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What is important for the BGA fanout of SBU structures

HDI PCB KSG Header BGA SBU structure

Ball Grid Array (BGA) is a popular packaging technology for integrated circuits that enables a high pin count and compact design. Compared to traditional pin connection methods, BGA offers better thermal and electrical performance. A critical aspect of using BGA is the fanout design, which describes the connection of the pins of the BGA chip to the traces of the printed circuit board (PCB).

What is BGA fanout?

The term Fanout refers to the method of routing the electrical connections from the ball terminals of a BGA chip to the traces on the PCB. Since the BGA pins are placed under the chip, the design requires special methods and approaches to make these connections effective and reliable.

Important considerations for the BGA fanout design

Pad design and spacing:
The pads that are connected to the balls of the BGA must be precisely positioned. The distance between the pads must be sufficient to avoid short circuits and ensure a reliable solder connection.

Via types and placement:
Plated-through vias (through-hole vias): These vias penetrate the entire PCB and connect all layers with each other. They are easy to manufacture, but can take up more space.
Blind vias (blind vias): These vias only connect the outer layer to one or more inner layers without penetrating the entire PCB. They save space and are often used in HDI (High-Density Interconnect) PCBs.
Buried vias (buried vias): These vias are located entirely within the inner layers of the PCB and are not visible from the outer layers.

Conductor routing:
The conductor tracks must be routed in such a way that they do not cross each other and have sufficient distance between them to avoid short circuits. Tighter routing techniques, such as microvias and thinner traces, are often necessary for BGAs with high pin density.

Signal and power integrity:
Minimizing signal reflections and crosstalk is critical, especially with high-speed signals. Supply paths must be designed in such a way that they can deliver sufficient current without causing excessive voltage drop or noise.

Thermal management:
The fanout design can also influence thermal management. Good layouts take heat dissipation into account to prevent components from overheating.

HDI-SBU-Multilayer

Steps to create an optimized design

KSG Digital Design Compass live Seminar Thumbnail PCB Layout
The Digital Design Compass - The smart platform for fast and reliable PCB development.
  1. Select design software
  2. Study component data sheet
  3. Design pad and via layout
  4. Routing conductor paths
  5. Apply design rules
  6. Simulation and verification
  7. Prototype production and testing

For point "3. Design pad and via layout", our Digital Design Compass with the articles

3.1.1 HDI/SBU circuit board 
16.2 Design solutions | BGA

Valuable decision-making aids for the minimum necessary layer structure and the minimum necessary viatypes, which ultimately has an impact on cost efficiency - Design to Cost.

Location L1 (Top):

Layer L1 (Top) BGA fanout grid Layout design PCB circuit boards

Position L2:

Layer L2 BGA fanout grid layout design PCB circuit boards

Position L3:

Layer L3 BGA fanout grid layout design PCB circuit boards

Layer structure:

Added value of an optimized BGA fanout

High connection density

Error avoidance
A carefully designed BGA fan-out design reduces the risk of soldering errors and mechanical problems. This reduces the failure rate and increases the reliability of the PCB, which is particularly important in safety-critical applications.

Thermal management
Heat can be dissipated more efficiently through the targeted placement and design of vias and conductor paths. This extends the service life of the components and increases the reliability of the entire system.

Cost efficiency

Reduced rework and downtime
Avoiding design errors reduces the cost of rework and warranty claims. This leads to lower overall costs and higher customer satisfaction due to less downtime.

Efficient use of the PCB area
A good fanout design allows for a more optimal use of PCB space, which can reduce manufacturing costs as less material is required.

Location Top BGA Unbundling Location Top of the KSG Group
Top layer for BGA unbundling

Improved production quality

Automated inspection and testability
A precise fan-out design simplifies automatic optical inspection (AOI) and other test procedures. This improves quality assurance in production and ensures that only flawless products are delivered.

Simpler assembly processes
By optimizing the fan-out, the soldering process is simplified, resulting in higher production efficiency and lower production costs.

Greater design flexibility

Multilayer PCBs
Advanced fan-out techniques such as blind and buried vias enable the creation of complex multilayer PCBs. This leads to higher integration density and more compact designs that meet the requirements of modern, space-saving electronic products.

Scalability
A well thought-out BGA fanout design facilitates future adaptations and upgrades of the PCB. This gives customers the flexibility to further develop their products without having to undertake extensive new developments.

Higher performance

Signal and power integrity
An optimized fanout design reduces signal reflections, crosstalk and other interference factors, which improves signal quality. This is crucial for high-speed applications such as communication devices and computer hardware. In addition, a well-designed power supply and ground routing ensures stable voltage levels and minimizes electrical interference, allowing components to operate more efficiently.

Conclusion

BGA fanout design is a complex and critical part of PCB design that requires careful planning and precise execution. By following the above considerations and steps, designers can ensure that their PCBs function reliably and meet the requirements of modern electronic devices. As the miniaturization and complexity of electronic components continues, the importance of a well-designed BGA fanout will continue to grow, and mastering this technique is essential for PCB designers.

It is crucial for the manufacture of high-performance, reliable and cost-efficient electronic products. Customers benefit from lower failure rates, higher power reserve and lower total cost of ownership. In addition, a well-designed fanout allows for greater flexibility and scalability, making it easier to adapt products to ever-evolving market requirements.

Investing in a high-quality BGA fanout design pays off in the long term by significantly improving the overall quality of the end product and thus maximizing added value for the customer.

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