In the modern electronics manufacturing industry, particularly in the circuit board
assembly process, the application of soldering technology is becoming increasingly
widespread, and the reflow oven is a key piece of equipment that enhances the efficiency
of soldering. A reflow oven is not a simple heating device, but a sophisticated heat
engine. Through the precise control of heat, the solder paste melts and then cools,
allowing components and circuit boards to be firmly combined. In this paper, we will
focus on the importance of the reflow oven in the PCB assembly process and how to
optimize the soldering process to explore.
A reflow oven, also known as a reflow soldering machine, is divided into four internal
temperature zones: preheating zone, temperature rise zone, welding zone, and
cooling zone. By providing a heated environment, the solder paste is heated and
melted, so that the surface mount components and PCB pads through the solder paste alloy
are reliably bonded together, and then, after solidification and cooling, the components
are firmly welded to the PCB and will not fall off. Precise temperature control ensures
that the melting and cooling process of the solder is optimised.
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The Necessity of Solder Paste Application
SMT components are
positioned by brushing the solder paste on the PCB in advance by the brushing
machine. The solder paste is a mixture of powdered metal and flux.
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The Transformation of the State of the Solder Paste Needs
The metal powder in the
solder paste needs to be melted at a specific temperature, flow and wet
component pins and PCB pads, form solder joints, and then cool through the
reflow oven to solidify the solder joints, to achieve a permanent fixation.
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Precise Thermal Control of the Stringent Requirements
The process of melting,
flow, wetting, and solidification of the temperature profile is extremely
demanding:
- Insufficient temperature: The solder will not be able to
fully melt, resulting in false soldering or unreliable connection.
- Too high a temperature or too long: Will damage the
components, PCB board, or lead to solder oxidation and other defects.
With the popularity of surface mount technology (SMT), SMT components are smaller,
higher density, better performance, so the reflow oven plays a very critical role in
this process.
The current reflow oven adopts multi-temperature independent temperature control,
usually now more than 8-14 temperature zones, forced hot air convection, or infrared
heating technology.
- Through precise setting and real-time monitoring of the temperature of each
temperature zone, conveyor speed, and the formation of the optimal temperature
profile.
- Ensure that the entire PCB board, regardless of component size and positional
offset, can experience exactly the same thermal history to ensure soldering
consistency.
- Able to weld ultra-small pitch (fine pitch) IIC, such as BGA, CSP, QFN, etc.
- Avoid adjacent solder joints short-circuiting and component end warping and other
common welding defects.
- The optimised temperature profile of the reflow oven ensures sufficient melting and
wetting to form a good intermetallic compound layer (IMC layer) with high joint
strength, low resistance, and excellent electrical properties.
- Controllable cooling rate helps to form a fine solder joint structure with improved
resistance to thermal fatigue and mechanical shock.
- Integrated nitrogen protection reduces solder oxidation and improves wettability.
- Continuous reflow oven enables PCB boards to pass through various temperature zones
uninterruptedly with a fast production pace.
- High degree of automation, with the front and rear ends of the brush tin machine and
placement machine to form an SMT production line, greatly improving the production
efficiency.
Adjust the temperature configuration. According to different soldering materials to
adjust the temperature configuration to ensure that the temperature of the soldering
process is reasonably distributed to achieve the best soldering results.
Use an oven temperature tester (KIC, Datapaq, etc.) to find the shortest duration of
peak temperature (Time Above Liquidus, TAL) and the lowest necessary peak temperature.
- Reduces thermal stress, protects components and PCBs, reduces overall reflow time,
improves furnace throughput, and reduces energy consumption.
- Optimise the spacing of the PCBs on the tracks by rationally arranging the boards,
reducing the board spacing as much as possible, and increasing the number of boards
fed per unit of time under the premise of ensuring no collision and temperature
uniformity.
- Within the scope allowed by Profile, increasing the conveyor speed as much as
possible can also improve efficiency.
- Regular maintenance: Clean fans/filters, calibrate thermocouples,
check chains/rails for wear, lubricate drive parts, etc.
- Use the temperature monitoring and airflow monitoring functions that come with the
equipment, or add third-party sensors to detect the key parameters of the equipment
in real time.
- Carry out predictive maintenance to avoid sudden breakdowns and shutdowns.
- Consider whether the quality improvement is sufficient to offset the high cost of
gas (not all products and solder pastes require nitrogen, and nitrogen use may
reduce furnace capacity).
- If nitrogen is used, regularly test the sealing of the furnace chamber to repair
leaks and reduce nitrogen consumption.
- Set a reasonable minimum oxygen content target according to soldering requirements
(e.g., component sensitivity, solder paste specifications) to avoid excessive
pursuit of ultra-low PPM and gas waste.
Operating engineers and process engineers need to deeply understand the principle of
reflow soldering, the role of each stage of the Profile, defects, and the correlation
between the temperature profile.
- Be skilled in furnace temperature testing, curve analysis, furnace operation, and
maintenance skills to effectively carry out daily optimisation and problem solving.
In order to achieve high efficiency PCB assembly, a reflow oven is not just a simple
heating box. As electronic products continue to develop in the direction of smaller,
faster, and more complex, the requirements of the reflow soldering process are also more
and more stringent. PCBASAIL through the use of a reflow furnace to implement a series
of measures to optimise the soldering process, significantly improve the quality and
efficiency of welding, to ensure the reliability of the product, reduce costs, and
produce a large number of high-quality PCBAs.
30 May 2025 16:38:07 GMT
PCBASAIL