Electronics Assembly Knowledge, Vision & Wisdom
Activator Technology for Lead-Free Paste
Activator Technology for Lead-Free Paste
The printing performance, coalescence, wetting, BGA voiding and head-in-pillow for halogen-free, no-clean solder pastes are discussed.
Materials Tech

Authored By:
Xiang Wei, Ph.D., Adrian Hawkins, Ph.D.
Kester, Inc. Itasca, IL USA
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Transcript

The Surface Mount Technology industry has been faced with several challenges in the past decades. Two of the most recent are R.O.H.S compliant lead-free assembly and the adoption of fine-pitch components assembly processes.

Moreover, halogen-free is another new requirement for assembled PCB reliability, environmental and health concerns.

All these requirements create fundamental challenges of developing a solder paste to satisfy everything.

One of the resolutions for these challenges can be the development of the activator package with the advanced organic chemistry technology.

Serial innovative activator system was developed recently for solder paste flux, tacky flux and liquid flux formulation.

This paper will discuss three type 4 lead-free, halogen-free, no-clean solder pastes developed based on different innovative activators, which respond to these challenges.

The printing performance, coalescence, wetting, BGA voiding and head-in-pillow characteristics, are compared and discussed in detail.

Summary
The Surface Mount Technology (SMT) industry has been faced with several challenges in the past decades. Two of the most recent ones are RoHS compliant lead-free assembly and the adoption of fine-pitch components assembly processes. Moreover, halogen-free is another new requirement for assembled PCB reliability, environmental and health concerns. All these requirements create fundamental challenges of developing a solder paste to satisfy everything. One of the resolutions for these challenges can be the development of the activator package with the advanced organic chemistry technology.

Serial innovative activator system was developed recently for solder paste flux, tacky flux and liquid flux formulation. This paper will discuss three Type 4 lead-free halogen-free no-clean solder pastes (ROL0) developed based on different innovative activators, which respond to the challenges described above. The printing performance, coalescence, wetting, BGA voiding and head-in-pillow characteristics, are compared and discussed in detail. The testing results show all three pastes with the new activators are fully capable of printing and reflowing 01005 components with different board/device finishes, even in air reflow. They can handle a wide variety of print variables, including print speed, long abandon time and a wide range of temperature and humidity. Post-soldering, the paste offers minimized defects, including head-in-pillow and BGA voiding.
Conclusions
The current test results show that the innovative activator packages are capable of providing desired flux activity for the developed solder pastes to meet not only J-STD and other reliability specifications, but also the most recent SMT requirements as discussed previously. The printing and reflow performance of solder pastes DA1, DA2 and DA3 are excellent. They can also help to mitigate the recent SMT defects issues, e.g. head-in-pillow and voiding. Further studies on QFN/MLF voiding, ICT, and conformal coating compatibility will be carried out soon to fully understand the solder paste performance.
Initially Published in the IPC Proceedings
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