Laser Soldering Beam Control to Prevent Scorching and Residue
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Solution Overview
Problem
Laser soldering techniques face issues with scorching of substrates and heat-susceptible components due to abrupt heating, leading to residue scattering and solder ball formation, and there is a need for weight reduction in laser soldering devices for automated soldering on wiring boards.
Innovation Solution
An automatic soldering method using a laser soldering device with a Z-axis drive for height adjustments, employing preliminary and main heating steps with varying laser irradiation diameters to control temperature and prevent scorching, and incorporating an image capturing device for monitoring the soldering process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If laser light is irradiated with a small irradiation diameter to avoid scorching the substrate, then substrate scorching is prevented, but residues are scattered outside the soldering region and solder balls are produced
Solution Approach 1:
The patent applies preliminary heating before main soldering heating. The preliminary heating step heats the flux solvent to its boiling point to volatilize the flux and prevent bumping, while the solder powder remains unmelted. This preliminary action prepares the solder droplet and flux environment to prevent residue scattering and solder ball formation during the subsequent main heating step, while keeping the irradiation diameter small to avoid substrate scorching.
Solution Approach 2:
The patent performs continuous laser irradiation with two distinct heating steps: preliminary heating followed by main heating. The laser irradiation continues without interruption, first heating the flux solvent to volatilize it, then heating the solder powder to melting temperature. This continuous action ensures complete soldering while preventing harmful effects through controlled temperature progression.
2Manufacturing precision
If laser light is irradiated with a large irradiation diameter to melt solder powder completely, then soldering is achieved, but the substrate and heat-susceptible components are scorched
Solution Approach 1:
The patent applies local quality by concentrating laser energy precisely on the solder droplet and flux region with a small irradiation diameter. The laser beam is focused to heat only the solder powder and flux solvent, melting the solder completely while leaving the surrounding substrate and heat-susceptible components unaffected. This localized heating achieves complete solder melting without substrate scorching.
Solution Approach 2:
The patent changes the temperature parameter through two staged heating processes. First, the flux solvent is heated to its boiling point temperature to volatilize it. Second, the solder powder is heated to its melting temperature to achieve complete melting. By controlling and changing the temperature parameter in stages, the patent achieves complete solder melting while preventing substrate scorching.
3Reliability
If a heater is used for preliminary heating to prevent bumping, then flux solvent volatilization is achieved, but device weight increases
Solution Approach 1:
The patent replaces the mechanical heater system with a laser-based heating system. Instead of using a physical contact heater to perform preliminary heating, the patent uses laser irradiation to heat the flux solvent to its boiling point. This substitution eliminates the need for additional heavy heating equipment while achieving the same bumping prevention effect through non-contact laser heating.
Solution Approach 2:
The patent uses laser light as an intermediary to transfer energy for preliminary heating. The laser beam serves as the medium to heat the flux solvent without direct contact, replacing the need for physical heater elements. This intermediary approach enables preliminary heating while keeping the device weight low, as the laser system is already present for the main soldering process.
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
Prevents scorching and residue formation while enabling weight reduction in laser soldering devices, ensuring precise and efficient soldering on wiring boards.
Implementation Method 1
irradiating solder droplet S with the laser light to heat the solder droplet S to a temperature at which a flux solvent component volatilizes and a solder powder does not melt
Implementation Method 2
irradiating solder droplet S with the laser light to heat the solder droplet S to a temperature at which the solder powder melts
Implementation Method 3
an optical fiber guiding laser light from the laser device to enter the irradiation hole
Implementation Method 4
a mirror guiding the laser light to the lower opening by reflecting the laser light or allowing the laser light to pass therethrough
Data Source
AI summary
A laser soldering technique prevents generation of scorching of a substrate or heat-susceptible components in the surroundings, residues, etc. A method includes adjusting a height of the laser soldering device 1 to a position at which laser light has a preset irradiation diameter D1 larger than a diameter of a solder droplet S, irradiating the solder droplet S with the laser light to heat the solder droplet S to a temperature at which a flux solvent component volatilizes and a solder powder does not melt; adjusting the height of the laser soldering device to a position at which the laser light has a preset irradiation diameter D2 smaller than the diameter of the solder droplet S, and irradiating the solder droplet S with the laser light to heat the solder droplet S to a temperature at which the solder powder melts, and performing soldering.