5 Wave Soldering Profiling. IPC IPC-7530A

IPC-7530A provides guidelines for developing thermal profiles to produce acceptable tin-lead and lead-free electronics assemblies. It is a comprehensive document which covers various aspects of temperature profiling for mass soldering processes, including reflow and wave soldering. This document is intended for managers, design and process engineers and technicians who deal with mass soldering processes.

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IPC-7530A Draft Document for Industry Consensus Only August 2016

While all the primary fluids can be classed as perfluorocarbons, the basic structure (amine, cyclic or ether) will determine the key properties of in-use stability, solder paste chemicals solubility and overall process economics.

The choice of a fluid is normally based on the melting point of the solder alloy to be reflowed.

For the range cited, the lower temperatures are suitable for the typical tin-lead or tin-lead-silver alloys used for standard attachment processes. The upper end of the range will permit reflow of high-lead alloys, which are used to attach pins to pin grid array (PGA) packages. Users faced with reflow of a specialty alloy have been successful in mixing two primary fluids to tailor a vapor-phase system for a specific stable boiling point. Higher temperatures will permit shorter times, which may be advantageous with some solder pastes.

The primary vapor phase should be inert and not introduce contaminants that must be removed later. Solder paste chemicals that dissolve in the fluid are carried in the high-boiling vapor then deposited onto the surface of the boards. Such residues tend to be difficult to remove. Minimizing solder paste residue in the primary fluid will maximize the lifetime of the fluid, prevent boiling point elevation due to dissolved paste ingredients and simplify cleaning.

The secondary vapor blanket was originally CFC-113, a lower-boiling fluorinated material, which formed a low-cost sacrificial “lid” over the costlier primary fluid. The constant exposure to the high-boiling primary fluid at the interface of the two fluids would cause the secondary fluid to undergo thermal decomposition at the interface, generating HCl (hydrochloric) and HF (hydrofluoric) acid vapors. These corrosive vapors often attacked the soldering equipment over time. While in theory the vapors could be absorbed in flux residues and cause problems for high-reliability products, this was rare in comparison to the attack on the equipment. With the phase-out of

CFC-113, a low-boiling perfluorocarbon was introduced to replace it. This second-generation secondary blanket fluid was more stable than CFC-113 for prolonged exposure to the high-boiling vapor-phase fluids.

As surface mount technology grew, most users converted to the higher throughput in-line machines, which used the single-fluid approach. Defluxing after vapor-phase reflow should be done with either a polar solvent formulation or include an aqueous cleaning formulation that can ensure removal of all solder paste residues, with the choice of cleaning process based on the composition of the solder paste. Secondary factors influencing the decision would be compatibility and the component-to-PWB surface spacing. In addition, most companies gave serious thought to considering the potential chemical loss from using this type of equipment since many perfluorinated compounds are very long-lived global warming compounds.

5 WAVE SOLDERING PROFILING

By definition, mass wave soldering implies creating many solder connections simultaneously in a semiautomated or automated process. Equipment designed for this task generally has four basic characteristics:

• Product conveyance

• Fluxing capability

• Preheating capability

• Molten pot of solder with a nozzle

The key feature of the wave soldering machine is the type of wave nozzle that is used, this will determine the quality of solder for both through-hole and surface-mount components. Solder waves commonly used are singlewave, or dual-wave where the first wave is turbulent either rough and also or oscillating-wave. The other key feature of a solder wave is whether the solder falls in one direction or in both directions back into the solder pot.

In general, the number of defects (e.g., icicles or bridging) are much lower in waves where the solder falls only in one direction – backward.

IPC-7530A Draft Document for Industry Consensus Only August 2016

The differences between manufacturers are in the application of these basic concepts and the equipment controls.

Each machine has unique characteristics that need to be taken into account when developing a thermal profile.

Traditional wave soldering machines are used for mass soldering of through-hole and some surface-mount components (typically chip resistors and capacitors). When bottom-side surface-mount components are soldered, they are secured in place with a cured adhesive prior to soldering.

The wave soldering system automatically performs the soldering process, which is flux application, heating of the area to be soldered, application of molten solder and solidification, as all of these characteristics act together to ensure proper soldering. A solder recipe is developed by recording the optimum process parameters selected for conveyor speed, flux application, preheaters and solder temperature.

When profiling assemblies for wave soldering, the following areas should be monitored. See Figure 5-1 for an example of a dual wave soldering profile.

Preheat: The rate of temperature increase is controlled to ensure the PWB, components and flux have sufficient time to reach soldering temperatures without degradation.

Thermal shock/peak temperature: Thermal shock and peak temperature is measured to ensure components are not exposed to excessive shock and/or temperature that can result in damage.

Dwell time: Dwell time is measured to ensure excessive time in the solder does not occur, which could result in damage to components.

Peak topside temperature: Maximum topside temperature is monitored to ensure solder joints formed by reflow do not revert to a liquid state.

FIRST

WAVE

SECOND

WAVE

200

180

160

150

140

130

280

270

260

250

240

230

220

210

120

110

100

TOO RAPID

HEATING RATE

15 30 45 60 75 90 105 120 135 150 165 180 195

TIME (SECONDS)

Figure 5-1 Dual-Wave Solder Profile

Key features

Thermal Profile Development for Mass Soldering
Reflow and Wave Soldering Processes
Temperature Profiling Requirements
Guidelines for Solder Alloy Selection
Optimizing Profiles for Different Applications
Solder Joint Quality and Reliability
Troubleshooting Common Soldering Defects

Frequently asked questions

The primary purpose of this document is to provide practical information to those responsible for developing thermal profiles for mass soldering processes, including reflow and wave soldering. It aims to ensure the production of high-quality solder joints by optimizing the temperature profile during the soldering process.

Temperature profiling is crucial for ensuring consistent and reliable solder joints. It helps to control the heating and cooling rates during the soldering process, preventing damage to components and the printed wiring board (PWB). A well-defined thermal profile ensures that all solder joints reach the required temperature for proper metallurgical bonding.

This document primarily focuses on two common mass soldering processes: reflow soldering and wave soldering. It provides specific guidelines for developing thermal profiles for both processes, considering the unique characteristics and challenges of each.

IPC-7530A provides guidelines for developing profiles that accommodate both tin/lead and lead-free components. It highlights the importance of considering the different melting points and temperature requirements of each type of component during profile development.

User questions

Patricia K.

What factors are important when creating a wave soldering thermal profile?

The solder alloy and flux limitations, component and substrate specifications including their limitations, web width for conveyor speed calculation, preheat zone temperature settings, solder pot temperature setting, and cooldown settings are crucial factors for developing a wave soldering thermal profile with preheat, soldering, and cool down phases.

Linda L.

How can heat sink effects be minimized during mass wave soldering?

Use thermal relief for large metallic planes like ground planes to minimize thermal sinking and ensure even heat distribution.

Linda L.

How can good soldering quality be ensured with surface mount components in mass wave soldering?

Align surface mount components parallel to the wave to ensure smooth solder flow and consistent contact with component leads.

Linda L.

What are considerations for using selective wave soldering pallets?

Ensure adequate clearance for components and proper alignment to prevent soldering failures. Proper clearance for older components and proper alignment for surface mount components are crucial.

Linda L.

How can component movement be prevented during mass wave soldering?

Secure large components like connectors and sockets to prevent movement and avoid misalignment or damage during soldering.

Mary J.

What is the lifespan of a type K thermocouple?

The viewed document does not specify the lifespan of a type K thermocouple. However, the lifespan of a standard thermocouple and sample board is estimated at 15-30 profiles, depending on factors such as PWB thickness and laminate type. Reattaching the thermocouple to multiple assemblies reduces lifespan to 3-5 profiles.

Linda L.

How does the distance of soldering connections to the PWB edge affect mass wave soldering?

The distance from soldering connections to the PWB edge affects heat conduction and the thermal profile. Connections should be sufficiently far from the edge to prevent soldering problems.

Linda L.

How does PWB rigidity at maximum soldering temperature impact mass wave soldering?

PWB rigidity affects its ability to withstand heat and deformation during soldering. A rigid PWB helps maintain a consistent thermal profile, ensuring good soldering quality.

Michael I.

What are the guidelines and requirements in IPC-7530A for creating thermal profiles in mass soldering processes?

IPC-7530A provides guidelines and requirements for developing thermal profiles to ensure high-quality solder joints in reflow and wave soldering. It covers key terms, profiling methods for various soldering types, temperature profiling tools, and troubleshooting soldering defects.