SMTA International

PDC11: Design and Assembly Process Challenges for Bottom Terminations Components (BTCs) such as QFN, DFN and MLF in Tin-Lead & Lead Free World.

*Ray Prasad, Ray Prasad Consultancy Group
Monday, October 15 | 8:30am — 12:00pm


Course Objectives
Bottom Termination surface mount Components (BTCs) go by various names such as QFN, DFN, SON, LGA, MLP, and MLF, which utilize surface to surface interconnections. BTCs are like BGAs which also have hidden terminations, but they are also very different. BTCs do not have spheres but rather metallized terminations or pads underneath the package. This minor difference in the physical I/O shape makes all the difference in design, assembly and rework between BTCs and BGAs.
Since there are no leads or balls in BTCs to take up any slack from package or board warpage, you essentially need perfection in design and assembly process. When was the last time you saw every thing perfect on any manufacturing floor?
One must also keep in mind that these parts are not the only components that must be mounted on the board. Look at any board. It will have other packages such as BGAs, fine pitch and even some through-hole components; and those components have their own unique design and assembly implementation requirements. So designing for BTCs may involve trial and error and lot of frustration by many companies. Additional frustration is caused by fast-paced changes in packaging technologies and the advent of Lead Free has compounded the designer’s task.
When it comes to inspection, BTCs pose even more challenge than BGAs. What you may see in visual inspection may look bad but may really be acceptable. And what you don’t or can’t see may really be critical. And the fact that the Process Engineer must worry about both too much solder and too little solder on the same BTC package makes the quality engineer nervous about field returns.
The objective of the course is to get away from the trial and error approach and provide you successful design and process practices commonly used by the industry. This course will cover the practical details of BTC design and assembly processes.
This course is based on Surface Mount Technology: Principles by Ray Prasad and Practice and IPC 7093 Design and Assembly Process Guidelines for BTCs also co-chaired Ray. This course identifies many of the characteristics that influence the successful implementation of robust and reliable BTC assembly processes.
This is not a theoretical course. It s based on Mr. Prasad's over two decades of experience at Boeing, Intel and numerous clients and deals with "real-world" problems in lead free and tin-lead BTC implementation.

Topics Covered
1. Introduction
Pros and Cons of BTC
Pull Back Vs Non Pull Back
BTC Package Manufacturing Process
2. Major Design Considerations for BTCs
Laminates and Surface Finish Considerations
Land Pattern and Stencil Design Guidelines
Component considerations
3. Assembly Process Guidelines for BTC
Solder Paste Printing- the Key Process Step
Reflow Process Guidelines
BTC Solder Joint Quality Requirements
BTC Rework Process
4. Key strategies in design and manufacturing processes to prevent field returns