1. INTRODUCTION
Mass production of high quality ferrite
cores requires a fundamental knowledge of processing rules
dedicated to each material and the use of advanced production
techniques.
Existing products specifications are
achieved mainly by the implementation of a reliable Quality
Assurance System using Statistical Process Control(SPC) in
the manufacturing processes.
At each manufacturing step, the capabilities
of processes are demonstrated through various controls performed
on the related test vehicles.
2. STANDARDS AND SPECIFICATIONS
Our ferrite cores are manufactured
and controlled in accordance with GB standards (National Standards
of P.R.China ), SJ standard(Trade Standards of Electronics
Industry of P.R.China) and IEC standards (Standards of International
Electrotechnical Commission).
The standards are divided into three
levels:
GS=Generic Specification
SS=Sectional Specification
DS=Detail Specification
Concering soft ferrite parts and accessories,
the following standards are important for quality assessment
and for choice of standardized core types and materials.
● GB System:
GB9623 Inductor and transformer
Cores for Telecommunications
Part
1: Generic Specification
GB9624 Inductor and transformer
Cores for Telecommunications
Part
2: Sectional Specification Magnetic Oxide Cores for Inductor
Applications
GB9626 Inductor and transformer
Cores for Telecommunications
Part
3: Sectional Specification Magnetic Oxide Cores for Broad-Band
Transformers
GB2628 Inductor and transformer
Cores for Telecommunications
Part
4: Sectional Specification Magnetic Oxide Cores for Transformers
and Chokes for Power Application
GB9630 Dimensions of Pot Cores
Made of Magnetic Oxide and Associated Parts
GB9631 Detail Specification
Assessment Level A of UYF10Magnetic Oxide Cores
GB9632 Measuring Methods of
Inductor and Transformer Cores for Telecommunications
GB9634 Guidelines of Limit Specification
External Shape Defects of Magnetic Oxide Parts
GB10192 Dimensions of Spire
Cores Made of Magnetic Oxides
GB11439 Inductor and Transformer
Core for Telecommunications
Part
2: Drafting Guidelines of Performance Specification
● IEC System:
IEC367-1 Cores for Inductors and Transformers
for Telecommunications/ Measuring Methods
IEC404 Information/Ferrite Materials
Appearing in Manufacturers Catalogues of Transformer and Inductor
Cores
IEC410 Sampling plans and Procedures
for Inspection by Attribute
IEC431 Dimensions of Square Cores
(RM Cores) made of Magnetic Oxides and Associated Parts
IEC525 Dimensions of Toroids Made
of Magnetic Oxides or Iron Powder
IEC723-1 (GS)Inductor and Transformer
Cores for Telecommunications
IEC723-2 (SS)Magnetic Oxide Cores
for Inductor Applications
IEC723-3 (SS)Magnetic Oxide Cores
for Broadband Transformers
IEC723-4 (SS)Magnetic Oxide Cores
for Transformers and Chokes for Power Applications
IEC1185 Dimensions of Magnetic Oxide
Cores for Power applications(ETD Cores)
3、 QUALITY ASSURANCE
3.1 System
Our system complies with GB/T19002-ISO9002,
GJB9002 and IECQ.
Our corporate control plan can be
divided into three main parts:
---Incoming inspection on raw materials
Not only there is restriction on the
scope and number of suppliers, but also the key parameters
of each batch of raw material are inspected by our inspected
when it enters our factory and is put in storage.
---Process inspection
At each process, semi-finished products
are tested or controlled by SPC method so that the finished
products comply with the specification.
Each important process is followed
by a Quality Control Point (QCP) where the decision is made
to continue or stop the batch if unacceptable parameters are
found (nonconforming batch procedure).
On the other hand, results from one
process stop can be used to monitor the following step, e.g.
results of granulation are used to define the pressing conditions
of the relevant batch.
Remark: A typical example of manufacturing
flow chart dedicated to U/E cores for power applications is
shown hereafter. For each process step, QCP controls are performed
on the defined test vehicles. The relevant test vehicles could
be powder samples or pieces of semi-finished ferrite parts.
The complete flow chart is split into
two main parts: powder reparation and core production.
Note：Fig.1
Typical Manufacturing Flow Chart of U/E Cores
In Fig.1,QCP is Quality control Point and SPC is statistical
Process Control.
---Outgoing Inspection
Each lot must pass through a final
outgoing inspection before entrance into the sales warehouse.
During the outgoing inspection, all results collected on relevant
lot are checked, some samples are controlled and test report
is printed upon request.
3.2 Traceability
The following information can be got
from the label stuck on each packing unit:
--customer name and customer’s part number
--material brand and type of core concerned
--code name of the inspector
--lot number
--name of the manufacturer and its address
4. QUALITY CONTROL
4.1 Classification of Defects
A ferrite core will be considered defective
if it does not comply with the standard specification of our
factory. Two levels of defects are defined:
Major defects: may lead to an operation
malfunction in the final winding or mounting processes.
Minor defects: do not affect the operation
or mounting of the wound components. Generally they are mechanical
and visual defects such as cracks and chips.
Table 1 giver hereunder defines the
parameters, which must be considered as major or minor defects
versus the type of product and applications.
Note:
Table
1 Electrical and Magnetic properties of Ferrite Cores-Classification
of Defects
Remarks: If required by customers’specifications,some
minor defects in Table 1 may be changed into major defects.
Consequently specific number must be given. Concerning dimensional
inspection on ferrite cores, major and minor defects related
to primary and secondary dimensions are summarized in the following:
