Circuit boards are more complex today than ever before,
but despite how severely damaged they may be, they can
be repaired. Indeed the high value of many circuit boards
demands that they be repaired. Even less expensive assemblies
require repair because just-in-time manufacturing and
tightly controlled production runs leave little room
Just a few years ago, circuit boards were much simpler
and repairs were relatively easy. Today's circuit boards
have fine pitch components, ball grid arrays and fine
line circuits making them a challenge to repair. Yet,
we're driven by simple economics and must repair damaged
circuit boards whenever possible. This Circuit Board
Repair Guide is designed to help you repair and ship
good, reliable circuit boards that might otherwise be
consigned to scrap.
Because of its high demands,
circuit board repair
has been accurately compared to surgery. Whether repairing
surface mount pads or repairing damaged internal circuitry,
the technical knowledge and manual skills needed for
high reliability repair and rework are indeed demanding.
Since today's repair procedures are more sophisticated
than ever before, you need a comprehensive guidebook.
The repair specialists at Circuit Technology Center,
Inc. have used this guidebook to repair thousands of
circuit boards. Circuit Technology Center, Inc. is the
world's leading specialist in circuit board repair and
modification and the procedures described herein are
the same procedures they use to repair and modify circuit
boards. They have been repairing circuit boards for
decades for companies including Digital Equipment Corporation,
IBM, Hewlett Packard, Siemens, Compaq Computer, AT&T,
Allied Signal Aerospace and hundreds of other commercial
and military manufacturers.
Damaged circuit boards may be compared to patients in
a hospital. Some will need a stitch or two while others
will need open heart surgery. To expect a reliable outcome,
each repair project must follow proven and well established
procedures. This guidebook covers the repair and rework
of both surface mount and through hole circuit boards
and assemblies. Not only will this guidebook give you
the details for most circuit board repair procedures,
but it will also explain why certain procedures are
important and answer many questions that you're bound
1.2 - Purpose
This guidebook includes procedures for modifying, reworking
and repairing printed boards and printed board assemblies.
It complies with standards set by the IPC, in Northbrook
IL. The main IPC documents to refer to when using this
Soldered Electrical and Electronic Assemblies
||Rework of Electronic
and Repair of Printed Boards and Electronic Assemblies
Revision levels for each procedure are recorded in the
header section. A complete log of engineering changes
is maintained at Circuit Technology Center, Inc.
1.3 - Classes of
Three Classes of Products are referred to in this guidebook.
Class 1 General Electronic Products
Includes consumer products, some computer products and
computer peripherals, and hardware suitable for applications
where the major requirement is the function of the completed
Class 2 Dedicated Service Electronic
Includes communications equipment, sophisticated business
machines, and instruments where high performance and
extended life is required, and for which uninterrupted
service is desired but not critical. Typically, the
end use environment would not cause failures.
Class 3 High Performance Electronic
Includes equipment for commercial and military products
where continued performance or performance-on-demand
is critical. Equipment downtime cannot be tolerated,
end-use environment may be uncommonly harsh, and the
equipment must function where required, such as life
support and critical weapons systems.
1.4 - Printed Board
Four Printed Board Types are referred to in this guidebook.
Rigid Printed Boards and Assemblies
A printed board or assembly using rigid base materials
only. These may be single sided, double sided or multilayered.
Flexible Printed Boards and Assemblies
A printed board or assembly using flexible or a combination
of rigid and flexible materials only. May be partially
provided with electrically nonfunctional stiffeners
and/or cover lay. These may be single sided, double
sided or multilayered.
Discrete Wiring Boards and Assemblies
A printed board/assembly using a wire technique to obtain
Ceramic Boards and Assemblies -
A printed board or assembly using ceramic as the base
material with interconnections separated by dielectric.
1.5 - Conformance
Conformance Level indicates how closely the repaired
or reworked product will be to the original specifications.
The Conformance Level listed for each procedure should
be used as a guide only. Conformance Levels include
Most closely duplicates the physical characteristics
of the original and most probably complies with all
the functional, environmental and serviceability factors.
Some variance with the physical character of the original
and most likely varies with some of the functional,
environmental and serviceability factors.
Significant variance with the physical character of
the original and may vary with many of the electrical,
functional, environmental and serviceability factors.
Class 3 Products must use procedures rated High unless
it can be demonstrated that a lower level procedure
will not adversely affect the product's functional characteristics.
Class 2 and 1 Products should use procedures rated High
for assured safety and dependability but Medium or Low
Level procedures can be used if it has been determined
that they are suitable for the specific product's functional
Procedures in this manual are given a "Conformance Level"
rating which is described in the following table.
TABLE 1 - Conformance Level
|Electrical - Resistance
|Electrical - Inductance
|Electrical - Capacitance
|Electrical - Cross
|Electrical - High
Future Repair or Mod.
||Procedure may not
comply with functional consideration.
comply with functional consideration but should
be tested to verify.
||Procedure will normally
comply with functional consideration.
1.6 - Skill Level
In the circuit board manufacturing and assembly environment,
most processes are tightly controlled and one-directional.
The technicians who run these processes have certain
defined characteristics and training. As you look deeper
into the repair operation, the first thing that becomes
apparent is that an entirely different set of skills
is needed. Repair skills are more specific. They require
a higher degree of manual dexterity, patience, and a
thorough understanding of the repair process. There
are more steps involved in any single repair operation
than the typical assembly technician would be confronted
with. It becomes a personnel issue as well as a training
one. You must not only have the proper training program,
but the right people.
Repair personnel can't be part-timers and repair circuit
boards only one day a week or on a rotational basis
with other duties. They should be dedicated to the repair
operation and do nothing but repair. For challenging
procedures to be done reliably, they must be done repeatedly.
Furthermore, some repair skills are so specific that
they should be limited to certain individuals who demonstrate
an affinity for the job, rather than attempting to train
a general number of persons to do the same difficult
Considerable supervision is required during the basic
phase of the training operation, with lots of individual
help and attention. The key is not to attempt to move
people too fast on the road to proficiency. It's a step-by-step
approach. Regardless of who provides the training, you
will find that the greatest cost and investment is in
personnel. Personnel are key to the success of the whole
operation. Repair skills training is available from
Circuit Technology Center, Inc..
Three Skill Levels are referred to in this guidebook.
The Skill Level recommended should be used as a guide
Intermediate - I
Technician with skills in basic soldering and component
rework but inexperienced in general repair/rework procedures.
Advanced - A
Technician with soldering and component rework skills
and exposure to most repair/rework procedures but lacking
Expert - E
Technician with advanced soldering and component rework
skills and extensive experience in most repair/rework
1.7 - Tools and
Repair is and may always be a highly labor intensive
operation relying more on individual operator skills
than automation. Despite the availability of very good
tools for repair, many in-house repair operations are
poorly equipped. Here are a few guidelines for the basic
equipment needed in an up-to-date repair operation.
1.8 - How To Set
Up An In-House Circuit Board Repair Department
- Ergonomic Workstation
Good repair work can't be done at an old workbench
or makeshift setup. Performing circuit board repair
requires a high degree of concentration and dexterity.
A proper workstation that is ESD grounded with proper
lighting, outlets, and comfort is therefore essential.
When possible, commonly used systems can be bolted
to the work surface to improve efficiency.
- High Quality Stereo Microscope
Precision repair cannot be done without a microscope
of this type available to the repair operation 100%
of the time. Limited access will not do since it
must be used constantly. Use of video cameras and
monitors, although they may be fine for inspection
or training, should be avoided. They cannot provide
the clarity that quality optics offer. Also, the
microscope needs a good light. Halogen, or fiber
optic lighting systems with flexible goosenecks
to direct the light are the best for this application.
Precision soldering is vital to modern repair operations.
Repair technicians can't get by with the traditional
soldering tools that were commonly used as recently
as a few years ago. They need the very best soldering
irons that are highly controlled, ergonomically
designed and feature a wide assortment of small
- Component Removal Tools
Today's expanding variety of large and small components
require an array of special use tools and methods
for safe, efficient component removal. These tools
generally use either conductive heating (by contact),
convective heating (by hot gas) or infrared heating
(by focused infrared lamps). Each method has its
own advantages and disadvantages depending on the
- Preheating Station
When possible, you should preheat the entire circuit
board before SMT component removal. Preheat minimizes
thermal shock due to localized heating in the rework
area, and speeds up the rework process. Most facilities
have a curing/drying oven, but a preheating station
for maintaining heat in addition to the oven is
often necessary. A hotplate-style preheater or infrared
heater will maintain the temperature of the board
after it is taken out of the oven, or can heat the
board up from ambient temperature.
Some manufacturers of ceramic
chip capacitors recommend
that the Preheat Ramp Rate not exceed 2-4 °C/Sec.
- Micro Drilling and
Bulky, hand-held drilling and grinding tools that
have both the motor and power supply contained within
the handpiece are difficult to manipulate for the
kind of detailed work that is necessary in repair.
The type needed is preferably a lightweight, high
quality, dental style drilling tool.
- Precision Drill System
Repair and rework projects often require the need
to make precise holes, slots, grooves etc. Precision,
accurate depth control and high speed are a must.
The ideal system should have a base plate to pin
circuit boards in place and an optional microscope
- Replacement Circuits
Circuits and surface mount pads can be replaced
using liquid epoxy, but liquid epoxy can be messy
and unreliable when replacing fine pitch pads. Pads
are available with a dry film adhesive on the back.
These replacement pads and circuits are heat-bonded
to the board surface, and are available in any pattern
that you might need.
- Gold Contact Plating System
Plating gold edge contacts or any metal surface
is a serious business. The chemicals used are hazardous
and must be handled properly. The power applied
to the plating surfaces must be controlled accurately
to expect reliable results. A good plating systems
should include the following: a DC power supply
with voltage and current meters, plating anodes
sized for gold edge contact plating, a solution
tray to collect the solution runoff, a support for
the circuit board and a tray to hold and store the
various chemicals safely.
- Base Board Repair
Kits and Coloring
For many repair operations you need high strength,
high temperature epoxies. You should select a two-part
epoxy because they offer the high strength, thermal
resistance and durability that one-part and quick-setting
epoxies do not have. It is also important to have
masks or coloring agents so that you can restore
the cosmetic appearance of the board. It is best
to cure the epoxies in an oven if possible.
- Circuit Board Eyelets
and Circuit Board Eyelet
Solder plated copper eyelets and an eyelet press
to repair damaged plated through holes is generally
It's a fact that far more printed circuit assemblies
are damaged during the manufacturing process than they
are in the field. And even though circuit boards are
more complex today than ever before, they are still
repairable. Ten years ago boards were much simpler,
and repairs were easy; but the assemblies also cost
a great deal less. Today's printed circuit manufacturers
and assemblers are driven by simple economics. They
must repair damaged circuit boards. The primary question
is whether to develop and maintain a full repair department
in-house, or to contract the repair out. Which choice
makes the most sense?
IPC defines Rework and Repair as follows. Rework - The
act of reprocessing non-complying articles through the
use of original or equivalent processing, in a manner
that assures full compliance of the article with applicable
drawings or specifications. Repair - The act of restoring
the functional capability of a defective article in
a manner that precludes compliance or the article with
applicable drawings or specifications.
Repair encompasses much more than simply rework, i.e.
removing/reattaching components. You must be prepared
to make a real commitment in several key areas if you
plan to complete repair work in-house. If not, you are
better off contracting the work out to a reputable repair
facility. In reality, more damage can be done to a board
from a botched repair than from most other causes. Aside
from soldering and desoldering, other aspects of repair
can include replacing damaged circuits, gold contacts,
and SMT pads; re-plating solder-contaminated gold contacts,
repairing burns or physical damage to the laminate,
repair of through-holes, and more. Both contract manufacturers
and OEMs will benefit from establishing a good in-house
Five Keys to Reliability
There are five basic requirements needed for successful
implementation of a high quality circuit board repair
1. Documented Standards
2. Documented Procedures
3. Comprehensive training
4. Modern, Up-To-Date Equipment
5. Highly Skilled Technicians
- Documented Standards
The key starting point, of course, is a good set
of documented standards. Standards will establish
which types of defects are acceptable as is, and
which are not. Although most major manufacturers
have their own set of acceptance standards, the
small manufacturer can obtain commercially-available
guidelines, in particular from the IPC. Specific
documents include IPC A-600 and IPC-A-610. A good
working knowledge of these standards can prevent
- Documented Procedures
Every repair operation, whether it be replacing
a pad or re-plating a gold contact, requires a specific
set of procedures. The goal of this book is to provide
you with a detailed explanation of each procedure.
If you need more information, an excellent additional
reference source are the IPC's publications IPC-7711
Rework of Electronic Assemblies, and IPC-7721 Repair
and Modification of Printed Boards and
These IPC publications, along with this Guidebook,
should be an integral part of your repair department
and can serve as a tool for training repair personnel.
To obtain copies of these publications, contact
the IPC in Northbrook, IL. Copies can also be obtained
from Circuit Technology Center, Inc.
Once you know what can be repaired and have the
necessary guidance to proceed, the next step is
completing the repair, and that requires qualified
personnel. Of course, even the most highly skilled
technicians require training if they are to perform
their best. For your Rework and Repair Program to
obtain successful results, operators and technicians
must be properly trained.
- Comprehensive Training
Repair personnel can't be part-timers and repair
only one day a week or on a rotational basis with
other duties. They should be dedicated exclusively
to the repair operation. The reason for this is
to develop a high level of skill and maintain it
through repetition. For many challenging aspects
of repair to be done reliably, they must be done
repeatedly, such as the replacement of fine-pitch
surface mount pads.
Furthermore, some repair skills are so specific
that they should be limited to certain individuals
who demonstrate an affinity for the job, rather
than attempting to train a general number of persons
to do the same difficult task. Considerable supervision
is required during the basic phase of the training
operation, with lots of individual help and attention.
The key is not to attempt to move people too fast
on the road to proficiency. It's a step-by-step
approach. Other companies may do it differently,
but this is our method. Regardless of who provides
the training, you will find that the greatest cost
and investment is in personnel. Personnel are key
to the success of the whole operation. Equipment
costs are actually quite low in comparison. Why?
- Modern, Up-To-Date Equipment
Repair is and may always be a highly labor intensive
operation relying more on individual operator skills
than automation. Despite the availability of very
good tools for repair, many in-house repair operations
are poorly equipped.
- Highly Skilled Technicians
In the circuit board manufacturing and assembly
environment, most processes are tightly controlled
and one-directional. The technicians who run these
processes have certain defined characteristics and
training. As you look deeper into the repair operation,
the first thing that becomes apparent is that an
entirely different set of skills are needed by repair
personnel compared to assembly personnel. Repair
skills are more specific. They require a higher
degree of manual dexterity, patience, and a thorough
understanding of the repair process. There are more
steps involved in any single repair operation than
the typical assembly technician would be confronted
with. It becomes a personnel issue as well as a
training one. You must not only have the proper
training program, but the right people.