Cleaning circuit boards of solder flux residue

I don't recall exactly. This was during the 1970's so please forgive my lack of total recall. As I vaguely recall, it was purchased in 55 gallon drums from some industrial supplier for use in restaurant and cafeteria kitchens. Production later changed to a different product in order to remove the chlorine compounds.

The phosphate alternatives are typically zeolites, sodium carbonate, nitrilo-triacetic acid, and citric acid. There are some other formulations that are being tested or used.

Note that the formulation already has considerable sodium carbonate. The citric acid is where the "lemon fresh" advertising mantra originated. However, in the US, the phosphate restrictions apply mostly to consumer products, because the substitutes don't work as well as the real thing.

Here's a summary of the situation:

Make sure that it includes a surfactant to reduce surface tension. In the dishwasher, it reduces water spots and hard water stains on the dishes and PCB's. It can be added to the rinse while washing. I used only a few drops of Kodak Photo Flo for the purpose: which is:

Propylene glycol 25-30% (anti-freeze)

Octylphenoxypolyethoxyethanol 5-10% (Triton X-100 non-ionic surfactant)

phone call from paying customer... gone.

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Jeff Liebermann     jeffl@cruzio.com 
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** Looks like a fool's errand to me.

FYI:

Inside a typical condenser microphone is a node where the mic element (effe ctively a capacitor of about 50pF) connects to the gate of a JFET or the gr id of a small triode. To maintain response down to 20Hz and minimise noise, resistors of 1 to 2Gohms are employed to supply around 50-100V DC bias the element and about 1.5V DC to the gate or grid involved.

Any leakage current from one PCB trace to another would upset bias conditio ns and/or add noise, which needs to be kept sub 1uVrms at this point.

Normal PCB materials, cannot be relied on so the simple solution is to lift the node proud of the PCB and join the parts in mid air, then coat with qu ick drying lacquer to keep out moisture.

BTW:

A 1Gohm resistor has over 500uV of thermal noise in the audio band, which t he 50pF capacitance of the element attenuates to under 1uV.

... Phil

Reply to
Phil Allison

You can buy phosphate-loaded dishwash detergent online, and it works a lot better than the greenie stuff. I've only found the powder, not the tablets.

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John Larkin         Highland Technology, Inc 
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John Larkin

We used filtered tap water. Not as good as deionized or demineralized, but good enough for our requirements. We also hit the rack of PCB's with filtered and dried compressed air to speed up drying.

Yep, I can see why... SODIUM TRIPOLYPHOSPHATE DENSE ANHYDROUS 12-15% SODIUM SULFATE ANHYDROUS 40-45% SODIUM CARBONATE DENSE 35-40% SODIUM SILICATE 2.4R 42% 5-10% SODIUM DICHLOROISOCYANURATE 0-1%

The difference is the STPP detergent, which is partially banned in 17 states in consumer products, and voluntarily by major manufacturers, but not industrial products:

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Or you can add TSP to the greenie stuff to make it useful again.

Reply to
krw

That's more of a problem in semiconductor lithography. Chemically-amplified resist is very sensitive to amines, which prevent it from developing. (My stuff was all 248-nm, not the modern stuff.)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

Bad idea. TSP produces a precipitate when it reacts with the minerals in hard water. You want STPP (sodium tripolyphosphate). Check out stores that sell soap making supplies: Note that this is a concentrate. Even the most phosphate loaded laundry detergent contains no more than about 15% STPP, so don't dump in too much.

Storage of STPP is also a bit of a problem: "STPP has one weakness, and that is that over time, with exposure to water, it will decompose into a mono-phosphate, or "orthophosphate", called trisodiumphosphate, or TSP. TSP is often used for cleaning hard surfaces where a precipitate is not a problem, but due to its precipitate formation is not favored for laundry use."

Get some now, before it's banned.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

In all the justification for elimination of phosphate from detergents (laundry and dishwashing), a critical piece of information has been omitted: Detergents account for no more than 0.5% of phosphate use. The bulk is used in fertilizers - food just won't grow otherwise. It is runoff from farms that causes eutrophication.

.

Joe Gwinn

Reply to
Joe Gwinn

Wafers tend to be transported in big sealed plastic casettes these days, and plugged into process machines. I don't see why anybody needs clean rooms any more.

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John Larkin         Highland Technology, Inc 
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John Larkin

Belt and braces. You have to open the mini-environments at some stage, and having them in a Class 1 clean room helps a lot.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

The above URL is only about phosphoric acid (and phosphate acid) fertilizer and makes no mention of laundry detergents or other phosphate bearing compounds (TSP, STPP, etc). Where did you find the

0.5% figure for detergent use?

I couldn't find anything more current or authoritative right now: The general feeling around the late 1960s was that the nation's lakes and streams were getting more polluted each day, and phosphate detergents were the primary reason. Half the phosphorus input to Lakes Erie and Ontario came from municipal and industrial sources, of which 50% to 70% came from detergents. Over half of the phosphorus input to the Potomac estuary also came from detergents in municipal and industrial effluents (Congressional Report HR 91-1004 April 14, 1970). It was generally agreed that detergents accounted for about 50% of the wastewater phosphorus nationwide (Hammond 1971). There was a growing public consensus that in order to save lakes (like Lake Erie), phosphates must be banned from detergents.

Your 0.5% figure might be true in farming areas, where phosphate fertilizer laced runoff is more common, but in more densely populated urban areas, the 50% figure cited above is more likely.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

You claim that I pick on you unjustly. But it is your making comments like this that make you stick out like the proverbial nail. For an otherwise intelligent person you say the dumbest things. Reminds me of the Art Linkletter show.

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Rick
Reply to
rickman

I expect the deionized water rinse is where the real work is done to get the high Z. This gives you a tiny glimpse into what it takes to purify and process silicon for semiconductors.

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Rick
Reply to
rickman

The distinction between urban areas and agricultural areas is pointless. The rivers and lakes don't care where the pollution comes from. For example the Potomac river drains 14,700 square miles of which perhaps some 1000 to 2000 is urban.

I kayak the Potomac river and it is still not what many would call "clean". I can't say what the phosphate pollution level is, but it shows many signs of pollution nearly everywhere along the lower 100 miles including excrement floating along. The James river is not any better. Once on a paddle my girl friend counted the condoms floating by. On both of these rivers and many others in the area, it is not recommended that you eat many of the fish.

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Rick
Reply to
rickman

It *is* favored for dishwasher use. Works great.

It already is in weenie states.

Reply to
krw

The above URL showed that ~90% of phosphorus produced is used in agriculture, specifically as fertilizers, so right away we know that detergents cannot be the main story - everything else accounts for only

10%.

The 0.5% came from research I did circa 2010 when everybody's dishwasher suddenly failed to get glasses clean. In my case, the initial symptom was a swamp smell, followed by milky glassware. I figured it out before any glassware was ruined. (I imaging that straight battery acid would have rescued the glassware, but I never had to go that far.)

One use for AlcoJet was to clean the innards of the dishwasher, to get rid of the smell. Worked the first time.

The key bit of hidden-in-plain-sight misdirection is the qualifier "wastewater". Runoff from agriculture is not considered wastewater, and neither are "municipal and industrial sources", so the above statements can be absolutely true, and yet be deeply misleading. When I went looking for the *entire* phosphorus budget, I found the 0.5% estimate.

I'll dig the cites up again.

Joe Gwinn

Reply to
Joe Gwinn

I won't argue that your conclusion is wrong, but your logic is clearly flawed. When you use phosphates for cleaning nearly 100% of it ends up in our waters. Agricultural use has a portion which runs off into streams. I don't know what percentage that is, but that number is needed before you can say agricultural runoff is a bigger problem than cleaners.

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Rick
Reply to
rickman

This might help, although there's little mention of phosphate detergent use: "Phosphorus in agriculture, Problems and solutions"

A few quotes:

Agriculture is by far the main user of mined phosphorus globally, accounting for between 80-90% of the total world demand (Childers et al, 2011). However, only about 20% of the phosphorus used in agriculture reaches the food we consumed, most of the rest is lost in inefficient steps along the phosphorus cycle (Cordell et al, 2011) (Figure 4). Globally, this lost phosphorus ends up in water systems causing widespread pollution in lakes, rivers and coastal areas, algal blooms, and dead zones in the oceans (together with nitrogen).

Mined phosphate rock is principally used for agricultural fertiliser (80%), the remainder being used for animal feed additions (5%) and industrial applications (15%) including detergents and metal treatment (Smit et al, 2009).

I can probably quibble over the numerical details, but the bulk of the phosphorus (64-72% of global demand) that appears in the worlds water systems seems to come from inefficient agricultural use. Looks like you're right. It also appears that phosphorus resource depletion might eventually become a problem.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

What do you mean by "it"? TSP is not recommended for dishwasher because of the precipitatates. STPP is, or rather was, a standard ingredient in dishwasher detergent.

Yep. "Global Phosphate ban status Oct 2009"

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Water consumption is not proportional to land area. I don't have any numbers, but I suspect urban areas with high populations have more washing machines and dishwashers per square mile than rural agricultural areas.

The JRA director, Bill Street, emphasized that "agricultural" runoff is now the "predominate source of pollution" in the river. The 2013 "State of the James River" report: looks like there are plenty of problems that still need to be addressed. Phosphorus pollution appears to be mostly under control at

75% of target value.

Looks like Washington DC used phosphates to sequester the lead left in the water pipes in 2004. I couldn't find anything that indicated if it worked.

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Jeff Liebermann     jeffl@cruzio.com 
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