PCB News - Common quality problems in PCB solder mask process

Common quality problems in PCB solder mask process

Solder mask is a layer of ink printed on the surface of the PCB. It not only plays a role in insulation, but also protects the copper surface. It also plays a beautiful and beautiful role. It is like a piece of clothing worn on the outside of the PCB proofing. It is easy to find any flaws, so solder mask is also the most prone to customer complaints among all processes. In the PCB solder mask process, you who are smart and experienced may also encounter various quality problems. The following Shenzhen circuit board manufacturers summarize some common problems for you, and hope to inspire and help you. The common ones are as follows:

problem: penetration, blur

Reason 1: The ink viscosity is too low.

Improvement measures: increase the concentration without adding diluent.

Reason 2: The screen printing pressure is too high.

Improvement measures: reduce stress.

Reason 3: Bad squeegee.

Improvement measures: Replace or change the angle of the squeegee screen.

Reason 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-make a new screen version.

problem: sticky film

Reason 1: The ink is not dried

Improvement measures: check the degree of ink drying

Reason 2: The vacuum is too strong

Improvement measures: check the vacuum system (the air guide strip may not be added)

Problem: Poor exposure

Reason 1: Poor vacuum

Improvement measures: check the vacuum system

Reason 2: Improper exposure energy

Improvement measures: adjust the appropriate exposure energy

Reason 3: Exposure machine temperature is too high

Improvement measures: check the temperature of the exposure machine (below 26 degree Celsius)

Problem: White spots in printing

Reason 1: White spots in printing

Improvement measures: the thinner does not match, use the matched thinner [please use the company's supporting thinner]

Reason 2: The sealing tape is dissolved

Improvement measures: use white paper to seal the net

Problem: Excessive development (corrosion test)

Reason 1: The concentration of the potion is too high and the temperature is too high

Improvement measures: reduce the concentration and temperature of the potion

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: The developing water pressure is too large

Improvement measures: lower the developing water pressure

Reason 5: Ink mixing is uneven

Improvement measures: Stir the ink evenly before printing

Reason 6: The ink is not dried

Improvement measures: Adjust the baking parameters, see the question [Ink does not dry]

Problem: The ink does not dry out

Reason 1: The oven exhaust is not good

Improvement measures: check the exhaust air condition 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: Too little thinner

Improvement measures: increase thinner, fully dilute

Reason 4: The thinner dries too slowly

Improvement measures: use matching thinner [please use company supporting thinner]

Reason 5: The ink is too thick

Improvement measures: appropriately adjust the ink thickness

Problem: Green Oil Bridge Broken Bridge

Reason 1: Insufficient exposure energy

Improvement measures: Increase exposure energy

Reason 2: The sheet is not handled properly

Improvement measures: check the treatment process

Reason 3: Too much pressure for developing and washing

Improvement measures: check the developing and washing pressure

problem: post-baking and exploding oil

Reason 1: There is no segmented baking

Improvement measures: stage baking

Reason 2: Insufficient viscosity of plug hole ink

Improvement measures: adjust plug hole ink viscosity

Problem: Poor upper tin

Reason 1: The development is not clean

Improvement measures: improve several factors of poor image development

Reason 2: Post-baking solvent contamination

Improvement measures: increase oven exhaust or machine cleaning before spraying tin

Problem: Foaming on the tin

Reason 1: Excessive development

Improvement measures: improve the development parameters, see the problem [over development]

Reason 2: The pre-treatment of the board is not good, and the surface is oily and dusty.

Improvement measures: do a good job of pre-treatment of the board and keep the surface clean

Reason 3: Insufficient exposure energy

Improvement measures: check the exposure energy and meet the ink usage requirements

Reason 4: Abnormal flux

Improvement measures: adjust flux

Reason 5: Insufficient post-bake

Improvement measures: Baking process after inspection

Problem: Ink discoloration

Reason 1: Insufficient ink thickness

Improvement measures: increase ink thickness

Reason 2: Oxidation of the substrate

Improvement measures: check the pre-treatment process

Reason 3: The post-baking temperature is too high

Improvement measures: the time is too long, after checking the baking parameters

Problem: The development is not clean

Reason 1: It takes too long after printing

Improvement measures: control the storage time within 24 hours

Reason 2: The ink runs out before development

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

Reason 3: Not enough developing potion

Improvement measures: The temperature is not enough Check the concentration and temperature of the medicine

Reason 4: Development time is too short

Improvement measures: extend the development time

Reason 5: Exposure energy is too high

Improvement measures: Adjust exposure energy

Reason 6: The ink is over-baked

Improvement measures: adjust the baking parameters, not to burn to death

Reason 7: Ink mixing is uneven

Improvement measures: Stir the ink evenly before printing

Reason 8: The thinner does not match

Improvement measures: use matching thinner [please use company supporting thinner]

Problem: Ink matte

Reason 1: The thinner does not match

Improvement measures: use matching thinner [please use company supporting thinner]

Reason 2: Low exposure energy

Improvement measures: Increase exposure energy

Reason 3: Excessive development

Improvement measures: improve the development parameters, see the problem [over development]

Problem: Blocking the Internet

Reason 1: Drying is too fast.

Improvement measures: add slow-drying agent.

Reason 2: The printing speed is too slow.

Improvement measures: increase the speed and slow down the drying agent.

Reason 3: The ink viscosity is too high.

Improvement measures: add ink lubricant or extra slow drying agent.

Reason 4: The thinner is not suitable.

Improvement measures: use designated thinners.

problem: ink adhesion is not strong

Reason 1: Ink type selection is inappropriate.

Improvement measures: Change to appropriate ink.

Reason 2: The ink type selection is inappropriate.

Improvement measures: Change to appropriate ink.

Reason 3: The drying time, temperature is not correct, and the exhaust air volume during drying is too small.

Improvement measures: use the correct temperature and time, and increase the exhaust air volume.

Reason 4: The amount of additives is inappropriate or incorrect.

Improvement measures: adjust the dosage or switch to other additives.

Reason 5: The humidity is too high.

Improvement measures: improve air dryness.