In SMT processes, how to increase solder paste or solder volume locally

In SMT processes, how to increase solder paste or solder volume locally?

With the miniaturization and increasing precision of electronic products, SMT is widely used in electronics manufacturing. The amount of solder paste directly affects the quality and reliability of solder joints. In some cases, increasing solder paste or solder locally is necessary to meet specific welding requirements.

1. Necessity of Increasing Solder Paste or Solder Volume Locally

Increasing solder paste or solder volume locally is essential for:

Heat Dissipation: More solder improves thermal conductivity for high heat-generating components.

Mechanical Strength: Additional solder forms stronger joints in stress-prone areas.

Compensating for Dimensional Tolerances: Extra solder ensures reliable connections despite variations in component leads and PCB pad sizes.

2. Methods to Increase Solder Paste or Solder Volume Locally

In SMT processes, consider these methods:

a. Adjusting Stencil Aperture Design

Modifying stencil aperture size can control the amount of solder paste. Enlarged or specially shaped apertures can increase solder at pad edges. This method is simple and cost-effective, but improper adjustments may affect quality and are limited by stencil size constraints.

b. Multiple Printing

Perform multiple printings to increase solder deposition. This allows precise control over solder volume but increases production time and cost, with potential misalignment risks.

c. Using Solder Preforms

Place preformed solder on pads before reflow. This provides precise volume control, ideal for high-solder needs, but manual placement is time-consuming, and automation may need extra steps.

d. Dip Soldering or Wave Soldering

Use for through-hole components or specific pads to add more solder. It's fast and effective for bulk addition but not suitable for all SMT applications, with risks of solder bridging.

e. Adjusting Solder Paste Composition

Use solder paste with higher metal content or adjusted rheology to boost post-reflow solder volume.

Advantages: Suitable for whole boards or specific areas; no stencil redesign required.

Disadvantages: Can affect reflow profile and process, needs specialized pastes, raising costs.

Conclusion

The decision to locally increase solder paste or solder volume in SMT processes requires careful evaluation, weighing the benefits against potential drawbacks. Each method has its ideal application, and often a combination of techniques is necessary. Engineers must consider assembly requirements, component characteristics, and production efficiency to determine the most effective approach.