Vapor Phase Technology is a Viable Solution, but Carries a Learning Curve

Estimated reading time: 6 minutes

Talk to electronics manufacturers about vapor phase (VP) reflow solder technology and you'll find people who either love it or hate it. The reason for this diversity of opinion is due to fact that it is a technology that many people still do not fully understand. Yet, it is also a technology that has come of age in an era where its efficiency in reflowing densely packed printed circuit board assemblies is highly valued, since the vapor blanket immersion process ensures perfect wetting and void-free, high-quality solder joints.

Firstronic's electronics contract manufacturing operation in Juarez, Mexico has installed two VP reflow soldering systems over the last year. The facility also uses convection reflow soldering.

Figure 1: Firstronic has added two vapor phase reflow soldering systems to its Juarez, Mexico facility.

On the positive side of the equation, VP reflow soldering offers several advantages:

• Fewer process windows, which reduces changeover time

• Cleaner solder joints at lower temperatures

• More even heating for even large PCBAs

• Can eliminate need for wave solder or selective solder on mixed technology PCBAs

• Lower energy costs than convection reflow technology.

However, there can also be learning curve issues and tradeoffs:

• While the oven is in line and operates as a pass-through system, VP technology is still a batch process and the machine capacity must be sized to projected line volume

• The efficiency of the VP process can generate surprises in initial process development

• The fluid utilized in the process is a consumable which adds to cost.

An Excellent Solution for Lean Manufacturing

One of the big advantages in VP reflow soldering technology is that relatively few unique profiles are required. There is zero wait state between products and VP requires far fewer profiles than found in convection reflow soldering. Comparatively, convection reflow oven stabilization can add as much as 15 minutes to a changeover process.

That said, VP reflow is a batch process and throughput can't be changed. While that works well with the smaller lot size focus of Lean, the system can become a constraint if sized below the likely line volume. For example, Firstronic selected an IBL CX600 VP reflow soldering system when it added the technology in November 2014 because the facility was ramping production and a conservative approach seemed justified. The machine is sized for medium- to high-volume production environments, which typically would have no more than two SMT placement machines feeding the reflow process. When the second system was added in mid-2015, a higher volume CX800 system was selected because production volumes had grown faster than anticipated. SMT line configurations included three SMT placement machines and the smaller CX600 system was becoming a constraint. The larger system supports the three placement machine configuration with no throughput issues.

Significant Quality Advantages

VP reflow soldering involves immersing PCBAs in a vapor blanket. This contributes to even heating and the vapor penetrates under every component. From a quality standpoint, this vapor blanket ensures perfect wetting and void-free, high quality solder joints. It also produces cleaner solder joints at lower temperatures (typically 240°C), eliminating the defect opportunities that can be caused by thermal shock during a convection reflow process that may reach 270°C.

Figure 2: A vapor phase “blanket” provides even heating and the vapor penetrates under every component.

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