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Common problems with legend in PCB manufacturing

Legends are necessary to identify components and circuits during PCB production. However, there are still some unexpected problems with legends during manufacturing. Let's understand what problems there are and whether they are within the acceptable range.
Common problems with legend in PCB manufacturing
25 June 2024
Views: 279
Legends are necessary to identify components and circuits during PCB production. However, there are still some unexpected problems with legends during manufacturing. Let's understand what problems there are and whether they are within the acceptable range.

Problem description:The ink stains on the legend on the fingerboard surface have not been cleaned off.

Acceptance criteria: Not accepted
Problem description: There is excess ink

Acceptance criteria: It is acceptable if it does not affect identification
Problem description:There is excess ink

Acceptance criteria: It is acceptable if it does not affect identification
Problem description: Legends with overlap

Acceptance criteria: It is acceptable if it does not affect identification
Problem description:Legend damaged

Acceptance criteria: It is acceptable if it does not affect identification
Problem description: The legend is incomplete.

Acceptance criteria: It is acceptable if it does not affect identification
Problem description: Marking ink is printed on the lead tin/gold surface

Acceptance criteria:
1. The width of the pad/tin surface meets the requirements;
2. In the case of non-character overall graphic displacement, defects of 5% or 0.05MM position on the edge of the square pad are allowed. If the customer has requirements, it is not allowed;
3. BGA pad/SMT pad/IC position and button position are not allowed.
Problem description: Marking ink is printed on the lead tin/gold surface

Acceptance criteria:
1. The width of the pad/tin surface meets the requirements;
2. In the case of non-character overall graphic displacement, defects of 5% or 0.05MM position on the edge of the square pad are allowed. If the customer has requirements, it is not allowed;
3. BGA pad/SMT pad/IC position and button position are not allowed.
Problem description:Incorrect carbon oil coverage.

Acceptance criteria:
1. B must be < 20% of the width C, and A must be < the width C;
2. Each carbon oil PAD can only have one gap, and copper exposure is not allowed;
3. When the carbon oil PAD width C>0.9MM, A is controlled to be less than or equal to (C+0.1MM)/2 of the carbon oil PAD.
Problem description:Improper carbon oil coverage results in copper exposure.

Acceptance criteria:
1. The gap width must be < 20% of the carbon oil width, and the gap length must be < the carbon oil width;
2. Each carbon oil PAD can only have one gap, and copper exposure is not allowed;
3. When the carbon oil PAD width is > 0.9MM, the gap length is controlled to be less than or equal to (carbon oil width + 0.1MM)/2 of the carbon oil PAD.
Problem description:Ink bleeds from the edges of carbon ink graphics.

Acceptance criteria:Does not affect the minimum spacing of 20%.
Problem description:The pattern deviates from the specified position when screen printing carbon ink.

Acceptance criteria:If there is only a slight printing deviation, it is acceptable as long as the entire row of PADs deviates in the same direction and ensures that the PAD is ≥0.1MM.
Problem description: The blue glue failed to cover the required location.

Acceptance criteria: Not accepted
Problem description: Blue gel screen printing into unspecified VCUT slots or masked holes.

Acceptance criteria: Not accepted
Problem description: The blue glue fell off.

Acceptance criteria: Not accepted
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