TOC
REF
GLOSSARY QUIT
Section 4
Printed Board Characteristics
IPC Designer Certification Study Guide
TOC
REF
GLOSSARY QUIT
Section 4.1
Board and Assembly Panelization
Printed Board Characteristics
TOC
Fig
3-29
REF
GLOSSARY QUIT
The definition of a panel is a rectangular
sheet of base material, of predetermined
size, that is used for the processing of
one or more printed boards, and when
required, one or more test coupons.
There are two types of panels: one is for
the production of the bare printed board,
the other is for the production of the
board assembly.
Board and Assembly
Panelization - 4.1
TOC
SM782
Fig
3-14
REF
GLOSSARY QUIT
The development of each panel has a
set of rules to follow that make the
process of building boards and
assemblies more productionized.
Some of the rules deal with the extra
material that is required around the
border and the room between each of
the boards. Techniques for separation
must also be taken into account.
Board and Assembly
Panelization - 4.1
TOC
REF
GLOSSARY QUIT
Board fabrication companies try to use the
largest panel possible to make the most
efficient use of the manufacturing process
and ease printed board handling. The
size is usually based on the common size
sheet in the market place. In the United
States the common sheet size is 36 x 48
inches; in Europe and Asia the common
sheet size is 1 meter square.
Board and Assembly
Panelization - 4.1
TOC
REF
GLOSSARY QUIT
The designer should be aware of the board size
that the manufacturer of choice uses in
production so they will be able to optimize the
board to panel yield and cost relationships.
There was a time that it was sufficient to simply
take the board dimensions, divide them into the
fabrication dimensions, and allow sufficient room
for borders. The issues are more complex today
since many assembly companies do not want to
assemble boards in individual format. They also
want boards delivered in panels.
Board and Assembly
Panelization - 4.1
TOC
REF
GLOSSARY QUIT
The use of the largest panel in board
fabrication provides the most effective
labor cost per unit area. The industry
processes panels. Being able to get
twelve boards on a panel instead of six
(3 x 4 versus 2 x 3), immediately
increases the yield by 100%. The most
common panel in the US is 457 x 610mm
[18 x 24 inches].
Board and Assembly
Panelization - 4.1
TOC
REF
GLOSSARY QUIT
Some of the processing equipment can
accommodate larger panels, however,
human factors such as strength, reach
and control, preclude the use of much
larger panels. Borders and margins are
usually required and range between
9.5 to 38mm [.38 to 1.5 inches].
Board and Assembly
Panelization - 4.1
TOC
2222
5.2.1.1
REF
Tooling holes, coupons, and other
manufacturing entities such as
serialization or customer control
numbers are also contained in the
borders of the panel.
Board and Assembly
Panelization - 4.1
GLOSSARY QUIT
TOC
REF
GLOSSARY QUIT
Separating boards or assembly panels
from the fabrication panel varies
depending on the next use of the board,
material, the shape and size, and volume
of production. Higher volume production
tends to utilize punching or blanking dies
to excise boards, or assembly panels,
from fabrication panels.
Board and Assembly
Panelization - 4.1
TOC
SM782
3.6.4.5
Fig
3-30
Fig
3-31
Fig
3-32
REF
GLOSSARY QUIT
Fixturing is relatively expensive and
requires careful maintenance to assure
good quality board edges.
Freshly sharpened blanking dies will
generally provide a relatively smooth
board edge. However, as the die is used,
the board edges tend to roughen with
exposed broken fibers.
Board and Assembly
Panelization - 4.1
TOC
REF
GLOSSARY QUIT
Scoring and routing are two of the most
common methods used for excising
printed boards or assembly panels. The
easiest way to separate the board is to
score each side with a diamond grinder
and break the boards or panels apart. The
board must be square or rectangular, in
shape, in order to use scoring and care is
required to not have conductors too close
to the scored area, as the score wheel is
chamfered.
Board and Assembly
Panelization - 4.1
TOC
2222
5.3.1
Fig
5-2
Table
5-2
SM782
3.6.4.5
Fig
3-30
Fig
3-31
Fig
3-32
REF
GLOSSARY QUIT
It is required to score the board on each
side to approximately 1/3 of the thickness.
If the boards are routed, an amount should
be left between the boards to accommodate
the router bit. This is usually 4.8, 5.0 or
6.3mm [.19, .20, or .25 inches]. When
boards are routed the edges are usually
very smooth. Scoring leaves the edges a
bit rough where the remaining board
thickness has exposed broken fibers.
Board and Assembly
Panelization - 4.1
TOC
Extra
4.1b
REF
GLOSSARY QUIT
Assembly panels also require borders
but these are usually related to the
conveyor of the assembly machines.
The borders also contain tooling holes
or fiducials. Borders are only on
opposite sides of the panel where the
conveyer grips the panels, however,
some material is necessary at the
leading and trailing edge where the final
board comes close to the panel edge.
Board and Assembly
Panelization - 4.1
TOC
Extra
4.1
REF
GLOSSARY QUIT
The relationship of the final board and
the two panel concepts must be
understood and considered in the
design to maximize the manufacturing
operations. Some companies find it
useful to develop a panelization drawing
in order to maintain control of the tooling
features of the assembly panel.
Board and Assembly
Panelization - 4.1
TOC
REF
Section 4.2
Tolerancing Methods
Printed Board Characteristics
GLOSSARY QUIT
TOC
REF
GLOSSARY QUIT
A tolerance is the total amount that a
specific dimension is permitted to vary.
Therefore a toleranced dimension is a
dimension that has a specified amount of
variance that is acceptable. These
principles are intended to allow for
interchangeability of parts and the form,
fit, and function of mating products.
Tolerancing Methods - 4.2
TOC
2221
5.4.1
REF
GLOSSARY QUIT
A dimension may also be specified
without a tolerance. In this instance the
term basic is assigned to the dimension or
the dimensional location. The variation of
the basic dimension then controls the
variation usually in relation to some datum
or datum reference.
Tolerancing Methods - 4.2
TOC
REF
GLOSSARY QUIT
There are many methods of dimensioning
and tolerancing for mechanical parts, all
of which are defined in ASME Y14.5M. A
printed board assembly, although
performing an electrical function, has
many mechanical attributes that require
dimensioning and tolerancing. These
include the location of the parts, the
features (holes, conductors, legend, etc.),
and board outline in relation to the datum
from which dimensions are taken.
Tolerancing Methods - 4.2
TOC
2221
5.4.1
REF
GLOSSARY QUIT
Physical characteristics are also
mechanical in nature and require
dimensions and tolerances. Examples
are parts, diameter of holes, cutouts or
notches, plating thickness, in fact any
feature that requires a control to assure
the final product is consistent from lot
to lot.
Tolerancing Methods - 4.2
TOC
REF
GLOSSARY QUIT
All the methods in ASME Y14.5M work,
but it should be recognized that some
work better than others and some
methods cost less to inspect or
evaluate the final product than others.
One of the main considerations in
evaluating a system for dimensioning or
tolerancing is to recognize that every
mechanical feature has a maximum
material condition (MMC) and a least
material condition (LMC).
Tolerancing Methods - 4.2
TOC
2615
3.3.1
2615
3.3.4
Table
3-1
Table
3-2
Table
3-3
REF
GLOSSARY QUIT
Although a tolerance can be expressed
as a variation from nominal, unless that
dimension is the true target value it is
better to specify the range for the upper
or lower limit of the tolerance. At times it
may be necessary to provide a
dimension that is only specified as a
maximum (MMC) or minimum (LMC).
But, it should be remembered that the
opposite condition can also result.
Tolerancing Methods - 4.2
TOC
REF
GLOSSARY QUIT
Plated-through holes are usually
specified as needing a minimum of 20
microns [.0008”] of plated copper in the
hole. This requirement is intended to
establish the reliability of the platedthrough hole to serve its function as a
conductor. Many holes are also used as
component mounting holes, therefore
another dimension must be specified to
provide the hole diameter range.
Tolerancing Methods - 4.2
TOC
2221
9.2.1.1
9.2.2.2
Table
9-5
2615
3.3.4
REF
GLOSSARY QUIT
A hole that is specified to be 1.0-.85mm
[.040”-.034”] has a range of 0.15mm
[.006”] from the maximum material
condition (when the hole is at its smallest)
to the least material condition (when the
hole is at its largest). The plating
thickness on each side wall of the hole
must be included in those requirements.
Thus, the board fabricator drills the hole
slightly larger to allow for the plating to
reduce the drilled diameter.
Tolerancing Methods - 4.2
TOC
REF
GLOSSARY QUIT
Location of the feature is also
important. Most holes or other critical
features are located at a basic
intersection of some orthogonal grid.
That point has no tolerance and is
expressed as being the true position of
the feature (basic location). The
tolerance is then applied as a zone
about that location in which the center
of the feature must be located.
Tolerancing Methods - 4.2
TOC
2221
5.4.1
2221
Fig 5-4
2221
5.4.2
REF
GLOSSARY QUIT
Bilateral tolerance zones are square
(plus or minus from true position);
geometric tolerance zones (diameter
or radius of true position) are circular.
Both systems work, however, the
geometric method is preferred.
(Will discuss in next section).
Tolerancing Methods - 4.2
TOC
REF
GLOSSARY QUIT
Section 4.3
Hole Types and Their Tolerances
Printed Board Characteristics
TOC
REF
GLOSSARY QUIT
Dimensions and tolerances are important
characteristics for determining the
location of holes as well as their final
size. Dimensioning principles are
established by ASME Y14.5M. This
document contains a lot of good
information which is followed in
mechanical dimensioning strategies.
Hole Types and
Their Tolerances - 4.3
TOC
REF
GLOSSARY QUIT
There are very few examples of printed
boards or electronic components so the
organizations that develop those
standards have adopted the ASME
Y14.5M principles and provided additional
information for their users; i.e., IPC-2615,
EIA 100, and JEDEC 95. All support the
idea of datums, datum features, and the
various dimensioning systems to allow
manufacturing to produce consistent,
interchangeable parts.
Hole Types and
Their Tolerances - 4.3
TOC
REF
GLOSSARY QUIT
The principles for hole location consists of
three different methodologies. These are:
• The bilateral methoddevelops a
tolerance zone made up of a plus or
minus from a true position or location.
This zone is a square when the plus or
minus dimensions are equal.
Hole Types and
Their Tolerances - 4.3
TOC
REF
GLOSSARY QUIT
• The positional tolerance zonea circular
zone that essentially is equal to the
hypotenuse of the right triangle formed by the
bilateral method (which provides for
additional variation capability in the North,
South, East and West sectors of the zone).
The theory being that if a feature could be off
true position on the diagonal of the square
there isn’t much difference if it were off along
the X Y coordinate lines.
Hole Types and
Their Tolerances - 4.3
TOC
REF
GLOSSARY QUIT
• A third method allows additional
misalignment in that the requirement is
specified as being applicable at Maximum
2221 Material Condition (MMC). Since holes are
5.4.1 at their least dimension they could
theoretically move a small additional
amount from true position considering the
Fig
5-4
difference between the maximum and
minimum hole diameter. Dimensions of this
type are expressed as being a specific
diameter or radius of true position (DTP).
Hole Types and
Their Tolerances - 4.3
TOC
Extra
4.1c
REF
GLOSSARY QUIT
Currently holes in boards are
produced using mechanical drilling.
But, new techniques are being
explored that employ lasers or
plasma etching. Drill sizes come in
increments of 0.05mm [.002"].
Usually the manufacturer prefers to
select the drill to be used in
achieving the desired result.
Hole Types and
Their Tolerances - 4.3
TOC
REF
GLOSSARY QUIT
2222
9.2.1.2
9.2.2
9.2.2.2
Fig
9-3
Table
9-5
Table
9-3
Therefore, most documentation
principles require that the final hole
size is specified. It is best to specify
a range for the hole diameter, as
opposed to the indication of a plus
or minus tolerance from some
imaginary nominal dimension.
Table
9-2
Table
9-4
Hole Types and
Their Tolerances - 4.3
TOC
2222
9.3
Table
9-7
REF
GLOSSARY QUIT
Once the maximum and minimum diameters
are identified the manufacturer can select
the appropriate drill to achieve the desired
end result considering material shrinkage or
plating thickness in the hole. The designer
does, however, need to have an idea of
what drill might be used especially for
determining the annular ring for internal
layers of a multilayer board. The
acceptance requirements are based on
measuring the minimum annular ring from
the wall of the drilled hole.
Hole Types and
Their Tolerances - 4.3
TOC
REF
GLOSSARY QUIT
Hole sizes are either provided in inches
or in millimeters. Drill sizes are in
millimeters and using that method is
preferred on all new designs according
to the international grid identified in IEC
97. This document states that all
features should be on a 0.5mm or
0.05mm grid as opposed to the original
grid of the past which was .100", .050",
.025", or increments of .005".
Hole Types and
Their Tolerances - 4.3
TOC
2222
9.3
Table
9-7
REF
GLOSSARY QUIT
It is not recommended to intermix grids
on the same design. Rather, the best
solution is to select a grid that will
accommodate the majority of the
components. Since component
manufacturers are all supporting metric
dimensioning, most design facilities are
switching their libraries to prepare for
the day when everything is in metric
dimensions.
Hole Types and
Their Tolerances - 4.3
TOC
2221
9.2.7.3
Table
9-4
Table
9-5
REF
GLOSSARY QUIT
Through-holes come unsupported, or
as plated holes (supported). Platedthrough holes go through the entire
board thickness. There are also blind
via holes (open to one side), and buried
vias (inside the board and not exposed
to the outside). All vias are plated
holes. All holes should use the same
system for describing their size limits
and their location.
Hole Types and
Their Tolerances - 4.3
TOC
REF
GLOSSARY QUIT
Section 4.4
Conductive Pattern Location to
Datum References
Printed Board Characteristics
TOC
REF
GLOSSARY QUIT
A datum is the theoretically exact point,
axis or plane, that is the origin from which
the location of geometric characteristics
of features of a part are established. For
printed boards and printed board
assemblies the datum is usually
established by some feature of the board.
The datum feature is the actual feature of
a part that is used to establish a datum.
Conductive Pattern Location
to Datum References - 4.4
TOC
2615
3.3.2
Fig
3-1
REF
GLOSSARY QUIT
Datum features can be holes, tooling
holes, lands, symbols, fiducials, or any
part of the board that the designer
wishes to use in order to control the
board and/or assembly characteristics.
Fig
3-2
Conductive Pattern Location
to Datum References - 4.4
TOC
2221
5.4.3
Fig
5-5A
thru
Fig
5-5E
Fig
5-6
REF
GLOSSARY QUIT
Characteristics that demand very fine
controls may require the use of localized
datum features. Datum features are
used to establish the datum reference.
A datum reference is a point, line, or
plane that is used to locate the pattern
or layer for manufacturing, inspection
purposes, or both.
Conductive Pattern Location
to Datum References - 4.4
TOC
REF
GLOSSARY QUIT
Typically, the designer establishes the
single board image as s/he develops the
circuitry and positions all of the
components. The board manufacturer,
however rarely produces one board at a
time. Board manufacturers panelize the
one-up board and position as many as
possible on a production panel.
Conductive Pattern Location
to Datum References - 4.4
TOC
REF
GLOSSARY QUIT
The assembler also prefers to work in a
panel format. An individual board is
positioned several times on an assembly
panel; several assembly panels are
positioned on the board fabrication
panel. It is for these obvious reasons
that the description of the individual
board feature locations must be clear
and unambiguous.
Conductive Pattern Location
to Datum References - 4.4
TOC
Extra
4.1
2221
5.4.3.1
Fig
5-7
REF
GLOSSARY QUIT
Boards are positioned in many different
orientations (work and turn) to
accommodate plating uniformity or
placement sequencing, thus the
relationship of the original datum
reference is critical in order to maintain
the board feature location perspective.
Conductive Pattern Location
to Datum References - 4.4
TOC
REF
GLOSSARY QUIT
Most designs are accomplished with
the individual board being viewed
having the primary side up, or facing
the viewer. The primary side of the
board is established by the designer
and is usually the side that contains the
most or the most complex components,
however, the selection can be based on
testing or inspection focus.
Conductive Pattern Location
to Datum References - 4.4
TOC
REF
GLOSSARY QUIT
Once established, the first conductive
layer on this side is labeled layer one.
Thus, layer one also faces up. This
orientation and the datum features
establish three mutually perpendicular
planes. The names of these planes are
primary, secondary, and tertiary.
Conductive Pattern Location
to Datum References - 4.4
TOC
2221
5.4.3
Fig
5-5A
thru
Fig
5-5E
Fig
5-6
D325
4.2
Table
4-1
REF
GLOSSARY QUIT
The primary datum plane is opposite the
primary side of the board. When
viewing layer one, which would
essentially be the top of the board, the
last layer would be on the bottom of the
board; it becomes the primary reference
plane from which any Z axis dimensions
should be defined.
Table
4-2
Conductive Pattern Location
to Datum References - 4.4
TOC
REF
GLOSSARY QUIT
The secondary and tertiary datums then
become the X and Y axis of the board.
As such they control the positioning of
the pattern and all other features,
conductive, nonconductive, circuitry,
masking or legend. It is a requirement
that the secondary datum reference be
located with the feature that identifies the
point of origin of all the dimensional
characteristics (i.e. coordinate zero).
Conductive Pattern Location
to Datum References - 4.4
TOC
2221
5.4.3
Fig
5-5A
thru
Fig
5-5E
Fig
5-6
REF
GLOSSARY QUIT
There are cases where only one datum is
necessary for inspection or definition of
dimensions and tolerances. If only one
datum reference is established it would be
the secondary datum, however, angular
deviation could not be specified nor could Z
axis variation from true perpendicular.
These conditions may only affect
acceptance of the final product and may not
be necessary for the manufacturer or
assembler to interpret the location or
dimensional requirements.
Conductive Pattern Location
to Datum References - 4.4
TOC
2221
5.4.3
Fig
5-5A
thru
Fig
5-5E
Fig
5-6
REF
GLOSSARY QUIT
Datums are usually within the
periphery of the board, however there
are times that the point of origin is off
the original single board. It may be a
part of the assembler panel, thus this
is where any inspection and
acceptance of the delivered product
occurs.
Conductive Pattern Location
to Datum References - 4.4
TOC
REF
GLOSSARY QUIT
Section 4.5
Through-Hole Land and Tolerance
Requirements
Printed Board Characteristics
TOC
REF
GLOSSARY QUIT
A through-hole is used for mounting a leaded
component, or it may be used as a via to
make a connection between various layers. A
component hole is a hole used for the
attachment and electrical connection of
component terminationsincluding pins and
wiresto a printed board. A via is a platedthrough hole used as an interlayer connection
where there is no intention to insert a
component lead or other reinforcement
material.
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
REF
GLOSSARY QUIT
There are two varieties of through-holes:
• An unsupported holea hole in a printed
board that does not contain plating or
other conductive reinforcement.
• A supported holea hole that has the
inside surfaces plated or otherwise
reinforced. Two techniques for
reinforcement is metal plating, in the form
of plated-through holes, or the use of
metal eyelets, or eyeleted holes.
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
2222
9.2.1.1
9.2.2
Table
9-3
REF
GLOSSARY QUIT
All through-holes have a copper land
that fully circumscribes the hole.
Landless holes are currently not an
industry standard although many
boards designed for non-severe
environments have used this practice.
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
REF
GLOSSARY QUIT
The accepted design practice is to make
certain that the land (no matter what its
shape) can accommodate the hole. An
allowance for manufacturing tolerances which
includes hole location accuracy, material
movement, layer-to-layer registration and
other variations should be part of the
analysis. Therefore, the hole size plus the
desired resulting minimum annular ring, and
the manufacturing allowance are the
important features that determine land size.
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
2221
9.1.1
REF
GLOSSARY QUIT
The annular ring is the portion of
conductive material completely
surrounding the hole. Annular rings on
external layers of printed boards are
measured by including the plating
thickness in the hole as a part of the
measurement. For internal layers of
multilayer boards, the annular ring is
measured from the drilled hole and
therefore does not include the plating.
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
2221
1.6.3
9.1.2
Fig
9-2
Fig
9-3
Table
9-2
REF
GLOSSARY QUIT
Manufacturing minimum requirements
are organized into three levels of
complexity (Level A, B, and C) to reflect
progressive increases in sophistication of
tooling, materials, and processing.
Minimum annular ring requirements are
defined according to internal supported,
external supported, and external
unsupported. It is good practice to avoid
using minimums unless the design is so
dense that it can not be avoided.
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
REF
GLOSSARY QUIT
To determine the minimum land size all
conditions must be taken into account
including whether or not etchback is permitted
in the hole cleaning process. Etchback is the
controlled removal to a specified depth, of
nonmetallic materials from the side walls of
holes in order to remove resin smear and to
expose additional internal conductor surfaces.
The acid used in the process removes both
the epoxy and glass reinforcement when used
on glass epoxy (FR4) material, as well as
similar copper clad laminate.
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
REF
GLOSSARY QUIT
The following analysis for a non etchback hole is used to
determine minimum land size:
Minimum Land Size = a + 2b* + c
The elements of the equation include:
 (a)  the maximum drilled hole for inner layers
and
finished hole for outer layers
 (b)  the minimum annular ring desired on the
end product at either side of the hole
 (*)  if etchback is permitted, the maximum
amount allowed
 (c)  manufacturing allowance that is based on
the capability of the manufacturers and the
maximum board size
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
REF
GLOSSARY QUIT
If e is the etchback, then:
Minimum Land Size = a + 2(b+e) + c
The elements of the equation include:
 (a)  the maximum drilled hole for inner
layers and finished hole for outer layers
 (b)  the minimum annular ring desired
on the end product at either side of the
hole
 (c)  manufacturing allowance that is
based on the capability of the
manufacturers and the maximum board
size
Through-Hole Land and
Tolerance Requirements - 4.5
TOC
REF
GLOSSARY QUIT
Section 4.6
Coatings and Markings on Printed
Boards
Printed Board Characteristics
TOC
REF
GLOSSARY QUIT
There are several methods used for
coating a bare printed board. The
materials vary in their purpose and
constituents, however, they must all be
compatible with one another if they are
intended to exist on the same board.
All coatings or markings are organic.
Coating and Markings
on Printed Boards - 4.6
TOC
2221
4.5.1
4.6
D325
4.2
Table
4-1
Table
4-2
REF
GLOSSARY QUIT
Solder resist is used as the solder mask
that covers conductors and leaves exposed
areas for attaching surface mount parts.
Permanent marking ink is also nonconductive and consists of a material that
offers a high contrast with the solder mask
and will properly adhere to the mask. The
marking ink must also be able to withstand
all the assembly attachment and cleaning
processes without degrading clarity.
Coating and Markings
on Printed Boards - 4.6
TOC
REF
GLOSSARY QUIT
The materials that come with the
printed board are documented on the
master drawing. Compatibility is key
and the drawing notes must indicate
the requirements in sufficient detail to
avoid a particular process or
temperature exposure at the assembly
from deteriorating the particular coating
or marking.
Coating and Markings
on Printed Boards - 4.6
TOC
2221
4.5.2
4.5.2.1
REF
GLOSSARY QUIT
Conformal coatings are usually used to
protect the assembly from surface
moisture, and in most instances, they
are added after the assembly processes
have been completed and the board
assembly has been tested electrically.
Coatings, like the solder mask may be a
variety of types. The most popular
coatings are: acrylic, epoxy,
polyurethane, silicon, and paraxylene.
Coating and Markings
on Printed Boards - 4.6
TOC
REF
GLOSSARY QUIT
Each has a specific recommended
thickness for coating the assembly,
usually in the range of .05 to 0.1 mm
[.002" to .004"]. There are times when
the coating is added at the bare board
level in selective locations. This is done
for those components that have a large
profile with a small stand-off height,
which would preclude all but the
paraxylene (applied in a vacuum) from
getting under the component.
Coating and Markings
on Printed Boards - 4.6
TOC
2221
4.5.2.1
D325
4.2
Table
4-1
Table
4-2
REF
GLOSSARY QUIT
The coating area is then specified on
the master drawing and becomes the
responsibility of the printed board
manufacturer. Coatings, whether
applied to the assembly or the bare
board, must be compatible with the
solder mask and marking ink if they
are also present.
Coating and Markings
on Printed Boards - 4.6
TOC
REF
GLOSSARY QUIT
Tarnish protective coatings have come
into more use as assembly companies
want to protect the open areas that are to
be soldered and they don’t want to solder
coat them. There are many platings or
metallic coatings that can be used to
protect the copper prior to adding solder.
Some are noble metals such as gold or
palladium, others are non-noble such as
tin or a tin/lead combination.
Coating and Markings
on Printed Boards - 4.6
TOC
2221
4.5.3
REF
GLOSSARY QUIT
Each has a cost associated with the
process or the materials so many
companies are exploring organic
coatings as a method to protect the
copper until the board is ready to be
soldered. The coatings quickly
dissipate when exposed to soldering
temperatures, leaving a surface that
readily attracts solder.
Coating and Markings
on Printed Boards - 4.6
TOC
2221
4.5.3
REF
GLOSSARY QUIT
There are several different types in use today
with the generic name of Benzotriazole,
Imidazole, and Benzimidazole. Each of the
azole’s have a different temperature rating at
which they dissipate. This is required when
exposing the two sides of an assembly to
soldering temperatures at different times.
The higher temperature coating is on the
second side to be soldered, so that it stays in
place; however, it now requires higher
temperatures to expose the lands for
soldering.
Coating and Markings
on Printed Boards - 4.6
TOC
REF
GLOSSARY QUIT
• One of the most popular surface finish types uses
solder as the surface protection metal. What is the
acronym for this process?:
–
–
–
–
OSP
HASL
HAST
SMOBC
Answer:
Quiz 3
HASL
TOC
REF
GLOSSARY QUIT
• What two factors are used to establish the size of an
assembly array?:
–
–
–
–
–
The unit cost per panel
Conveyor width capability
The probe concentration at electrical test
The number of boards required for a production run
The number of assembly arrays that can fit on a fabrication
panel
Answer:
Conveyor width capability and the number of
boards required for a production run
Quiz 3
TOC
REF
GLOSSARY QUIT
• In determining how a board or array will be excised
from its manufacturing panel what three
considerations must the designer take into account:
–
–
–
–
–
–
Copper distribution
Component arrangement
Board construction lay-up
Tooling hole accessibility
Manufacturing removal preference
Maximum conductor clearance from the edges
Answer: Component arrangement
Manufacturing removal preference
Maximum conductor clearance from the edges
Quiz 3
TOC
REF
GLOSSARY QUIT
• Which two factors are the primary influence for the
layer assignment in a multi–layer printed board
structure:
–
–
–
–
–
–
The drilling datum
The primary datum
The secondary datum
The tertiary datum
The zero-zero datum
The component datum
Answer:
The secondary and tertiary datums
Quiz 3
TOC
REF
GLOSSARY QUIT
• Find the minimum land size for plated thruhole in a Class 2, level B board using a 2 mm
drill. Assume etch back is 0.1 mm
From Table 9.1, c = 0.25 mm for Level B design
From Table 9.2, b = 0.05 mm for Class 2 design
Thus, minimum land size = a + 2(b + e) + c
= 2 + 2(0.05 + 0.1) + 0.25
= 2.55 mm