What are the top 3 ways to remove conformal coating from a localised area of the PCB?
It is possible to remove small areas of coating for 99% of conformal coatings without damaging the circuit board below.
The three main techniques generally used are:
- Local chemical stripping of the conformal coating
- Mechanical Abrasion of the conformal coating
- Soldering through the conformal coating
Each process has its own issues.
Local Chemical Stripping of conformal coating for localised repair
The simplest process for local area rework around a device for instance is using a cotton bud soaked in stripping fluid or a device such as a conformal coating rework pen to remove the coating. The process involves rubbing gently across the area to be removed, which will dissolve the conformal coating.
If the coating is fresh, it tends to come off in a matter of seconds, whatever the type of coating applied, since the coating is not fully cured. However, if the coating is old, having been coated many years ago, or it is fully cured then it could take a little longer and patience is required. Polyurethanes with full chemical resistance naturally can be tricky to strip with chemicals!
The key to stripping with chemicals is
- Ensure that the chemical stripper is compatible with the circuit board being stripped. No use causing damage to the PCB while removing the coating.
- Ensure that any active ingredients from the stripping process are inert after processing or removed by cleaning after rework to avoid corrosion effects on the board.
- Correct stripping solution selection is critical for compatibility with the coating and this is why conformal coating manufacturers have several stripping products.
Mechanical Abrasion of conformal coating for localised repair
Several systems on the market now exist which use the concept of “shot blasting” / erosion of the conformal coating from the circuit board. However aggressive this sounds it can actually be a very successful method for localised removal.
The principle is simple. Fire particles of material at the surface of the coating and erode it away. Using “soft” particles of material instead of hard helps ensure the coating erodes before the circuit board in most cases.
The key to Mechanical Abrasion of conformal coating is
- Care has to be taken in the operation of the system to avoid damaging the circuit below. If the coating and the board parts are a similar hardness then this can be very difficult and a skilled process.
- Ensure the system is designed to minimise static since the machine generates very high static charges, which must be neutralised.
- Ensure the PCB is cleaned after processing to remove all the debris.
Soldering through the conformal coating for localised repair
Localised rework of components that are conformal coated can be achieved using a soldering Iron.
The coating volatises away with the application of heat, leaving the joint clear of coating. Occasionally, with certain coatings, the material may char slightly but this is generally a cosmetic issue and you need to discuss this with your quality department and the material supplier.
The Key to Soldering through the conformal coating is
- Ensure that no gases are released that are toxic
- That the finish achieved is cosmetically acceptable
- The heat used does not damage the circuit board
For further information on conformal coating removal and stripping contact SCH to discuss your needs.
Contact us here at +44 1226 249019 or email sales@schservices.com
How can I remove a polyurethane or silicone conformal coating from a printed circuit board using a chemical stripping fluid?
Removing a coating like a urethane or silicone is not as easy as stripping an acrylic from a circuit board especially if its optimal properties have been reached for chemical binding. A urethane cross links with time giving it resistance to chemical attack. Therefore, any stripping fluids used on the crosss linked coating will need to be very aggressive.
To find out more click Removing a polyurethane conformal coating.
Conformal Coating Removal and Stripping part of Subcontract Conformal Coating Service
SCH offer a conformal coating strip and removal service for customers who want conformal coatings removed from printed circuit boards (PCBs).
Stripping of unwanted conformal coating from a PCB can be a simple process but depends on what conformal coating is to be removed or stripped, the area of coating to be removed, where the conformal coating is and the type of components on the board.
SCH specialise in removal and stripping of all conformal coatings including Humiseal 1B31, 1B73, 1R32, 1R32A2, 1A33, 1A68, Electrolube HPA and SCC3 and Dow Corning Silicones such as 2577.
Click for further information on the conformal coating service.
Click for the video for the WS100 Conformal Coating Wet stripping System.
Click for the brochure for the WS100 Conformal coating Wet Stripping system.
Removal of Conformal Coating made Easy on Video
Stripping of unwanted conformal coating from a PCB can be a simple process but depends on what conformal coating is to be removed or stripped, the area of coating to be removed, where the conformal coating is and the type of components on the board.
Click for the video for the WS100 Conformal Coating Wet stripping System.
Click for the brochure for the WS100 Conformal coating Wet Stripping system.
Conformal Coating Removal Video Using the WS100 Wet Stripping System
Stripping of unwanted conformal coating from a PCB can be a simple process but depends on what conformal coating is to be removed or stripped, the area of coating to be removed, where the conformal coating is and the type of components on the board.
The WS100 Conformal coating Stripping System has been designed for complete removal & stripping of conformal coating from circuit boards.
The WS100 consists a workstation of four tanks contained behind a safety screen, filled with appropriate stripping materials for the conformal coating material to be removed.
The principle of operation is that the circuit board to be stripped is manually placed by the operator in the first of the tanks for initial ‘rough’ removal and softening of the coating. Each tank has a rinse pipe and solvent pump fitted for gentle circulation and rinsing of the fluid and the operator working behind the safety screen is able to gradually remove the majority of coating, leaving a small amount of residue remaining.
Click for the video for the WS100 Conformal Coating Wet stripping System.
Click for the brochure for the WS100 Conformal coating Wet Stripping system.
Conformal Coating Stripping and Removal Technical Bulletin
Stripping of unwanted conformal coating from a PCB can be a simple process but depends on what conformal coating is to be removed or stripped, the area of coating to be removed, where the conformal coating is and the type of components on the board.
Removal of conformals coatings such as 1A33, 1R32A-2 and 1B31 can be easy with the WS100 Wet Stripping system from SCH.
SCH have a technical bulletin on conformal coating removal available.
Removing Conformal coating from PCBs -stripping successfully!
Removing & stripping conformal coating materials like Humiseals acrylic’s 1B31 & 1R32 and polyurethane’s 1A33 is made easy using the WS100 Wet Stripping System.
Removal of unwanted conformal coating from a PCB can be a simple process but depends on what conformal coat is to be removed or stripped from the PCB, the area of c0nformal coating to be removed on the PCB, where the conformal coating is and the type of components on the board.
Removal of unwanted conformal coating from a PCB can be a simple process or a very messy difficult job. It depends on what coating you need to remove, where the coating is and the type of components on the board.
The simplest coatings to remove are the acrylics. They have little chemical resistance and therefore are the easiest to remove with stripping fluids like Humiseal’s 1080. These coatings generally re-dissolve back into solution so a combination of soaking and gentle mechanical abrasion works well.
The simplest process for local area rework around a device for instance is a cotton bud soaked in stripping fluid and then rubbed gently across the area to be removed which will dissolve the coating. If the coating is fresh, it comes off in a matter of seconds whereas if the coating is old, having been coated many years ago, then it could take a little longer and patience is required!
If the area to be removed is larger or the whole board is to be stripped then submersion in a tank correctly selected stripping fluid and abrasion using a soft bristle brush will also dissolve the coatings. A word of warning must be given here. First, when submerging in a stripping material check there are no compatibility issues with the PCB. Stripping fluid could attack components and or writing on the boards occasionally although for acrylic coatings the 1080 stripper is not too aggressive.
The other issue that can be a major headache with full stripping of a board is that because the coating re-dissolves into the stripper, there will now be coating residue all over the PCB even where you didn’t want it. This can be a real problem with certain components such as low profile connectors! To remove these residues you will need several tanks of stripping fluid and the PCB will need to be fully rinsed in each, gradually flushing the residue out of the wrong areas. Once completed the PCB should then be cleaned in a cleaning system to remove any unwanted ionics.
These two processes also work for coatings such as polyurethanes and silicones although since they have chemical resistance they are tougher to remove. Correct stripping solution selection is critical and this is why Humiseal have several stripping products including 1063 for polyurethanes.
Click for further information on conformal coating removal.
De-masking of conformally coated PCBs made easy
SCH have a technical bulletin on de-masking conformal coated boards on its website.
Click for further info on conformal coating de-masking.
Conformal coating Removal made easy
Removing conformal coatings like Humiseals acrylic’s 1B31 & 1R32 and polyurethane’s 1A33 is made easy using the WS100 Wet Stripping System.
Removal of unwanted conformal coating from a PCB can be a simple process but depends on what conformal coat is to be removed or stripped from the PCB, the area of c0nformal coating to be removed on the PCB, where the conformal coating is and the type of components on the board.
Removal of unwanted conformal coating from a PCB can be a simple process or a very messy difficult job. It depends on what coating you need to remove, where the coating is and the type of components on the board.
The simplest coatings to remove are the acrylics. They have little chemical resistance and therefore are the easiest to remove with stripping fluids like Humiseal’s 1080. These coatings generally re-dissolve back into solution so a combination of soaking and gentle mechanical abrasion works well.
The simplest process for local area rework around a device for instance is a cotton bud soaked in stripping fluid and then rubbed gently across the area to be removed which will dissolve the coating. If the coating is fresh, it comes off in a matter of seconds whereas if the coating is old, having been coated many years ago, then it could take a little longer and patience is required!
If the area to be removed is larger or the whole board is to be stripped then submersion in a tank correctly selected stripping fluid and abrasion using a soft bristle brush will also dissolve the coatings. A word of warning must be given here. First, when submerging in a stripping material check there are no compatibility issues with the PCB. Stripping fluid could attack components and or writing on the boards occasionally although for acrylic coatings the 1080 stripper is not too aggressive.
The other issue that can be a major headache with full stripping of a board is that because the coating re-dissolves into the stripper, there will now be coating residue all over the PCB even where you didn’t want it. This can be a real problem with certain components such as low profile connectors! To remove these residues you will need several tanks of stripping fluid and the PCB will need to be fully rinsed in each, gradually flushing the residue out of the wrong areas. Once completed the PCB should then be cleaned in a cleaning system to remove any unwanted ionics.
These two processes also work for coatings such as polyurethanes and silicones although since they have chemical resistance they are tougher to remove. Correct stripping solution selection is critical and this is why Humiseal have several stripping products including 1063 for polyurethanes.
Click here for further information on conformal coating repair.
Conformal Coating 