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Lifted Leads on QFP Components
After placement and reflow, we have a random lifted lead problem on some QFP's. What might be the cause? Where should we look?
Phil Zarrow, ITM Consulting With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall, ITM Consulting A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.
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One of the major causes for lifted leads for QFP type components is handling. Examples are below:
1. QFP tray holds 20 components
2. Purchasing orders 110
3. Vendor/manufacturer has to re-package 10 components in another tray
3a. They might not use the right tray which can cause bent leads
3b. Just moving these parts to a good tray can cause bent leads
4. You buy components from your customer stock and their handling can cause bent leads, plus 3a and 3b
5. Internal kitting might be moving parts from 1 tray to another causing bent leads
6. Most machines can be stepped through a process, with QFP attached to nozzle, to determine if the machine is bending any leads
6a. Check program to see where failed QFP's are rejected ... dump box or belt.
A good inspection/training program would be able to reduce or eliminate the possibility of bent leads.
Dean Edwards, Quality Engineer, APT Electronics, Inc.
When I was with a prior company we experienced problems with lifted leads. We discovered something that was not mentioned in your material. The design of the board. The size and distribution of the components on the board provide different heating indexes in different places, this along with the material of the board itself. Let's say that a large QFP is properly aligned but the board flexes in the oven. You end up having what looks to be a lifted lead problem, but do you have a problem with the QFP?
What if you don't have a center guide to keep the board from flexing? What if the board is already bent from the first reflow?
The problem we saw was because the board was large and the QFP was placed near one corner. The flexing of the QFP and the flexing of the board had an effect on this defect. The solution was to change the board, change our design spec and add a temp stress simulation to the design cycle.
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The Juki KE2080 flexible placement system successfully places the widest range of ICs, connectors, and unique shaped components on the market. Juki Automation Systems, Inc.
Components encapsulated in plastic or organic compounds are susceptible to moisture damage. So are PCBs, all can cause early field failures. Control MSDs per IPC J-Std-033b.1 and 1601. Super Dry®
Components encapsulated in plastic or organic compounds are susceptible to moisture damage. So are PCBs, all can cause early field failures. Control MSDs per IPC J-Std-033b.1 and 1601. Super Dry®
Multicore TFN700B is a no-clean, halide-free tacky flux formulated to address the challenging requirements of package-on-package applications. Henkel Corporation
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Use the form below to submit a comment.
1. QFP tray holds 20 components
2. Purchasing orders 110
3. Vendor/manufacturer has to re-package 10 components in another tray
3a. They might not use the right tray which can cause bent leads
3b. Just moving these parts to a good tray can cause bent leads
4. You buy components from your customer stock and their handling can cause bent leads, plus 3a and 3b
5. Internal kitting might be moving parts from 1 tray to another causing bent leads
6. Most machines can be stepped through a process, with QFP attached to nozzle, to determine if the machine is bending any leads
6a. Check program to see where failed QFP's are rejected ... dump box or belt.
A good inspection/training program would be able to reduce or eliminate the possibility of bent leads.
Dean Edwards, Quality Engineer, APT Electronics, Inc.
What if you don't have a center guide to keep the board from flexing? What if the board is already bent from the first reflow?
The problem we saw was because the board was large and the QFP was placed near one corner. The flexing of the QFP and the flexing of the board had an effect on this defect. The solution was to change the board, change our design spec and add a temp stress simulation to the design cycle.
Guillerma Velazquez, RainBird