There are two principle aspects in getting good bare die product into assembly:
- Electrical test - Please see here for our wafer testing capabilities
- Mechanical quality - Assessed by visual inspection either automated or manual.
The baseline quality for a bare die is that it passes electrical test at wafer level and passes visual inspection after the singulation and handling process into the shipping media.
Pass wafer level test + Pass visual post processing = Bare Die considered good (relative to the electrical test performed).
The sawing process is critical in that it is a majority contributor to mechanical quality and by default has an impact on yield, the number of good die per wafer.
What processes are available?
There are several wafer singulation methods practiced in the industry:
- Mechanical dicing
- Scribe & break (Fragile or hard compound and opto semiconductors)
- Dice before grind (DBG),
- LASER dicing
- Chemical etch dicing.
The most prevalent methods in use today are mechanical dicing and scribe & break. This is largely due to cost effectiveness in terms of throughput, cost of ownership and setup flexibility.
Specialist dicing methods such as LASER and chemical etch are typically useful when:
- Processing volumes exceed the trade-off point between price and throughput versus traditional dicing costs
- The wafer physically requires specialist singulation which these methods can provide
- An extreme highest quality outcome is required where price is no object.
COMING SOON - Our in-house mechanical dicing process
At Die Devices we are in the process of offering a mechanical dicing service which is suitable for a broad range of semiconductor materials. Where specialist dicing methods are needed we combine working partnerships with equipment makers and our own process knowledge to manage your project.
A diamond embedded blade is used to remove material while process water cools the blade and workpiece
At all times strict control must be made on the processing water quality:
The correct blade choice is then made which takes into account multiple factors:
- The width of the sawing street on the wafer
- The total thickness of the wafer
- The intended dicing process
- Any history or experience with this material.
Where street sizes are small or wafer thickness is high it can be beneficial to thin the wafer before dicing.
There are two types of dicing method available, single pass or step cut, each cut has pros and cons.
We recommend the process most suitable for the situation.
- Fast throughput
- Suitable for thin wafers
- Suitable for narrow streets.
- Can reduce topside and backside chipping
- Can reduce effect from blown test pads
- Suitable for thicker wafers
- Requires customer to accept sidewall step.
Tape & Frame Choice
Wafers are mounted onto tape which is held on a Film-Frame. There are multiple tape options and the choice is dependent on the product type and further processing required either at Die Devices or at the customer's facility. For example, ultra-thin die are highly recommended to be sawn on UV tape.
The standard frame we use is the Disco FFP-200 frame, other output frames such as Ring-Frame are possible subject to setup tooling and volume levels.
First time wafer dicing always involves a trial cut to set key machine variables and evaluate blade choice such as:
- Feed speed
- Spindle speed
After first article dicing each saw process is typically optimised over time with volume to produce the best quality for a given setup.