SMTA International Conference Proceedings


PROCESS CAPABILITY, WETTING BEHAVIOR AND TEMPERATURE DEPENDENT SHEAR STRENGTH OF ALTERNATIVE LEAD FREE SOLDER JOINTS

Authors: Th. Herzog , S. Rudolph, and K.-J. Wolter
Company: Dresden University of Tech.
Date Published: 9/22/2002   Conference: SMTA International


Abstract: There are three ways in the current discussions for using lead free solder materials. As first, to use a nearly compatible lead free solder alloy to the current used SnPb, like SnAgCuX is starting in some electronic reflow manufacturing. The rising demands on solder materials for permanent system temperature of 125°C-150°C and higher stress in power cycling are coming more of interest as second.

The solutions therefore are the use of special reaction (composite) solder with two or more alloys in the paste. They have a compatible melting point but a higher creep strength and creep resistance after soldering [1]. And as third there are investigations to find alternatives for lowcost applications like toys or consumer electronic, which will use alloys with a melting point below 150°C like Sn42Bi58.

At this background our work is dealing with different lead free solder pastes to evaluate their process capability and wetting behavior on different pad metallizations. The influence on the printing results of solder pastes at different force and speed parameters was observed. As an objective evaluation criterion we‘ve investigated the shear strength of lead free solder joints at different temperatures. Therefore passive components (R0805, R0603) were assembled on FR-4 PCBs with optimized reflow profiles assessed by wetting behavior. The measurement of wetting angle and monitored micro voids by x-ray can be used for the evaluation.

To compare the different solder alloys and the heating effects we’ve used the same homologue temperature during the shear tests for each solder. Fracture surface analysis and micro structural observations examine the fracture behavior of solder joints. The influence of different intermetallics for the fracture toughness by using different metal combinations was discussed.

Key words: lead free solder, wetting behavior, shear strength, composite solder.



Members download articles for free:

Not a member yet?

What else do you get when you join SMTA? Read about all of the benefits that go along with membership.

Notice: Sharing of articles is restricted to just your immediate work group. Downloaded papers should not be stored on an external network or shared on the internet.


Back


SMTA Headquarters
6600 City West Parkway, Suite 300
Eden Prairie, MN 55344 USA

Phone 952.920.7682
Fax 952.926.1819