How to Clean Parts Prior to Soldering

Question:
Need to clean parts to be soldered prior to applying solder.


Answer:
To clean parts prior to solder you need to consider what residues you are trying to remove from the parts and how you want to clean.  For general purpose oils and residue cleaning by manual, soak or ultrasonic cleaning methods, we recommend using a warm or hot 1% Liquinox solution followed by a thorough rinse.  If you want to remove surface oxides and brighten the parts, we recommend using warm or hot 2% Citranox solution followed by a thorough rinse.

Removing RMA Solder Flux

Question: 
We need to remove RMA solder flux on indium/lead soldered subassemblies. Most aqueous cleaners attack this solder.


Answer:
According to the Materials Handbook by GS Brady et al, indium lead solders are alkali resistant solders.  Rosin based RMA fluxes are best cleaned by alkaline/saponifying cleaners with no conductive cations such as Detergent 8.  


The organic amine in Detergent 8 forms a water soluble soap with the rosin. Because Detergent 8 is cation free, it cannot leave conductive residues.  We recommend using a 3% Detergent 8 solution for ultrasonic immersion cleaning or a 5% Detergent 8 solution for manual cleaning of indium/lead soldered subassemblies.  


Detergent 8 is a hazmat that most package sizes must ship by ground.  You can ship a 5 gallon jerrycan of Detergent 8 by air.

Removing DNA Residue

Question:

We are currently using Alcojet for routine labware cleaning. Since we work on DNA plasmid isolation, I wonder if using Alcojet could remove residual DNA. If not, how much residue could be left? I would really appreciate your answer as unfortunately we have continued using the labwares for a year already. Your comment will be much appreciated.

Answer:

Thank you for your question about DNA plasmid cleaning. Alcojet is capable of removing DNA plasmids as whole strands. However, Alcojet is not the best product to use for cleaning DNA Plasmids. Alcojet is a high pH alkaline cleaner. DNA is not labile to alkaline hydrolysis.

It is more effective to clean with an acid detergent rather than an alkaline detergent. For manual and soak cleaning I would recommend using a warm 2% Citranox solution (20 mL/L). For machine cleaning I would recommend using a 1% Citrajet (10 mL/L) solution. See prior 2009 Tech Note: Removing DNA.

Note that your washer may not be set up to dose liquid detergents. If your washer does not have liquid dosing pumps and hoses, then I would recommend choosing a washing cycle that does not have a presoak cycle in it and dosing the correct amount of liquid detergent in to the bottom of the washer and then turning on the machine so that it goes directly to a hot, long, wash cycle. Do not use a pre-wash cycle which will be short and with ambient temperature water that will use up all the detergent ineffectively and there will be no detergent present when the machine goes to the long, hot wash cycle.

Consult the owner’s manual of the washer to see how much water is used in the wash cycle. A typical under counter washer will use 8 L of water in a wash cycle, so you need to dose 80 mL of Citrajet in to the bottom of your washer at the beginning of the hot wash cycle. If your washer has liquid dosing capability, then simply hook up the Citrajet bottle to the washer by the tubes that are in the washer. If you have been using Alcojet for a year, this does not mean you definitely have had cleaning failures, but it does mean that you are not cleaning the best way and you do have some risk of cleaning failures.

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Alconox and the Environment

Question:

I will be sampling sediments in a lake with a drilling unit. I am wondering if Alconox is harmful to the environment. i.e. if it got into the lake, is there a possibility of harm? I plan on using it to rinse drill bits. Also, what concentration is typical??

Answer:

Alconox is recommended for use at a 1% concentration (10 g/L).

In sufficient quantity, Alconox, like just about anything, will impact the environment. If you discharge 5,000 lbs of Alconox at once, you would be discharging an EPA reportable quantity under CERCLA regulations. I presume you have no intentions of discharging anything like this quantity.

Alconox does contain phosphates which are essential nutrients and can promote algae growth in phosphorous limited ecosystems. The algae can deplete oxygen and then die causing silting up of surface waters - this is eutrophication. You would need large quantities of Alconox to cause significant eutrophication.

Alconox contains surfactants, which in high enough concentration are hazardous to fish - typically you would have to reach 100s of mg/L in concentration to be harmful to fish.

Alconox has been widely used for field cleaning of environmental sampling equipment for decades and we have never had any reported incident of environmental impact. Alconox is biodegradable.

If you spill enough Alconox directly in to a lake, I imagine it could form a stable detergent foam that might take a few hours to dissipate. Although this foam would not be particularly harmful, it would be unsightly. I suspect that a bucket full of Alconox dumped briskly in to a lake might make enough foam to be unsightly.