1 Introduction
It may be the case that a customer's chip or wafer products will be or have been stored for an extended period of time. This document provides information to help our customers better understand decisions about how to better store these products and what problems may arise .
2 General
Receiving, storage, packaging, handling and shipping procedures shall prevent mechanical or electrical damage or degradation of chip wafer semiconductor devices during normal handling, shipping and storage. All packaging materials shall be conductive or antistatic, including waffle wrap, reel , bags and fillers (see EIA-583). Appropriate ESD precautions must be taken (see JESD625). Product dry or vacuum bagged at all times up to and including shipping to the user should follow industry standard practices. This includes Re-baked and re-bagged if necessary. Reseller or user is responsible for verifying compliance with all customer receipt, storage, packaging and shipping requirements prior to use.
3 Inventory Control
When multiple batches of the same part number and packaging type exist in inventory, they should be based on a first-in, first-out (FIFO) inventory method (i.e., delivered according to an earlier date code or an earlier batch number).
4 main questions
4.1 Moisture-related mechanics
It is possible that during storage, especially if not stored in a controlled atmosphere, moisture may have penetrated into the vacuum-sealed bags that seal the product and protect it from moisture. While semiconductor wafers and chips themselves are not sensitive to moisture, wire bonding Pads are very sensitive and moisture can accelerate failure mechanisms that may only arise during product packaging, such as adhesion issues and delamination.
4.2 Chip front and back contamination
Wafers or dies that may be stored for extended periods of time may become contaminated due to age, foreign objects or improper storage conditions. This may cause problems such as Non-Stick-On-Pad (NSOP), topside delamination, Poor die attach or other such issues. Tested to monitor surface cleanliness, wire bonding and should be subjected to adhesion (e.g. water droplets) and should be plasma cleaned if necessary, assembly process. Limited trial run on wire bonding Or assemble evaluation and mold accessories to guarantee good results before the product goes into mass production.
4.3 Improper storage conditions
If the chips and wafers are not stored properly, the probability of the above problems may be greater. Chips and wafers should be stored at a relative temperature between 18°C and 24°C with less than 30% humidity and cleaned , in a dry, inert atmosphere (such as nitrogen), and in a vacuum-sealed bag.
4.4 Handling related wafer or chip damage
Handling may damage the wafer or die. Dies stored in the Waffle Pack should be handled with care to avoid possible chip edge chipping. Dropping the Waffle Pack may cause damage to the die. Handling the wafer or die with tweezers may result in scratches on the top marks that may cause chip failure or use through subsequent manufacturing processes or degraded applications. It is recommended not to use tweezers when handling wafers or chips. Automated pick and place should set up handling equipment to ensure that wafer or chip surfaces or edges do not appear Scratches. Proper training, procedures and precautions are required to avoid handling related damage to wafer and chip products.
4.5 Risk of KGD Parts
KGD parts are usually shipped on tape and reel, and it is more difficult to ensure long-term reliability due to the nature of the transmission medium. For very long-term storage, it is recommended to purchase the product in wafer form.
4.6 ESDS Precautions
Systems used for Electrostatic Discharge Sensitive (ESDS) protection shall comply with JESD625. When removing the device from the reel, the cover tape shall be removed at a speed of 10 mm\/sec or less and at an angle of 10 mm from the embossed carrier tape. Between 165 degrees and 180 degrees to reduce static electricity.
5 Conclusion
Generally speaking, the quality and reliability of long-term storage semiconductor IC wafers and die products should be comparable to newer products. However, to ensure that no problems will arise during the assembly process, it is recommended to start large-scale Products for long-term storage are evaluated prior to production. It is recommended to purchase these products for long-term storage in wafer form.
It is also recommended that storage locations and facilities, including distributors, contract manufacturers, programming houses, etc., should be regularly qualified and audited to ensure storage conditions, handling and associated precautions are systematic, specified and followed. This will help Improve wafer success probability and mold management.
6 References
▪ Joint IPC\/JEDEC Standard J-STD-020, Moisture\/Reflow Sensitive Classification of Unsealed Solid State Surface Mount Equipment
▪ Joint IPC\/JEDEC Standard J-STD-033, Standard for Handling, Packaging, Shipping, and Use of Moisture\/Reflow Sensitive Surface Mount Devices
▪ JEDEC Standard JESD31, General Requirements Equipment for Commercial and Military Semiconductor Distributors
▪ JEDEC Standard JESD625, Requirements for Handling Electrostatic Discharge Sensitive (ESDS) Equipment
▪ EIA Standard EIA-541, Standard for Packaging Materials for ESD Sensitive Items
▪ EIA Standard EIA-583, Standard for Packaging Materials for Moisture Sensitive Articles