Shipping Methods
Supply Forms - Capabilities of Micross your franchised distributor
- Wafer
- Wafer sawn on foil (sawn is optional)
- Wafer on foil with visual defects inked
- Waffle Pack (conductive or non-conductive)
- Gel Pack (Adhesive)
- Tape on reel
Alternatively we can custom package them to your requirements, please see the products and services section of the site for more information.
Supply Forms for Bare Die - The concept
Once the wafer has been sawn the next process the bare die must undergo is determined completely by the die supply form the customer requires.
There are two main factors which drive choice of the end bare die supply form:
- The capacity for the product to be handled safely and stored appropriately without deterioration of physical & electrical quality.
- The suitability for the customers manufacturing process at their end.
Packaging
Safe carriage of the bare die is important to maintain overall quality and ensure the best yields when they are assembled. It is paramount to pick the appropriate carrier conditions for the bare die. For example, allowing a wafer freedom to move within its container is extremely likely to cause major damage during transport. Although the previous example may seem like common sense, the reality is that a combination of factors such as allowable movement, topside surface contact, susceptibility to ESD (Electro-Static-Discharge) or even exposure to air can contribute to the correct choice of bare die carrier. Through long term practical experience and a developed knowledge of the available carriers Micross as your franchised die distributors are well equipped to advise those new to using bare die on the best method for them.
Storage
Another safety factor to consider in choosing the correct die supply form is the method in which the bare die are stored. Improper storage no matter how appropriately the bare die have been carried will still result in defective product at the point of assembly. Due to both the physical and electrical sensitivity of the material, life of a bare die product is severely affected by the conditions in which the dice are stored. There are two major problems the bare die user is faced with, the first is electrical protection, all die product must be protected from ESD (Electro Static Discharge), circuit tracks can deteriorate due to the excessive ESD charge forced through them therefore dropping the overall performance of the dice. In the worst cases the dice can be destroyed entirely!
The second problem is direct corrosion of the physical bare die surface which occurs when the dice are not stored in the right atmospheric conditions. If dice are stored in air then the result is a high level of oxidisation growth on the bare die surface which renders the die unusable, another important factor to consider is the level of cleanliness in the storage area, the number of foreign particles in the atmosphere surround the bare die can still result in 'dirty' die and a drop in product quality. The essentials needed for a basic level of bare die storage are to contain the die within an Electro Static Preventative carrier stored within an atmosphere of nitrogen to preserve the metalisation quality. Once again Micross as your die distributors can provide technical advice on this issue or alternatively store your die product for you where necessary.
End Use
The final contributor to choosing supply form is purely practical and is determined by the type of operation due to be performed on the bare die at the customer's facility. Speed and accuracy often determine this, for example a customer may request that bare die product remains sawn on its ring frame in order to increase the speed it can be processed at their end. This speed is usually associated with equipment such as an automatic Pick & Place machine where the bare die can be rapidly removed from the foil. For example, Ring frame supply form is ideal for those looking for a fast turn-around or high volume as equipment can easily be calibrated for fast processing due to the linear nature of the bare die orientation. For customers using higher volume machines they may wish to perform this task with minimal need for equipment calibration to size & orientation and would in this instance request a 'Tape & reel' option from the distributors where the bare die are placed directly into a pre-defined tape with set dimensions and can literally be fed automatically into a rapid assembly machine. (see tape & reel picture below). However, flexibility in handling can also be an important requirement and is usually related to medium to low volume dice requirements, the most common supply form chosen here is bare die in waffle pack. Supplying die in waffle pack allows assembly by both manual and automatic methods and is considered to be the most versatile carrier form overall in terms of handling, die orientation and storage lifespan. In summary choosing the right supply form boils down to level of experience in handling bare die, knowledge of the correct storage conditions and the appliance of practicality in relation to the products future assembly process and equipment that will be used. As franchised die distributors we should be well equipped to advise those unsure in this choice.
Supply Forms - The Process
Die in Waffle Tray
Bare die are placed in the tray by use of either 2 methods, by hand or by use of a Pick & Place machine (See Pick & Place). For manual placement each die is manually peeled from the ring frame tape and placed in it's cavity by use of a vacuum pencil. The dice are lifted by the their side in order to prevent damage to the active surface of the die, once positioned over their cavity the vacuum running through the pencil is released and the die are placed into their cavity. This task requires a great deal of skill and is measured by a strict training schedule before staff are allowed to work 'active' die. The waffle trays themselves come in various sizes where once again the size of the cavity varies to accommodate the bare die that are placed in it. To prevent the trayed die from ESD damage an ESD protective Tyvek slip is placed over the tray top once die loading is complete and the lid is placed on.
Die in Gel Pak
The bare die are placed by a similar method as the waffle pack. The gel uses a sticky surface tension in order to minimalise potential movement of the dice in transport. Gel-Paks are orientated to more specialist handling where often the die size can very large and requires particular dexterity.
Wafer Forms
Customers may wish to perform their own sawing in which case they can receive the wafer uncut or placed onto foil ringframes ready for sawing direct from the distributors.
Wafer on Foil
Wafer is cut at the distributors and attached to its foil ring-frame (see sawing). In this case the die remain attached to the tape & its ringframe for fast removal at the customers facility. The length of time the die remain on tape before use is a key issue here as tape resistivities can vary. Please ask us as your distributors for a recommendation.
Tape & Reel
The die are placed into pre-designed cavities on a specialised tape reel by the Pick & Place machine. The tape reel can then be directly loaded into a customer's fast automation equipment to assemble.
To view our full list of Wafer Services and Process Flow please click here.
To view our full Bare Die Linecard please click here.