Three Bond Technical News—Underfill Agent for BGA/CSP Mounting
Underfill Agent for BGA/CSP Mounting
Introduction ________________________________________________
With the rapid evolution of such mobile information equipment as cellular telephones, PHSs, laptop PCs, and VTRs with built-in cameras, the market is demanding that electric and electronic equipment be made smaller, lighter, and faster, even as more features are in demand. As part of this trend, ICs (LSIs) need to be made smaller. At the same time, ball grid arrays (BGAs) and chip size/scale packages (CSPs) are becoming increasingly popular to make the packages smaller, to similar sizes of bare chips, and to improve their properties. This miniaturization is being achieved by protecting the bare chips, and by making use of package functions, such as stress relaxation, dimension matching, and standardization (generalization).
On a circuit board, a BGA or a CSP is connected to electrodes by means of solder balls. Stresses such as heat cycling, shock, or bending can cause the connection of the BGA or CSP to be broken. To prevent this, a sealant (an underfill agent) is applied to the clearance space between the BGA or CSP and the circuit board; this helps to relax the stress and to hold BGA or CSP in place.
This issue briefly discusses BGAs and CSPs and the need for the underfill agent. It also introduces underfill agents that Three Bond has developed for mounting BGAs and CSPs to meet a variety of customers’ requirements.
Contents
Introduction
1. What is BGA/CSP?
2. BGA/CSP post-mounting problems
3. Underfill agent for BGA/CSP mounting
3-1. Effects of using underfill agent
3-2. Requirements of underfill agent
4. Underfill agent with repairability
4-1. Problems with underfill agent
4-2. What is repairability?
4-3. Underfill agent with repairability
4-4. Repair techniques
5. Grades of ThreeBond underfill agent for BGA/CSP mounting
5-1. Characteristics of the underfill agent of each grade
Conclusion
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