Lead-free reflow puts new demands on rework equipment
5 May 2004Manufacturing / Production Technology, Hardware & Services
Security Services & Risk Management
Lead-free solder is a subject that must be addressed today because it will be a requirement soon. The process parameters required for high reliability solder joints put new and tougher demands on reflow and rework equipment. The hot air rework systems that are currently used for BGA rework will have a difficult time trying to achieve a proper lead free profile. However, Ersa's IR technology is perfectly suited to meet these lead-free demands.
Forced convection
Forced convection reflow systems are the standard in the industry for production. Quality lead-free BGA reflow can be achieved in the enclosed environment of a reflow oven. Rework, however, cannot be done in a completely enclosed environment. The heating conditions required for lead free BGA reflow are difficult to achieve when blowing hot air through a nozzle (Figures 1 and 2).
Figure 1. The air flow dynamics in a hot air rework nozzle are difficult to control and, depending on the nozzle construction, can lead to hot and cold spots on the package
Figure 2. Two separate hot air rework nozzles were lowered down to a heat sensitive surface and the reflow program was started. The burn patterns shown here indicate how the heated air molecules move in the nozzle and transfer heat to the component. Dark areas are hotter
The process
The process window for lead-free solder paste reflow is much tighter than for eutectic or low melt alloys (Graphs 1 and 2). The activation time is sacrificed in order to reduce the oxidation which takes place much faster in the absence of lead. The reflow or rework heating system must be able to achieve the optimal soak from 150 to 220°C in 50 seconds also on heavy thermal mass PCBs. Slow heat rework systems, like hot air, can take too long in this critical phase, causing oxidation to form during soak.
Graph 1. Kester reflow profile for lead-free alloy (SnAgCu)
Graph 2. Typical eutectic paste profile
Due to the increase in temperature range and the tight process window, controlling the DT across the entire PCB in reflow and across the complete area array package in rework will be the ultimate challenge. Most hot air rework systems are poorly suited to meet these tougher demands. Ersa's 2nd generation proprietary IR technology was specifically designed for lead-free BGA rework.
By using the closed-loop reflow technology (Figure 5) of Ersa's 1600 W IR 550 A a perfect process window can be guaranteed, with uniform heat distribution with minimum DT, and proper peak temperature for high reliability lead-free solder joints.
Figure 3. The dark areas are hotter, revealing nonuniform heat distribution across the package. This DT is unacceptable for lead-free solders and will cause oxidation to form in the lighter areas
Figure 4. The ERSA IR technology guarantees minimum DT across the entire BGA package
The role of drones in farm protection
Agriculture (Industry) Security Services & Risk Management
Laurence Palmer reminds us of the role drones play in agricultural security and offers a free security risk assessment template for downloading (link at the end of the article).
Read more...SMART Surveillance Conference in Johannesburg Arteco Global Africa Technews Publishing SMART Security Solutions Axis Communications SA neaMetrics
Editor's Choice Surveillance Security Services & Risk Management Logistics (Industry) AI & Data Analytics SMART Security Solutions hosted its annual SMART Surveillance Conference in Johannesburg in July, welcoming several guests, sponsors, and speakers for an informative and enjoyable day examining the evolution of the surveillance market.
Read more...September exclusives at PCBWay: Big savings on PCBs and 3D printing PCBWay
Manufacturing / Production Technology, Hardware & Services
[Sponsored] This September, PCBWay is bringing you two exciting, limited time offers that showcase both style and versatility. Whether you are designing with PCBs or prototyping with 3D printing, these will help you create more while spending less.
Read more...Understanding solder paste viscosity and thixotropy Truth Electronic Manufacturing
Manufacturing / Production Technology, Hardware & Services
A solder paste’s viscosity and thixotropic properties, a measure of its resistance to flow, influence its performance in different production environments.
Read more...Your Wi-Fi router is about to start watching you
News & Events Surveillance Security Services & Risk Management
Advanced algorithms are able to analyse your Wi-Fi signals and create a representation of your movements, turning your home's Wi-Fi into a motion detection and personal identification system.
Read more...Global electronics trade in an age of disruption
Manufacturing / Production Technology, Hardware & Services
Governments should invest in domestic strengths, coordinate with international partners, and align trade and industrial policy with the realities of a globally connected electronics sector.
Read more...The new tool design of IWISS Startech Industrial
Manufacturing / Production Technology, Hardware & Services
Rooted in IWISS’ dedication to reliability, comfort, and efficiency, the company’s new design refresh elevates craftsmanship by incorporating a rich cultural influence.
Read more...Cybersecurity and insurance partnership for sub-Saharan Africa Sophos
News & Events Information Security Security Services & Risk Management
Sophos and Phishield Announce first-of-its-kind cybersecurity and insurance partnership for sub-Saharan Africa. The SMARTpod podcast, discussing the deal and the state of ransomware in South Africa and globally, is now also available.
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.
printer friendly version