What is MSD components? PCB assembly - What problems do MSD elements cause?

MSD mean Moisture Sensitive Device. These components are commonly used in PCB assembly. Therefore, it is required to protect these elements against moisture, and if the moisture appears on a PCB, it requires specialized treatment that will eliminate the risk factors arising during the assembly and soldering of MSD boards. What are the most common problems with the use of MSD components and how can they be eliminated?

The main risk to MSD components is moisture.

Excessive moisture is one of the major risk factors in the assembly and processing of PCBs and MSD components. The specific surface of these plates absorbs the vapour which then reaches the base material. When the vapour absorption coefficient is too high, there is a serious risk of damaging the board within the area of semiconductors and the bonds. Excessive moisture in the soldering process can also damage the composite material. What is worse, it is not always possible to detect the damage, which will only manifest itself as a defect in the final product or after some time of use.

The greatest risk of damage occurs at the time of reflow soldering, when MSD components are applied to the PCB. Then, sudden and very distinct changes in the ambient temperature may lead to the expansion of the casing, and finally to its cracking. The phenomenon of internal delamination is also a very common problem.

Why are MSD components so fragile?

MSD components are hermetically sealed electronic components made of plastics and organic materials. Excessive moisture can pass through the casing and locate on the joints of the materials used to manufacture the component. In the production process, one should pay attention to a number of factors: dimensions, type of materials and their properties, casing design and reflow soldering temperature. Only the proper handling of MSD components will guarantee their expected service life.

How to prevent problems in assembling and soldering MSD components?

The sensitive SMD components have a separate sensitivity classification. There are eight levels of moisture sensitivity. Each level is accompanied by detailed guidelines on how to store, transport, assemble and braze MSD components. All guidelines are described in a standard marked with the code IPC / JEDEC-J-STD-033A. This standard is recognized all over the world and should be followed by companies that manufacture PCBs using MSD components.

Standards for the processing of MSD components effectively reduce the risk of defects caused by excessive moisture. In terms of compliance with these standards, the level of technological advancement on the production line is important. For precise control of components, you need specialized equipment or a supervision system for sensitive components in order to avoid moisture. This is the only way to detect minor defects at the production stage and prevent faulty products from being released to the market.