Many contract manufacturers want to improve their conformal masking techniques—those steps taken to prevent the conformal coating from contaminating connectors, components, and other keep-away areas. This article will share steps to improve or eliminate conformal masking techniques.
Conformal masking is a crucial process in PCB assembly that involves using materials such as tape, boots, caps, and peelable masks to protect keep-away areas on the PCB from conformal wicking and overspray. This method is commonly employed alongside manual conformal spraying and automated spray systems. Despite advanced robotic spray technology, PCB assemblers still rely on manual conformal coating for some or all of the boards they produce. Here are several reasons why manual conformal coating is preferred over robotic spray technology in some instances:
Manual conformal spray coating is still heavily employed for a variety of reasons as discussed below.
Some areas on the PCB require extra protection, as they contain sensitive components or connectors. Some operators feel that manual conformal coating allows for precise application and avoidance of these delicate areas.
Many PCB assemblers have used manual conformal spray coating for a long time and are accustomed to its process and results.
Robotic spray machines can be quite expensive, often exceeding $100,000. Some PCB assemblers may find manual conformal spray coating more cost-effective than investing in expensive equipment.
The timing and frequency of conformal coating may vary depending on production requirements. Manual coating allows for flexibility in adjusting the coating process according to specific project needs.
Switching between different products or coatings may require time-consuming machine changeover on robotic spray systems. Manual conformal coating allows for quicker and more convenient transitions.
Certain PCBs may not work well with robotic spray technology due to their design complexity or surface characteristics. Manual coating provides greater versatility in accommodating diverse board requirements.
Manual conformal spray coating does not require special skills, with a basic level of training, anyone can spray PCBs with cans aerosol conformal coating. LIkewise the application of masking does not require special skills.
In some cases, manual conformal coating is easier and more suitable for small-scale production or when specific coating requirements must be precisely met.
By considering these factors, PCB assemblers can decide whether to adopt robotic spray technology or continue using manual conformal coating for their production needs.
Improving conformal masking techniques begins with a review of various elements, including:
The first step to improve or eliminate conformal masking is to review the PCB layout. What components, connectors, and switches are used, and how are they situated to require protection in the first place? For example, open-bottom connectors often require masking. Look for a comparable closed bottom part that will do the same job. Some processors are often masked because they generate heat, and keeping them open will improve heat dissipation. In many cases, such parts can be conformally coated without loss of heat dissipation or impact. Redesigning a board or swapping out parts is no easy task, but starting with that in mind will reduce or eliminate masking in the long run.
There are many forms of masking, including the peelable liquid, tape, reusable boots, caps, and stick-on dots. Some are more labor intensive than others, with tape and peelable masking being probably the most labor intensive. Investigate if the use of tape can be replaced with caps or dots, which are easier to remove. These items are reusable only to a point after they have become encrusted with coating. As these reusable items get covered in the coating, their blocking performance may decrease, so consider swapping them out sooner for better protection.
Certain conformal coatings require less masking than others. Silicone has a high propensity to wick into areas even if masking is applied. The thin conformal coating will run and get into places more than thick coating. Switching to an acrylic conformal coating with lower capillary properties, or a thicker mix of coating might be possible to prevent wicking.
Some coating methods and systems require more masking than others. For example, manual spray coating involves the most masking because of its inaccuracy. As much as a one-third of the aerosol conformal coating may be wasted in the form of overspray. Manual brush coating requires less masking, but it is tedious, costly, and inconsistent. Automated spray systems deliver more consistent results and deposit coating more accurately, but come with steep price tags. Automated spray systems have more controlled sprays, and depositors may not eliminate the need for masking.
Finding the right equipment to reduce conformal masking is vital for maintaining productivity and maximizing value. Check out our latest blog on what to look for in automated conformal coating machines and make the right decision for your business.
While managing and improving masking techniques is a solid method for reducing costs, the most effective approach is to eliminate overspray altogether using Invention House’s Raphael 4040, an automated conformal coating robot.
This innovative machine uses precision pumps to deliver conformal coating and thinner to the brush stem where it is mixed according to the desired ratio and deposited by the flow-through brush tip. The brush movement is guided over an optimized X, Y, and Z path to avoid keep-away areas. The brush can be controlled to increase or decrease the coating speed, thickness, and path width, and it can even hover above a tight space to drip coating between components. This means no overspraying and no masking. Download the case study where we document $11/board savings across 12 different PCB layouts.
Contact Invention House today to learn more about the Raphael 4040 and why it’s superior to other coating methods.
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