Solve teh following problem:
Q: You have been asked to determine the feasibility of using an impinging jet in a soldering operation for electronic assemblies. The schematic illustrates the use of a single, round nozzle to direct high velocity, hot air to a location where a surface mount joint is to be formed
For your study, consider a round nozzle with a diameter of 1 mm located a distance of 2 mm from the region of the surface mount, which has a diameter of 2.5 mm.
(a) For an air jet velocity of 70 m/s and a temperature of 500°C, estimate the average convection coefficient over the area of the surface mount.
(b) Assume that the surface mount region on the printed circuit board (PCB) can be modeled as a semi-infinite medium, which is initially at a uniform temperature of 25°C and suddenly experiences convective heating by the jet. Estimate the time required for the surface to reach 183°C. The thermo physical properties of a typical solder are p = 8333 kg/m3, c p = 188 J/kg · K, and k = 5] W/m · K.
(c) For three air jet temperatures of 500, 600, and 700°C, calculate and plot the surface temperature as a function of time for 0 < t="">< 150="" s.="" on="" this="" plot,="" identify="" important="" temperature="" limits="" for="" the="" soldering="" process:="" the="" lower="" limit="" corresponding="" to="" the="" solder's="" eutectic="" temperature,="" tsol="183°C" and="" the="" upper="" limit="" corresponding="" to="" the="" glass="" transition="" temperature,="" tgt="250°C," at="" which="" the="" pcb="" becomes="" plastic.="" comment="" on="" the="" outcome="" of="" your="" study,="" the="" appropriateness="" of="" the="" assumptions,="" and="" the="" feasibility="" of="" using="" the="" jet="" for="" a="" soldering="">
