Demand for flip chip packaging & flip chip interconnect technology is being driven by a number of factors from all corners of the silicon industry. To support this demand, Amkor is committed to being the leading provider of Flip Chip in Package (FCiP) technology. By partnering with proven industry leaders, Amkor has brought high volume  flip chip packaging and assembly to the subcontract market. Since being the first OSAT to provide FCiP solutions in 1999, Amkor has continued to introduce innovative packaging solutions utilizing Flip Chip interconnect, and offers the broadest range of FCiP solutions on the market. Super Flip Chip (SuperFC®), Flip Chip BGA (FCBGA), fcLBGA, fcLGA, FlipStack CSP, and Flip Chip CSP (fcCSP) are qualified and are in production. Flip Chip production capability exists in our Philippines, Korea, Taiwan, and China factories. Wafer Bumping, Wafer Level Packaging (WLP), and Flip Chip packaging solutions are qualified in lead-free options.

 

Flip Chip Technology Overview

 
Flip Chip (FC) is not a specific package (like SOIC), or even a package type (like BGA). Flip Chip describes the method of electrically connecting the die to the package carrier. The package carrier, either substrate or leadframe, then provides the connection from the die to the exterior of the package. In "standard" packaging, the interconnection between the die and the carrier is made using wire. The die is attached to the carrier face up, then a wire is bonded first to the die, then looped and bonded to the carrier. Wires are typically 1-5 mm in length, and 15-35 μm in diameter. In contrast, the interconnection between the die and carrier in flip chip packaging is made through a conductive "bump" that is placed directly on the die surface. The bumped die is then "flipped over" and placed face down, with the bumps connecting to the carrier directly. A bump is typically 60-100 μm high, and 80-125 μm in diameter. The flip chip connection is generally formed one of two ways: using solder or using conductive adhesive. By far, the most common packaging interconnect is solder.

Current solder options are: Eutectic Sn/Pb or lead-free (98.2% Sn, 1.8% Ag) compositions. The solder bumped die is attached to a substrate by a solder reflow process, very similar to the process used to attach BGA balls to the package exterior. After the die is soldered, underfill is added between the die and the substrate.

Underfill is a specially engineered epoxy that fills the area between the die and the carrier, surrounding the solder bumps. It is designed to control the stress in the solder joints caused by the difference in thermal expansion between the silicon die and the carrier. Once cured, the underfill absorbs the stress, reducing the strain on the solder bumps, greatly increasing the life of the finished package. The chip attach and underfill steps are the basics of flip chip interconnect. Beyond this, the remainder of package construction surrounding the die can take many forms and can generally utilize existing manufacturing processes and package formats.

More recent package solution introductions have begun to utilize an alternative flip-chip interconnect technique called TCNCP (Thermal Compression Non-Conductive Paste). Rather than a two step solder-then-underfill process, TCNCP accomplishes both in a single step. Solder tipped, non-melting Cu Pillar bumps are pushed through a liquid epoxy underfill, then heat is applied to both form a metallurgical bond and cure the epoxy. The use of TCNCP + Cu Pillar allows for finer bump pitch geometries by maintaining standoff and reducing shorting issues.

 
Flip Chip Cross Sections
 
 

Benefits of Flip Chip Technology

 
Using flip chip interconnect offers a number of possible advantages to the user:

  • Reduced signal inductance - Because the interconnect is MUCH shorter in length (0.1 mm vs 1-5 mm), the inductance of the signal path is greatly reduced. This is a key factor in high speed communication and switching devices
  • Reduced power / ground inductance - By using flip chip interconnect, power can be brought directly into the core of the die, rather than having to be routed to the edges. This greatly decreases the noise of the core power, improving performance of the silicon
  • Higher signal density - The entire surface of the die can be used for interconnect, rather than just the edges. This is similar to the comparison between QFP and BGA packages. Because flip chip can connect over the surface of the die, it can support vastly larger numbers of interconnects on the same die size
  • Die shrink - For pad limited die (die where size is determined by the edge space required for bond pads), the size of the die can be reduced, saving silicon cost
  • Reduced package footprint - In some cases, the total package size can be reduced using flip chip. This can be achieved by either reducing the die to package edge requirements, since no extra space is required for wires, or in utilizing higher density substrate technology, which allows for reduced package pitch

 

Wafer Bumping Technology

In support of Flip Chip assembly, Amkor has established wafer bumping production lines within their Korea, Taiwan and China manufacturing facilities. Amkor’s bumping is based on its proprietary electroplating solder technology which is considered the most advanced, robust, reliable and high yielding process available in the marketplace. Eutectic Sn/Pb, Pb Free (98.2% Sn/1.8% Ag) and Cu Pillar bumping are all available in volume production on 200 mm and 300 mm wafers.

Features:

  • Wafer sizes from 150 mm to 300 mm diameter
  • Full area array pitch available to 130 μm -- perimeter pad pitch to < 100 μm
  • Eutectic Sn/Pb and Pb Free (98.2Sn / 1.8Ag) compositions available
  • Low alpha (< 0.02 cph) and ultralow alpha (<0.002 cph) solders available
  • Polyimide repassivation available
  • Redistribution layer using plated Cu (Copper) available

 

Packaging Options Using Flip Chip

Depending on the specific die and application requirements, different package level solutions are required. Thus flip chip interconnect can be used in a wide range of package solutions, each focused on specific benefits that serve a given market. Amkor offers the widest possible range of flip chip packaging solutions to meet the diverse needs of customers and end users. Combining their extensive manufacturing knowledge with all types of packaging interposers and further leveraging their leadership role in flip chip interconnect technology, Amkor continues to pursue new package solutions. This kind of focus is essential to insure that as new market needs emerge requiring flip chip interconnect, Amkor is ready with the optimum package to meet those needs.

Flip Chip BGA Package:

Amkor fcBGA packages are assembled around state-of-the-art, single unit laminate or ceramic substrates. Utilizing multiple high density routing layers, laser drilled blind, buried, and stacked vias, and ultra fine line/space metallization, fcBGA substrates have the highest routing density available. By combining flip chip interconnect with ultra advanced substrate technology, fcBGA packages can be electrically tuned for maximum electrical performance. Once the electrical function is defined, the design flexibility enabled by flip chip also allows for significant options in final package design. Amkor offers fcBGA packaging in a variety of product formats to fit a wide range of end application requirements.

The variety of fcBGA package options allows package selection to be tailored to the specific thermal needs of the end product. High performance ASIC products typically utilize a lidded format that features a controlled bondline die attach direct to a copper heat spreader. This feature produces the lowest possible thermal resistance (Theta JC) between the package and any externally applied thermal solution. The copper heat spreader effectively spreads heat laterally away from the die to the package perimeter and into the motherboard.

Lower wattage products generally utilize bare die or molded configurations. In these cases, the flip chip construction, with solder bumps and core vias, provides a lower resistance path from the active side of the die through the substrate, allowing heat dissipation both from the package surface and into the motherboard.

This IC packaging technology is applicable for high pin count and / or high performance ASICs. Large body fcBGAs provide package solutions for the demands of internet, workstation processors and high bandwidth system communication devices. By incorporating flip chip interconnect technology, packages supporting thousands of connections are enabled in conventional surface mount package sizes. fcBGAs are also the package of choice for gaming system processors and graphics, as well as high-end applications processors for leading-edge portable devices.

fcBGAfcBGA Technology Options:

  • Substrates
    • 4-16 layer laminate build up substrates
    • High CTE ceramic
    • LTCC Alumina ceramic
    • Coreless (in development)
  • Bump Types
    • Eutectic Sn/Pb
    • Pb Free
    • Cu Pillar (array and fine pitch peripheral)
  • Package Formats
  • Bare Die
  • Overmolded (FCMBGA)
  • Lidded
  • 150 μm minimum array bump pitch (130 μm in development)
  • <100 μm minimum peripheral bump pitch
  • Die sizes up to 26 mm
  • Package sizes from 10 mm to 55 mm
  • 0.65 mm, 0.8 mm, and 1.0 mm pitch BGA footprints

 
fcBGA Additional Package Options:

  • Wafer Node: ≥ 28 nm qualified (20nm in development)
  • SMT components on top or bottom side
  • Multi-Die capability
  • Memory components on top side
  • Variety of lid material options
  • Grounded lid
  • Custom BGA footprints
fcCSP FC


fcCSP Package:

Flip chip solution for CSP package technology.

fcCSP Features:

  • Designed for high frequency applications
  • Target market – cell phones, hand-held electronics
  • Thin core laminate or ceramic package construction
  • Overmolded for handling and second level reliability
  • Accommodates package sizes from 3 mm to 15 mm
  • Flip chip bump pitches of 150 μm min. for peripheral array, 250 μm min. for area array
  • Available in 0.5-1.0 mm BGA ball pitch, as well as LGA interconnect
  • Minimum package thickness of 0.80 mm for LGA interconnect, 1.0 mm for 0.5 mm BGA pitch and 1.2 mm for 0.8 mm BGA pitch


Flip Chip SiP (fcSiP) Package:

Flip Chip SiP package is an extension of the SiP product offering from Amkor with the device interconnect technology being flip chip rather than traditional wirebond interconnects. The package may contain multiple passive components, Silicon and/or GaAs devices bumped with traditional solder bumps or solder coated 'Copper-Pillar' bumps housed in 2-Layer or 4-Layer high density substrates. This package format is gaining traction in RF power amplifier and RF front end module applications for size, performance and cost reasons.

Controlled collapse of the bumps leads to predictable interconnect impedance and hence more stable product performance. The low solder volume in the 'wetting tip' allows for the elimination of the solder mask from underneath the die which reduces the substrate complexity and cost and removes a major barrier for adopting the fine pitch FC interconnection technology in the RF application space. Flip chip interconnection may also preclude the need for wafer backgrinding (for mold cap thickness ≥ 0.9 mm) which leads to further reduction in product cost and simplification of the process flow.

The devices in this application space have low to medium I/O count and are fairly small in size. This, in conjunction with the solder mask being removed from underneath the die (which increases the standoff), makes these products viable candidates for transfer molding applications. Thus, the underfill operation can be eliminated from the process flow which leads to significant cost savings. Studies have shown that transfer molded packages are more reliable (MSL as well as extended reliability testing such as temperature cycling, HAST, etc.) than their underfilled counterparts due to balanced die stresses and better solder CTE matching.

Wafer Level Packaging (WLP) - CSPnl:


CSPnl is a true wafer level package to address improved second level board reliability, that incorporates a thin film redistribution process to route the pads to JEDEC standard pitches. Standard "CSP" solder bumps are formed on the re-routed pads. The CSPnl is designed to utilize standard surface mount assembly and reflow techniques. By using standard SMT placement equipment, and avoiding the need for underfill, the end user experiences many of the cost benefits associated with other JEDEC standard area array packages.

Features:

  • Incorporates standard JEDEC pitches and CSP solder ball diameters
  • Compatible with standard SMT assembly and test techniques
  • Utilizes cost-effective thin film redistribution technologies
  • Backside laser mark compatible
  • No need for underfill in most applications
  • Full turnkey CSPnl™processing including test and tape & reel support
  • Eutectic lead-free solder balls
  • Available with polyimide repassivation
  • Qualified and in volume production
  • Proven reliability; exceeds all current handset mechanical reliability tests including: drop, bend and key punch

 

 

fcBGA

fcBGA / fcLGA (Bare Die)

Flip chip packaging solution for most graphics, PC chipset and low end ASIC applications.

 

fcCeramic

fcCeramic CBGA / CLGA / CLLGA / Solder Column Interposer

Original packaging solution for flip chip products.

 

Wafer Bumping Technology:

In support of Flip Chip assembly, Amkor has established wafer bumping production lines within their Korea, Taiwan and China manufacturing facilities. Amkor’s bumping is based on its proprietary electroplating solder technology which is considered the most advanced, robust, reliable and high yielding process available in the marketplace. Eutectic Sn/Pb, Pb Free (98.2% Sn/1.8% Ag) and Cu Pillar bumping are all available in volume production on 200 mm and 300 mm wafers.

Features:

  • Wafer sizes from 150 mm to 300 mm diameter
  • Full area array pitch available to 130 μm -- perimeter pad pitch to < 100 μm
  • Eutectic Sn/Pb and Pb Free (98.2Sn / 1.8Ag) compositions available
  • Low alpha (< 0.02 cph) and ultralow alpha (<0.002 cph) solders available
  • Polyimide repassivation available
  • Redistribution layer using plated Cu (Copper) available

 

For more information on the Flip Chip (FC) Packaging Technology Solutions, please contact an Amkor Regional Sales Office near you or fill out the Request Form.

Packaging



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