How to Create a Reflow Profile for a PCB？

This Gold Phoenix PCB Knowledge Center article explains how to create a reflow profile for a 16-layer, 2mm thickness PCB with a high density SMT connector, including thermocouple placement, soak time and TAL, preheat and cooling set points, and 7-zone oven temperature data.

How to Create a Reflow Profile for a 16-Layer, 2mm Thickness PCB with a High Density SMT Connector?

A high density SMT connector, such as a .050" high-speed, high-density open pin field array connector, has up to 500 I/O contact pins with a solder charge termination.

This type of connector looks like a standard BGA type of SMT device. A proper thermal profile for reflow must be evaluated by the process engineer prior to production.

• Thermocouple (TC) location: To verify the correct reflow profile, 2~3 thermocouples should be placed beneath the connector: one (1) in the leading corner position, one (1) in the middle of the connector, and one (1) at the trailing corner (optional). These thermocouple placements ensure that all areas of the connector receive even heating simultaneously.

• Soak time and TAL consideration: To ensure proper temperature equalization of the whole area beneath the connector, it is recommended that the soak time is long enough as well as the time above liquidus be long enough for a total reflow. Of course, all data must meet with the solder paste manufacturer’s specifications.

• Preheat and cooling set point: A PCB’s physical properties are also a critical consideration for correct profile adjustment. In this case, the PCB has 16 layers and a 2mm thickness. This means that this bare board has a high thermal resistance. So, the preheat set point can be adjusted higher than normal; however, the cooling point may lower than normal in order to meet TAL within the specifications.

The following profile data is provided as a reference example only: (Note: this is for reference only):

• Reflow oven: Concept 7 zone

• TAL: 60 sec

• Peak temperature: 245℃