TN0991 STMICROELECTRONICS | Alldatasheet
Document overview
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- PDF pages: 21
Technical content
Datasheet sections
- 1 Package description
- 1.1 Overview
- 1.2 Mechanical description
- 1.3 Device marking
- 2 Packing specifications and la belling description
- 2.1 Carrier tape
- 2.2 Cover tape
- 2.3 Reels
- 2.4 Final packing
- 2.5 Labelling
- 2.6 Storage and shipping recommendations
- 3 Soldering assembly recommendations
- 3.1 PCB design recommendations
- 3.2 PCB assembly guidelines
- 3.2.1 Protection against light exposure
- 4 Manual rework
- 4.1 Rework procedure
- 4.2 Component rework equipment
- 5 Package changes
- 6 Package quality
- 6.1 Electrical inspection
- 6.2 Visual inspection
- 7 Conclusion
- 8 Revision history
Description of WLCSP for STMicroelectronics EEPROMs and recommendations for use Introduction This document describes the 5 and 8-bump WLCSPs (wafer level chip size package) used for STMicroelectronics EEPROM products, and pr ovides recommendation on how to use them. The competitive market of portable equipment, in particular the mobile phone market, is driven by the challenging development of highly integrated devices. T o allow manufacturers of portable equipment to minimize the dimension of their devices, STMicroelectronics has developed WLCSP with reduced size, thickness and weight. The electrical performance of such components is improved by using shorter connections than in standard plastic packages such as TSSOP, SSOP or QFN. The WLCSP family has been designed to fulfill the same quality levels and same reliability performance as standard semiconductor plastic packages. As a consequence these new WLCSP can be considered as new surface mount devices which are assembled on a printed circuit board (PCB) without any special or additional process steps. In particular these packages do not require any extra underfill to increase reliability performance or to protect the device. These packages are compatible with existing pick-and-place equipment for board mounting. Only Lead-free RoHS compliant WLCSP are available in mass production. This document addresses the following topics:
- Package description
- Device marking
- Packing specifications and labelling
- Storage and shipping recommendations
- Soldering assembly recommendations
- Package changes
- Package quality
1 Package description
1.1 Overview
compatible with the PCB design rules used for standard ICs. flat and allows picking it as for standard SMD packages. and are not protected against aggressive actions. WLCSP Devices are 100 % electrically tested. The device references are marked on the top flat side of the device (see Figure 1). Figure 1. WLCSP bump views
1.2 Mechanical description
Table 1. Die size and ball count are adapted to the connection requirements. Refer to device datasheet for package mechanical data and outline. vertical focuses show a ball-plus-die coplanarity well below 50 μm. Figure 2. 8-bump - 160µm ball WLCSP outline T ypical device marking for the flat backside of the die is shown on Figure 3. has been designed so that it can be detected by standard vision systems. Table 1. 8-bump - 160µm ball WLCSP mechanical dimensions
1.3 Device marking
- Pin 1 identification
- ST logo
- Marking areas composed of: – Commercial product name – T raceability code – Wafer fab code – T esting and finishing production location codes – Country where the product was assembled
Figure 3. WLCSP device marking
2 Packing specifications and labelling description
and IEC 60286-3 standards and EIA 763 (783).
2.1 Carrier tape
be used for larger die size to be in line with EIA standards. Figure 4. T ypical tape dimensions for WLCSP packages in 8 mm carrier tape
- A1 bump location varies with the device layout.
- The dimensions shown in the above figure are for illus trative purpose. Actual carrier tape dimensions may
Figure 5. T ypical tape dimensions for WLCSP packages in 12 mm carrier tape
- A1 bump location varies with the device layout.
- The dimensions shown in the above figure are for illus trative purpose. Actual carrier tape dimensions may
bumps. Refer to Table 2 for the cavity dimension according to the die size.
or flake residue that rubs off.
2.2 Cover tape
tape tensile strength is higher than 10 N. between 165 and 180 °, and the test is performed at a speed of 120 ± 10 % mm/min.
2.3 Reels
may vary depending on supplier. compliance with the IEC 60286-3, each reel contains a maximum of 0.1 % empty cavities. trailer is located at the end of the reel and consists of empty sealed cavities. Table 2. Tape cavity size
Figure 6. 7 inch reel schematics Table 3. 7 inch reel dimensions
2.4 Final packing
cardboard boxes. A full description of the packing process is shown in Figure 7. Figure 7. Packing process
2.5 Labelling
is able to trace a lot history from the wafer fab to the customer location.
2.6 Storage and shippi ng recommendations
handling, reels are packed in a cardboard box.
- Relative humidity between 15 and 70 %
- Temperature ranging from -55 to +150 °C.
- Components in a non opened sealed bag can be stored for 6 months after shipment.
- Components in tape and reel must be protected from exposure to direct sunlight. Note: Moisture sensitivit y level (MSL as per JEDEC J-STD-020) is not applicable to WLCSP devices since there is no plastic encapsulation.
3 Soldering assembly recommendations
3.1 PCB design recommendations
design guidelines listed in Table 4 and Table 5. effect of the WLCSP on the PCB. the pads must be connected to the lower layers using micro vias.
3.2 PCB assembly guidelines
compatible with the use of near-eutectic SAC solder paste with no-clean flux.
- Dwell time in the soldering zone (with temperature higher than 220 °C) has been kept as short as possible to prevent component and substrate damages.
- Peak temperature must not exceed 260 °C.
- Controlled atmosphere (N 2 or N2H2) is recommended during the whole reflow, especially when the temperature is above 150 °C.
Table 4. PCB design recommendation for 0.5 mm ball pitch packages Table 5. PCB design recommendation for 0.4 mm ball pitch packages
prevent any bump cracks, ultrasonic cleaning methods are not recommended. Figure 8. JEDEC STD-020D soldering reflow profile
3.2.1 Protection agai nst light exposure
exposed to various light sources such as incandescent light or sun light. the lateral edges of the device.
4 Manual rework
WLCSP can tolerate one repair in addition to the two reflows mentioned above. Like other BGA packages, the use of laser systems is the most suitable solution to repair WLCSP. Manual hot gas soldering is acceptable while iron soldering is not recommended. The maximum temperature allowed for Lead-free WLCSP manual rework is 260 °C. The typical soldering profile shown Figure 8 can be used.
4.1 Rework procedure
To perform manual rework on a WLCSP, it is recommended to follow the steps below: 1. Remove the device To remove the device, heat must be applied to melt the solder joints so that the component can be lifted from the board. Large area bottom side preheaters may be used to raise the temperature of the board. This may help to minimize board warpage and the amount of heat that must be applied on the component. Top heating may be applied to the component by using a laser or a convective hot gas nozzle. Nozzle size must be selected to match the component footprint. After top heating has melted the solder, vacuum is applied through the pick-up nozzle, and the component is lifted from the board. The heat should be carefully directed at the component which must be removed to prevent adjacent components solder joints from being reflowed. Shielding, control of the gas flow from the nozzle, and accurate temperature control are the key parameters. 2. Remove the solder Automatic tools are recommended due to space constraints and the need for accurate temperature control, Typical cleaners are controlled non-contact gas heating and vacuuming tools. The objective is to remove the residual solder from the area without damaging the pads, solder masks or adjacent components, and to prepare the area for the insertion of the new component. 3. New device soldering a) Place the new device There are several solutions to place the new device: – Use a mini-stencil and solder paste, then place the device. This is the solution recommended to ensure homogeneity of assembly conditions if solder paste is used, even if small footprints and tight dimensions make this operation difficult. – Use no-clean flux on the area and place the device over the flux on the board. – Dip the WLCSP in no-clean flux, and place it on the board. b) Reflow the solder joint by applying controlled heat to the component. The steps are similar to those required to remove a component. However, accurate temperature control is recommended to ensure good joint soldering. A alternative solution is to put the whole board in a furnace. See Figure 8 for reflow profile recommendations.
4.2 Component rework equipment
compressing the WLCSP top or bottom sides (ball side). Figure 8. shows an example of semi-automatic equipment for component rework. For more information, refer to Comintec web site at http://www.comintec.it. Figure 9. Comintec ONYX32 semi-automatic equipment for component rework
5 Package changes
STMicroelectronics reserves the right to implement minor changes of geometry and manufacturing processes without prior notice. Such changes will not affect electrical characteristics of the die, the pad layout or the maximum die size. However for confirmed orders, no variation will be made without prior customer’s approval.
6 Package quality
6.1 Electrical inspection
All the critical parameters defined in the WLCSP device datasheet are 100 % electrically characterized. The other parameters are guaranteed by technology, design rules or by continuous monitoring systems.
6.2 Visual inspection
A visual control is performed on all manufacturing lots according to JESD22_B101B specification.
7 Conclusion
Lead-free WLCSP have been developed by STMicroelectronics for electronic applications where integration and performance are designer’s main concerns. STMicroelectronics WLCSP key features are:
- Remarkable board space saving: package size equal to die size and total height less than 650 μm
- Enhanced electrical performance: minimized parasitic inductance due to very short electrical paths. WLCSP are delivered in tape and reel and are fully compatible with other high volume SMD components (standard plastic packages or CSP/BGA packages) in regards to existing pick- and-place equipment, standard solder reflow assembly equipment and standard PCB techniques.
8 Revision history
Table 6. Document revision history 03-Apr-2013 1 Initial release. packages in 12 mm carrier tape.. Updated Table 3: 7 inch reel dimensions.