The hazards of using expired PCB

1. Expired PCB may cause oxidation of the solder pad on the PCB surface

Oxidation of the soldering pad will cause poor soldering, which may eventually lead to the failure of the PCB function or the risk of dropping parts. Different surface treatments of circuit boards will have different anti-oxidation effects. In principle, ENIG requires it to be used up within 12 months, while OSP requires it to be used up within six months. It is recommended to follow the shelf life of the PCB board factory. OSP boards can generally be sent back to the board factory to wash off the OSP film and re-apply a new layer of OSP, but there is a chance that the copper foil circuit will be damaged when the OSP is removed by pickling, so it is best to contact the board factory to confirm whether the OSP film can be reprocessed. ENIG boards cannot be reprocessed. Generally, it is recommended to perform “press-baking” and then test whether there is any problem with the solderability.

2. Expired PCB may absorb moisture and cause board burst

 If the circuit board absorbs moisture, it may cause problems such as popcorn effect, bursting or delamination when the circuit board undergoes reflow. Although this problem can be solved by baking, not all board are suitable for baking, baking may cause other quality problems.

Generally speaking, OSP board is not recommended to bake, because high-temperature baking will damage the OSP film, but some people take OSP to bake, but the baking time should be as short as possible, and the temperature should not be too high. It is necessary to complete the reflow furnace in the shortest time, which is a lot of challenges, otherwise the solder pads will be oxidized, which will affect the soldering.

3. The bonding ability of expired PCB may be degraded and deteriorated

After the circuit board is produced, the bonding ability between the layers will gradually degrade or even deteriorate over time, that is to say, as time increases, the bonding force between the layers of the circuit board will gradually decrease.

When such a circuit board is subjected to a high temperature in the reflow furnace, because circuit boards composed of different materials have different thermal expansion coefficients, under the action of thermal expansion and contraction, it may cause delamination of the circuit board and surface bubbles, which will be seriously affect the long-term reliability of the circuit board, because the delamination of the circuit board may break the vias between the layers of the circuit board, resulting in poor electrical characteristics. The most troublesome thing is that intermittent defects may occur. It may cause a micro short circuit without knowing it.

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