In the welding process of multifunctional ball bonding machines, controlling thermal damage to thermistors is a core aspect of ensuring welding quality. Thermistors (such as sensor chips, enzyme electrodes, and temperature compensation circuits) are typically extremely sensitive to temperature, with their upper temperature limits far below the heat-affected zone (HAZ) of traditional welding processes. Without effective protective measures, this can easily lead to component performance failure or even permanent damage. Multifunctional ball bonding machines achieve precise protection of thermistors through multi-dimensional technological collaboration, with core strategies encompassing four major areas: light source selection, energy control, process optimization, and environmental management.
Laser, as the welding heat source, is fundamental to reducing thermal damage in multifunctional ball bonding machines. Compared to traditional soldering irons or hot air soldering, lasers have higher energy density and shallower penetration depth. Their effective range can be precisely controlled within the solder joint contact area, with the HAZ typically not exceeding 30 micrometers. This "localized instantaneous heating" characteristic ensures that heat is only applied to the bonding surface between the solder ball and the pad, significantly reducing heat radiation received by surrounding thermistors. For example, when welding enzyme electrodes with a temperature resistance below 80°C, laser welding can control the temperature rise of the component to within 15°C, far lower than the hundreds of degrees Celsius rise caused by traditional processes, thus avoiding loss of enzyme activity or deformation of the electrode structure.
Pulsed heating technology and dynamic power adjustment are key to controlling heat input. The multifunctional ball bonding machine breaks continuous heating into multiple short energy pulses through pulsed energy output, preventing heat accumulation on the component surface. Simultaneously, the equipment can adjust the laser power and pulse interval in real time according to the heat absorption characteristics of the pad material (such as copper, gold, and stainless steel). For example, when welding copper pads, the system increases the peak power to compensate for copper's high thermal conductivity while shortening the pulse duration to prevent heat dissipation; while welding gold pads, the power is reduced and the pulse interval is extended to ensure sufficient welding. This dynamic adjustment mechanism keeps the thermistor within a safe temperature range.
High-purity inert gas protection is an auxiliary means to prevent thermal damage. The multifunctional ball bonding machine creates a localized nitrogen environment in the welding area, using 99.999% pure nitrogen to isolate oxygen and suppress oxidation reactions during the welding process. Oxidation not only degrades solder joint quality but also exacerbates the thermal load on components due to its exothermic effect. For example, when welding implantable medical sensors, high-purity nitrogen can stabilize the thickness of the intermetallic compound layer at the solder joint at 2-3 micrometers, avoiding additional thermal stress caused by an excessively thick oxide layer. Simultaneously, the flow of nitrogen accelerates heat dissipation in the welding area, further reducing the temperature rise of the heat-sensitive components.
The five-axis linkage system and sub-pixel vision positioning technology provide spatial precision for thermal damage control. Traditional welding equipment, due to insufficient positioning accuracy, is prone to laser spot deviation, causing heat to concentrate at the component edges and resulting in localized overheating. The multifunctional ball bonding machine achieves precise movement of the welding head in three-dimensional space through five-axis linkage, and combined with a 5-megapixel sub-pixel vision system, it can control the solder ball positioning accuracy within ±0.002 mm. This precision ensures that laser energy is always focused on the center of the weld joint, preventing the expansion of the heat-affected zone due to misalignment, making it particularly suitable for welding micro-weld joints with a spacing of less than 0.25 mm.
Closed-loop control and real-time monitoring of process parameters are the final line of defense against thermal damage. The multifunctional ball bonding machine integrates a temperature feedback module, which monitors the temperature of the welding area in real time through an infrared sensor and transmits the data to the control system. If the temperature approaches the upper limit of the temperature resistance of the thermistor, the system automatically reduces the laser power or shortens the pulse time; if the temperature rises abnormally, a protection mechanism is immediately triggered, stopping welding and triggering an alarm. This closed-loop control mechanism transforms the risk of thermal damage from a passive response to an active prevention, significantly improving welding reliability.
The multifunctional ball bonding machine constructs a complete thermistor protection system through five technical paths: laser characteristic optimization, dynamic energy management, gas protection, precise positioning, and intelligent monitoring. Its core advantage lies in compressing the heat-affected zone to less than one percent of that of traditional processes, reducing the damage rate of thermistors to below 0.3%, while achieving high-yield welding of ultra-micro weld joints as small as 0.2 mm. This technological breakthrough not only meets the demand for high-precision welding in fields such as medical and consumer electronics, but also provides a reliable guarantee for the mass production of miniaturized and highly integrated electronic products.
