4. Requirements for PCBs to be tested

(a) In principle, it should be made from the entire reflowed products suitable for this reflow machine to ensure its temperature changes

within the reflow oven are reflected really.

(b) If substitutes are used, they should meet the following requirements: The same base-panels, the same base-panel sizes, the same

base-panel thicknesses, almost the same number of components, and similar heat ab sorptivity or heat resistance of components.

5. Other precautions

(a) When PCBs and memory device are placed together into the oven, attention shall be paid that distance between memory device and

PCBs should be above 100mm to avoid heat disturbance.

(b) Relevant experimental data show that reflow oven can only achieve oven-body heat balance after starting up for 30 minutes. Therefore,

profile test and formal production can only be started after oven has been run for at least 30 minutes.

(c) After profiles are printed out, equipment should be adjusted, based on preheat temperature and time, reflow peak temperature, reflow

time, temperature rise and cooling rates and so on, until profile requirements are met. Due to different heat capacities of various test points

as well as non-uniformities of characterized reflow oven temperatures, certain differences among three test points' profiles will still exist.

(d) Records of profiles: In addition to printing out profiles, scopes and actual values of their parameters, device's settings, test points'

location distributions, PCBs' entrance directions, testing times, test results and judgments, etc. should also be recorded.

(e) Measurement frequency: In principle, tests are performed once a week (or based on customers' requirements). If settings or products

are changed, tests are needed for new profiles.

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