The need for EMI shielding is increasingly important as highly-sensitive components become more tightly packed in circuit assemblies. To accommodate the move toward miniaturization and to reduce weight and thickness, each individual package may require EMI shielding. Sputtering and plating are commonly used to apply component-level EMI shielding layer between 3 and 6 µm thick. These methods add substantial cost to the process, are limited to moderate throughput, and add complexity to the process flow.
New EMI shield coating materials recently available in the market are high-density slurries with proprietary formulations that produce a continuous conductive layer on the substrate after coating. These new materials provide excellent EMI shielding characteristics for package-level shielding. Since these coatings can be applied with a much simpler, more scalable, and cost-effective spray coating process, such as T-CAT, they enable manufacturers a straightforward path to higher board densities, increased design flexibility, and simplified the bill of materials for smaller, lighter device designs.
EMI Shield Coating Process
The EMI shield coating application process is simple and fast with this direct spray method. The components are first placed on the dicing tape using standard placement equipment. The carrier is then loaded onto the coating system conveyor and it is transported into the coating location inside the system. The coating process recipe is then activated and the EMI shield coating is applied to the components on the carrier. Once the coating process is complete the carrier moves on the conveyor to exit the coating system. The carrier is placed into a batch oven at the specified temperature and time period for curing.
Spray Sequence to Apply EMI Shield
In order to ensure that a uniform coating is applied to the top and side surfaces of the components on the carrier a defined coating sequence is required. This four (4) layer coating sequence operates as follows. A 5-position rotate and tilt mechanism is used to position the ultrasonic spray head during the coating process; the spray head has two (2) rotational positions (0 & 90 degrees) and two (2) tilt positions (forward and reverse up to 45 degrees) providing four (4) possible approach angles for the coating process. The tilt and rotate position of the spray head is defined for each layer so that every exposed surface of the components is coated.
Video - Coating Application Sequence
This video shows the four layer application sequence of an undiluted high-solids (>70%) EMI shield material using USI’s tCAT technology.
The EMI shield coating thickness on the top and side surfaces of the components can be measured after the component is cross-sectioned. In most cases, the average side surface thickness is approximately 60% of the top surface thickness. The following images show the measured thickness of various EMI shield materials applied with USI technology:
Henkel EMI Shield Material
Tatsuta EMI Shield Material
Clariant EMI Shield Material
With up to 400% faster than PVD/sputtering, 90% lower CAPEX cost, and a compact footprint, USI’s high-performance spray coating equipment is the perfect solution for your EMI shielding process.
Contact us to discuss your EMI shielding requirements.