux dipping assembly processes for 0.4 and 0.5mm pitch lead-free WLCSPs and the corresponding assembly results and thermal cyclic reliability obtained. Variables evaluated include reflow ambient, paste type, and stencil design. Reliability is also compared to results for the same components assembled under identical conditions using SnPb solder.
