PCB assembly of the huge impact factor - humidity

About reducing moisture effects on any type of printed circuit board. From material fusion, PCB layout, prototyping, PCB engineering, assembly to packaging and order delivery stages, attention should be paid to the effect of moisture in PCB manufacturing to avoid damage and other problems with PCB functionality. In addition, let's take an in-depth look at the important measures to control humidity levels during laminating, the controls implemented during PCB assembly and control storage, packaging and transportation.

Rigid/flexible printed circuit board components, cable bundles, boxed components or wire harnesses PCB components are made from a variety of types of materials that fully conform to the attributes required for strong mechanical and electrical performance in electronics used in all major industries worldwide. It requires high frequency, low impedance, compactness, durability, high tensile strength, low weight, versatility, temperature control or humidity resistance. PCBS can be single, double or multilayer, depending on the complexity of the circuit. Of all the serious problems that should be noted in the initial phase of PCB manufacturing, humidity or humidity is the main factor that leads to the creation of space for electronic and mechanical failures in PCB operation.

How can moisture cause huge trouble on printed circuit boards?
By being present in the epoxy glass prepreg, diffusing in the PCB during the stored process, upon absorption, moisture can form various defects in the PCB components. Wet process time in PCB manufacturing, exists in microcracks or can form a home in the resin interface. Moisture absorption occurs because the high temperature and steam pressure are parallel to the quadcopter structure in PCB assembly.

As adhesive and cohesion failures in the printed circuit board lead to delamination or cracking, moisture can make metal migration possible, resulting in a low impedance path with dimensional stability changes. With the decrease of glass transition temperature, the increase of dielectric constant and other technical damage, it will lead to circuit switching speed reduction and high propagation time delay.

The main effect of moisture in PCBS is that it reduces the quality of metallization, lamination, solder resistance film and PCB manufacturing process. Due to the influence of moisture, the limit of thermal stress becomes excessive as the glass transition temperature decreases. Sometimes it can also cause severe short circuits that allow moisture to enter, leading to ionic corrosion. PCB components in the hygroscopicity of other common properties include flame retardant or layering, increasing (DF) and dissipation factor (DK) dielectric constant, the thermal stress on the plated through hole and copper oxide.

Ways to reduce moisture in PCB manufacturing:
Whether a PCB is manufactured using simple or complex techniques, there are many operations in PCB engineering that require the wet process and removal of residual water. The raw materials used in PCB manufacturing need to be protected during storage, handling and stress handling during PCB assembly. Here is a brief guide to implementing controls at all stages of PCB operation:

1. lamination
Laminating is the dewatering step in PCB manufacturing, as the core and prepreg billet are stacked on top of each other to glue the layers into the laminate. The main factors controlled during lamination are temperature, time used and heating rate. Sometimes, when dryness is low, measures are taken to reduce vacuum to reduce the possibility of internal voidage attracting moisture absorption. Therefore, the use of gloves when handling prepregs provides good control over the level of moisture. This reduces cross contamination. Non-corroding humidity indicator cards should have flexibility to address humidity levels if needed. The laminate should have a short wash cycle and be stored efficiently in a controlled environment, which helps prevent moisture pockets from forming in the laminate.

2. Post lamination process and PCB assembly
After drilling, photographic imaging, and etching operations in PCB manufacturing, the absorption rate of water captured in the wet process is higher. Screen curing and welding mask baking are treated steps to relieve entrained moisture. This is more effective in reducing water absorption levels by minimizing the holding time between steps and even actively managing storage conditions. By ensuring that the PCB is sufficiently dry during the early stages of laminating, the board can help reduce baking operations after laminating. In addition, a high quality surface treatment is used to prevent cracks during the drilling process and humidity is removed from the residue by baking prior to the hot air solder smoothing process. Baking time should be maintained by taking into account the determined level of moisture content, the complexity of PCB manufacturing, PCB surface treatment and the required adequate thickness of the circuit board.

Therefore, it is vital to know the latest status of the effect of moisture in PCB manufacturing to avoid failure, damage and short circuit on the PCB, while increasing the cost of rework. Now, researchers are on the verge of introducing even more advanced solutions that save time, energy and cost by using eco-friendly PCB technology to control the moisture element in every step of PCB manufacturing.