Many friends encounter frequent defects during the silkscreen process, despite using high-quality inks and equipment. Often, the issue stems from seemingly minor pitfalls. Most of these pitfalls arise from "empiricism" or attempts to "cut costs." Today, we will address these misconceptions one by one in a Q&A format to help everyone avoid these common traps.

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**Question 1: To save costs, many factories reuse recycled silkscreen ink. Is this practice acceptable?**

Answer: This is one of the most common misconceptions in silkscreen production. While reusing recycled ink may seem cost-effective, it often leads to a high rate of defective products, ultimately increasing costs. Recycled ink poses three main issues:

1. **Uncontrolled viscosity and composition**: After multiple uses, solvents in recycled ink evaporate, causing viscosity to increase. Mixing inks from different batches disrupts the composition ratio, making it impossible to ensure consistent silkscreen results.

2. **High impurity content**: Recycled ink often contains dust, fibers, PCB debris, and other impurities. During printing, these impurities can clog the screen mesh, leading to defects such as blurry patterns or pinholes.

3. **Degraded performance**: The resin cross-linking density in recycled ink decreases, significantly reducing key properties like adhesion and temperature resistance. This can later cause issues such as peeling or discoloration.

**Correct approach**: Ink should ideally be used once. Unused new ink should be stored sealed and not exceed its shelf life. Recycled ink should only be used for non-critical areas (e.g., internal markings). Before use, it must be filtered to remove impurities, adjusted for viscosity, and tested in small batches.

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**Question 2: To improve efficiency, many people increase the curing temperature or shorten the curing time after silkscreening. Is this correct?**

Answer: This is incorrect. Excessively high curing temperatures or insufficient curing time can lead to "false curing," where the ink appears dry but has not fully cross-linked. False curing is highly detrimental:

1. **Poor adhesion**: Inadequate resin cross-linking within the ink layer weakens its bond to the board surface, making it prone to peeling.

2. **Insufficient temperature resistance**: Exposure to soldering temperatures may cause the ink to blister, discolor, or decompose.

3. **Layer cracking**: Rapid solvent evaporation under high temperatures can create internal bubbles in the ink layer, leading to micro-cracks upon cooling and compromising protective performance.

**Correct approach**: Strictly follow the curing curve provided by the ink supplier. Do not arbitrarily adjust temperature or time. To improve curing efficiency, consider using UV-curable or dual-cure inks instead of compromising curing quality.

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**Question 3: During silkscreening, many believe that higher squeegee pressure ensures better ink transfer and clearer patterns. Is this true?**

Answer: This is a classic "empirical misconception." Squeegee pressure is not "the higher, the better." Excessive pressure can actually cause more defects:

1. **PCB misalignment**: Excessive pressure can shift the PCB on the printing table, causing misalignment.

2. **Screen wear**: High pressure accelerates wear on the squeegee and screen, shortening the screen's lifespan.

3. **Pattern deformation**: Under high pressure, the screen may stretch and deform, leading to blurred patterns and jagged edges.

**Correct approach**: Apply the "minimum effective pressure" principle—the optimal pressure is just enough to ensure complete ink transfer. Gradually adjust pressure and observe the printing results to determine the best setting.

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**Question 4: Many factories skip PCB surface cleaning before silkscreening, assuming "the surface looks clean." Is this acceptable?**

Answer: This practice is highly risky. Contaminants such as oil, dust, and oxidation layers on the PCB surface, though often invisible to the naked eye, severely impact ink adhesion. Inadequate cleaning can lead to:

1. **Reduced adhesion**: Oily residues act as a barrier between the ink and board, causing peeling. Dust can result in pinholes or craters.

2. **Blurry patterns**: Oxidation layers hinder ink wetting, causing smudged edges.

3. **Soldering issues**: If ink peels off, it may contaminate solder pads, affecting soldering quality.

**Correct approach**: Always include a surface cleaning step before silkscreening. Choose methods like electrostatic dust removal, plasma cleaning, or solvent wiping based on the level of contamination. PCBs stored for over 24 hours must be re-cleaned before printing.

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**Question 5: Some believe screens should only be replaced when completely worn out, thinking "as long as patterns print, it's usable." Is this correct?**

Answer: This is incorrect. Screen tension loss and pattern wear are major causes of silkscreen defects. Screens should not be used until failure:

1. **Tension loss**: Over time, screen tension gradually decreases, causing stretching and deformation during printing and leading to misalignment.

2. **Pattern wear**: The emulsion on the screen wears down, making pattern edges rough and resulting in jagged or blurred prints.

3. **Clogged mesh**: Prolonged use can clog mesh openings with ink, reducing ink deposition and causing faint patterns.

**Correct approach**: Establish a screen lifespan standard—typically 5,000–10,000 prints for regular screens. Check screen tension before each production run; replace if tension loss exceeds 15%. Repair or replace screens promptly if pattern wear or mesh clogging is detected.

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**Question 6: Many believe "thicker ink produces clearer patterns" and reduce thinner additives. Is this accurate?**

Answer: This view is one-sided. Ink viscosity should be adjusted based on printing requirements, not simply made thicker. Overly thick ink can cause:

1. **Poor ink release**: High viscosity prevents ink from fully filling mesh openings, leading to insufficient ink deposition, faint patterns, or broken lines.

2. **Pattern deformation**: Thick ink flows poorly, failing to spread evenly after squeegee action and resulting in burred edges.

3. **Screen clogging**: Thick ink dries quickly in mesh openings, clogging the screen and shortening its lifespan.

**Correct approach**: Adjust ink viscosity according to pattern precision and mesh count:  

- Fine patterns: slightly thicker ink (200–300 dPa·s).  

- Regular patterns: medium viscosity (100–200 dPa·s).  

- Thick-film printing: slightly thinner ink (50–100 dPa·s).  

When adding thinners, follow the "little and often" principle to ensure uniform viscosity.

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**Question 7: Some think temperature and humidity control in the silkscreen workshop "only needs to be roughly right" and precise control is unnecessary. Is this mindset correct?**

Answer: This is incorrect. Even minor fluctuations in temperature and humidity can affect ink stability and printing quality:

1. **High temperature**: Lowers ink viscosity, increases flowability, and may cause bleeding or blurring.

2. **Low temperature**: Raises ink viscosity, hindering ink release and leading to faint patterns.

3. **High humidity**: Causes board surface moisture absorption, reducing ink adhesion and leading to peeling.

4. **Low humidity**: Increases static electricity, attracting dust to the board surface and causing pinholes.

**Correct approach**: Maintain workshop temperature at 20–25°C and humidity at 40–60%. Install temperature and humidity recorders for daily monitoring. Adjust air conditioning and dehumidification equipment promptly if deviations occur.

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Most misconceptions in PCB silkscreen production stem from "eagerness for quick results" or "empiricism." The key to avoiding these pitfalls is to "respect science and adhere to standards." Do not sacrifice silkscreen quality for cost-saving or efficiency gains. Remember: high-quality silkscreening is crucial for PCB reliability and forms the foundation for a company's long-term development.