Technical Library | 2020-05-08 18:22:31.0
A customer contacted the Helpline to perform analysis on a lead-free assembly which exhibited intermittent functionality. The lead-free assembly exhibiting intermittent functionality when pressure was applied to the ball grid array (BGA) packages. Industrial adaptation of a Restriction of Hazardous Substances (RoHS) compliant solder standard has created a new host of failure modes observed in lead-free assemblies. Pad cratering occurs when fractures propagate along the epoxy resin layer on the underside of the BGA connecting pads. While originating from process, design, and end use conditions, it is the combination of a rigid lead-free solder with inflexible printed circuit board (PCB) laminates that has advanced the prevalence of this condition. Pad cratering is simply the result of mechanical stress exceeding material limitations.
Technical Library | 2007-08-16 13:34:31.0
While experienced inspectors may be able to determine the aesthetic differences between a lead-free PCB assembly and a tin-lead version, one cannot rely on the "experienced eye". "Less wetting out to the pad edges" (Figure A) and "graininess and lack of shininess of the solder joint" (Figure B) are typical comments about some lead-free solder joints. However, in cases where a Nitrogen atmosphere was present during the reflow of the solder joint (Figure C), there will be little visual differences between the lead free alloys and their tin-lead counterparts.
Technical Library | 2007-01-31 15:17:04.0
The goal of this project is to evaluate the reliability of lead-free BGA solder joints with a variety of different pad sizes using several different BGA rework methods. These methods included BGAs reworked with both flux only and solder paste attachment techniques and with or without the use of the BEST stay in place StencilQuick™. The daisy chained test boards were placed into a thermal test chamber and cycled between -25ºC to 125ºC over a 30 minute cycle with a 30 minute dwell on each end of the cycle. Each BGA on the board was wired and the continuity assessed during the 1000 cycles the test samples were in the chamber.
Technical Library | 2019-10-24 14:23:49.0
Presentation given by Fred Dimock during a seminar at the American Competitiveness Institute, ACI. •Recipe vs. Profile •Material Properties •Why profiles are shaped like they are. •Obtaining profiles •TC Accuracy •Profilers •Test vehicles •Process Window – Eutectic vs. Lead Free •Heat transfer •Oven Control
Technical Library | 2013-12-19 16:57:50.0
With the adoption of RoHS and implementation of Lead Free solders a major concern is how this will impact reliability. Both commercial and military hardware are impacted by this change even though military hardware is considered exempt from the requirements of RoHS. As the supply chain has moved to the new lead free alloys both markets are being forced to understand these impacts and form risk mitigation strategies to deal with the change. This paper documents the effect of mixing Leaded and Lead Free alloys on BGA devices and how this impacts reliability. Three of the most common pitch BGA packages are included in the study to determine if the risk is the same as pitches decrease
Technical Library | 2015-02-12 13:32:52.0
Market forces, particularly legislation against the use of lead in electronics, have driven electronics manufacturers towards lead-free solders for PCB assembly and rework. This approach creates challenges because of the relatively high temperatures needed for lead-free soldering. Additionally, lead-free solder alloys typically do not wet or wick as easily as Sn63Pb37 leaded types. As PCBs often include both BGAs and simpler discrete devices, a lead-free rework capability should include a suitable soldering station and a BGA rework station. This article shows how such equipment can be adapted to overcome the lead-free issues and provide a successful reworking facility.
Technical Library | 2008-04-08 17:42:27.0
Concern about the failure of lead-free BGA packages when portable devices such as cell phones are accidentally dropped and a general concern about the resistance of these packages under shock loading has prompted an interest in the impact strength of the soldered BGA connection. This paper reports the results of the measurement of the impact strength of lead-free 0.5±0.01mm diameter BGA spheres on 0.42mm solder mask defined pads on copper/OSP and ENIG substrates using recently developed equipment that can load individual BGA spheres at high strain rates in shear and tension.
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 | 2012-10-04 18:52:43.0
First published in the 2012 IPC APEX EXPO technical conference proceedings... Due to the obsolescence of SnPb BGA components, electronics manufacturers that use SnPb solder paste either have to use lead-free BGAs and adjust the reflow process or re-ball t
Technical Library | 2023-09-26 19:14:44.0
The transition from tin-lead to lead free soldering in the electronics manufacturing industry has been in progress for the past 10 years. In the interim period before lead free assemblies are uniformly accepted, mixed formulation solder joints are becoming commonplace in electronic assemblies. For example, area array components (BGA/CSP) are frequently available only with lead free Sn-Ag-Cu (SAC) solder balls. Such parts are often assembled to printed circuit boards using traditional 63Sn-37Pb solder paste. The resulting solder joints contain unusual quaternary alloys of Sn, Ag, Cu, and Pb. In addition, the alloy composition can vary across the solder joint based on the paste to ball solder volumes and the reflow profile utilized. The mechanical and physical properties of such Sn-Ag-Cu-Pb alloys have not been explored extensively in the literature. In addition, the reliability of mixed formulation solder joints is poorly understood.
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