When choosing a PCB supplier, site inspection and qualification testing
are important, but doing your homework ahead of the facility visit can
save time and money.
Many large original equipment manufacturers (OEMs) have a detailed
procedure and a significant capital investment in place for the
selection of printed circuit board suppliers. This approval process
typically involves one or more site audits, which, as we know, now
involves a significant amount of overseas travel, and non-destructive
and destructive qualification testing by a third-party laboratory.
This is all well and good if your company has what seems like unlimited
funding to carry out this process, but where does this leave the small
OEM? This paper is intended to help smaller OEMs get the most for their
money and purchase a quality product. I was recently in a meeting with
a new IPC member who was also new to the electronics industry, and he
made the following statement regarding qualifying suppliers: “We go to
the PCB supplier’s facility for a tour. They take us to lunch, and they
are approved.” He also asked in this same meeting: “Where in IPC
can I go for help to better understand what I should do?” We did not
have a good answer to his question.
Within the past year and a half, a blue ribbon committee has been
started to assess the feasibility of IPC having a PCB Qualified
Suppliers List similar to that of the military for MIL-PRF-31032,
MIL-PRF-55110 and MIL-P-50884. This will most likely take a few years
before we see this come to fruition. In the interim, this paper will
provide some basic guidelines in assessing your supplier’s board at a
cost that is reasonable to your company.
Hypothetical Case Study
A military/commercial ODM (original design manufacturer) has been
supplying Class 3 product to its customers. Its product is incorporated
into the guidance system of a commercial airplane. The ODM believes
that it has the quality of its circuit boards under control by
specifying IPC-6012, Class 3 on its drawings. The OEM begins to report
failures of the unit, luckily without the loss of lives. The OEM
experiences downtime and flight delays. The OEM is holding the ODM
responsible. The ODM receives the failed unit for a complete root cause
failure analysis. The analysis of this lot of assemblies and other lots
from the same supplier show plating cracks attributed to a copper
ductility issue. The ODM visits the PCB manufacturing facility for the
first time to review these findings and to audit the facility and
discovers that the manufacturer states that it builds to IPC-6012,
Class 3, but that it has done none of the qualification, conformance or
acceptance testing to verify that its product, indeed, meets the Class
3 requirements. Of course, the ODM can hold the PCB manufacturer
responsible but not before enduring numerous court battles and the loss
of its largest client’s confidence in them.
Could this happen to you? Do you have an approved PCB supplier list?
How did you qualify those suppliers? As can be ascertained by the
hypothetical case study above, responsibility for purchasing PCBs for
assembly and incorporation into an end product must not taken lightly.
The Military’s Qualified Products List
The military was the first to develop a Qualified Product List (QPL)
for PCBs, and much can be learned about developing an Approved Supplier
List by reviewing the military process of maintaining a QPL.
MIL-P-55110 governed rigid boards and MIL-P-50884, flexible circuits.
In the past, the Department of Defense (DoD) was on the forefront of
advancing technology. Currently, the commercial industry has taken the
lead, and the military is benefiting from these advances. The military
has now moved to maintaining a QML or Qualified Manufacturers List.
What is the difference between a QPL and a QML? The QPL was geared
toward qualifying specific products, based on material type and design
complexity. The current QML system is based upon military certification
of a supplier’s process. PCB manufacturers who have a greater
understanding of their processes, a mature quality system and a
Technical Review Board (TRB) follow the MIL-PRF-31032 document. The PRF
stands for performance. MIL-PRF-31032 allows the manufacturer greater
flexibility to advance to more complex technology levels without having
to wait for new specification revisions to be released.
Commercial PCB Standards
“In the fall of 1957, six printed circuit board manufacturers came
together to create the Institute for Printed Circuits. What did they
have in common? A desire to promote the new technology of printed
wiring boards and the need for industry standards to create common
ground between themselves and their customers. From that day, IPC was
dedicated to removing supply chain obstacles, creating industry
standards, and supporting the advancement of the industry.” (Excerpt
from IPC Review, Vol. 48, No. 1: January 2007, page 12.)
Engineers in the field 50 years ago were in it from the beginning. They
have seen PCB products evolve over the years. This group of individuals
has knowledge that our new engineers lack -- where the PCB came from.
Having a historical perspective allows one to understand the PCB board
process and what attributes are acceptable and which are not. Due to
the shift of founding members out of the industry and into retirement,
less experienced engineers are given the position of supply chain
manager and are given the responsibility of generating and maintaining
an Approved Supplier List. Often, individuals promoted to this position
within a small OEM lack the knowledge of how a PCB is made because
their company specializes in assembly processes, not board design.
There are a number of things that can be done to determine if a PCB
supplier will be a good fit for your company. The usefulness of a tour
of a potential PCB shop should not be discounted, but there are often
serious quality issues that cannot be uncovered by a tour alone.
Qualifying Your PCB Supplier
Assessing a potential PCB supplier can be very simple to very complex
based on the resources available to the company. This guideline is
aimed at smaller ODMs and OEMs. A few inexpensive microsections would
add significantly to the “tour” approach of qualifying PCB suppliers.
An outline of steps that may be taken to generate a list of potential
suppliers and how to go about qualifying your supplier is shown in
Figure 1. It is not necessary to complete all of the steps to gain
confidence in the supplier, but completing as many as funding allows is
key.
Determine how many suppliers are needed. The trend today is limiting
the number of companies on the Approved Supplier List. The purchase of
PCBs is no exception. Narrowing the list to a few technically strong,
reasonably priced suppliers gives the purchaser greater power to get
what they want because they will be a major customer. Providing a
recommendation for the exact number with which to start is not possible
because this number will vary based on the range in products required
for purchase. One word of caution: do not sole-source if at all
possible. The uncertainty in the electronics industry, particularly in
PCB production, can put you at risk of losing a single supplier of a
high-demand part number (P/N). If your target is to have at least two
suppliers for each P/N, then starting with at least three or four for
consideration is probably a good idea.
The initial list of names may be gathered from an Internet search
and/or attending industry meetings or tradeshows. Tradeshows are the
best way to make an initial contact and have face-to-face discussions.
Although the initial contact is often with a sales representative,
technical support staff are often available to visit your facility
following the tradeshow. As most people are well aware, a tradeshow
allows you to meet with several potential suppliers in one convenient
location.
Furthermore, DSCC (Defense Supply Center Columbus), QPL and QML lists
are publicly accessible. Considering a PCB supplier that is on one of
these lists allows you the benefit of knowing that they have quality
processes in place and have been held accountable to the government
with regards to product quality. Additionally, IPC’s PCQR2, Printed
Board Process Capability, Quality, and Relative Reliability listing is
a paid subscription to a supplier database. Finally, PCB suppliers who
are contributing members to the IPC-6012 rigid board and/or IPC-6013
flex circuit technical committees are also more likely to be up-to-date
on the latest industry technology and requirements.
Determine if the location of the supplier is important. Are there any
restrictions placed by your end customers regarding overseas
production? This restriction is most common in the defense industry.
Purchase orders and drawings must be carefully evaluated to determine
if this restriction applies. Can your company afford overseas travel to
visit/audit your supplier? Is your company willing to deal with
communication difficulties and a 12-hour time difference? Assessing
cost versus projected obstacles is typically the means used to make
this decision. Having a sales representative or technical liaison
present in the overseas country can alleviate unforeseen issues
tremendously. If having US suppliers is critical to your company, is
the location within the US important? If you are located on the West
coast, is it important that you be able to drive to or take a short
flight to visit a supplier to discuss a problem immediately?
Determine which suppliers are capable of building the product you
require. To begin, Web site advertising of capability level may be
useful. From your search up to this point, isolate those suppliers that
are capable of meeting the layer count that you require. Determine
which suppliers specialize in the materials you are required to use.
For example, shops dealing with high-speed materials can be very
specialized. Do you need to purchase rigid boards or flexible boards or
both? Are you dealing with high-density interconnect (HDI) designs? Do
you require a manufacturer capable of building a high-current board? Is
there a particular company that specializes in circuit boards for the
industry you serve; for example, implantable medical devices; medical
equipment; military; telecommunications; Class 2 commercial products
such as cell phones or televisions; or Class 3 high-reliability
products, such as airplane controls or automotive safety
devices)? Make a checklist of the capabilities required before
starting a search, and you will be certain not to waste time completing
the steps below.
When narrowing the search for suppliers, also consider national and
international accreditations and customer certifications. If a circuit
board supplier is on the Approved Supplier List of a large OEM who
performs detailed quality audits and qualification testing, you may be
able to skip this step yourself.
Request references and obtain recommendations from colleagues in the
industry. New personnel taking on the responsibilities of supply chain
manager often do not have the knowledge to know where to start in
choosing the “best” suppliers. The gentleman that was mentioned above
that entered an IPC meeting with the question of how to qualify his
circuit board supplier had definitely come to the right place, and he
did the right thing by asking the experts. Technical conferences such
as these are the best place to make contacts and ask questions
regarding how to determine which suppliers are best.
Also, look to
those who are more experienced within your company. You may not be
aware of the fact that the project manager down the hall used to fill
your exact position within another company. With all of the new
technology appearing daily, we often forget that those with years of
experience can offer the greatest input with regards to assessing
quality and long-time reliability of potential PCB suppliers.
It is also useful to contact potential suppliers and ask for a list of
references; take the time to actually contact these references. Ask
about product quality. Ask if they have received any defective product
and, if so, what percentage. Determine if the technology level is
similar to your company’s requirements for comparison purposes. Ask
about on-time delivery. What percentage is typical? Ask about the
company’s initiative to take responsibility when there is an issue and
its willingness to work as a team to resolve such issues. If the
reference is not a competitor, he may be willing to offer additional
information regarding other potential suppliers. It never hurts to ask.
Provide a few designs for quote. Provide each potential supplier within
the same technology range with the same part numbers for quoting. Price
is typically the deciding factor, but quality and delivery are also
keys. You often get what you pay for; so do not eliminate suppliers
solely on cost until completing the audit and board quality assessment
if you can afford to visit the supplier.
Narrow the list based on information gathered. Narrowing the list is a
bit subjective based on the weight that you place on the information
gathered thus far. Make a list comparing each supplier with regards to
the following attributes:
1. Location
2. Number of part numbers supplier is capable of producing
3. Quality credentials
4. References and recommendations
5. Cost.
Audit the facilities. When fiscally possible, choose one or two
individuals from your facility who are experts in the area of PCB
manufacturing, lean manufacturing and quality audits to travel to the
potential suppliers to perform audits. This will help narrow the search
for the best suppliers meeting your capability requirements. IPC-1710
is a good guidance document for data collection at the manufacturing
site.
Test suppliers’ products. As resources permit, have a third-party lab
or your internal lab perform qualification testing on the suppliers’
products. This can be your actual product build or another similar
build that the manufacturer is producing for another client. A full
qualification will provide you with the most information, but even a
few thermal stress microsections performed at a minimal cost can
provide a wealth of information. Ongoing verification of supplier
quality can be accomplished through acceptance testing and periodic
conformance. IPC-6012 and IPC-6013 are good guidelines for vendor
certification.
Add the passing supplier to the approved supplier list. Now that your
evaluations are complete, setup a matrix that outlines the pluses and
minuses of those companies that have not been eliminated for any
specific reason. Choose those that you consider meeting or exceeding
your expectations in critical areas.
What to Do if You Cannot Do it All
There is minimal cost involved in performing Internet searches, polling
colleagues and checking a supplier’s quality credentials and industry
involvement. Attending conferences is slightly more costly, but this
will be time well spent with industry experts. Testing a supplier’s
product will provide a wealth of information. An expert from a
knowledgeable test laboratory would be able to assist you in gaining
the most knowledge with the funds available. Often, PCB suppliers are
willing to pay for testing or split the costs if the anticipated orders
are large enough to justify this expense. If resources are available to
fund travel, auditing the supplier’s facility will give you an inside
look at the type of production facility with which you are
dealing.
PCD&F
Ed. note: This paper was originally published in the IPC Midwest Conference Proceedings, September 2007.Renee Michalkiewicz is laboratory director with Trace Laboratories Inc., Hunt Valley, MD;
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