I'm new in SMD technology and i would like to share with you my issue.
I bought an oven toaster in order to convert it to a SMD Reflow Oven having in mind to use an arduino board with a K-type thermocouple as the PID controller.
As a first step i modified the oven adding an SSR to control the heating elements. I connected a K-type thermocouple to an MAX31855 in order to read the temperature and i added some extra gold thermal tape in the inside of the oven to increase the heat reflection. The code i used is the rocketscream reflow example modified according to my needs.
Configuration values of the code:
// ***** CONSTANTS ***** #define TEMPERATURE_ROOM 50 #define TEMPERATURE_SOAK_MIN 150 #define TEMPERATURE_SOAK_MAX 200 #define TEMPERATURE_REFLOW_MAX 245 #define TEMPERATURE_COOL_MIN 100 #define SENSOR_SAMPLING_TIME 1000 #define SOAK_TEMPERATURE_STEP 5 #define SOAK_MICRO_PERIOD 9000 #define DEBOUNCE_PERIOD_MIN 50 // ***** PID PARAMETERS ***** // ***** PRE-HEAT STAGE ***** #define PID_KP_PREHEAT 100 #define PID_KI_PREHEAT 0.5 #define PID_KD_PREHEAT 20 // ***** SOAKING STAGE ***** #define PID_KP_SOAK 300 #define PID_KI_SOAK 0.05 #define PID_KD_SOAK 250 // ***** REFLOW STAGE ***** #define PID_KP_REFLOW 300 #define PID_KI_REFLOW 0.5//0.05 #define PID_KD_REFLOW 350 #define PID_SAMPLE_TIME 1000
The solder paste i use is sn62pb36ag2
This is the thermal curve output of the oven and this is the result of the reflow As you can see the reflow result isn't as it was expected to be.
1) Is this a problem of the reflow curve?
2) How can i tune the PID in order to achieve the ideal curve?
3) Shouldn't this curve reflow the solder paste?