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DISCO HOME > Solutions > Kiru, Kezuru, Migaku Topics > DBG + DAF Laser Cut

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DBG + DAF Laser Cut

DBG (Dicing Before Grinding)*1process is capable of reducing backside chipping by separating the dies during grinding, which also improves die strength. In addition, because the wafer is separated into dies at the end of the grinding process, a reduction in the risk of wafer breakage can be expected during thin grinding. By applying DAF (Die Attach Film)*2 to the DBG process, it is possible to develop a DBG process for the manufacturing of packages with stacked thin dies, such as SiP (System in Package).
When applying DAF to the DBG process, it is necessary to attach the DAF on the backside of the die separated wafer and then cut just the DAF. DISCO engineers have developed an application to laser cut the DAF at this juncture.
*1 DBG (Dicing Before Grinding) : The DBG process reverses the usual process of backside grinding and then full cut wafer dicing. The DBG process first half-cuts the wafer and then separates the dies during the backside grinding process.
*2 DAF (Die Attach Film) : DAF is bonding material attached to a film and is used for thin die stacking.
Application
Cutting DAF with blade dicing after the DBG process, currently has the following issues.
<Blade DAF cutting issues after the DBG process>
- Die Alignment
Die shift (kerf shift) may occur when attaching dicing tape and peeling the backside protection tape. If the die shift amount is large, it may not be possible to secure sufficient street width for the blade to pass.
- Blade Width
Since a blade that is thinner than the street width (distance between dies) is necessary, precision processing is required.
- Processing Speed
To maintain sufficient quality of the DAF after cutting, it may be difficult to process at high speed.
On the contrary, by using a laser to cut the DAF after the DBG process, it is possible to process the wafer corresponding to the die shift and improve the processing speed.
DBG + DAF Laser Cut Process
After the DBG process, the mounter transfers the wafer onto a frame. After the mounter peels the backside protection tape from the wafer, the laser dicer performs a laser full cut on the DAF from the backside of the wafer. Since the wafer is already separated into dies, the laser passes between the dies and cuts only the DAF.
Merits of DAF Laser Cut
Improves the DAF edge quality
By employing a laser dicer, it is possible to suppress the burring that occurs during blade DAF cutting.
Figure 1: Backside SEM photograph of a DAF laser cut
(70µmSi + 20µmDAF)
Improves productivity by increasing the cutting speed
Compared to blade dicing, it is possible to increase the processing speed when performing DAF full cut with a laser.
Process example: One pass DAF cutting at a processing feed speed of 100 mm/sec - 300 mm/sec.
(Depending on the DAF type, DAF thickness, wafer thickness and kerf width, processing conditions are different)
Responds to die shift with special alignment
If die shift occurs in the wafer after the DBG process, it is possible to follow the die shift by using special alignment. The special alignment remembers the position of the kerf center for every alignment point of each line, and then cuts through this center with the laser.
Figure 2: Image of DAF Cut
Equipment
DFL7160 (DBG + DAF cut specification)
DFL7160
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