4. Mounting with Solder
When to Use: When you need minimal outgassing; when the TEC is smaller than 19mm; when you need a high-strength junction; when high thermal conductivity is required. IMPORTANT: The device to which the TEC is being soldered should be placed on a thermal insulator. This will allow the device to become hot enough to reflow the solder. If necessary, the device may be placed on a hot plate set at 100°C to help heat it to the solder melting point.
Step One: Clean the surfaces to be soldered with methanol, acetone or a general-use solvent to remove oils and residues, which would inhibit soldering.
Step Two: With a soldering iron and a new tip, pre-tin the bottom of the TEC (the side with lead wires) using Marlow Industries' Solder 96°C or 117°C and General Purpose Acid Flux. Use small amounts. You can heat the soldering iron to a maximum of 150°C, but extreme care must be taken since most TECs are constructed with 138°C (min.) solder. CAUTION: Do not mix solders. Use a separate soldering iron (or a new tip) for each solder.
Step Three: With soldering iron, pre-tin the header or heat sink with the same solder and flux as used in pre-tinning the TEC. Use small amounts.
Step Four: To minimize flux residue, clean both the header and TEC. Rinse them first in hot water, then scrub with Marlow Industries' Cleaning Solution and rinse again with hot water, brushing away any excess flux residue. Finally, wash with methanol and use forced air to blow dry.
Step Five: Prior to mounting the TEC to the header, add a small amount of Marlow Industries' Blue Mounting Flux to the mounting site on the header.
Step Six: Hold TEC with tweezers and align on header. While doing this, maintain a steady, downward pressure.
Step Seven: While holding the TEC in place, put the soldering iron to the header near the solder seam. When the solder junction flows, remove the soldering iron. The downward pressure on the TEC will expel excess solder. REMEMBER: The solder that holds the TEC together flows at 138°C (min.), so if you are using the 117°C solder, do not leave the soldering iron on the header surface too long, or you will melt the TEC solder as well.
Step Eight: Continue holding the TEC in place until the solder solidifies.
Step Nine: Check along all four edges of the TEC, looking for voids, cracks or bubbles. A smooth seam ensures proper thermal conduction.