ICSR (Soldering and Reliability) Conference Proceedings


Authors: Andreas Flechtmann and Andreas Thumm
Company: IBL-Löttechnik GmbH
Date Published: 5/22/2009   Conference: ICSR (Soldering and Reliability)

Abstract: Vapor Phase Soldering is known today as one of the proven reflow soldering methods, however it is still seen being exotic to many users and also the discussions on benefits and shortfalls are not necessarily considering today´s technology.

The Vapor Phase process was reinvented in the 90s overcoming the challenges of the original process. Based on this renewed Vapor Phase procedure, various new machines were developed. Vapor Phase Soldering now offers new features, in particular when it comes to lead free soldering. The main advantages of a state of the art Vapor Phase system are low process temperatures, freely adjustable temperature gradients and profiles, automatically controlled time above liquidus and a perfectly inert process atmosphere without using cost intensive protective gas measures.

The task in reflow soldering is to evenly heat up PCB boards to a level that soldering can be accomplished even on sockets or in the center of large BGA’s but at the same time to be sure that nothing is overheated or delaminated. So especially for lead free soldering the process window becomes pretty small. With Vapor Phase Soldering even FR4 boards, double sided densely packed, can be soldered reliably and with no danger of overheating since the maximum board temperature is physically limited to the vapor temperature (e.g. 230-235°C for lead-free SnAgCu).

Because of it´s perfect inert atmosphere the wetting with lead free solder paste in a Vapor Phase oven is the best possible wetting today. A thorough temperature gradient control in Vapor Phase becomes crucial as soon as tombstoning is becoming immanent in the process. Like in convection reflow, the sensitivity of tombstoning is significantly influenced by the temperature profile.

The advantages of the Vapor Phase heat transfer in combination with new machines and options offer an excellent tool for easy and defect free reflow soldering, independent whether lead free or leaded solders are used.

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