SMT Processing Workshop Specifications for Temperature and Humidity Control

 Controlling the environment in the factory is a key measure to prevent defects on printed Circuit Boards (PCBs). Incorrectly managing humidity and temperature can damage expensive electronic components and lead to costly quality problems. Many factors affect the production environment, such as the location of the factory and the equipment used to manufacture the boards. Manufacturers must monitor and adjust temperature and relative humidities in the workshop, even in mild climates around the world.

Relative Humidity

Humidity in a room is determined by the "relative humidty" (Rh), which reflects a ratio between the partial water vapor pressure and the saturated water vapour pressure at the same temperature. Relative humidity is the quantitative measurement of the amount water vapor present in the air.

High Humidity

High humidity can lead to serious problems in manufacturing environments.

Slippage: The welding paste absorbs excessive water, causing it to bridging when reflowing.

welding balls (or "popcorn"): Poor coalescence is caused by excessive water absorption of the welding paste.

Outgassing: When large amounts of water are sprayed on the surface (especially BGAs), they can increase pressure. This can sometimes cause the lid of the device to come off.

Low Humidity

This rapid evaporation can cause the paste to dry up. This can cause poor stencil release or welding joint defects.

High Temperature

The viscosity is reduced by high temperatures. It can lead to a variety of problems, including uneven application and collapses in the welding paste. High temperatures can also cause the welding to oxidize excessively, which can affect welding ability.

Low Temperature

The viscosity may increase if the temperature is too low. The welding paste can become too solidified to print accurately, causing undesirable effects like curling and mold release.

Acceptable Ranges of Conditions

Different experts have different recommendations regarding relative humidity (Rh), and temperature ranges. Some experts recommend a wider range of relative humidity, such as 35-70%, 40-70% or 20-50%. Some experts warn that exceeding the upper and lower RH limit of 60% can cause defects or affect the lifespan of the product. It is more about preference and experience than anything else when it comes to choosing an RH range.

Experts are generally in agreement that the best temperature for welding paste is between 68 and 78 degrees Fahrenheit, which is the range of temperatures where humans feel comfortable. It's important to note that different products of welding paste may perform differently under not the same conditions. It is important to keep in mind some flexibility when designing a product.

Watching

Certain geographic locations, like areas that are extremely humid or dryer, may require advanced environmental control measures. Regardless of where the factory is situated, certain climate control strategies will always be maintained.

Humidity sensors: It is important to invest in high-quality relative humidities (Rh) and to install them correctly for accurate measurement. Even small changes in temperature and humidity can cause major problems. Regular inspections of sensors are also necessary, particularly in high-humidity environments where the Rh sensors tend to fail more easily.

Heating/Air Conditioning Equipment: It is important to invest in a quality heating and air conditioning system. This is a long-term fight. You should be aware of the potential problems caused by temperature fluctuations if you are able to regulate the room's temperature. Dehumidifiers are also important for high-humidity areas.

Nitrogen for reflow: Excessive moisture can cause unwanted oxidation in welding paste. Nitrogen can be used to effectively stop this oxidation.

Moisture-Sensitive Components

Shenzhen Icchip7:Moisture sensitive components are also a key consideration. Moisture-sensitive electronic parts should only be exposed to high humidity environments for a short time, based on the level of sensitivity. If the right humidity can be maintained then this problem should be handled properly.

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