Surface Mount Technology Printing and Reflow

Introduction

This section covers the Surface Mount Technology (SMT) Printing and Reflow challenges in electronics manufacturing. These technologies are critical parts of the electronic assembly process. Technology issues and solutions have been identified by industry experts comprised of printing and reflow equipment manufacturers and engineers who are involved in this area on a daily basis. A total of 14 issues are reviewed in the area of printing and 11 issues are reviewed in the area of reflow.

Conclusions

Printing and reflow continue to be challenging areas in electronics assembly operations due to the increased miniaturization and densification of components and assemblies. Technology issues have been identified and projected by industry experts who are investigating the assembly of product on a daily basis.

There are many key issues in Printing, which include the following:

1. Stencils to improve print quality of small apertures on mixed-component applications.

2. Enabling low area ratio printing through advancements in laser-cut stencil fabrication.

3. Step stencil print quality.

4. The need to increase automation in the printing process (changeover, process control and changeability). Less manual operation of the printing process.

There are many key issues in Reflow, which include the following:

1. Demand for higher throughout/conveyor speed ovens (Longer ovens to meet process time and throughput)

2. Need low voiding during reflow which will affect reflow oven throughput (e.g., for MOSFET type and BTC components) (Need to look at the types of heating zone methods to address this challenge)

3. Vacuum/vapor (Formic acid/hydrogen atmosphere) phase oven contamination. Effect of flux chemistry on reflow oven and maintenance requirements.

4. Improve flux extraction and removal for convection ovens

5. Need to have different types of heating methods to address reducing Delta T between small and large components (<5°C to <15°C Delta T and limiting time over liquidus). This causes overheating of small components.

6. Sustainability and energy consumption for reflow ovens (Need for less N2, power consumption, etc. and a lower carbon footprint).

It is important to understand that as designs produce assemblies with miniaturized components with tighter component spacings and with the advent of larger components, the challenges for printing and reflow are increasing and will continue to increase in the future. The printing and reflow equipment manufacturers continue to research equipment, materials, designs and methods to address the challenges faced in this area.

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