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Temperature Profile Testing

A project log for T-962A Reflow Oven Modifications

Modifications to a T-962A reflow oven which turn this cheap oven to a surprisingly effective piece of hardware.

LanceLance 04/25/2021 at 17:200 Comments

Introduction

Before I started to run PCBs through the oven, I wanted to characterize the behavior.  I ran a series of trials where I measure the temperature at a PCB with a multimeter.  That way I could compare the temperature at the PCB with the oven's programmed temperature profile.

Initial Observations

I quickly noticed a few things.  Most of these items were not surprising, but they are important to be aware of.  Notably:

Temperature Profiles

The standard temperature profile for leaded solder that comes with the Unified Engineering firmware.  It was consistently slightly low for the solder paste I was using.  Therefore, I created two new profiles for testing which reached a slightly higher temperature.

After some initial testing, it seemed that the oven could not keep up with the temperature profile (temperature climb rate).  In addition, some testing showed that the standard profile that came with the oven could reflow the solder when testing without part.  Therefore, I decided to slightly modify the standard profile rather than trying to use the profile provided on the solder paste data sheet.  The profiles are compared in the graph below.

Temperature Profile Comparison
Temperature profile comparisons for a solder paste, the built-in profile from the Unified Engineering firmware, and two custom profiles.

Methodology

The temperature probe of a multimeter was hooked to a multimeter, ran through a slot at the bottom of the oven drawer, and attached to a PCB (a piece of protoboard) in the center of the oven.  See the picture below.  Readings were taken for:

Each combination of variables was run 3 times. 

Temperature Probe Placement
The placement of the temperature probe in the oven. This is for runs with the stand-offs. For board was directly on the drawer for some runs.

Results

The results are shown below.  You can download the excel file with all the data and each of the temperature profiles used from the main page.

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