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 impact of harsh environments and ionic contamination on post-reflow circuit assemblies MyKay Tronics
Manufacturing / Production Technology, Hardware & Services
There is well documented historical proof that post-reflow circuit assemblies, when subjected to harsh environments, are particularly vulnerable to failure mechanisms, but modern electronic assemblies are far more susceptible to this phenomenon.
Read more...Engineering copper grain structure for high-yield hybrid bonding in 3D packaging Testerion
Editor's Choice Manufacturing / Production Technology, Hardware & Services
The way copper grains are sized and distributed forms the metallurgical foundation of hybrid bonding, enabling lower bonding temperatures, greater reliability, and stable grain structures throughout integration.
Read more...Understanding solder dross: causes and control strategies Truth Electronic Manufacturing
Editor's Choice Manufacturing / Production Technology, Hardware & Services
Dross formation is an inevitable consequence of wave soldering. It occurs when molten solder comes into contact with oxygen, forming metal oxides that float on the surface of the solder bath. Over time, this oxidation byproduct accumulates and must be removed to maintain solder quality and process consistency.
Read more...Implications of using Pb-free solders on X-ray inspection of flip chips and BGAs MyKay Tronics
Manufacturing / Production Technology, Hardware & Services
With the move to Pb-free soldering, most of the attention has been paid to reflow temperatures, component compatibility, and reliability concerns, but the implications for inspection, particularly X-ray inspection, are equally important and often underestimated.
Read more...The causes of solder balls in robotic soldering
Manufacturing / Production Technology, Hardware & Services
Solder balls (also known as solder splatter) are a major concern in many production sites as they may potentially cause shorts, leading to long-term impacts on product reliability.
Read more...Material challenges for superconducting quantum chips
Manufacturing / Production Technology, Hardware & Services
To achieve the scalable and repeatable production of superconducting circuits for quantum technology products, players in the industry are leveraging semiconductor fabrication techniques.
Read more...UV curing oven for high-efficiency PCB production Techmet
Manufacturing / Production Technology, Hardware & Services
The jCURE-2UV+ from JTU is a cutting-edge ultraviolet curing oven engineered for fast, reliable curing of UV-sensitive coatings in SMT production environments.
Read more...Automatic stencil cleaning ZETECH ONE
Manufacturing / Production Technology, Hardware & Services
The MBtech N29 series delivers high-precision stencil cleaning with a focus on efficiency, economy and the environment, and is ideal for SMT adhesive and solder paste stencil maintenance.
Read more...Versatile wave soldering MyKay Tronics
Manufacturing / Production Technology, Hardware & Services
The EMST Stallion fc - PLC is a highly capable wave soldering machine engineered for precision and productivity in electronics manufacturing.
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