The following is a study Guide Snapshot on the topic INTERRELATED
CONSIDERATIONS FOR DESIGN.
This topic relates to QODs #116; #117; #118.
The end product requirements are the characteristics of an
individual part or assembly in its final completed state. To be
sure that the part or assembly will work as intended, the
environment in which it will operate should be known at the time
of the design. Equipment environmental conditions such as ambient
temperature, heat generated by components, ventilation, shock,
vibration etc. necessitate different materials, tolerances and
final product configurations.
To facilitate communication between the designer and
manufacturers different performance classes have been developed
to reflect progressive increases in sophistication, functional
performance, and frequency/intensity of inspection or stress
testing. These are identified by a class designation, where Class
1 are General Electronic Products; Class 2 are Dedicated Service
Electronic Products; and Class 3 are High Reliability Electronic
Products. Each has its definition which can be related to end use
environments such as computers, telecommunications, aerospace,
automotive (both in-the-cab and under-the-hood) etc.
applications. The user has the responsibility to determine the
class to which his product belongs.
Producibility levels have also been established to help
communicate the design complexity to the manufacturer. There are
also three levels of producability. These are Level A (General
Design Complexity-preferred); Level B (Moderate Design
Complexity-standard); Level C (High Design Complexity-reduced
producibility). Most printed board manufacturers (95%) can
produce level A products at a very high yield, therefore, a
reasonable cost. The number of available manufacturers that have
the precision capability to manufacture product at the C level
drops to approximately 20%. There are also those products that
need even greater sophistication of tooling, materials and
processing (state-of the-art) where the number of manufacturers
able to accommodate the design is around 1%. State-of-the Art can
not be standardized, however, every few years the levels shift
and that which was moderate becomes general, and so on.
Since the design is intended to meet all the requirements of the
product, including performance, cost, reliability, etc.,. all of
the issues need to be discussed at the beginning of the design
process. These discussions should include manufacturing
engineering for both the board, assembly and test. The days of
tossing the design over-the-wall are gone if a company wishes to
stay competitive with the products that they hope to sell to the
costumer. Thus design for excellence is design for producibility
and involves all the disciplines needed to manufacture and
maintain the product.
Resources: IPC-T-50 Specific Terms and IPC-D-275 para 1.2; 1.2.2;
1.2.3; 3.2; 3.2.4 and IPC-SM-782 para 3.4; 3.4.4; 3.4.5; 3.5.2; 3.5.3;
table 3-6
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Please send comments, constructive critique, or suggestions to
Lisa Williams at [log in to unmask]
Dieter Bergman
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