96 PCB007 MAGAZINE I OCTOBER 2024
7. Substitute the values of exponents in the
main equation, and form the non-dimen-
sional parameters by grouping the vari-
ables with the exponents:
e Reynolds Number can now be used as
the pseudo-independent variable to produce
the famous Moody diagram for friction loss in
fluids flowing through pipes (Figure 5).
Example
e Reynolds Number is just one of 154
dimensionless parameters used in engineer-
ing. Figure 6 shows 77 of the 154 DPs and also
highlights the Mach Number which is not
velocity but the inertia force/elastic force of a
moving body.
Summary
Hopefully, this Tech Talk has introduced you
to some new PCB metrics and/or FOMs. It is
important to understand where your organiza-
tion fits into the Five Stages of Metrics:
1. Age of Anarchy (60%): Where anything
goes (over-the-wall approach).
2. Age of Folklore (25%): Where wisdom is
passed from one generation to another
over pizza and beer (an attempt is made).
3. Age of Methodology (10%): e way
DFM/A is to be engineered is documented
and is actually done that way (using a
figure of merit).
4. Age of Metrics (4%): Both the product and
the manufacturing processes are measured
in standardized ways.
5. Age of Engineering (1%): Producibility
is achieved through continuous quality
improvements for both design and man-
ufacturing, much like it is in enlightened
management. PCB007
References
1. Chapter 10, 24 Essential Skills for Engineers,
by Happy Holden.
2. Chapter 19, 24 Essential Skills for Engineers,
by Happy Holden.
3. Chapter 9, 24 Essential Skills for Engineers,
by Happy Holden.
Happy Holden has worked
in printed circuit technology
since 1970 with Hewlett-Packard,
NanYa Westwood, Merix,
Foxconn, and Gentex. He is
currently a contributing technical
editor with I-Connect007, and
the author of Automation and Advanced Procedures
in PCB Fabrication, and 24 Essential Skills for
Engineers. To read past columns, click here.
