What is meant by reflow?
1 : to flow back : ebb. 2 : to flow in again. Other Words from reflow Example Sentences Learn More About reflow.
Why is it called reflow?
Etymology. The term “reflow” is used to refer to the temperature above which a solid mass of solder alloy is certain to melt (as opposed to merely soften). If cooled below this temperature, the solder will not flow.
Why is nitrogen used in reflow?
Nitrogen replaces oxygen, and due to its inert (non-reactive) nature, provides greater profile flexibility and widens the process window; Prevents oxidation of solderable surfaces (promotes wetting) and of the molten solder.
What is convection reflow?
Forced convection reflow is the preferred method of SMT reflow soldering of surface mounted components to a printed circuit board (PCB) today. The oven is typically separated into zones in which each zone is independently controlled to optimize the thermal profile of the oven’s process zone.
What does it mean to reflow a chip?
R. (1) The process of heating and melting the solder that has been screen printed onto a printed circuit board in order to bond chips and other components to the board. Surface mount chips (SMT) use the reflow method. Contrast with wave soldering.
What is infrared reflow?
The infrared reflow soldering process is a common method for the rapid mass production of printed circuit boards (PCBs). The process involves the application of a solder paste (composed of solder and solder flux) to the necessary areas of a circuit board. This causes the solder paste to melt (reflow).
What is nitrogen soldering?
Nitrogen provides a suitable protective atmosphere for soldering processes. Wave soldering, selective soldering and reflow soldering are processes for joining different materials. Nitrogen provides a suitable environment for avoiding oxidation and helps to prevent the adverse effects of oxygen on the soldering process.
How many zones are in reflow?
The standard reflow profile has four zones: preheat, soak, reflow and cooling.
What is reflow oven used for?
A reflow oven is a machine used primarily for reflow soldering of surface mount electronic components to printed circuit boards (PCBs).
How can I prevent the formation of solder oxide during reflow?
The prevention of oxide formation during reflow can be accomplished in numerous ways. Currently, the most common approach is to coat the wafer with flux prior to reflow. The coated wafer is then reflowed in a nitrogen atmosphere that further discourages the formation of solder oxides.
Why is hydrogen used in the reflow process?
In the reflow process, elimination of solder oxide is important. Processing in hydrogen, therefore, prevents further oxidation of solder. Spiking the heat allows the process to dissolve oxide while not damaging bumped wafers. In the next few years, bump pitches will fall below 150 µm (Figure 2).
How to remove solder oxide from wafer bump reflow?
Solder oxides can be eliminated during wafer bump reflow by using a hydrogen processing atmosphere. The hydrogen process takes oxygen from the system, so solder oxide cannot be produced. Hydrogen combines with the oxygen to form water. The reduction of oxide, a chemical reaction, happens in the presence of hydrogen combined with heat.
What is the difference between flux-free reflow and flux residue?
While flux-free reflow has been used for many reflow processes at both board and package levels, flux residue interferes with wafer bump reflow. This has led to increased use of flux-free processing. Solder oxides can be eliminated during wafer bump reflow by using a hydrogen processing atmosphere.