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How to Clean a PCB Board – Methods and Steps

How to Clean a PCB Board – Methods and Steps

Knowing how to clean PCB board contaminants can help prevent many problems, given the different ways to do it and the various cleaning agents you can use. The modern circuit board is also becoming smaller and more challenging to clean. Here, we take you through the rules of the process.

Why Clean a PCB?

You clean a printed circuit board to rid it of contaminants. These can be residues from drilling, plating, etching chemicals, and soldering flux compounds. Assembly components may also bring conductive and non conductive materials like oils.

Apart from manufacturing contaminants, a printed circuit board accumulates dust and dirt in its end-use product over time, requiring cleaning.

Surface contaminants affect a printed circuit in many ways, either during its fabrication or application in the real world, making them less reliable and shortening their lifespan. Removing unwanted materials helps ensure the following.

  • It enhances the PCB’s visual appeal. A clean PCB board looks defect-free and professionally assembled or repaired.
  • It protects the board from corrosion that residual flux might cause (flux attracts moisture).
  • It prevents current leakage that dendritic growth from ionic flux particles and etching chemicals may cause.
  • Cleaning removes flux and allows the application of conformal and other coats.
  • It helps prevent overheating that dust and dirt accumulation could cause
  • It improves the circuit board’s reliability. Sensitive circuits, such as those used in the medical industry, must remain dirt-free to avoid potential failure.

How to Clean a PCB Board

Different contaminants require different solvents and steps. PCB cleanliness standards also vary across industries. For example, medical circuits require higher cleanliness levels than basic consumer electronics.

Here, we take you through the steps of ridding PCBs of corrosion, soldering flux residue, and other unwanted materials.

1. How to Clean Circuit Board Corrosion

It’s not uncommon for printed circuit surfaces to become corroded. That usually happens when they come into contact with moisture. You can remove corrosion using baking soda, isopropyl alcohol, and de-ionized water. Here’s how to go about it.

  • Make a paste by mixing a large amount of baking soda with a small amount of water
  • Apply the paste on the PCB to
  • Allow it to sit for around 20 minutes and dissolve the corrosion
  • Use your PCB board cleaning brush to scrub corroded parts
  • Finally, clean the board using IPA and de-mineralized water
  • Dry the board using appropriate means, such as air or low-heat

2. How to Clean a PCB with Alcohol

Alcohol is one of the most used printed circuit board cleaning chemicals. It evaporates quickly and can dissolve dirt in a matter of seconds. It’s also non-conductive. Most often, this is isopropyl alcohol with more than 90% concentration. Follow these steps.

  • Pour some amount of the solvent into a bowl or other open container
  • Dip a cotton or foam swab in the cleaner and use it to wipe the board
  • Allow the board to dry
  • In cases where the board is heavily contaminated, immerse it in the alcohol solvent instead

3. How to Clean a PCB that Got Wet

Liquids can cause PCBs to stop functioning or get damaged later on. That said, you can easily save yours if liquid spills on it (or if it gets submerged). You only need these supplies: a lint-free cloth, a soft brush, distilled water, isopropyl alcohol, and a cotton swab. Here is how to clean PCB board parts wet from submersion or a spill.

  • Safely disconnect the affected device as soon as you can.
  • If not outlet-powered, remove its battery
  • Disassemble the device to remove the wet circuit board
  • Using a lint-free cloth, gently soak up any spilled residue
  • If there are particles or dried-up liquid, remove them using a brush.
  • For sticky spills, use distilled water
  • Dip the cotton swab with IPA and clean the board.
  • You may also soak it in the alcohol solvent
  • Dry the circuit board. You may use a lamp or air drier
  • Assemble the device and test it
  • Repair or replace damaged components

4. How to Clean a PCB after Soldering

The remains of soldering flux contain ionic compounds that can corrode your printed circuits. These residues also make coating the board difficult. There are three main ways of cleaning flux: de-ionized water, isopropyl alcohol, and flux remover.

  • De-ionized water – use de-ionized water to clean off water-soluble flux residue, and then dry it using air jets. This water contains no ions, making it safe on electronic circuit boards.
  • Isopropyl alcohol – spray the surface with the solvent. Use the brush to clean its surface and a cloth (lint-free) to wipe it off. You may also apply the solving using the brush instead of spraying.
  • Flux remover – this commercial PCB cleaner is more effective than water and IPA. It’s also safer. Spray it on the circuit board. Using a soft brush, clean off the flux remains. You may also soak the PCB in the cleaner.

For more thorough PCB cleanup or if cleaning activated flux compounds, we recommend swabbing it with isopropyl alcohol and then rinsing it using a flux remover.

ultrasonic PCB cleaning
Ultrasonic PCB cleaning
Resource: https://www.youtube.com/watch?v=8DYWfYnI9_o

PCB Cleaning Methods

There are two ways to clean a printed circuit board surface: the manual (benchtop) method and placing it in an automatic PCB cleaning machine. Here’s when and why to use each.

Manual Cleaning

In this method, you manually spray or apply solvent onto the surface. It may also involve immersing it in a PCB cleaning solvent or using a brush or solvent-laden cotton swab to wipe it off.

The manual method is suitable if you only have a few pieces to clean or if carrying out repair work; it takes more time and doesn’t produce consistent results.

Automatic Cleaning

Automated cleaning is a preferred method for more than just a few pieces. It offers the advantage of uniformity, plus it’s less laborious. This method involves using a stationary machine or a conveyor system.

Depending on the method, the boards are immersed in heated solvents or rinsed with vapor degreasers. You may also place them on racks where the machine sprays solvents or takes them through a water-based washer.

In some cases, ultrasonic sound waves are used alongside the solvent to break down residues and dirt or grime, such as flux remains, and make them easier to remove.

Using PCB cleaning equipment
Using PCB cleaning equipment
Resource: https://epp-europe-news.com

Ultrasonic PCB Cleaning

Ultrasonic cleaning is a popular way of removing residual flux, solder balls, and other contaminants (dust and grime) from printed circuit boards. In this method, a PCB board cleaning machine emits high-frequency, or ultrasonic, sound waves to dislodge unwanted materials. Let’s see how it works:

A sound generator generates high-frequency sound waves (above 18 kHz). Transducers then change the waves into mechanical vibrations, creating thousands of tiny bubbles in the cleaning solution. The bubbles implode to loosen contaminants on the PCB surface and other hidden areas.

This machine also often heats the cleaning solution to make it more powerful. Ultrasonic PCB cleaning offers several benefits.

  • It’s faster and more effective than most other methods
  • The cleaning bubbles reach every spot, making it a more reliable PCB cleaning process.
  • With no physical contact with the board and its components, it’s safer than using a brush and suitable for surfaces with hidden spots or sensitive components.

Conclusion

Unwanted materials can affect a printed circuit board in many ways, from causing corrosion to overheating and leaking current. After reading this article, we believe you understand when and how to clean PCB contaminants using various methods and solvents. Always remember to follow the recommended steps, or the cleaning methods may result in more problems and damage your board.

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