3.4.2 IR vs Convection. 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

• Edge-rail or center-support capability

Some of these options will be discussed in 3.4.2 through 3.4.7.

3.4.2 IR vs Convection

Reflow ovens are typically either IR or convection reflow. In an IR oven, ceramic heaters are used to transfer heat to the assembly using radiation. In a convection reflow process, fans are used to force heated air to the assembly.

Recent advances in reflow processes and oven configurations have evolved the use of vacuum reflow. Vacuum reflow helps in applications which require very low levels of solder voiding in the attachment of a device.

3.4.3 Heating Zone Selection

The number of heating zones in standard reflow ovens range anywhere from seven to 12 and possibly more. There are usually top and bottom heaters that can be set independently when setting up a reflow profile. For lead-free applications, a minimum of seven heating zones should be selected. For reflow ovens that are being put in line with other pieces of equipment, throughput may be another consideration in terms of length of the oven and number of heating zones needed to balance throughput with an optimal reflow profile.

3.4.4 Clearance Height/Conveyor Belt Type/Conveyor Belt Width/Edge-Rail Support

In terms of a clearance height selection, normally the oven clearance height is kept to a minimum to maintain consistent heating within and between zones. The height of the product needs to be taken into account when defining the clearance height required for a particular oven. The type of product being assembled also impacts whether the conveyor belt is fine-mesh or not. If a device is fairly small, a fine-mesh belt may be needed to eliminate the use of added fixturing to transfer the part through the oven. The necessary belt width also is determined by the size of the assembly passing through the oven. If an assembly is double-sided, edge rails can be added to the oven so additional fixturing may not be required to support the assembly above the conveyor belt and to allow for better airflow around the assembly.

3.4.5 Cover Gas

Standard reflow ovens can be configured in such a way that either the oven is run in an open-atmosphere environment or with a cover gas such as nitrogen being used during reflow. Determining the need for using nitrogen gas is related to the type of flux in the solder paste for the particular application. It also depends on the plating on the PWB and the terminals of the ICs being assembled.

Nitrogen helps to slow oxidation or prevent reoxidation on metal surfaces. It also promotes better wetting during the reflow process, especially when soldering to NiAu and bare-copper lands. With advances in solder paste, the need for nitrogen has reduced, especially if an aggressive flux is used in the solder paste selected. This, however, can be a trade-off on whether a cleaning process is needed to remove flux residues. The major drawback of adding a nitrogen package to an oven is not only the initial cost of adding the feature but also the long-term cost of ownership of having house gas plumbed to the oven.

3.4.6 Profiling

In most cases, reflow ovens are configured such that on-board reflow profiling can be accomplished. In this, one end of a thermal couple is attached to the oven, and the other end of the thermal couple is attached to the product traveling through the oven. This option eliminates the need for the purchase of an added data recorder for profiling capability.

3.4.7 Product Trackers

Ovens can also be configured with product trackers to allow for traceability of parts through a reflow oven. These trackers have sensors mounted at the entrance and exit of an oven to sense when a product enters and exits the oven.

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.