THR Reflow Process
Temperature Profile According to DIN EN 61760-1
Standard DIN EN 61760-1 describes a specially optimized temperature profile with an upper and lower tolerance band for SMD methods, which can be set particularly well with a convection soldering oven. For processes that still contain lead it is important to warm up all components equally to just before liquidus point of the solder at 183°C (361.4°F). A temporary load with peak temperatures occurs in the range of 220 - 225°C (428 - 437°F). For future lead-free processes, this profile is expected to increase by approximately 30°C in total. THR male connectors are adapted to these temperature profiles and can be easily soldered with other SMT components in the reflow oven.
Convection Reflow Oven
With a current market share of approximately 80%, reflow profiles are generated with a convection reflow oven. The profile is generated with hot gas and the profile passes through various areas differing in heat. As can be seen from the profile, all requirements of the standard are met.
The Individual Phases of the Soldering Process
The soldering flux starts to flow before the liquidus temperatures are reached and the individual soldering globules move closer to one another. This is indicated by a dull surface similar to the "head of a match" (1). The compression of the soldering globules increases and the concentration at the soldering pin points is clear (2,3).
As the pin point reaches liquidus temperatures, the solder is already melted in this area (4). This solder mass moves up the edges of the pin towards the drill hole and draws the remainder, that is not quite melted, behind it (5). The solder is completely melted and and flows towards the bore hole (6).
The majority of the solder reaches the lower drill hole opening (7), a capillary effect occurs here, the solder is sucked into the drill hole and forms the characteristic soldering globule (8,9).
Filling Ratio of Bore Holes According to the Standard
