Jet Solder Bath Dual Heater Control for Erosion Prevention
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Solution Overview
Problem
The use of lead-free solder with high Sn content in jet solder baths leads to erosion of stainless steel components due to the peeling off of the chromium oxide layer, causing overheating and potential short-circuits, and existing solutions like nitriding and heat conduction plates are inadequate in preventing this erosion.
Innovation Solution
A jet solder bath design that includes a temperature-detecting mechanism and dual heater control to alternately turn on/off the heaters once the solder reaches the melting point, preventing excessive heating and reducing power consumption, thereby preventing erosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-free solder with high Sn content is used in jet solder bath, then environmental compliance is improved, but erosion of stainless steel components occurs due to peeling of chromium oxide layer
Solution Approach 1:
A heat conduction plate made of aluminum or copper is introduced as an intermediary between the heater and the solder bath. This plate distributes heat uniformly across the solder bath surface, preventing localized overheating that causes chromium oxide layer peeling and subsequent erosion of stainless steel components.
Solution Approach 2:
The heating method is changed from direct heater contact to indirect heating through a heat conduction plate. This parameter change in the heating system prevents excessive temperature rise at specific locations, thereby preventing erosion while maintaining the benefits of lead-free solder.
2Productivity
If electric heater continuously heats the solder bath to maintain melting temperature, then soldering operation is maintained, but excessive heating causes erosion and power consumption increases
Solution Approach 1:
The heater operates periodically rather than continuously. The control unit turns the heater on and off based on temperature detection, providing heat only when needed to maintain solder at melting temperature. This periodic operation reduces power consumption while preventing erosion from continuous overheating.
Solution Approach 2:
A temperature detection device provides feedback to the control unit, which adjusts heater operation accordingly. When solder reaches melting temperature, heating is reduced or stopped; when temperature drops, heating resumes. This feedback control maintains productivity while minimizing energy loss and preventing erosion.
3Temperature
If high temperature heating is applied to melt lead-free solder, then soldering function is achieved, but chromium oxide layer on stainless steel peels off due to thermal expansion difference
Solution Approach 1:
The heat conduction plate serves as a mediator between the heat source and solder, distributing thermal energy uniformly. This intermediate layer prevents direct, concentrated heating that causes rapid thermal expansion and chromium oxide layer peeling, while still achieving the necessary solder melting temperature.
Solution Approach 2:
The heat conduction plate creates uniform local heating conditions across the entire solder bath surface. Instead of localized high-temperature zones that cause oxide layer peeling, the heat is distributed evenly, maintaining chromium oxide layer stability while achieving solder melting.
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 solution effectively prevents erosion of stainless steel components by controlling the heating process and reducing power consumption, extending the lifespan of the jet solder bath components and reducing the risk of overheating.
Implementation Method 1
The electric heater is set so that its temperature is not lower than 500 °C if a melting point of lead-free solder is, for example, 220 °C
Implementation Method 2
the oxidized film of Cr formed on a surface of the stainless steel is broken out because the solder and the stainless steel are rubbed by expansion and contraction of the solder and the stainless steel based on the difference in the coefficient of thermal expansion between them
Implementation Method 3
tin Sn contained in the solder is alloyed with Fe, Ni, and/or Cr in the stainless steel and they dissolve gradually in the molten solder
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
To provide a jet solder bath which prevents erosion from occurring. A thermocouple detects a temperature of solder 20 contained in the bath main body portion 2, a first heater portion H1 heats the bath main body portion 2, and the second heater portion H2 is provided near the first heater portion H1 and heats the bath main body portion 2. On the assumption of this, a thermoregulation portion drives both of the first and second heater portions H1, H2 until the temperature of the solder 20 which the thermocouple detects reaches a melting point thereof and drives any one of the first and second heater portions H1, H2 after the temperature of the solder 20 has reached the melting point. This can prevent the bath main body portion 2 from being heated more than necessary and enables consumed power of the jet solder bath to be reduced, which can prevent the erosion from occurring.