The Five Core Tools – A Detailed Guide to PPAP Application 

1. What is PPAP?
Full Name: Production Part Approval Process
Essence: A standardized “evidence package” and “qualification” process. Its core purpose is to prove one crucial thing to the customer:
“Our production line is not just capable of making a few good samples in the lab, but has demonstrated the ability to produce qualified products consistently and stably in large volumes over the long term, under our specified requirements.”
Analogy: “The Supplier’s Driver’s License Test”
You learned the rules and practiced driving (completed product and process design via APQP).
But you can’t just drive on the road; you must pass the official test.
PPAP is this “driving test.” You must submit your proof of learning (documents), driving skills (production samples), and test performance (test data) to the examiner (the customer).
After the customer audits and approves, they grant you the “driver’s license” (PPAP approval), allowing you to officially “drive on the road” (start series production and supply).

For our factory, PPAP is the process of proving to our customers (e.g., in automotive, medical) that the design, materials, processes, and production system we have established for a specific model of TFT/LCD display have reached a mature state capable of volume production and supply.

2. What is the Core Purpose of PPAP?
In sectors like automotive, industrial, and medical, a minor defect can lead to catastrophic consequences. PPAP role is to build trust and ensure fail-safe operation:

1. Risk Transfer & Trust Building: The PPAP documents we submit represent a legally binding quality commitment. They are the “entry ticket” that earns the customer’s trust and allows us into their supply chain.
2. Ensuring Process Capability, Not Just Sample Quality: PPAP emphasizes that “production parts” must come from a continuous, stable production run (typically 300+ parts in a production environment). It focuses not on one or two perfect samples, but on the stability and consistency of the entire production system. This is critical for key characteristics of LCD displays like uniformity, pixel defect rate, and lifespan.
3. Unified Language, Efficient Communication: PPAP provides a set of globally recognized standards and document formats. Regardless of our customer’s location, they know how to review our submissions, avoiding misunderstandings and rework due to differing standards.
4. Preventing Unauthorized Changes: Once PPAP is approved, it becomes the production “baseline.” Any subsequent changes to design, materials, or processes require notifying the customer and may necessitate a new PPAP submission. This effectively prevents quality degradation caused by suppliers making unauthorized changes for cost reduction.

3. Specific Control and Application of PPAP in Our TFT/LCD/LCM Manufacturing Process
Using a car center console TFT display currently under development in our company as an example.

Core Evidence for PPAP Submission (Key elements from the 18 possible items)

1. Design Records & Engineering Change Documents:
What it controls: The definitive source for all design aspects of the display we produce.
Our Process Link: Customer-provided or internally designed TFT array design files, LCD cell gap specs, CF (Color Filter) parameters, IC drive scheme, FPC (Flexible Printed Circuit) drawings, backlight design files, etc. Any subsequent engineering changes must be documented.
2. Authorized Engineering Approval (if applicable):
What it controls: Formal customer approval of the design, if it was done by our company.
3. Process Flow Diagram:
What it controls: The overall picture and sequence of production.
Our Process Link: A clear diagram showing each step: TFT Array Fabrication -> CF Fabrication -> LCD Cell -> (COG/COF) Bonding -> FPC Attachment -> Backlight Assembly -> Aging Test -> Final Inspection.
4. PFMEA (Process Failure Mode and Effects Analysis):
What it controls: A “devil’s advocate” analysis for each step in the process flow.
Our Process Link:
Failure Mode: During cell assembly, cell thickness might become non-uniform.
Effect: Leads to display brightness non-uniformity, Mura defects.
Cause: Poor spacer distribution design or unstable sealant dispensing pressure.
Current Control: In-line Automatic Optical Inspection (AOI).
PPAP Proof: We must demonstrate that we have analyzed all such risks and implemented effective preventive and detection measures.
5. Control Plan:
What it controls: Quality controls during mass production.
Our Process Link: Explicitly defines at which TFT manufacturing station, which characteristic is checked (e.g., luminance, color gamut, contrast ratio, number of defective pixels, response time), the inspection method (e.g., CA-310 color analyzer, AOI equipment), the frequency, and the reaction plan (e.g., if luminance is out of spec, immediately stop the machine to calibrate the equipment).
6. MSA (Measurement Systems Analysis):
What it controls: Proof that our measurement tools are accurate and reliable.
Our Process Link: All measurement equipment used to test luminance, chromaticity, voltage, current, etc., must undergo MSA studies to prove acceptable Repeatability (same person, multiple measurements agree) and Reproducibility (different people’s measurements agree). If the measurement data itself is unreliable, all inspection results are invalid.
7. Initial Process Capability Study (SPC):
What it controls: Proof that our production process is stable and capable of producing conforming products.
Our Process Link: Continuous sampling (at least 100 data points) for key characteristics (e.g., operating current, center luminance, viewing angle) to calculate Ppk/Pp values.
The automotive industry typically requires Ppk ≥ 1.67. This indicates our process is very stable, with an extremely low risk of producing out-of-spec products.
This directly proves our process’s capability to consistently produce qualified automotive displays.
8. Dimensional Reports, Material/Performance Test Reports, Laboratory Accreditation:
What it controls: Hard evidence related to the physical product.
Our Process Link:
Dimensional Report: Proves the screen’s outline dimensions, mounting hole positions, FPC lead-out locations, etc., fully conform to the drawing.
Performance Test Reports: Provide complete reliability test data per customer standards, e.g., temperature cycling, damp heat storage, mechanical vibration, ESD, lifespan testing, etc. This is mandatory for automotive and medical applications.
9. PSW (Part Submission Warrant):
This is the “graduation certificate” for PPAP. Once all the above evidence is complete and meets requirements, an authorized person from our company signs this document, formally committing to the customer: “Our company has fully met all requirements and is ready for mass production.”

Summary: The Operational Impact of PPAP in Our Company

For EASTERN DISPLAY, with over 30 years of experience as an LCD/LCM/TFT manufacturer, PPAP is not merely a paperwork exercise. It represents a comprehensive system for controlling development, production, and quality.

It demands that we:
Focus not just on “being able to make” but on “being in control” of the entire manufacturing process.
Rely on data, not just experience: All conclusions must be supported by data (capability indices, MSA results, test reports).
Assume responsibility for the customer’s risk: Especially in automotive and medical sectors, the more complete and robust our PPAP evidence chain, the greater the customer’s confidence in us, leading to a more solid cooperative relationship.

Ultimately, through PPAP, we deliver to the customer not just an LCD display, but an entire, scientifically validated, reliable, and traceable manufacturing assurance system behind it. This is the core value we bring to competition in high-end markets.