CircuitWorks Flux Pens

Using a flux dispensing pen, whether it's a no-clean, rosin, or aqueous flux, is a straightforward process. Flux is used in soldering to remove oxidation and improve the wetting of solder, ensuring better solder joints. Here's a step-by-step guide on how to use a flux dispensing pen:

1. Preparation:

Ensure you have the appropriate flux pen for your application (no-clean, rosin, or aqueous flux). The specific type of flux depends on your soldering needs and the type of components you are working with.

2. Clean the Surface:

Before applying flux, make sure the surface you are about to solder is clean and free from any debris, dust, or oxidation. Clean it with a lint-free cloth if necessary.

3. Prepare the Flux Pen:

• Remove the cap of the flux pen.
• Tap the tip on a flat surface to saturate the tip.
• If there is dried flux or other residue on the tip, rub it off on a wipe.

4. Apply Flux:

• Hold the flux pen like you would hold a regular pen or marker, with the tip facing downwards.
• Gently press the tip against the surface where you want to apply the flux. Be careful not to apply too much pressure as it may lead to excessive flux application.
• Move the pen across the area where you want to apply flux. The flux will flow out through the tip as you move it.

5. Soldering:

Once you have applied the flux, proceed with the soldering process immediately.

6. Clean Residue (if applicable):

If you are using a no-clean flux, it is designed to be left on the board without cleaning, depending on the requirements the electronics. If you used a rosin or aqueous flux, you should clean the board after soldering to remove any residue. Use a cleaning solution that is compatible with the type of flux you used.

7. Recap the Flux Pen:

After use, make sure to recap the flux pen tightly to prevent the flux from drying out or leaking.

If it is not fully activated (brought up to solder temperature), you should not leave any ionic residue behind. You might have to clean if...
1. Flux is being used so liberally that it all isn’t being heated along with the solder.
or
2. The non-ionic residue can impede with the function of the devise either short-term or long-term.

CircuitWorks® flux pens are available with a variety of fluxes to fit your specific shop requirements, including: no-clean, high temperature no-clean for lead-free soldering, rosin, and water soluble. Flux pens are an excellent way to dispense flux for benchtop soldering. You just hold the pen vertically and briefly depress the tip to start the liquid flow. This will saturate the tip of the pen with flux. Draw flux on the area to be soldered. Gently press the tip again when more flux is needed to keep the tip damp with flux.

In a production or repair environment where the flux is specified and can’t be changed, or when an aqueous flux is needed, you can add your own flux to this type of braid. Unfluxed wick will not remove solder unless flux is added. Different types of fluxes are available in pen packaging, which is ideal for fluxing braid.

The shelf life of a product can be found on either the technical data sheet (TDS), available on the product page, or by looking on the certificate on conformance (COC). The COC can be downloaded by going to https://www.chemtronics.com/coc. Once you have the shelf life, you will need to add it to the manufacture date for a use-by date. The manufacture date can be identified by the batch number. The batch code used on most of our products are manufacture dates in the Julian Date format. The format is YYDDD, where YY = year, DDD = day. For example, 19200 translates to the 200th day of 2019, or July 19, 2019. This webpage explains and provides charts to help interpret our batch numbers: https://www.chemtronics.com/batch-codes.

Yes, flux should be cleaned off of a printed circuit board (PCB) after soldering is completed. The following are the reasons to remove flux residues:

• Improve Aesthetic Appearance of PCB - If you are a contract manufacturer of PCB’s, the visual appearance of the board reflects on your work. A clear, greasy-looking residue around a solder joint may raise flags for your customer’s incoming QC inspectors. If the flux residue chars and forms spots on the solder joints, it may look like a true defect like a solder joint void or “blow hole”. If the flux residue is from a rework process, it acts as a fault tag in the rework area, calling attention to the work even if there shouldn’t be a concern.
• Improve Reliability of PCB - Reliability requirements are generally driven by the nature of the final product. For a disposable product like a computer keyboard, nobody loses their life if it stops working. In that case, an EMS supplier may use no-clean flux and forgo the cleaning process. On the other end of the scale, requirements for pacemaker electronics, where board failure could directly lead to death, are going to be much stricter. In that example, cleaning will be required after assembly and any subsequent rework, and the process will be thoroughly tested for effectiveness and repeatability. Long-life durable goods may fall somewhere in-between, with cleaning a requirement, but without the rigid testing and controls.
• Prevent Corrosion on Components and PCB - Flux residues left on electronic circuit boards are acidic. If they aren’t removed with a cleaning process, the residues can draw in ambient moisture from the air and lead to corrosion of component leads, and PCB contacts.
• Avoid Adhesion Problems with Conformal Coating - Most people understand that when painting something, the surface must be prepared so it is absolutely clean. Otherwise, the paint will quickly lift off the surface and peel off. The same logic applies to conformal coating, even when the contamination is from no-clean flux. “No-clean” refers to the amount of ionic material left after soldering. It has nothing to do with whether or not coating can stick to it. When there are flux residues left on the PCB before the coating process, it is common to see the coating lift or delaminate from the surface of the board. This is evident when the pockets are isolated around solder joints rather than the overall surface (the exception being the bottom of a wave soldered PCB). To make matters worse, coatings are generally semi-permeable, so breathe to a certain extent. Moisture can enter and soak into the flux residue, and potentially lead to corrosion.
• Prevent Dendritic Growth from Ionic Contamination - Polar or Ionic particles left from flux residue and other sources, when exposed to moisture from the ambient air and when current is applied, can link into a chain or branch called a dendrite. These dendrites are conductive, so form an unintended trace that cause current leakage or, over a longer period of time, even a short circuit. This is not as much of a concern for no-clean flux. No-clean flux contains minimal ionic material that is fully consumed when the flux is activated, or in other words, brought to soldering temperature. If all of the flux isn’t activated, like when you apply a lot of flux but only solder a small area, you still need to clean the PCB.