Packaging -fundamentals and testing
This repository documents Divya Gupta's specialized training in advanced semiconductor packaging and assembly techniques. The comprehensive program bridged theoretical concepts with practical applications, covering cutting-edge technologies including 2.5D/3D packaging, multilayer RDL routing, and silicon interposer integration. Hands-on ANSYS simulation labs provided real-world experience in thermal modeling, stress analysis, and structural optimization. This repository serves as both a technical portfolio and a knowledge resource.
Why is Semiconductor Packaging Needed? Modern ICs are born in ultra-clean fabs as fragile bare dies. Before these can enter our phones, laptops, and cars, they must be packaged to:
Protect the die (corrosion, moisture, physical shock)
Enable connectivity with the real world
🔗 The die is the heart of every semiconductor device — it's the tiny square or rectangular piece of silicon that holds the actual integrated circuit (IC). All the transistors, logic gates, memory cells, and functional units are etched into this small chip during the fabrication process.
Semiconductor Workflow:
1.Design (Fabless or IDM)
2.Wafer Process (Foundries)
3.Package & Test (OSAT or in-house IDM)
.Wafer Test
.Package
.Package Test
4.Assembly
The image illustrates the integration hierarchy from the die (chip) to the final PCB (board): 
Chip: The silicon die containing the core logic.
Package: Encapsulates the die and provides external I/O access.
Board (PCB): Hosts the packaged components and connects them to other system parts.
Packaging Example: BGA (Ball Grid Array) 
Below hierarchical structure of electronic integration—from chip to package to board—highlighting the critical role of packaging in connecting and protecting semiconductor devices. The right side presents key factors in choosing the right package, including:
Application type (logic, memory, power) Form factor Reliability and durability Cost Thermal dissipation Pin count (I/O pins)
This diagram illustrates the typical structure of an electronic package, which serves as a bridge between the silicon die and the system board (PCB). Key components include:
. Mold compound: Protects the internal components from environmental damage.
. Die: The actual semiconductor chip performing the electronic functions.
. Die-to-carrier interconnections: Enable electrical connectivity between the die and the carrier.
. Carrier: Provides mechanical support and routing for signals.
. Carrier-to-board interconnections: Link the package to the system board.
. System Board (PCB): The final platform where the package is mounted and integrated into the device.
Electronic component packaging is essential for protecting semiconductor devices and enabling their integration into systems. Packaging types are broadly classified into Through-Hole Mounting and Surface Mount Technology (SMT). Each type offers unique benefits in terms of size, performance, and application.
- Through-Hole Mounting
. DIP (Dual In-line Package): Rectangular package with two rows of pins for insertion into a PCB.
. TO (Transistor Outline): Cylindrical or flat package for transistors with leads extending from the bottom.
. PGA (Pin Grid Array): Package with a grid of pins underneath for socket or solder mounting.
- Surface Mount Technology (SMT)
. QFN (Quad Flat No-lead): Leadless package with solder pads underneath for compact mounting.
. QFP (Quad Flat Package): Flat square package with leads on all four sides.
. CSP (Chip Scale Package): Ultra-compact package nearly the same size as the chip itself.
. PBGA (Plastic Ball Grid Array): BGA package using plastic substrate with solder balls underneath.
. LGA (Land Grid Array): Package with flat contact pads instead of pins for board connection.
. PoP (Package on Package): Stacked ICs in a single package to save space and enhance performance.
. MCM (Multi-Chip Module): Multiple chips integrated into one module for higher functionality.
. CoWoS (Chip-on-Wafer-on-Substrate): Advanced 2.5D packaging integrating chips on a silicon interposer.
Semiconductor packaging is categorized into Leadframe, Laminate, and Advanced package substrates, each offering different levels of complexity, performance, and integration. These packages protect the chip, provide electrical connections, and support thermal and mechanical stability.
- Leadframe Packages
. DIP (Dual In-line Package): A rectangular package with two rows of pins for through-hole mounting.
. QFN (Quad Flat No-lead): A compact surface-mount package with no leads, using pads underneath.
. Leadframe-CSP: A chip-scale package built on a leadframe for minimal size and cost.
. Leadframe-QFP: A flat package with leads on all four sides, using a leadframe base.
- Laminate Packages
. Wire bond PBGA: A plastic BGA package using wire bonding to connect the die to the substrate.
. Flip chip PBGA: A BGA package using flip-chip bonding for better electrical performance.
. PBGA (Plastic Ball Grid Array): A cost-effective BGA package with plastic encapsulation.
. LGA (Land Grid Array): A package with flat contact pads instead of pins for board-level connection.
. FC-CSP (Flip Chip Chip Scale Package): A compact package using flip-chip technology for high I/O density.
- Advanced Package Substrates
. 2D FCBGA Substrate: A flat flip-chip BGA substrate for high-performance applications.
. 2.1D FCBGA with RDL: Adds a redistribution layer to enhance signal routing and connectivity.
. 2.3D FCBGA with Si Interposer: Uses a silicon interposer to connect multiple dies efficiently.
. 2.5D CoWoS: Integrates SoC and HBM on a silicon interposer for high bandwidth and performance.
This graphic provides a structured overview of modern semiconductor packaging technologies and how different types of chips (single, multi-chip, SoCs, chiplets, etc.) are integrated with package substrates and ultimately connected to a Printed Circuit Board (PCB).
Once the package is assembled, it is placed onto the PCB. The PCB provides:
. System-level integration
. Power and data communication
. Final product form factor
This section aids in evaluating package types based on key factors such as, Performance, Cost, Space limitations, Thermal performance and Reliability. Selecting the most suitable package requires balancing these factors according to the specific needs of the application, system design, and business objectives.
This outlines the key stages in the semiconductor supply chain, detailing the flow from initial design to the final product
. Design House: The process begins with designing integrated circuits (ICs) using EDA tools and foundry PDKs. The output is an IC design file (GDSII) and a test program.
. Wafer Fabrication: Silicon wafers are manufactured using specialized equipment, gases, chemicals, and materials. The result is a wafer with fabricated ICs.
. Package Assembly and Test: Individual ICs are separated from the wafer, assembled into packages with substrates and other materials, and tested for quality.
. Board Assembly and Test: Multiple packaged ICs are mounted onto printed circuit boards (PCBs), assembled using various tools and materials, and then tested.
. Product Assembly and Test: The final stage involves assembling the tested boards and other components into the end product, such as a smartphone, which undergoes final testing before reaching the market.
Each stage is crucial for ensuring the performance and reliability of the final electronic product.
Wafer Preparation Steps are done in controlled cleanroom environment where the wafer processing begins. ISO Class 7 ensures minimal particle contamination, whcih invilve this steps
1.Wafer Preparation Area – Cleanroom (ISO Class 7) for contamination-free processing.
2.Incoming Wafer Carrier – Wafers arrive in protective carriers.
3.Wafer Inspection – Visual/optical check for defects.
4.Front Tape Lamination – Protective tape applied to wafer front.
5.Backside Grinding – Wafer thinned using grinding tools.
6.Tape Frame Mounting – Wafer mounted on tape frame for stability.
7.Two-Step Dicing – Laser grooving followed by blade cutting to separate chips.
This process is part of the back-end semiconductor manufacturing flow, where individual dies are packaged and made ready for integration on PCBs.
KEY STEPS:
1.Die Attach
. Epoxy is dispensed.
. The chip is picked and placed onto a substrate using Die Attach Film (DAF).
2.Curing
. The epoxy is hardened by controlled heating to ensure strong bonding between die and substrate.
3.Wire Bonding
. Fine gold or aluminum wires connect the die to the package pins using ultrasonic welding and thermal compression.
4.Molding (Transfer Molding)
. The assembly is encapsulated using a mold compound, protecting the die and wires with resin flow.
5.Marking
. The package is laser-marked for identification and traceability.
6.Singulation
. The wafer is diced into individual packaged units using a precision blade.
click on thumbnail to watch video.
Flip Chip Packaging is a modern method of mounting a semiconductor die face-down onto the package substrate using solder bumps. It is different from traditional wire bonding and offers better electrical, thermal, and mechanical performance.
Solder bumps (also called micro-bumps) replace wires in this approach.
They:
1.Provide direct electrical connections between the chip and substrate.
2.Allow shorter signal paths → higher speed and lower inductance.
3.Enable higher I/O density.
4.Offer better thermal dissipation.
how it looks
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Bump Formation on Silicon Die • Solder bumps are deposited on the die's bond pads. • After reflow, bumps solidify and prepare the chip for mounting.
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Flip the Chip • The die is flipped upside-down to face the substrate for bump contact.
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Flux Dispensing • Flux is applied on the substrate to aid in soldering and oxidation removal.
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Chip Placement • The chip is placed carefully over the substrate, aligning the bumps with pads.
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Solder Reflow • Heat is applied to melt the solder bumps and form solid electrical connections.
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Flux Cleaning • Residual flux is removed using solvents to avoid contamination.
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Underfill Dispensing • Epoxy is filled between the die and substrate to: – Improve mechanical strength – Distribute thermal stress – Prevent solder crack failures
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Underfill Curing • The epoxy is hardened by heating, locking the chip in place Uploading Ansys Electronics Desktop Student 2024 R2 - Project2 - IcepakDesign4 - 3D Modeler - [Project2 - IcepakDesign4 - Modeler] 2025-06-24 23-41-25.mp4…
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Molding • Resin is applied for external protection from environmental damage.
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Marking • Laser is used to inscribe IDs or codes for tracking and quality assurance.
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Ball Mounting & Final Reflow • BGA balls are mounted under the package and soldered for PCB connection.
Wafer-Level Packaging (WLP) is an advanced packaging technology where chips are packaged while still part of the wafer. It enables compact, high-performance, low-cost chip integration — especially for mobile and IoT devices.
RDL (Redistribution Layer) is a critical metallization layer added during WLP:
. Reroutes I/O pads to new positions to allow larger solder ball pitch.
. Enables fan-out designs (area beyond original die).
. Allows more I/Os in smaller form factor.
. Improves electrical performance and design flexibility.
Steps:
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Reconstitution : Allows known good dies to be used in a new wafer panel
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RDL (Redistribution Layer) : Enables fine-pitch routing and bump placement
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Dielectric + Metal Coating: Forms the electrical routing infrastructure
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Solder Ball Attach: Provides final I/O connections to PCB
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Singulation: Final step to separate packages from reconstituted wafer
have a look on the video click the thumbnail
Introduction With ANSYS Electronics Desktop
ANSYS Electronics Desktop (AEDT) is an integrated multi-physics simulation platform that combines tools for electromagnetic, signal integrity, thermal, and electro-mechanical analysis. It is extensively used for the design and evaluation of high-speed electronic circuits and systems.
STEP 1 SET THIS FIRST GO IN TOOLS> OPTIONS> GENEERAL SETTING THEN SET THIS
STEP 2 FIRST SELECT ICEPACK THEN SET THIS FLIPCHIP BGA
STEP 3 IN THESE SETTING PRESS OK
after ok Package generated by Icepak
DIE STRUCTURTE
SUBSTRATE
DIE UNDERFILL
DIE
STEP 4 SET THE SOURCE IN SUBSTRATE
STEP 5 ASSIGN THE MONITORS IN SUBSTRATE AS WELL AS SAME STEPS IN THE DIE PART AND UNDERFILL DIED PART AS WELL
SO TO THE POINT AND SELECT THE TEMPRATURE ALSO IN TEH DIE PART AND UNDERDILL DIE PART ALSO
NOW YOU SEE ALL THE THREE LAYERS IN THE MONITOR PART
STEP 6 GO TO Mesh > then in Simulations part > click on generate mesh
After the mesh is generated, review its quality metrics, including Face Alignment, Skewness, and Volume.
STEP 7 no go analysis choose this it shows ipack solve setup just click ok
then go to validate and assign all click
step 8 in underfill gp to this option then >select flipchip bga> then ok> also enble mesh fusion tick it > then agaain ok
STEP 9 Results
. validate the simulation setup
. Click the Validate button in the top ribbon and confirm that all checks pass successfully.
STEP 10 select the whole schematic then follow the image steps to set temprature
. Click on Analyze All button in the top ribbon
. After the simulation is complete, use the left mouse button to draw a selection rectangle in the 3D view and select the entire FC-BGA package.
. Right click and then select Plot Fields -> Temperature -> Temperature
then follow these and tick these things also select surface smoothing also tick the part enable gaussian smoothing from there
step 11 final setup
This module emphasizes the quality assurance and testing phases of semiconductor packaging, which are crucial for detecting functional defects and ensuring long-term reliability.
This diagram shows the complete packaging and testing pipeline starting from wafer fabrication (Foundry) to system-level testing (OSAT). It highlights key steps, process development, and failure analysis loops.
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Foundry Stage . Front-End Manufacturing
. Fabrication of the wafer using lithography, etching, deposition, etc.
. Known as "FEOL" (Front-End Of Line).
. Wafer Probe Test
. Electrical testing of each die before dicing.
. Good/bad dies identified for packaging.
. Wafer Sorting
. Dies are sorted based on test results.
. Only “known good dies” proceed to packaging.
- OSAT (Outsourced Semiconductor Assembly & Test) Stage
. Package Manufacturing
. Dies are attached to substrates and wire-bonded or flip-chip mounted.
. Includes die attach, bonding, molding, and singulation.
. Package Testing
. Post-packaging electrical tests to detect failures.
. Ensures packaged chip meets performance specs.
. System-Level Tests (SLT)
. Full end-product testing in a simulated real-world environment.
. Catches issues not seen at earlier test stages.
These are the last stages of testing before a chip is qualified and shipped. They ensure electrical integrity, early reliability, and long-term performance under various conditions.
1 AOST – Assembly Open and Short Test
. Detects open circuits (unconnected paths) and shorts (unintended connections).
. Ensures proper electrical assembly of the chip after packaging.
2 Burn-in
. Applies thermal and voltage stress to the chip.
. Detects early-life failures (infant mortality defects).
. Helps improve long-term reliability.
3 Final Test
. Conducted at both cold and hot temperatures.
Verifies:
. Functionality (chip performs correctly)
. Parametric performance (voltage, current, timing, etc.)
. Reliability specs across temperature range
🔹 AOST (Assembly Open and Short Test) – Key Highlights . Performed after singulation or Trim & Form.
. Detects opens, shorts, and missing/damaged balls/leads.
. Uses electrical testing + vision inspection.
. Common defects:
. HoP (Head on Pillow)
. Bridging (shorts)
. Non-Wet Opens (NWO)
. Die cracks
. PGSRT sorts units: Best (1) → Scrap (4).
. Ensures basic electrical integrity before advanced testing.
🔹 Burn-in Test
. Detects early-life (“infant mortality”) failures before customer shipment.
. Devices are placed on Burn-in boards, then tested in high-temperature ovens.
. Applies high voltage + high temperature to accelerate failure.
. Catches initial defects: dielectric breakdown, metal faults, electromigration.
. Test duration continues until failure rate curve flattens.
. Ensures only reliable units survive for customer use.
. Slightly shortens overall life, but improves field reliability.
FINAL TEST
summery from it
FLOW CHART FROM MODULE 4
Microcircuit Packaging Flow – Till Sealing Stage
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Wafer exits Fab → fabrication process completed.
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Probe Testing → checks for functional dies on wafer.
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Die Inking → marks bad dies for rejection.
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Wafer Thinning & Cleaning → reduces wafer thickness for packaging.
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Wafer Bake → removes moisture; improves die attach reliability.
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Wafer Dice → separates individual dies from wafer.
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Pick & Place → selects good dies and places them in packages.
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Die Attach / Eutectic Reflow → attaches die to package base.
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Wire Bonding → connects die pads to lead frame using wires (Au/Al).
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Sealing / Lid Placement → ceramic lid is sealed (air-tight or hermetic).
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Solder Dip → pre-coats leads with solder for board attachment.
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Part Marking → product info is printed on package.
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Lead Trimming & Forming → trims and bends leads to required shape.
step 1 LAUNCH QFN
STEP 2 CREATE A DIE Material: Silicon Dimensions: 3mm x 3mm Die Height: 0.2 mm
click on create rectangle
then select the rectangle > go to modeler >surface >thicken sheet then change the dimention to 0.2
click redctangle go to>edit properties and change these
Fig: AEDT 3D viewer with die created
STEP 3 CREATE THE SUBSTRATE
. Draw a rectangle with the same dimensions as the die (3 mm × 3 mm) and position it at the same coordinates (0, 0, 0).
. Set its thickness to -100 microns (-0.1 mm), since the DAM layer is located beneath both the die and the substrate.
Now change properties of substrate also
. location of substrate should be (-1,-1,-0.1) 0.1 as to make space between die ans substrate.
STEP 4 CREATE A DIE ATTACH . make a rectangle over the die >change its properties to (0,0,0) and x and y axis both to =3 . then same go for thicken sheet in modeler bar options make it (-0.1) . modify the name in edit properties and change the setting to
this is how a substrate die and die attach looks like
SUBSTRATE
DIE ATTACH
DIE
STEP 5 WIRE BONDING create a small rectangle on a die edit its properties to
change the thickness click the rectangle then go go to modeler
to this
NOW SIMILARLY CREATE A WIRE BOND ON SUBSTRATE
Change the properties to
now change the name of both to other no changes
change the colors
STEP 6 CONNECT THE BOND WIRE
IN the draw section select an arrow to draw wire bond
NOTE every die rectangle dimention would be
every substrate rectangle dimention would be
this is how a bond wire looks like
alll wires are attached
STEP 7 : Applying the Mold Compound and Finalizing the Package Model
. Create a rectangular enclosure with dimensions 5 mm × 5 mm and a thickness of 1.2 mm to encapsulate the die and bond wires.
. Position it at coordinates (-1, -1, -0.1) so that it sits above the substrate, fully covering the top side.
. The 1.2 mm thickness ensures complete coverage of the die and bond wires while providing sufficient clearance for laser marking or other post-packaging processes.
CHANGE THE PROPERTIES
. Ansys Electronics Desktop Student
Kunal Ghosh {Co-founder of VLSI System Design (VSD) Corp. Pvt. Ltd.}
Tarun Kumar Agrawal {Dept. of Electrical Engineering IIT Gandhinagar}