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How to Clean PCBA in the Safest and Most Effective Ways? [Solved]

PCBA cleaning
PCBONLINE Team Wed, Jun 09, 2021

If you assemble the printed circuit boards on your own, you might have to clean your PCBAs before you use them. On the manufacturing side, we also need to clean the PCB assemblies before we apply the conformal coating to the boards or before the PCB distribution. We clean the PCBA because the surface of the circuit boards is contaminated more or less inevitably. In this post, you are gonna understand why and how to clean PCBA from the below parts.

Why Do We Need to Clean the PCB Assembly

During the PCB assembly process, operators' handprints, dust in the factory, flux and activator residue, oxidation of the board surface and so on may contaminate the PCB assembly's surface. Usually, simple PCBs require no cleaning because they do not have high requirements for quality and precision. But for the advanced circuit board manufacturer, PCBONLINE, PCB cleaning is necessary. Here are some reasons for cleaning the PCBAs before packaging them to be the end products.

  • 1. Military/medical grade PCB requires extremely high precision

Military and medical-grade PCBs are typical advanced PCBs that require high precision and reliability. In a hot and humid environment, the contamination on the PCB surface may absorb moisture, corrupt the solder mask, and even cause a partial short circuit. On the contrary, the PCB assembly with a clean surface is more reliable and has a longer service life. Besides, it looks better.

  • 2. PCB cleaning is a must before applying the conformal coating

Three-anti paint is applied to the PCB assembly as a protective coating to lengthen its lifespan. To apply it, the cleanliness of the PCB assembly's surface should reach the IPC-A-610E-2010 standard. By cleaning the PCBA, the three-anti paint is applied 50% more tightly and evenly. If the three-anti paint is applied without cleaning the PCB surface, the resin residue can cause delamination or cracks of the protective coating, and activator residue can cause electrochemical migration under the three-anti paint coating, which leads to the coating's failure.

  • 3. All PCB surfaces were contaminated after the assembly

Believe it or not, every PCB assembly has more or less contamination on its surface, no matter how clean the factory is or how advanced the assembly techniques are. This is because flux residue is left on the board's surface. You may ask, isn’t there a no-clean flux? The no-clean flux has a low amount of solid content but still has residue on the PCB surface. For the advanced PCBs that require high reliability, any contamination on their surface is not allowed.

For these reasons, PCBONLINE cleans all our products before distribution.

How to Clean PCB Assembly in the Safest and Most Efficient Way

Cleaning PCB assemblies should use the most appropriate cleaner and cleaning solvent, which depends on the board's requirements. Here, different PCB cleaning ways and their pros and cons are illustrated.

Way 1: Ultrasonic PCB Cleaning

ultrasonic PCB cleaning

  • Pros: Cheap and easy; quick to remove dust and dirt
  • Cons: can't be used to clean aerospace and defense PCB; can't be used to clean PCBA

An ultrasonic PCB cleaner cleans bare PCBs quickly without cleaning solvent, and this is the most economical PCB cleaning method. Besides, this cleaning method doesn't restrict the PCB size or quantity. However, it can't clean PCB assembly because ultrasonic can harm electronic components and the assembly. It also can't clean aerospace/defense PCB because the ultrasonic can affect the board's electrical precision. As a leading advanced PCB manufacturer, we rarely use the ultrasonic PCB cleaning way. IPC-A-610E-2010 Class 3 forbids ultrasonic cleaning. This is appropriate for cleaning simple and normal PCBs that require less precision.

Way 2: Full Automatic On-Line PCBA Cleaning

on line full-automatic PCBA cleaning

  • Pros: on-line cleaning; safe and quick; can clean PCB and PCBA
  • Cons: expensive cleaning equipment; has requirements for clean solvent

The full automatic on-line PCBA cleaner is appropriate to clean large volumes of PCB assembly. Both the PCB and PCBA can be cleaned, and it won't affect the boards' precision. The PCBAs pass different solvent-filled cavities to complete the processes of chemical water-based cleaning, water-based rinsing, drying, and so on. This PCBA cleaning method requires the solvent to be compatible with the components, PCB surface, solder mask, etc. And we also have to pay attention to the special components in case that they can't be washed. Aerospace and medical-grade PCBs can be cleaned in this way.

Way 3: Half Automatic PCBA Cleaning

half automatic PCBA cleaning

  • Pros: can clean PCB and PCBA; safe and quick
  • Cons: has requirements for clean solvent; has requirements for the PCB quantity and placement

The half-automatic PCBA cleaner is appropriate for small-batch PCBA cleaning. Unlike the online PCBA cleaner, the half-automatic cleaner can be transported manually at any place on the assembly line, and it has only one cavity. Though its cleaning processes are the same as the online PCBA cleaning, all the processes happen in the same cavity. The PCBAs need to be fixed by a fixture or placed in a basket, and their quantity is limited. When placed in the cavity, they should be placed carefully in a certain tangle, or the cleaning effect is not good.

Way 4: Manual PCBA Cleaning

  • Pros: Appropriate for microphase cleaning; safe; can clean PCB and PCBA
  • Cons: Has requirements for temperatures

The manual PCBA cleaner is appropriate for small-batch PCBA that requires the MPC cleaning solvent. The PCBA completes the chemical water-based cleaning in a constant temperature bath.

Depending on the PCBA requirements, we choose the most appropriate PCBA cleaning method. Usually, these PCBA cleaning ways are combined for the best effect.

PCB Manufacturing and Assembly for Aerospace, Defense, and Medical

Both PCB and PCBA should be cleaned safely and effectively. If you or your company care about PCB manufacturing and assembly quality, choose to work with PCBONLINE. We are a one-stop PCB manufacturer for medical, aerospace, defense, communication, automotive, industrial, and so on. All PCBAs we manufacture and assemble are cleaned and tested before distribution to our clients.

PCB manufacturing

Here are some reasons to choose PCBONLINE.

    • We have full-automatic on-line, half-automatic, and manual PCBA cleaners for PCBA cleaning.
    • Our senior engineers and technicians have rich experience in PCBA cleaning.
    • Our PCB manufacturing bases and PCBA factory are ISO9001, REACH, RoHS, IATF, UL, and IPC certified.
    • Our PCB assembly follows the IPC-A-610 standards.
    • Free BOM check and DFM before giving a quote to you.
    • One-to-one engineering support.

PCBONLINE has no minimum order quantity limit for purchases. Click the "Online Quote" button to get an online quote now.


In this post, we answer why and how to clean PCB assemblies. If the PCB assembly is cleaned in the wrong way, its quality is affected and even the product can be a failure. If you want to get the highest level of PCB and PCBA quality, don't miss PCBONLINE, where your circuit boards are manufactured, assembled, cleaned, and tested to the IPC-A-610 Class 3 quality.


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