Electronics Forum | Thu Jun 25 22:25:24 EDT 2009 | boardhouse
In the life of this product that you have been doing this process, has the material alway's been IT180 material? One problem with Lead free material is that it is more fragile that standard FR4 Epoxy laminate. And is known to have chipping or fractu
Electronics Forum | Wed Jul 01 13:17:39 EDT 2015 | davef
Cheryl Tulkoff and Randy Schueller do a good job summarizing the thinks on pad cratering here: http://www.smta.org/chapters/files/uppermidwest_padcratering.pdf Potential Mitigations to Pad Cratering * Board Redesign * Solder mask defined vs. non-s
Industry News | 2013-10-21 16:05:48.0
IPC – Association Connecting Electronics Industries® presented Committee Leadership, Special Recognition and Distinguished Committee Service Awards at IPC’s Fall Standards Development Committee Meetings last week in Fort Worth, Texas.
Industry News | 2013-07-09 16:18:50.0
Flex Interconnect Technologies (FIT) announces that its CEO Chetan Shah recently held a successful presentation for the Silicon Valley Chapter of the IPC Designer Council.
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 | 2016-10-20 18:13:34.0
Pad cratering failure has emerged due to the transition from traditional SnPb to SnAgCu alloys in soldering of printed circuit assemblies. Pb-free-compatible laminate materials in the printed circuit board tend to fracture under ball grid array pads when subjected to high strain mechanical loads. In this study, two Pb-free-compatible laminates were tested, plus one dicycure non-Pb-free-compatible as control. One set of these samples were as-received and another was subjected to five reflows. It is assumed that mechanical properties of different materials have an influence on the susceptibility of laminates to fracture. However, the pad cratering phenomenon occurs at the layer of resin between the exterior copper and the first glass in the weave. Bulk mechanical properties have not been a good indicator of pad crater susceptibility. In this study, mechanical characterization of hardness and Young’s modulus was carried out in the critical area where pad cratering occurs using nano-indentation at the surface and in a cross-section. The measurements show higher modulus and hardness in the Pb-free compatible laminates than in the dicy-cured laminate. Few changes are seen after reflow – which is known to have an effect -- indicating that these properties do not provide a complete prediction. Measurements of the copper pad showed significant material property changes after reflow.
SMTnet Express, January 27, 2022, Subscribers: 25,985, Companies: 11,506, Users: 27,032 Fracture Toughness Analysis of Epoxy-Recycled Rubber-Based Composite Reinforced with Graphene Nanoplatelets for Structural Applications
SMTnet Express, October 20, 2016, Subscribers: 26,525, Companies: 15,001, Users: 41,289 Analysis of Laminate Material Properties for Correlation to Pad Cratering Carlos Morillo, Yan Ning, Michael H. Azarian, Julie Silk, Michael Pecht.; CALCE Pad
Heller Industries Inc. | https://hellerindustries.com/wp-content/uploads/2018/07/Vacuum-Void-Reduction-Reflow.pdf
. The test boards were fabricated with Panasonic R-1755V high temperature PCB laminate and Entek HT Plus organic solderability preservative (OSP) final finish
Surface Mount Technology Association (SMTA) | https://www.smta.org/icsr/speaker_forms/Paper-Format-Requirements.doc
side reflow Ensure a robust surface finish that remains solderable after 2 heat cycles. In circuit test strain limits could be larger with thicker boards. ICT stress must be minimal to prevent BGA fracture Ensure low contact resistance on test points
