PCBA Tech - SMT chip processing reflow soldering furnace analysis

SMT chip processing reflow soldering furnace is an equipment for soldering surface mount components. SMT patch processing reflow soldering furnaces mainly include infrared furnaces, hot blast furnaces, infrared heating blast furnaces, steam welding furnaces, etc. The most popular at present is the forced full hot blast furnace. This section mainly introduces the compulsory full hot air stove.

1. Classification of reflow soldering furnace for SMT chip processing

There are many types of SMT chip processing reflow soldering furnaces. According to the heating area of chip processing and reflow soldering, it can be divided into two categories: heating the SMT circuit board as a whole and refusing to heat the SMT circuit board.

For the overall heating of SMT patches, there are box-type and flow-type reflow soldering furnaces, hot plate, infrared,

full hot air, gas-phase SMT patch processing reflow soldering furnaces, and box-type reflow soldering furnaces are suitable for laboratory and small batch production. Flow-type SMT patch processing reflow soldering furnace is suitable for mass production.

2. Full hot air reflow soldering furnace

The hot air reflow soldering furnace is currently the most widely used reflow soldering furnace. The main body is composed of the furnace body, upper and lower heating sources, SMT patch transmission device, air circulation decoration, cooling device, exhaust device, temperature control device, nitrogen device, It is composed of waste gas recovery device and computer control system.

1. Air flow design

There are many domestic and foreign manufacturers producing SMT patch reflow soldering equipment, and the airflow design of each manufacturer is different, such as vertical airflow, horizontal airflow, large return air, and small return air. No matter which method is used, high convection efficiency is required, including speed, flow, fluidity, and permeability. The airflow should have a good coverage, and it is not good if the airflow is too large or too small.

Air flows. Air or nitrogen enters the furnace body from the inlet of the fan. After being heated by the heater, the forced hot air generator on the top transfers the heat of the hot air to the SMT patch assembly board. The cooled hot air flows through the channel and shoots out from the outlet. . Hot-air SMT processing and reflow welding is a process in which hot air continuously circulates according to the designed airflow direction, and heat exchanges with the heated part.

2. Heating source design

The heating efficiency of the reflow soldering furnace for SMT chip processing is related to the heat capacity of the heating source. The high-heat-capacity heating source with a large heating body has good temperature stability and can control temperature and airflow at the same time. The heat distribution in the furnace is relatively uniform, but the thermal response is slow and the cooling rate is slow; the low-heat-capacity heating source with a thin heating body has low cost. The thermal response is fast, but the temperature stability is poor, and the heat distribution, temperature and air flow in the furnace are not easy to control.