What??? You don�t have enough things to monitor?
The origin of some profiles is mysterious. It�s probably good to try to understand such mysteries. Certainly, the important determinants in the design of your reflow profile are: * Paste you�ve selected. * Assembly you want to solder. * Features and capabilities of your oven.
The principal types of profiles are: TRADITIONAL: four distinct temperature ramp rates in ovens that are primarily convection. TENT: two distinct temperature ramp rates in ovens that are primarily convection.
You appear to be using a traditional profile. Typical temperature control times of a reflow profile are: PREHEAT TIME: Time from when the profile starts and the beginning of the ramp to peak temperature. SOAK TIME: Portion of Preheat Time prior to the beginning of the ramp to peak temperature when the temperature change is small. LIQUIDOUS TIME: Time when the solder is liquid. COOLING TIME: The time after the assembly cools below liquid temperatures.
But these things are not controllable on a reflow oven. So a typical profile control points are: PREHEAT RAMP: 2-3�C/sec ramp to 100-125�C DWELL: Very low ramp to approximately 183�C over a 90-150 sec period REFLOW ZONE: Peak temperature 30-90 sec over 183�C and a max temperature of 230�C COOLING ZONE: 10�C/sec.
Before moving on, let�s be basic. Your solder is not liquid at 183�C. That temperature is the school boy answer to �What is the temperature when eutectic solder transitions directly between solid and liquid states?�. The liquidous temperature of your solder is at least 20�C higher than the school boy�s, because your solder is NOT eutectic, your are NOT measuring the solder temperature, nothing ever works like you think it should, etc.
REASONS FOR NOT MONITORING WHATEVER ... REASON #1: Your profile starts the ramp to peak temperature at 150�C. You selected 150�C to give the oven time for a running start in overcoming the thermal inertia of sitting below 150�C for a couple minutes and still get a running shot at hitting the peak. REASON #2: Who cares? As long as your flux has activated during soak, you have activated the flux too fast, you get above the minimum peak temperature, stay below the maximum peak temperature, and have a steep cool-down ramp; you should get good connections. So, how ARE your connections, anywho?
reply »