DFM for flex and rigid-flex PCBs utilizing surface mount technology

Abstract:

Developing a flexible circuit for surface mount component assembly entails a unique set of requirements. To quote a leading flexible circuit fabricator “Understanding how these requirements interact will allow the PCB designer to create a flex circuit that balances both electrical and mechanical features into a reliable, cost effective interconnect solution”. There are a broad number of reasons for developing the flexible and rigid-flex circuit;

• Increased wiring density- flexible circuits are capable of providing very narrow
conductors requiring only 25% of the space typically reserved for hard-wire
interconnect.
• SMT component interconnect- Land pattern features can be incorporated within the
flexible circuit pattern to accommodate the mounting and interconnecting both
passive and active surface mount components.
• Mechanical compliance- the thin base material is not only flexible but can be
shaped to fit unique and often complex 3D interconnect applications and enables
the inclusion of rigid materials when greater physical support is warranted.

Topics of discussion:

1. DfM principles for flexible and rigid-flex circuits

• Establishing flex circuit construction types
• Base materials for flexible and rigid flex
• Cover coating and film variations
• Conductor routing and physical feature planning
• Flexible circuit bending and folding guidelines
• EMI shielding and impedance control methodology

2. SMT component selection and land pattern development

• Passive R and C devices
• SOICs
• QFN and QFP
• BGA and CSP

3. DfM for SMT assembly processing

• SMT assembly process overview
• Preparation for SMT assembly
• Land pattern reinforcement
• Conductor to land interface
• SMT component area support