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发表于 2017-5-19 21:12:31
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Heatless (cold) Toner Transfer (for PCB)
Preface
Toner transfer tecnique for making PC boards is really practical and economical. The use of heat for transfering is not. Large boards expand with heat and toner does not adhere uniformly mainly because heat is applied to the paper side and not to the toner contacting the copper below. In this video I will describe a very simple technique I've been using for over 15 years. It is very fail-proof and involves the use of only 2 very common chemicals: Ethylic alcohol and Acetone. Alternatively to Acetone you can use Toluene or Xylene, (proportions may vary)
How It Works
1) ALCOHOL
In this experiment you can see that Alcohol is absolutely neutral to Toner and paper.
2) ACETONE
Here you can see that ACETONE (pure) dissolves the toner immediately. Paper remains unaffected.
By mixing Acetone and Alcohol in precise proportions, you will obtain a solution which will SOFTEN the toner enough to make it "STICKY" but not dissolve or blur.
Experimenting, I found this "magic" number to be:
8 parts Alcohol 3 parts Acetone
some toners may require a higher acetone ratio
You can store the solution in an airtight container. If it is a plastic one it should be made of HDPE (high density polyethilene) which is unaffected by ACETONE. Acetone is much more volatile than alcohol so exposing the solution to air will decrease its concentration.
Procedure
Clean the copper surface of the board with steel wool and water as you normally do. Rinse with water and dry with kitchen paper.
Spray board and LASER print with alcohol and wipe with kitchen paper. This will remove any oil and fingerprints. Do not touch.
Pour a small quantity of acetone-alcohol solution on the copper side of board. Spread uniformly with fingertipLfclean!).
Acetone is much more volatile than felcohol so these steps should be performed as quickly as possible, or acetone will lose concentration.
Place the print on the board and quickly position it in place avoiding perpendicular pressure. Once jn place, gently push down (no pressure yet) until the entire print is in contacting the solution.
Wait 5-10 seconds before applying firtal pressure. During this time ACETONE is reacting wttfi the toner, rendering it sticky.
Now give a perpenclicular pressure (na horizontal shift) firmly with the aid of kitchen paper for even distribution.
wait 2 or more minutes until all solvents are totally volatilized.
Dip the board in water for at least 2 minutes. Time may vary, depending on th^ paper used I use coated paper. Don't use transparency papers it won't allow for proper evaporation of solvents.
Carefully peel the paper off the board starting from a corner.
You can see there is absolutely no toner on the paper, It's all on the copper
For larger PC boards I place the board laser print between 2 blocks of wood, and press together with a C-Clamp. I add a few layers of kitchen paper between print and wood to distribute pressure evenly.
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For board etching, use your favorite technique. My favorite is the Sponge & Ferric-Chloride one I believe it's the most economical (very small quantity of etchant) and fast (you can actually see the progress). |
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