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Soft Water Versus Deionized

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Soft Water Versus Deionized | 26 January, 2007

What is the difference in using soft water to do the cleaning on reworked boards? Are the reliability concerns with this process?

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Soft Water Versus Deionized | 27 January, 2007

[clipped] Chemistry of Hard and Soft Water From Anne Marie Helmenstine, Ph.D., Your Guide to Chemistry.

Water Works I'm sure you've heard the terms 'hard water' and 'soft water', but do you know what they mean? Is one type of water somehow better than the other? What type of water do you have? Let's take a look at the definitions of these terms and how they relate to water in everyday life.

Hard water is any water containing an appreciable quantity of dissolved minerals. Soft water is treated water in which the only cation (positively charged ion) is sodium. The minerals in water give it a characteristic taste. Some natural mineral waters are highly sought for their flavor and the health benefits they may confer. Soft water, on the other hand, may taste salty and may not be suitable for drinking.

If soft water tastes bad, then why might you use a water softener? The answer is that extremely hard water may shorten the life of plumbing and lessen the effectiveness of certain cleaning agents.

When hard water is heated, the carbonates precipitate out of solution, forming scale in pipes and tea kettles. In addition to narrowing and potentially clogging the pipes, scale prevents efficient heat transfer, so a water heater with scale will have to use a lot of energy to give you hot water. Soap is less effective in hard water because its reacts to form the calcium or magnesium salt of the organic acid of the soap. These salts are insoluble and form grayish soap scum, but no cleansing lather. Detergents, on the other hand, lather in both hard and soft water. Calcium and magnesium salts of the detergent's organic acids form, but these salts are soluble in water.

Hard water can be softened (have its minerals removed) by treating it with lime or by passing it over an ion exchange resin. The ion exchange resins are complex sodium salts. Water flows over the resin surface, dissolving the sodium. The calcium, magnesium, and other cations precipitate onto the resin surface. Sodium goes into the water, but the other cations stay with the resin. Very hard water will end up tasting saltier than water that had fewer dissolved minerals.

Most of the ions have been removed in soft water, but sodium and various anions (negatively charged ions) still remain. Water can be deionized by using a resin that replaces cations with hydrogen and anions with hydroxide. With this type of resin, the cations stick to the resin and the hydrogen and hydroxide that are released combine to form pure water. [clipped]

So, from this you can see that your soft water will leave sodium and other negatively charged residues on the board. These residues can form corrosive and conductive componds on the surface of the board that can result in failure of the circuit of the board.

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Soft Water Versus Deionized | 27 January, 2007

Davef, great !!! Many thanks


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Soft Water Versus Deionized | 31 January, 2007

Would distilled water be considered deionized? I know that is not the typical process to produce deionized water but it is widely available in grocery stores if you need small amounts.

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Soft Water Versus Deionized | 31 January, 2007

Distilled water is a perfectly adeqaute alternative to DI water. As you say, they just are produced using different processes and technically could have slightly different properties, but for every day requirements can be used interchangeably.

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Soft Water Versus Deionized | 1 February, 2007

Distilled water normally removes ions as well as dissolved solids (non-volatiles). Deionized water has been stipped of ionic species, but non-ionic organics are left behind.

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Soft Water Versus Deionized | 5 February, 2007

Remember, deionized water is very corosive. If the water is too deionized, 10 mega ohm, it will leach the ions from exposed metals. I had a stencil cleaner where the welds completely dissolved. The stainless steel tank was fine but the welds were gone after prolonged use.

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