What are the common PCB defects

Modern PCBA electronics assembly is a complicated process, in the process of production, due to the PCB substrate, PCB processing factors lead to the defect of PCB. As small make up to introduce the common several kinds of the defects and the causes of the PCB.

In pcb factory process, common PCB defects are: white spot, micro crack, blister, layered, wet cloth, fabric, halo and resistance welding defects.

PCB defects

1, white spot,

Plate on the surface of glass fiber woven points, resin and fiber separation, under the base material surface appear white spots or "cross lines" and so on.

Reason:, (1) the impact of the plate subjected to undue external mechanical forces cause the separation of local resin and glass fiber.

(2) local pull material affected by the infiltration of fluoride chemical etching of glass fiber cloth woven points, form a regular white dots (more serious when can see the square).

Sheet (3) by improper thermal stress can cause white and white.

2, micro cracks

Occur within the laminate substrate, continuous white spot or "cross grain", can be defined as micro cracks.

Reason: the main affected by mechanical stress, micro cracks within the laminate substrate.

3, sparkling

Base material layer or between base material and conductive foil, base material with a protective coating between local inflation caused by the partial separation of imagination.

Reasons: (1) the surface contamination (oxidation, oily be soiled, glue mark, other alkaline pollution)

(2) after the curing time is not enough, most of the performance for an Angle on both sides of foaming oil, were found after the tin.

(3) check out tin not net, board face on which there is a thin layer of tin, the tin, the tin on the surface after high temperature melting will ink top up, form a bubble.

(4) hole water vapor without drying printing ink. After the tin in water form a circle on the side of hole shape of blister

(5) in the process of PCB welding processing, plate with water vapor, after reflow soldering are prone to imagine of bubbles.

4, layering,

Base material layer, insulating base material with conductive or laminated between any separation between the layers of imagination.

Reasons: (1) is not set up laminated parameters according to the requirements of specification

(2) does not reach the designated position, clean floor with sundry, lead to after welding is stratified.

5, wet cloth

Completely covered by resin and fracture in the sill of braid fiber, the surface rendering weave pattern.

6, fabric

With the surface of the substrate is not covered by resin completely or braid fiber fracture phenomenon.

7, halo

Under the base material surface or surface damage or layered imagination, usually performed around the hole or other machining parts around the white area.

Reasons: (1) the machine or electric board is not smooth, there is space between boards and wood.

(2) the board warping deformation, with empty space between

(3) the cutter wear

(4) the inspector not clear two drill halo standards targets.