Common Quality Problems and Solutions in PCB Solder Masking Process

Everyone in PCB design knows that solder mask is a layer of ink printed on the PCB surface. It not only plays the role of insulation, but also protects the copper surface. It also plays a beautiful and beautiful role. It is like wearing on the outside of the PCB. A piece of clothing, so any point of it is very easy to find, so solder mask is also the most likely to lead to customer complaints in all processes. In the PCB solder resisting process, smart and sophisticated you may also encounter a variety of quality issues. The following gives you a summary of some of the common problems of response measures, hoping to give everyone inspiration and help. Common as follows:

 

Problem: Infiltration, Blur

Cause 1: The ink viscosity is too low.

Improvement measures: Increase the concentration without diluent.

Reason 2: Silk screen pressure is too high. The

Improvement measures: Reduce pressure.

Cause 3: Bad squeegee.

Improvement measures: Replace or change the angle of the scratch screen printing.

Cause 4: The distance between the screen and the printing surface is too large or too small.

Improvement measures: Adjust the spacing.

Reason 5: The tension of the silk screen becomes smaller.

Improvement measures: Re-create a new screen.

Question: Sticky Film

Reason 1: The ink is not baked dry

Improvement measures: check the degree of ink drying

Reason 2: Vacuum is too strong

Improvement measures: check vacuum system (without air strip)

 

Problem: poor exposure

Cause 1: Bad vacuuming

Improvement measures: check the vacuum system

Reason 2: Improper exposure energy

Improvement measures: Adjust the appropriate exposure energy

Reason 3: Exposure temperature is too high

Improvement measures: Check exposure temperature (below 26°C)

Problem: Ink baking does not work

Reason 1: The oven exhaust is not good

Improvement measures: Check the exhaust status of the oven

Reason 2: The oven temperature is not enough

Improvement measures: determine whether the actual temperature of the oven reaches the required temperature of the product

Reason 3: Diluted diluent

Improvement measures: increase thinner, fully diluted

Cause 4: The thinner is too slow

Improvement measures: Use a matching thinner [Please use the company’s supporting thinner]

Reason 5: The ink is too thick

Improvement measures: Adjust ink thickness properly

 

Problem: White dots printed

Cause 1: White dots printed

Improvement measures: Thinner does not match Use matching thinner [Please use the company’s supporting thinner]

Reason 2: Closure tape is dissolved

Improvement measures: Switch to white paper

 

Problem: Over development (measurement)

Cause 1: Poison concentration is too high and temperature is too high

Improvement measures: reduce the concentration of the medicine and the temperature of the medicine

Reason 2: Development time is too long

Improvement measures: shorten the development time

Reason 3: Insufficient exposure energy

Improvement measures: increase exposure energy

Reason 4: Development water pressure is too high

Improvement measures: reduce the pressure of the developer

Cause 5: uneven ink stirring

Improvement measures: Stir ink evenly before printing

Cause 6: The ink is not dried

Improvement measures: adjust the baking parameters, see the question [ink baking]

 

Question: Green Oil Bridge Broken Bridge

Reason 1: Insufficient exposure energy

Improvement measures: increase exposure energy

Reason 2: The plate is not handled properly

Improvement measures: check processing procedures

Reason 3: Development, washing pressure too

Improvement measures: check the developing and washing pressure

 

Problem: Not developing properly

Reason 1: Too long time after printing

Improvement measures: control the placement time within 24 hours

Reason 2: The ink is depleted before development

Improvement measures: work in the darkroom before development (the fluorescent lamp is wrapped in yellow paper)

Reason 3: Not enough developer

Improvement measures: Insufficient temperature Check potion concentration, temperature

Reason 4: Development time is too short

Improvement measures: lengthen the development time

Reason 5: Exposure energy is too high

Improvement measures: adjust the exposure energy

Reason 6: Over-inking

Improvement measures: adjust the baking parameters, can not be baked

Cause 7: uneven ink stirring

Improvement measures: Stir ink evenly before printing

Cause 8: Diluent does not match

Improvement measures: Use a matching thinner [Please use the company’s supporting thinner]

 

Problem: bad on tin

Cause 1: Development is not clear

Improvement measures: Improve the factors of unclean development

Reason 2: post-baking solvent contamination

Improvement measures: increase oven exhaust or spray cleaning before spraying

 

Question: After baking oil

Reason 1: No batch baking

Improvement measures: step baking

Reason 2: Poor ink viscosity is not enough

Improvement measures: adjust the ink viscosity

 

Problem: Tin foaming

Reason 1: over development

Improvement measures: Improve the development parameters, see the question [overexposure]

Cause 2: The plate is not well treated before, and there is oil on the surface. Dust

Improvement measures: Do a good job of pre-treatment to keep the surface clean

Reason 3: Insufficient exposure energy

Improvement measures: Check exposure energy, in line with ink usage requirements

Cause 4: Abnormal flux

Improvements: Adjusting flux

Reason 5: After baking is insufficient

Improvement measures: check the post-baking process

 

Problem: Ink discoloration

Cause 1: Insufficient ink thickness

Improvements: Increase ink thickness

Reason 2: substrate oxidation

Improvement measures: check the pre-treatment process

Reason 3: After the baking temperature is too high

Improvements: Time is too long Check baking parameters

 

Problem: Ink Matte

Cause 1: Diluent does not match

Improvement measures: Use a matching thinner [Please use the company’s supporting thinner]

Reason 2: Low exposure energy

Improvement measures: increase exposure energy

Reason 3: over development

Improvement measures: Improve the development parameters, see the question [overexposure]

 

Problem: Blocking the Net

Cause 1: Dry too quickly.

Improvement measures: Add slow-drying agent.

Reason 2: The printing speed is too slow.

Improvement measures: Increase speed and slow drying agent.

Cause 3: The viscosity of the ink is too high.

Improvement measures: Add ink lubricant or special slow-drying agent.

Cause 4: The thinner is not suitable.

Improvement measures: Use the designated diluent.

 

Problem: Ink adhesion is not strong

Cause 1: Inappropriate choice of ink type.

Improvement measures: Use appropriate ink.

Cause 2: Incorrect ink type selection.

Improvement measures: Use appropriate ink.

Cause 3: The drying time, temperature is incorrect, and the amount of exhaust air during drying is too small.

Improvement measures: Use the correct temperature and time, increase the amount of exhaust.

Cause 4: The amount of additive is not appropriate or correct.

Improvement measures: Adjust dosage or use other additives.

Cause 5: The humidity is too high.

Improvement measures: Improve air dryness.