Flip Chip / WLCSP / CSP

CIL has the only UK based PacTech SB2-Jet triple laser based soldering system and has process capability of direct write solder balling ranging from 60um to 760um with wafer diameters up to 300mm. CIL is working on other 3D Heterogenous projects with solder joints of around 12um, but these smaller features are manufactured using wafer level depostion techniques. 

Flip Chip and WLCSP devices are sometime confused, and they are defined as such.

• Flip Chip - refers to bumps on semiconductor wafers which are in the range of 50 to 200 µm in height and are usually assembled using and underfill material between the die and the substrate
• Wafer Level Chip Scale Packaging / WLCSP - refers to bumps that are in the range of 200 to 500 µm in height and are usually assembled without an underfill material
• CIL has enabled both types to be fully UK manufactured

This PacTech SB2-Jet machine is not only capable of 60um to 760um solder ball sizes, but also in 4 different alloys for multiple markets, these are

• SAC305 / SAC405     Standard RoHS compliant alloy used for most commercial / industrial products
• SACQ                          Advanced RoHS compliant alloy used in High Rel applications
• Tin / Lead                  For use in Military / Defense / Aerospace / Space based products to eliminate Tin whisker growth
• Bismuth                     For use on Medical and Biomedical sensors that have low process temperatures

WLCSP / Flip Chip package technology offer a range of benefits including:

• High pin count
• High signal density
• Better power dissipation
• Low signal inductance, and good power/ground connectivity.
• Ideal for high speed interfaces (including RF) that wire bonds cannot support
• Die size can be shrunk when compared to wire bonding and therefore more die / wafer, hence lower die cost

WLCSP / Flip Chip substrate is in essence a small interposer substrate which can be Silicon, Glass or Organic (PCB) located inside the package.

• Substrate design consists of layout of all signals from the package external balls to the bumped internal pads. It is because of a more direct path on the substrate (as illustrated below) that gives flip chip some of its advantages
• Substrates can be made by different PCB materials: laminate, build-up, ceramic, and more. Substrate layout design rules vary from different suppliers.
• Substrates can consist of many layers ranging from 2-18 layers to allow proper routing of all signals for enhanced device performance

In order for the chip to be connected or mounted to a substrate, the die is turned or flipped over and brought into alignment with the pads located on the substrate. There are six (6) key process steps:  Fluxing, Placement, Reflow, Flux Cleaning, Capillary Underfill, and Cure.

CIL’s Flip Chip & WLCSP services are engaged in wide-range of industry applications, including defence, aerospace, automotive, premium motorsport, commercial, communication, industrial power, 5G and RF and many more. They are suitable for numerous assembly and packaging applications, such as:

• Flip Chip Package on Package (FC PoP)
• 3D Integrated Circuit (IC)
• 5D Interposer
• Flip Chip
• Embedded Integrated Circuit (IC)
• Fan-Out Wafer Level Packaging (FO WLP)
• Wafer Level Chip Scale Packaging (WLCSP)
• Chip Scale Packaging (CSP)
• Ball Grid Array (BGA)
• Ball Grid Array re-balling
• Printed Circuit Board (PCB) balling

            PacTech SB2-Jet 3 laser wafer bumping machine                                                    PacTech SB2-Jet 3 laser wafer bumping machine installed in CIL OSAT facility

To enable the UK / EU semiconductor community to gain access to advanced packaging technology, the CIL SB² – Jet system is the fully upgraded system which includes

• Ball Inspection System (2-D)
• Automatic Z-Height Measurement by both N2 pressure and laser sensor
• ESD Kit
• Heated chuck/work stage
• Specific heated work holder for BGA-like devices
• Solder Ball Rework Station
• Wafer Handling System - 300mm / 12”
• Specific heated work holder for BGA-like devices
• Expand working area > 320x320mm

Feel free to get in touch with our Advanced Technology Team and have a conversation regarding your particular requirements.