DFMEA

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Getting to the true root cause can be difficult. Suggestion is to keep asking the question… “Why?” Example: DC/DC converter – no output power.
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What is a DFMEA?
Design Review Process.
DFMEA is a procedure that allows the engineering team anticipate failures and prevent their occurrence.
PCB manufacturer error in process PCB pads not fully level or even
No output power
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Fishbone diagram
Output ripple has oscillation content
Root cause
Why?
New IC BGA package not fully soldered to PCB pads. Why? Not all BGA ball make contact with PCB pad. PCB pads not fully level or even. PCB manufacturer error in process. Requirements outside of manufacturing capability. Capture the teams inputs formally. Suggest a fishbone diagram tool. Why? Why? Why?
Incomplete DVT Test plan not covering all conditions 100% Tolerance / sensitivity analysis incomplete
All vendors not checked No mixed sourcing plan
Transformer inductance
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Why perform a DFMEA?
Helps to identify potential product/process failure modes Increases the likelihood that all product/process issues will be considered Documents the rational behind product/process design changes Assists in the development of process control plans Is a living document – meaning that when new issues are found the team needs to meet, consider the options for correction and update the DFMEA
Not all BGA ball make contact with PCB pad Not all BGA ball make contact with PCBside of manufacturing capability
Insufficient process controls Not all BGA ball make contact with PCB pad Not all BGA ball make contact with PCB pad
Evaluating the present control plan for preventing failures occurring.
For Design Verification Testing (DVT). This can help establish the required test plans to follow. Prioritising the actions that should be taken to improve the product.
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When to do the DFMEA?
If using an existing program to leverage… At the 1st schematic review stage and then… Up-date at the 1st PCB layout review stage If a new design … At design concept stage and then… Repeat at the 1st schematic review stage and then… Up-date at the 1st PCB layout review stage For production released products… After completing a problem solving activity
Effect
Severity (1-10)
Cause
Occurrence (1-10)
Controls
Detection (1-5)
Mechan ical
Power train
Logic / Control
This DFMEA template is used by HP.
There may be many other ways of presenting this information, however suggest to stay with this format for HP projects unless HP advise a new or revised format.
Audible Noise
Cores not glued/varnished
Not listed on drawing Transformer cores moving.
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Who does the DFMEA?
The team approach is recommended The responsible design engineer is expected to involve representatives from electrical, mechanical, quality, production, production test, sales, design testing, reliability, safety, purchasing
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Microsoft Excel Worksheet
DFMEA Template
Risk Priority # Action Responsibility Completion date Status
Category
Item #
Failure Mode
I can tell you everything that I know
As a team we have a lot more knowledge & experience
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Who up-dates the DFMEA?
The project manager. Summarize key actions from the long lists of individual items. When is a DFMEA up-dated? Whenever a change is being considered to a product’s… design, application, environment, material, manufacturing or assembly process. Take a look at the HP template for DFMEA…
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DFMEA
Design Failure Mode Effects Analysis
PM
Presented by Steve Airey
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Objective
To understand the use of DFMEA within the process of power supply product development Learn how to develop a DFMEA The main objective here is to thoroughly review of all the ways a product or process can go wrong. Continuously seek out information from the factory and field. Evaluate countermeasures to avoid the problems. Consistently learn from past errors. Feedback documented results for all other teams to review. Involve the whole team at all times.