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Stencil Printing vs. Jet Printing in PCB Assembly
In surface mount technology (SMT) PCB assembly, applying the correct amount of solder paste to component pads is a critical step that directly affects assembly yield, reliability, and manufacturing efficiency.
Two common methods used in modern PCB assembly lines are stencil printing and jet printing. Each approach has unique strengths, and the optimal choice depends on production volume, design complexity, and turnaround requirements.
At NeuronicWorks, we use both techniques as part of our PCB assembly process leveraging jet printing for flexible prototyping and high-mix builds while recently expanding our capabilities with a stencil printer for efficient production runs.
In this blog post, we explore how these two methods work and when each one makes the most sense.
What is Stencil Printing?
Stencil printing is the traditional and most widely used method for depositing solder paste in PCB assembly.
A thin stainless-steel stencil with laser-cut apertures matching the PCB pad layout is aligned with the board. Solder paste is then spread across the stencil using a squeegee, forcing paste through the openings onto the pads. When the stencil is lifted, precise deposits remain on the board ready for component placement.
Advantages of Stencil Printing
High production speed
Low-probability issues that seem harmless during testing inevitably surface at scale. A failure rate of 0.1% may appear negligible until thousands of devices are deployed. At that point, rare issues become guaranteed realities.
Excellent repeatability
Once optimized, stencil printing provides consistent paste volumes and placement across thousands of boards.
Low cost per board in production
Although a custom stencil must be fabricated, the cost per board becomes very low once production volumes increase.
Mature and widely adopted process
Stencil printing has been the backbone of SMT manufacturing for decades and integrates easily with automated production lines.
Limitations of Stencil Printing
Requires a custom stencil
Each PCB design requires a dedicated stencil, and any design revision typically requires a new one.
Less flexible for design changes
Frequent design updates can slow down development cycles because of stencil fabrication lead times, especially for complex boards when stencil manufacturing can extend to 72hrs or even more.
Challenges with complex paste volumes
Boards with widely varying pad sizes sometimes require stepped stencils, increasing cost and complexity exponentially.
Cleaning time and ecological footprint
Stencil printing requires cleaning of the stencil and printer components after every run to maintain consistent paste deposition and print quality. This process can take additional time and typically involves specialized stencil cleaning equipment, solvents, and wipes.
What is Jet Printing?
Jet printing (also called solder paste jetting) is a digital, stencil-free printing technology.
Instead of pushing paste through a stencil, a high-speed nozzle deposits tiny droplets of solder paste directly onto PCB pads based on a programmed design file similar to how an inkjet printer works.
Advantages of Jet Printing
No stencil required
Design changes can be implemented immediately without waiting for new tooling. With an OBD++ file the machine can be programed for a new board in 30 minutes or less.
Excellent flexibility
Paste volumes can be adjusted dynamically for different pad sizes on the same board. Even the shape of the deposited paste can be controlled and therefore optimized for each component type.
Ideal for prototypes and high-mix builds
Quick programming allows engineers to move rapidly from design revision to assembled prototype. It is the ideal choice for runs in the order of 10-25 PCBAs.
Reduced material waste
Only the required amount of solder paste is deposited, minimizing waste compared to stencil printing, resulting in much more economical use of the paste
Cleaning and ecological footprint
Significantly reduced time and effort required for cleaning compared to stencil printing. Since there is no stencil, the tedious cleaning process after each run is eliminated. The main consumables are the paste cartridges which must be handled and recycled properly.
Paste deposit verification
The jet printer uses an integrated camera to verify paste deposits at the end of each cycle. This two-in-one machine eliminates the need for a separate solder paste inspection (SPI) system required by stencil printers. If required, the jet printer automatically deposits additional paste after verification.
Limitations of Jet Printing
Slower printing speeds
Jet printing can take several minutes per board/panel, making it less suitable for high-volume production lines. For large, complex boards or volume manufacturing, the printing step can become a bottleneck in the assembly line, limiting overall throughput compared to stencil printing.
Higher equipment cost
Jet printers represent a significant capital investment, often several times higher than a comparable stencil printer.
Key Differences Between Stencil Printing and Jet Printing
| Factor | Stencil Printing | Jet Printing |
|---|---|---|
| Tooling | Requires custom stencil | No stencil required |
| Speed | Very fast | Slower |
| Best for | Medium-to-high volume production | Prototyping and high-mix builds |
| Design changes | Requires new stencil | Instant via software |
| Paste control | Fixed by stencil apertures | Dynamic droplet control |
In many modern assembly lines, these methods complement each other rather than compete.
How NeuronicWorks Uses Both Technologies
At NeuronicWorks, our PCB assembly strategy is built around flexibility and scalability.
For many prototype and high-mix projects, we use jet printing to enable fast turnaround and easy design iterations. As discussed in our earlier blog post on jet printing, the ability to program paste deposition directly from design files allows us to respond quickly to customer revisions and complex assemblies.
To further support our customers as designs transition toward production, we recently expanded our manufacturing capacity with a stencil printer. This addition allows us to deliver:
- Faster throughput for repeat builds
- Improved efficiency for production volumes
- Seamless scaling from prototype to volume manufacturing
By offering both solder paste deposition methods, we can select the most appropriate process for each project.
Final Thoughts
Both stencil printing and jet printing play essential roles in modern PCB assembly.
While stencil printing remains the industry standard for efficient production manufacturing, jet printing provides the flexibility and precision needed for prototyping and high-mix builds.
Rather than choosing one over the other, we combine both technologies to support the entire product development lifecycle, from first prototype to production ramp-up.
Whether you are prototyping a new PCB or ramping up to full production, NeuronicWorks has both experience and equipment- jet printing and stencil printing- to meet your assembly needs. Contact us today to see which method is right for your project.