PCB News - PCB pad and plated-through hole defects

The PCB circuit board is an important component that connects and carries thousands of electronic components.

In complex electronic equipment, the solder joints on the circuit board are densely packed and scattered. Among them, even if there is a dewetting non wetting solder joint or desoldering, it will lead to the paralysis of machinery and equipment, resulting in immeasurable catastrophic consequences. Therefore, the quality of PCB pads and plated holes is very important, and it is an important part of PCB quality control.

Let's take a look at the common defects of PCB pads and plated holes and some standards for quality control.

1. Pad defect

1.1 Non-wetting: The molten solder cannot form a metal bond with the metal substrate.

Non-wetting defects in PCB circuit boards

Ideal PCB soldering pad

Target conditions-Level 3, 2, 1

• All wet.

Acceptable conditions-level 3, 2, 1

• All conductor surfaces that require solder connections must be completely wetted. vertical

The surface (conductor and land) area can be left uncovered.

PCB non-wetting defect

Does not meet the conditions-Level 3, 2, 1

• The defect does not meet or exceed the above requirements.

1.2 Dewetting: A condition in which molten solder is applied to the metal surface and then the solder retracts, resulting in the formation of irregular solder piles separated by areas covered by a thin film of solder and not exposed to the metal substrate.

Non-wetting defects in PCB circuit boards

Defect-free PCB pads

Target conditions-Level 3, 2, 1

• No dewetting.

Acceptable dewetting non wetting solder Defects

Acceptable conditions-Level 3, 2

• There is dewetting on the conductor and on the ground or power layer.

• The dewetting area on each welding connection plate is less than or equal to 5%.

Acceptable conditions-level 1

• There is dewetting on the conductor and on the ground or power layer.

• The dewetting area on each solder connection plate is less than or equal to 15%.

dewetting non wetting solder defects of PCB pads that do not meet the requirements

Not eligible-level 3, 2, 1

• The defect does not meet or exceed the above requirements.

2. Plated through holes

The common defects of plated-through holes are nodules or rough plating, pink circles, copper plating voids and final coating voids, connecting pad warping, and plating of the covering layer of the plugging hole.

2.1 Nodules or rough plating

Target conditions-Level 3, 2, 1

• No nodules or signs of rough plating.

Acceptable conditions-level 3, 2, 1

• Nodules or rough coatings did not reduce the pore size below the minimum specified in the procurement documents.

Not eligible-level 3, 2, 1

• The defect does not meet or exceed the above requirements.

2.2 Pink circle

Acceptable conditions-level 3, 2, 1

• The pink circle generally does not affect the function of the PCB. But it needs our attention.

2.3 Voids in copper plating

Target conditions-Level 3, 2, 1

• No voids.

Acceptable conditions-level 3

• There are no signs of voids in the hole.

Acceptable conditions-level 2

• The number of voids in any hole is not more than one.

• The number of holes with voids does not exceed 5%.

• The length of any cavity is not more than 5% of its hole length.

• The void is less than 90° of the circumference.

Acceptable conditions-level 1

• No more than 3 voids in any hole.

• The number of holes with voids does not exceed 10%.

• The length of any cavity is not more than 10% of its hole length.

• All cavities are smaller than 90° of the circumference.

• The defect does not meet or exceed the above requirements.

2.4 Voids in the final coating

• No voids.

Acceptable conditions-level 3

• The number of voids in any hole is not more than one.

• The number of holes with voids does not exceed 5%.

• The length of the cavity is not more than 5% of the hole length.

• The void is less than 90° of the circumference.

• No more than 3 voids in any hole.

• The number of holes with voids does not exceed 5%.

• The length of any cavity is not more than 5% of its hole length.

• All cavities are smaller than 90° of the circumference.

• No more than 5 voids in any hole.

• The number of holes with voids does not exceed 15%.

• The length of the cavity is not more than 10% of the length of the hole.

• All cavities are smaller than 90° of the circumference.

2.5 The connecting plate is upturned-(can be inspected)

2.6 Plating of the covering hole of the plugged hole-(visible by sight)

The above is the introduction of PCB pad and plated hole defects. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.