PCB 101 - How To Build a Circuit Board

 How to Build a Circuit Board
PCB 101

 DELIVERING QUALITY SINCE 1952.

America's Oldest,
A History of Innovation


Privately held company, established in 1952.



Estimated 2013: Sales: US$40 Million



100+ Employees Worldwide
(70 – North America, 30 – Asia, 3 – Europe)



Design and manufacture customized, built-to-print,
performance-critical products for all sectors of the
electronics industry.



Leading provider of printed circuit boards, membrane switches, graphic
overlays, silicone rubber products, electronic heaters, fans, motors and
custom battery packs.



Integrated supply chain management solutions to handle the complexity of
today’s global marketplace while making sure that every order is being
manufactured at the “right” factory.
2

Global Operations

Significant Investment in People and
Facilities across the globe.
3

Our Customers - The Top Global
OEM’s In Growth Industries

4

Our Products

Battery Packs

Flex & Rigid-Flex PCB’s

User Interfaces

Fans & Motors

Cable Assemblies

Printed Circuit Boards

5

PCB Design and Layout
Our Capabilities Encompass The Full Design Flow From Start To
Finish Including:
Micro

BGA / Micro Via / Blind and Buried Vias
Rules Driven Designs
Schematic Capture
Library Development
Database Construction and Verification
Signal Integrity/Design Verification
EMI Checking
Full Document Package Creation
Electrical Engineering Expertise

We

are fully licensed and utilize industry leading tools, including Cadence Allegro, Mentor Expedition,
Mentor's PADS, Altium, Valor for DFM Analysis.
6

How to Build a Circuit Board
PCB 101


Customer Supplied Data
– CAD
• ODB++, Gerber, Gerber 274X
• Netlist (IPC-D-356)

– Drawing Package
• Fabrication drawing
• Readme File
• Specifications

7

PCB 101


Cam Deliverables
– Conversion of Customer Supplied Data to Tooling



Panelization
– Optimized manufacturing Panel
– Customer defined sub-panels or arrays



Artwork
–
–
–
–

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Inner Layer
Outer Layer
Soldermask
Legend

Drill and Rout Programs
– Excellon format ASCII
8

PCB 101


Engineering Strategy
– Epec’s Front End Engineering Department uses state of the art software to identify
and reduce or eliminate unnecessary manufacturing costs.



EpecDFx - Perfecting the DFM Process

– EpecDFx goes beyond DFM (Design for Manufacturability)
• Design for cost
• Design for functionality
– ALL jobs are processed through EpecDFx checking for:
• Shorts
• Opens
• Line widths
• Spacing issues
• Mask problems
• Legend problems
• Inner layer plane problems
• Controlled impedance
• Unused pads (and removal of same)
9

PCB 101


Cores/Laminate
– A thin laminate material (usually under .250” thick) consisting of a glass epoxy
substrate clad with copper on both sides.
– The size of the core is larger than the finished size of the board.

Copper Foil

Laminate
10

PCB 101


Laminate: CEM-1
Low cost – Single Sided Industry standard for low cost single sided PWB.

– Material of choice for low cost, single sided PWB applications
– Suitable for low to moderate board rigidity requirements (lowest rigidity of these
three laminates)
– May not be suitable in environments where moisture absorption is of high concern
COPPER FOIL

CEM-1: A 5-ply composite composed
of one ply of epoxy-resin impregnated
glass cloth above and below a 3-ply
epoxy-resin coated paper core.

EPOXY-RESIN GLASS CLOTH
3-PLY KRAFT PAPER CREATING AN
EPOXY-RESIN COATED PAPER CORE

EPOXY-RESIN GLASS CLOTH
11

PCB 101


Laminate: FR-4
– Industry Standard Rigid PWB Laminate
– FR-4 is truly the most generic laminate
– Many different manufacturers offer products with different characteristics

COPPER FOIL



FR-4: Eight weaves of fiberglass
cloth laminated together with an
epoxy resin. (60% Glass / 40% Resin)

EIGHT WEAVES OF FIBERGLASS
CLOTH LAMINATED TOGETHER
WITH AN EPOXY RESIN

COPPER FOIL
12

PCB 101


Dry Film Resist Coat
– A light sensitive film is applied by heat and pressure to the copper surfaces of the
core



Photo Tools & Artwork
– These are placed on the film coated surfaces of the core
– Artwork patterns are customer designs containing circuit and land patterns specific
to that part number
– Each surface has its own artwork pattern

Etch Photoresist
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PCB 101


Expose
– Panels are exposed to ultra-violet light
– Clear areas allow light to pass through and polymerize (harden) the film resist thus
creating a latent image of the circuit pattern



Develop
– The exposed core is passed through a chemical solution removing the resist from
areas not hardened (polymerized)

Artwork

14

PCB 101


Etch
– Copper is chemically removed from the core in all areas not covered by film resist
– This creates a discrete copper pattern
– Core surface now shows through in areas where copper was etched away

15

PCB 101


Strip Resist
– The developed dry film resist is now chemically removed from the panel
– Copper remains on the panel only in the patterns described by artwork

16

PCB 101


Oxide Coating
– Copper is chemically treated to “rough-up” surface
– Rough surface improves adhesion to prepreg during the lamination cycle
– Oxide is typically black, though other types exist, i.e. Brown and Red

17

PCB 101


Multilayer Lamination
– Materials Needed:
• Copper Foil
• Prepreg
• Cores



Prepreg
– Multilayer “glue”
– Fiberglass cloth preimpregnated with partially cured epoxy resin
– Also known as B-stage



Copper Foil
– Typically in sheets at ½ oz. or 1 oz. per square foot in weight (.0007 and .0014
inches nominal thickness respectively)

18

PCB 101


Laminated Blank
– Inner Layer Core, Copper Foil and Prepreg are bonded together under heat and
pressure, usually in a vacuum, during the lamination process
– Prepreg resin is activated and “melts”, flowing across the layer to create a bond.
– Half-sheets are produced during this step
– Half-sheets are then cut or fabricated (fabed) into panel size



Primary Drilling
– Double Sided/Single Sided Start here
• Holes are drilled through a stack of panels (usually 2 to 3 high)
• Drilled holes are typically .005” larger than finished plated through hole size

19

PCB 101


Drill
– Holes are CNC drilled to specific coordinates from the data supplied after it is
formatted

Inner Layer
Laminate
Copper Foil

20

PCB 101


Multilayer Stack-up
(Cross Section)
4 Layer

6 Layer

Copper Foil
(.5, 1, 2, ... ounces)

Double sided core
(.028 for 4 layer)
(.014 for 6 layer)
(.008 for 8 layer)
Copper weight up to 3 ounces

B-stage Prepreg
(Bonding Sheets)
8 Layer

21

PCB 101


Deburr & Clean
– A mechanical process where copper burs are removed from the panel
– All debris is cleaned from drill holes



Desmear
– Applies to multilayer boards only
– A chemical process where the coating of resin, produced by the heat of drilling, is
removed from the hole wall

22

PCB 101


Copper Deposition
–
–
–
–

Also called electroless copper
A thin coating is chemically deposited on the surface of the panel and hole walls
This creates a metallic base for subsequent electroplating operations
Typically thickness is 80-100 millionths of an inch

Electroless
Copper

23

PCB 101


Dry Film Photo Resist Coat
– The panel is pre-cleaned
– Light sensitive film is applied, using heat and pressure, to the copper surfaces of
the laminated “blank”
– Film also covers, or tents, all drilled holes

Inner Layer
Laminate
Copper Foil
24

PCB 101


Expose & Develop
– The panel is then exposed and developed
– Similar to the inner layer process for the core
– Holes that are to be plated have tents developed off

Photoresist
Artwork
25

PCB 101


Copper Pattern Plate
–
–
–
–
–

Also called electroplating
Additional copper is electrically plated onto the exposed electroless copper surfaces
Copper thickness is approximately 1 mil
Tin is also plated onto all copper surfaces
Typical tin thickness is .3 - .5 mils

Electroplated
Copper
Resist Metal (tin)
26

PCB 101


Etch
– Copper is now removed any place not covered by tin
– The tin acts as an etch resist
– Traces and pads, as defined by the artwork, are now left on the surface of the panel

27

PCB 101


Strip Resist
– The developed dry film resist is now chemically removed from the panel
– Tents that were placed have prevented plating to occur in holes designed to be
non-plated

28

PCB 101


Solder Mask & Cure
– A Liquid Photo Imagable mask, is applied to each surface and dried to the touch,
–
–
–
–
–
–

but not cured
Artwork is applied and exposed
Panel is developed, leaving mask in pattern described by artwork
Panels are cure baked
Mask protects panels from contamination and handling damage
Solder mask is a non-conductive material
Laminate is a natural color, solder
mask gives the circuit board its
final color, typically green

Solder Mask
29

PCB 101


Hot Air Solder Leveling (HASL)
– Panels are processed thru a bath of molten solder, covering all exposed copper
surfaces

– High pressure hot air, directed at both sides of the panel simultaneously, removes
excess solder from the holes and surfaces

– While HASL is still the most common
PCB surface finish, many other
options exist that will allow our
customers to meet their end
product needs.

Solder

30

PCB 101


Surface Finishes
– RoHS Compliant:
•
•
•
•
•
•
•
•

Organic Solder Preservation (OSP)
Single and Multi-Pass
Lead-free HASL
Nickel Plate
Nickel/Gold
Palladium – Nickel
Immersion Tin
Immersion Silver

– Not RoHS Compliant:
• Hot Air Solder Leveling (HASL)

31

PCB 101


OSP Surface Finishes
– Single-Pass – single soldering operation (or heat cycle)
– Multi-Pass - able to survive multiple heat excursions for SMT applications
– Coating is molecular in thickness and is compatible with most flux systems,
including “no wash” systems
– DOES NOT CONTAIN LEAD!

32

PCB 101


Lead Free HASL
– There are several types
• SN100 (most common in China)
– Tin – trace of Copper < 0.7%
• SAC305 – Limited availability
– Tin – 3.0% Silver - .05% Copper

– PCB is conveyed through the flux station, then through the solder bath and finally
through a set of air knives that remove (level) excess solder
– Thickness varies - Generally somewhat thinner than regular HASL:
• From .000100” to .001500”
– Lead Free HASL provides a solderable surface with most flux systems and is also
suitable for most surface mount applications

33

PCB 101


Ni / Au Plating
– Electroplated Deposit
• SMOBC – soldermask used as plating resist
• We will only plate Ni/Au after etching – we will not use Ni/Au as an
etching resist
• All circuits or features which will be electrically connected with plating buss (tie
bars)
• Thickness for Gold: .000005” to .000050”

– ENIG – Electroless Nickel/Immersion Gold
• Bussing (tie bars) not required
• Max. Thickness for Gold: .000002” to .000005”

34

PCB 101


Immersion Tin (Also known as White Tin)
– Excellent Co-planarity
– Shelf life equal to or exceeds HASL
– Will solder after multiple heat cycles – Solder paste, reflow, glue dot
and wave soldering
– Less dimensional stress than with HASL
– No special handling required

35

PCB 101


Immersion Silver
–
–
–
–
–

Totally flat topography
More solderable than copper
Does not require special handling like OSP (white gloves, etc.)
Shelf life is 6-12 months depending on storage conditions
Can withstand 5 temperature cycles

36

PCB 101


Hot Air Leveling (HAL, HASL)
63/37 Solder Coating
– PCB is conveyed through the flux station, then through the solder bath and finally
through a set of air knives that remove (level) excess solder

– Thickness varies:
• From .000100” to .001500”

– HASL provides a solderable surface for all flux systems and is also suitable for
surface mounted applications

– Still the most common protective coating used in PCB manufacturing

37

PCB 101


Legend & Cure
– Ink is silkscreened onto each side of the
panel as described by customer artwork
– The printing details component placement
and other surfaces details desired by
the customer
– Panels are baked to cure the ink



Legend & SMT

Nomenclature

Legends can create problems for the PCB manufacturers.
– Many designers put a box completely surrounding SMT pads to indicate component
placement
– Often the tolerances required to screen print legend are not considered. Avoid
narrow fonts, text height less than .040” and trace width below .006”
– Ask your designer to provide adequate clearances around SMT pads

38

PCB 101


Legend Placement Around SMD Pads

Too Tight

Good

39

PCB 101


Fabrication / Routing
– The board is cut to size
– Also known as routing, scoring, punching or profiling
– Chamfers and slots are also added during this step

40

PCB 101


V-Groove Scoring
Engineers see scoring as a way to save. It does save from a material utilization basis,
but there are tradeoffs. Tolerances must be relaxed on the finished piece part to allow
for these tolerances. Furthermore, scoring has one of the highest fallout rates of any
process in manufacturing.
Score line to Score line

+/-.005”

Score line to holes

+/-.007”

Score line to Artwork

.015 - .020

Finished part tolerance

+.015/-.010

Web Remaining

+/-.005”

Typical Web remaining for each laminate
CEM-1

.030”

CEM-3

.030”

FR-4

.015”

HIGH Tg FR-4

.012”

41

PCB 101
V-Groove Scoring
Scoring: Usually defined as “Web remaining.” This defines the amount of material remaining. The
cutter has a 30 degree included angle. (45 and 60 degree cutters available)
* Note how the width of the score line changes with the depth of cut.

0.008

Typical for FR-4

0.010

0.015

0.013

0.030



Typical for CEM1 and CEM-3
0.012

42

PCB 101


Copper Weight vs. Minimum Spaces
–
–
–
–
–

1 ounce copper - .008” between adjacent features

43

PCB 101


Electrical Test
–
–
–
–
–

Board is tested for electrical integrity, and if required, impedance
Data can be directly loaded from CAM to test machines in some cases
Most tests are feasible. Repairs of shorts and opens are also done at this point
Smaller lots tested on a flying probe, larger volume on a bed of nails test fixture
IPC Netlist is used if supplied by the Customer

44

PCB 101


Functions Performed Throughout the Process:
– AOI
• Automatic Optical Inspection
• Inner layers and outer layers are tested against downloaded CAM data for
integrity, and against design rules
• If allowed and feasible, repairs are made at this point
• Data is fed back to
appropriate departments
to correct process
problems

45

PCB 101


– Reliability Lab
• In-house capability to test for compliance to many customer and industry
requirements
• Environmental Cycling, Ionic Contamination, Surface Insulation Resistance are
a few tests performed.
• Data is fed back to departments and customers as required

46

PCB 101


– SPC
• Statistical Process Control
• Method used both on and off-line to determine if process and product is
performing as expected
• ONLY reliable method to make process changes
• Often required by customers

47

PCB 101


PCB Design Concerns
– Hole Size
• >10 Mils drilled standard
• 8 – 9 Mils, leading edge
• 5 Mils, bleeding edge
• Note: Drilled hole size typically
is .003”-.005’ larger than FHS



PCB Design Concerns
– Line/Space
• 5/5 standard
• 3/3 leading edge

– Aspect Ratio
• 8:1 standard
– 0.080” min hole size for 0.062”

– Pad Size
• 10 Mils over drilled hole

• 12:1 leading edge
– 0.005” hole for 0.062”

diameter standard
• 8 Mils leading edge
• PWG/GRD Clearance – 20 mils
over drill

48

PCB 101


PCB Manufacturing Concerns
4 Layer Off Center Construction

.024”

.024”

.006”

Warpage Issues

Meets flatness specification

49

PCB 101


Manufacturing / Design Concerns
Plating
– External copper thieving is recommended to be added to low-density areas to even
out copper distribution. Typical thieving pattern is .030” squares on .050” centers.
– The absence of copper thieving result in high, or over plating of isolated features,
typically differential pairs. It can also cause pitted appearance on fiducial pads,
which will cause assembly problems.

50

PCB 101


Panelization
– PWB’s are manufactured on standard
–
–

–
–

panel sizes
Cost is a factor of the number of individual
cards on a production panel
Impedance/Mil coupons, if required,
are placed in the production panel
May effect panelization yield, i.e. $$
Industry standard panel size is 18” x 24”
General rule:
• 0.750” border all 4 edges
• 0.100” spacing between images

51

PCB 101


Sample Fabrication Drawings/Notes

52

PCB 101


Price Considerations
– Low Cost Factors
•
•
•
•
•

Complex Routing/Scoring
Edge Routing
>0.093” Thick PWB’s
<0.030” Thick PWB’s
High Tg vs. low Tg Materials

– High Cost Factors
•
•
•
•
•
•

Advanced Technologies
Buried Vias
Layer Count
Material Utilization
Selective Plating
Line Width and Space

– Medium Cost Factors
•
•
•
•

High Drill Hole Quantity
Plated hole tolerance less than +/- 0.003”
Edge Plating
Drilled holes <0.010”

53

Industry’s Leading Online Tools


Sign up today and try InstantPCBQuote™, the most
flexible and user friendly internet quoting and ordering
tool in the PCB industry.



Try it Now!
www.epectec.com/instantpcbquote

54

World Class Quality Assurance
& Engineering


US Based QA Capabilities Include:

– Full Cross Section/Microsection Reporting and
–
–
–
–

Ionic Testing Equipment
X-Ray Fisherscope for all Metal Thickness &
Purity Measurement on every lot.
Scienscope DMP-1000 stereo zoom
microscope with digital picture capability up to
100x
Vision Engineering Mantis Elite for 10X full
range visual inspection.
World Class Electronics Test Lab
 Epec’s

superior on-time delivery rates
are the result of our significant,
dedicated engineering resources and
processes.
– Perform all DRC, DFM, Graphic Art and
Engineering reviews at our Engineering Center
outside of Boston, MA
– Documentation of all manufacturing and detailed
planning processes, for all special requirements,
– Consistent documentation and tooling at all
manufacturing locations to ensure seamless
prototype through production manufacturing.

55

Design Centers &
Technical Support










Battery Pack & Power Management – Denver, CO
User Interfaces – Largo, FL
Fans & Motors – Wales, UK
PCB’s – New Bedford, MA & Shenzhen, China
Flex & Rigid Flex – Toronto, Canada
Cable Assemblies – New Bedford, MA
Heaters & Sensors – Boston, MA
Our Engineering and Design teams are ready to help
our customers create world class and cost effective
product solutions.
56

Inventory Management


Customer requirements are always unique and customized, therefore
our inventory management system must accommodate for this type of
environment.



We Offer:
– Kanban
– Consignment
– JIT Programs
– Blanket Orders
– Customer Fulfillment
– Bonded Warehousing
– Kitting
– Safety Stock
– Other flexible solutions
57

The Difference is Quality and Delivery
1.

Quicker Delivery - Epec's technology infrastructure and people, including the

Asian and US based operations, manufacturing and engineering teams, enable jobs to
get started the same day the order is received with no delays.
2.

Accurate Information - Epec's proven supply chain and manufacturing

experience allows accurate daily Work In Process reporting so customers can receive
immediate order status information.
3.

Better Quality - Epec ensures higher levels of quality through actual investment
in all of our processes. Whether it is our 10+ people strong quality organization in
Asia, equiping our tech centers with the latest tech gear to test parts, or our
continuous improvement auditing process, real investment is made to ensure quality.

4.

Flexibility - Each of our manufacturing facilities have been selected for their

best-in-class niche product and delivery and techology solutions, ensuring our optimal
facility is building every order.

58



If you require additional information please contact us with any
questions or requests.
North American Headquarters
174 Duchaine Blvd.
New Bedford, MA 02745
Tel: (508) 995-5171
Fax: (508) 998-8694

Contact Us By Email:
Sales
Quotes
Engineering

sales@epectec.com
quoting@epectec.com
engineering@epectec.com

Visit Our Website For More Information
www.epectec.com

Stay Connected with Epec Engineered Technologies
Join our Social Community and keep in touch with all our latest technology investments, current news, upcoming
events, and promotions. Visit our Social Media Websites for more information.

59

PCB 101 - How To Build a Circuit Board

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