Reflow Furnace Hot-Air Heater Layout for Uniform PCB Soldering
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Solution Overview
Problem
Conventional reflow furnaces with hot air-blowing heaters struggle to simultaneously achieve a low Δt (temperature difference) and stable oxygen concentration, leading to inadequate heating profiles and potential thermal damage during soldering of printed circuit boards.
Innovation Solution
The reflow furnace design features a heater with a perforated plate in both the preheating and main heating zones, where the total area of discharge holes in the main heating zone is 1.5-5 times that of the preheating zone, ensuring a balanced hot air distribution to maintain stable oxygen concentration and minimize Δt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the total area of discharge holes in the main heating zone is increased to reduce temperature differences (Δt), then heating uniformity is improved, but oxygen concentration control deteriorates
Solution Approach 1:
The patent applies different hole area ratios to different heating zones: the preheating zone uses a smaller hole area ratio (0.5-2%) to maintain oxygen concentration, while the main heating zone uses a larger hole area ratio (2-5%) to achieve uniform temperature distribution. This local differentiation resolves the contradiction by optimizing each zone's discharge hole characteristics according to its specific heating requirements.
2Productivity
If the heating time in the main heating zone is shortened to prevent thermal damage, then productivity is improved, but heating uniformity deteriorates
Solution Approach 1:
The patent changes the physical parameters of the discharge holes (area ratio, distribution pattern) to optimize heat distribution. By adjusting the hole area ratio to 0.5-5% and distributing holes in specific patterns, the system achieves uniform temperature distribution faster, allowing shortened heating times without compromising heating uniformity, thus resolving the contradiction between productivity and manufacturing precision.
3Manufacturing precision
If the amount of hot air blown is increased to reduce temperature differences, then heating uniformity is improved, but oxygen concentration increases
Solution Approach 1:
The patent implements local quality control by setting different hot air discharge quantities for different zones. The preheating zone discharges hot air at a lower rate to maintain inert atmosphere, while the main heating zone discharges at a higher rate to ensure uniform temperature distribution. This zone-specific approach resolves the contradiction between heating uniformity and oxygen concentration control.
Solution Approach 2:
The heating system is segmented into distinct zones (preheating zone and main heating zone) with independently controlled discharge hole parameters. This segmentation allows each zone to be optimized separately: the preheating zone prioritizes oxygen concentration control, while the main heating zone prioritizes temperature uniformity, thereby resolving the overall contradiction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for uniform heating and stable oxygen levels, reducing thermal stress and ensuring complete melting of solder paste without overheating, thereby improving soldering quality and preventing defects.
Implementation Method 1
a reflow furnace using a heater which blows hot air... hot air flows into the furnace... hot air can flow around to the bottom of electronic parts or portions that are in shadows to perform heating
Implementation Method 2
far infrared heaters using only electrothermal heaters... far infrared rays can pass to the interior of an object being heated and perform heating
Implementation Method 3
in the main heating zone, solder powder in the solder paste is melted, and it wets and spreads over the portions to be soldered of a printed circuit board
Implementation Method 4
In the cooling zone, the printed circuit board which was heated to a high temperature is rapidly cooled, molten solder is solidified
Data Source
AI summary
A reflow furnace using a conventional heater for blowing hot air has difficulty in reducing Δt and in stabilizing the oxygen concentration at a low level. In addition, it is difficult to uniformly discharge hot air from the discharge holes in a perforated plate of a conventional heater for blowing hot air. In a reflow furnace according to the present invention, the total area per unit area of discharge holes formed in a perforated plate in a heater for blowing hot air installed in a main heating zone is 1.5-5 times the total area per unit area of the discharge holes formed in a perforated plate of a heater for blowing hot air installed in a preheating zone. A heater for blowing hot air has a body divided into three chambers by partitions.