Reflow profile basics

Q1: What are the basic requirements of thermal profiling? A1: Not sure what you�re looking for here, but when doing a profile, you�re trying to measure the temperature at specific points of the board, as the board moves through the oven.

Q2: How we can achieve better profiling? A2: Use a good profiler and thermocouple[s] and attach the thermocouple[s] properly.

Q3: What is the need of doing profiling? A3: Some purposes of profiling are: 1. Assuring that the settings of the zones of your oven a set to properly reflow solder. 2. Checking the proper operation of the oven 3. Measuring the temperature at specific points of the board, as the board moves through the oven. 4. Controlling reflow soldering process. 5. Qualifying ovens.

Q4: What precaution should one take while doing profiling? A4: Use hot pads when handling the type of profiler that travels through the oven.

Q5: A profile is compared with what? A5: Your profiler needs to be calibrated, your thermocouple needs to be correct type and operating properly.

To learn more: * Check profiler supplier [eg, KIC, ECD, etc] sites for technical papers * Search the fine SMTnet Archives for more on profiling and thermocouples. For instance: http://www.smtnet.com/Forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=6929&mc=12

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In answer to your questions.

(1) pls can any body throw some light on the reflow profiling?

Reflow profiling is the process of confirming that you PCB's that pass through your reflow oven are produced within specifications provided by solder paste and component manufacturers. Each solder paste as a defined process window in which good solder quality will be achieved.

what r the basic requirements of thermal profiling?

Key parameters to be measured are; (i) Time above liquidus - time spend above liquidus temp. of solder paste (measure in seconds( (ii) Heating rates : ensures PCB/components are not thermally stressed (measured in C/Sec) (iii) Peak temperature : typically 20 - 30 C above liquidus temp. but not too hot else possible component damage etc. (iv) Cooling rates (v) Soak time : ensure delta across PCB is adequately low and that is flux activation is correct as per the definition of the paste guys. (vi) ..... and more

how we can achive better profiling? Get a pass through profiler (i.e. it passes behind the PCB through the machine), long thermocouples are a pain in the arse and repeatable results are not guaranteed. I have yet (thankfully) to see a reflow oven with profiling software that is any where near up to the job.

what is the need of doing profiling?

(1) Ensure solder quality is good (2) Optimise through put (3) Minimise recipe count (4) Reduce rework, early failures (5) Keep me in a job

what precaution should one take while doing profiling?

(1) Make sure you use the heatshield to protect your logger!! Your datalogger won't last long without it (2) Ensure your datalogger & test PCB is adequately cooled before performing your next run

profile is compared with what?

Any form of calibration or process control. The aim is the same. Machine go wrong, people lose oven setups or load the wrong one. The result is a bad process & unhappy customers.

I hope this helped,

Mark SolderStar - Temperature Profiling for Reflow & Wave www.solderstar.com

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