Using Bare Die Directly¶
In some applications, you may want to use your wafer.space chips as bare die without traditional packaging. This approach offers the smallest possible form factor and can eliminate packaging-related parasitics, but requires careful handling and specialized assembly techniques.
When to Use Bare Die¶
Consider using bare die directly when:
Space-Critical Applications¶
Miniaturized devices where every micrometer counts
Multi-chip modules (MCMs) requiring tight integration
3D stacked assemblies where height is constrained
Embedded systems with strict size requirements
Performance-Critical Applications¶
High-frequency circuits where packaging parasitics matter
Precision analog circuits sensitive to package-induced noise
High-speed digital circuits where signal integrity is paramount
RF applications where package resonances cause issues
Research and Development¶
Circuit characterization requiring direct probe access
Failure analysis needing visual inspection of the die
Educational purposes for understanding semiconductor physics
Rapid prototyping where packaging time is prohibitive
Testing and Validation¶
Parametric testing of individual die
Burn-in testing at the wafer or die level
Qualification testing for reliability assessment
Production testing before packaging decisions
Challenges with Bare Die¶
Working with bare die presents several challenges:
Physical Handling¶
Fragility - Silicon is brittle and easily damaged
Size - Typical die are 1-5mm on a side, requiring precise handling
Static sensitivity - ESD can damage circuits instantly
Contamination - Particles and chemicals can affect performance
Electrical Connection¶
Wire bonding - Requires specialized equipment and skills
Flip-chip bonding - Needs solder bumps and precise alignment
Probing - Temporary connections for testing only
Conductive adhesives - Limited current capability and reliability
Environmental Protection¶
Moisture sensitivity - Bare silicon can be affected by humidity
Temperature cycling - Thermal stress without package protection
Chemical exposure - No barrier against contaminants
Mechanical shock - No protection from physical impacts
Bare Die Applications¶
Handling Best Practices¶
ESD Protection¶
Use ESD-safe workstations and equipment
Wear ESD wrist straps and use conductive mats
Store die in ESD-safe containers
Maintain proper humidity levels (30-70% RH)
Physical Handling¶
Use vacuum pens or tweezers designed for semiconductor handling
Work under magnification to avoid damage
Keep work areas clean and particle-free
Use anti-static packaging for storage and transport
Assembly Considerations¶
Plan for die attachment methods early in design
Consider thermal management without a package heat spreader
Design test points for electrical verification
Include alignment features for accurate placement
Tools and Equipment¶
Essential Tools¶
Die handling equipment - Vacuum pens, precision tweezers
Microscopes - For visual inspection and alignment
ESD protection - Wrist straps, mats, ionizers
Probe stations - For electrical testing (see die probing)
Advanced Equipment¶
Wire bonders - For permanent electrical connections
Flip-chip bonders - For solder bump attachment
Die attach systems - For automated placement
Environmental chambers - For testing under controlled conditions
Design Considerations¶
When designing for bare die use:
Pad Design¶
Ensure pads are accessible for your connection method
Consider pad size requirements for probe tips or bond wires
Include test pads for verification
Design for your chosen assembly process
Die Strength¶
Include corner reinforcement if possible
Avoid thin, fragile areas near the die edges
Consider the sawing street design
Plan for handling stress points
Testing Strategy¶
Design for wafer-level testing when possible
Include built-in self-test (BIST) features
Plan probe pad accessibility
Consider known good die (KGD) requirements
Cost Considerations¶
Using bare die can be cost-effective when:
Volume is low - Packaging costs are avoided
Speed is critical - No time for packaging and test
Size is paramount - Package size would be prohibitive
Testing requirements - Extensive characterization needed
However, consider these additional costs:
Specialized handling equipment
Higher assembly labor costs
Increased yield loss from handling damage
Custom assembly processes
Next Steps¶
If bare die usage makes sense for your application:
Review the die probing guide for testing approaches
Plan your assembly strategy early in the design phase
Consider partnering with assembly houses experienced in bare die
Prototype early to validate your approach
Document your process for repeatability
Using bare die requires careful planning and specialized techniques, but can enable applications impossible with packaged parts. Start with simple test assemblies to gain experience before committing to production volumes.