Increase knowledge! Cause Analysis of Common Poor Welding of Circuit Board

Date：2022-12-15 14:03:17Views：595

There are many common welding defects of circuit boards, and these factors may cause some dangers to the circuit boards. The common welding defects, appearance characteristics, hazards, and cause analysis are described in detail below. If you are interested in the content to be covered in this article, please read on.

Faulty soldering

Appearance characteristics: There is a clear black boundary between soldering tin and component lead or copper foil, and soldering tin is sunken towards the boundary. Hazard: It cannot work normally. Cause analysis: component leads are not clean, tin plated or oxidized. The printed board is not cleaned well, and the quality of the sprayed flux is poor.

Solder buildup

Appearance characteristics: loose, white and lusterless solder joints. Cause analysis: the quality of solder is poor. Insufficient welding temperature. When the soldering tin is not solidified, the component leads are loose.

Too much solder

Appearance characteristics: the solder surface is convex. Hazard: Solder is wasted and may contain defects. Cause analysis: Solder withdrawal was too late.

Too little solder

Appearance characteristics: the welding area is less than 80% of the pad, and the solder does not form a smooth transition surface. Hazard: insufficient mechanical strength. Cause analysis: poor solder fluidity or premature solder withdrawal. Insufficient flux. Welding time is too short.

Rosin soldering

Appearance characteristics: the welding seam is mixed with rosin slag. Hazard: insufficient strength, poor continuity, and possible on-off. Cause analysis: there are too many welding machines or they have failed. Insufficient welding time and heating. The surface oxide film is not removed.

overheated

Appearance characteristics: white solder joints, no metallic luster, rough surface. Hazard: The pad is easy to peel off and its strength is reduced. Cause analysis: The power of the soldering iron is too high and the heating time is too long.

Cold welding

Appearance characteristics: the surface is like bean curd dregs, sometimes with cracks. Hazard: low strength and poor conductivity. Cause analysis: The solder shakes before solidification.

Poor infiltration

Appearance characteristics: the interface between solder and weldment is too large and not smooth. Hazard: low strength, no connection or on/off. Cause analysis: the weldment was not cleaned. Insufficient flux or poor quality. The weldment is not sufficiently heated.

Asymmetry

Appearance characteristics: the solder is not full of the pad. Hazard: insufficient strength. Cause analysis: poor liquidity of solder. Insufficient flux or poor quality. Insufficient heating.

Loose

Appearance characteristics: the lead wire or component lead wire can be moved. Hazard: poor or no continuity. Cause analysis: the lead wire moves before the solder is solidified, causing the gap. The lead wire is not well treated (poor or not soaked).

Gib

Appearance characteristics: appearance of tip. Hazard: poor appearance, easy to cause bridging. Cause analysis: the flux is too little and the heating time is too long. The withdrawal angle of soldering iron is improper.

bridging

Appearance features: adjacent wires are connected. Hazard: electrical short circuit. Cause analysis: too much soldering tin. The withdrawal angle of soldering iron is improper.

pinhole

Appearance characteristics: holes are visible through visual inspection or low-power amplifier. Hazard: the strength is insufficient, and the welding spot is easy to corrode. Cause analysis: The clearance between the lead wire and the pad hole is too large.

Bubble

Appearance characteristics: the root of the lead has a flame spraying solder bulge, and there are cavities inside. Hazard: temporary conduction, but it is easy to cause poor conduction for a long time. Cause analysis: the gap between the lead wire and the pad hole is large. The lead wire is poorly infiltrated. The welding time of double-sided plate plug through-hole is long, and the air in the hole expands.

Copper foil cocks up

Appearance characteristics: copper foil is peeled off from the printed board. Hazard: The printed board is damaged. Cause analysis: the welding time is too long and the temperature is too high.

be stripped

Appearance characteristics: solder joints are peeled off from copper foil (not from copper foil and printed circuit board). Hazard: open circuit. Cause analysis: the metal coating on the bonding pad is poor.

The above is related to the analysis of the causes of poor soldering of the circuit board organized by the wound core detection team, and I hope it will be helpful to you. Our company has a team of professional engineers and industry elites, and has built three standardized laboratories with an area of more than 1800 square meters, which can undertake a variety of test projects such as electronic component test verification, IC authenticity identification, product design material selection, failure analysis, functional testing, factory incoming material inspection and tape weaving.