HDI PCB Supplier Quotes: Which Line Items Actually Move the Price
Three quotes, three different documents
You asked three HDI PCB suppliers for the same board. The totals came back
within a narrow band of each other, so the decision looks easy: take the lowest
one. Then you open the three documents side by side and discover they are not
the same kind of document at all.
One is a single line: part number, quantity, unit price. One has eleven lines,
several of which name operations you did not know were billed separately. One
has four lines plus a paragraph of notes, and the notes contain the words
"excluding" three times.
The totals are comparable only if the three quotes describe the same scope of
work, and they almost never do. The spread between the cheapest and the most
expensive is often smaller than the value of what one of them left out. So the
real question is not which number is lowest. It is what each number contains.
This article is a way to take any HDI quote apart. Every line on it belongs to
one of three categories, and knowing which category a line sits in tells you
whether a difference between quotes is real, cosmetic, or a hole you will pay
for later.
The three kinds of line item
Sort every line on the quote into one of these before comparing anything.
Cost drivers. These move when the design moves. Change the interconnect
structure, the layer count, the via scheme, the material, or the finish, and the
number on this line changes with it. A driver is tied to a physical attribute of
your board. Two quotes that disagree on a driver are telling you something
real: either they read your design differently, or they will build it
differently.
Allocation lines. These represent cost that exists either way, presented in
a particular place. Setup, tooling, programming, test fixture preparation,
engineering review, panel preparation: this work happens whether or not it
appears as its own line. One fab lists it; another folds it into the unit price;
a third splits it across the first article and the production units. The *total
cost* of the work may be identical in all three. Only its position differs.
Allocation differences look like price differences and are not.
Scope boundaries. These are not really line items at all. They are the
presence or absence of a line. Electrical test, coupon testing, specific
inspection levels, packaging format, documentation, certificates, data
retention, rework allowance, freight, duties: each is either inside the number
or outside it. When a quote is silent about one of these, the silence is the
cheapest possible answer, and you cannot tell from the total whether the fab
intends to include it.
The common comparison mistake is treating all three categories as if they were
the first one. A buyer sees fab A at one number and fab B higher, concludes B is
expensive, and awards to A. In fact B listed its setup separately and included
electrical test, while A buried setup in the unit price and excluded test. The
award went to a smaller scope, not a better price.
Why HDI widens the gap
Every board type has this problem. HDI has it worse, for a structural reason.
A conventional multilayer board is built in one lamination pass. The cost
structure is relatively flat: material, imaging, drilling, plating, finish,
test. An HDI board is built in stages, and each stage is a repeat of operations
the previous stage already performed. Laser drilling happens per microvia
layer. Fill and plating happen per sequential build. Lamination happens once per
cycle. Imaging and etching happen once per layer pair exposed.
That means HDI cost accumulates by count of operations, not by area alone.
The same board described with a different interconnect strategy can require a
different number of passes through the same equipment, with the same raw
material bill. Two fabs can read the same stackup and arrive at a different
number of sequential cycles, because the drawing left them room to choose.
A quote that charges per-operation makes this visible. A quote that gives one
unit price hides it completely. Neither is dishonest. But only one of them lets
you see what you are buying, and the one that hides it is usually the one that
looks simpler and therefore more attractive.
Reading the driver lines
When a line is a genuine cost driver, the useful question is not "why is this
higher than the other quote" but "what did you assume about my board to get
this number."
The drivers that matter on an HDI quote are the ones tied to how many times the
board goes through a process, and how hard each pass is:
- Interconnect structure. How the microvia layers stack, whether vias are
staggered or stacked, how deep the structure goes. This sets the number of
sequential cycles, which is the single largest lever on an HDI quote.
- Via formation and fill. Whether blind and buried structures need filling,
what has to be planarised afterwards, whether any structure requires a
separate plating sequence.
- Layer pair handling. How many imaging and etch passes the stackup implies,
and whether any inner layer carries features tight enough to need a different
handling class than the rest.
- Material. The laminate and prepreg system, and whether it was chosen by
you or assumed by the fab. A substitution changes the number on this line and
also changes the board.
- Surface finish. Which finish, applied to what area, with what masking.
- Panel format. How your board nests into the fab's working panel, how many
fit, and what the leftover becomes. Fabs with different panel sizes get
genuinely different per-board material cost from identical designs.
- Acceptance class and test coverage. The class you specified and the test
regime it implies. This is a driver when it changes handling and inspection
effort, and a scope boundary when it is simply omitted.
If two quotes differ on any of these, you have found a real difference. Resolve
it before comparing totals, because resolving it will usually change the totals.
Reading the allocation lines
Allocation lines are where comparison goes wrong most often, because they
produce the largest apparent differences while representing no difference at
all.
The work behind them is unavoidable. Someone has to prepare tooling, generate
drill programs, build the test fixture or program the flying probe, review your
data, and set up the panel. Every fab does this. The choice is only whether to
show it.
Three presentations of the identical cost:
- Separated. Tooling, setup and test preparation appear as their own lines,
usually one-time. The unit price looks low. The first-order total looks high.
- Amortised into the unit price. No separate lines. The unit price carries a
share of the one-time work, sized to the quantity quoted. The quote looks
clean and the unit price looks high.
- Split across first article and production. A higher price for the initial
units, lower afterwards.
All three can describe the same amount of money. But they behave completely
differently when something changes, and that is what you should be comparing:
When quantity changes. A separated one-time charge stays fixed, so the
per-board cost falls as quantity rises. An amortised charge was sized to the
quoted quantity, so a different quantity needs a new quote entirely — the unit
price you were given does not scale.
When you reorder. A separated tooling line gives you something to argue
about next time: it was paid, so should it be charged again. An amortised charge
is invisible, so there is nothing to point at, and you will pay it again in
every unit price forever without being able to see it.
When the design changes. A separated setup line tells you roughly what a
re-setup will cost. An amortised one does not.
So the honest comparison is not between two totals. It is between two totals at
your actual quantity, with one-time and recurring costs separated out in both.
A quote that will not break this out for you has made comparison impossible, and
that is itself information about how the rest of the relationship will go.
Reading the scope boundaries
This is where the money hides, because the boundary is marked by absence.
Ask of every quote: is each of the following inside the number or outside it?
- Electrical test. Which coverage, on what proportion of the delivered
boards, and what happens to the ones that fail.
- Test coupons and process verification. Whether coupons are produced,
evaluated, reported, or retained — and whether their cost sits in this number.
- Inspection level and reporting. What gets inspected, to what acceptance
basis, and whether you receive a record of it or only the boards.
- Documentation and certificates. Material declarations, process records,
certificates of conformance. Each one is work; each one is either included or
quotable later.
- First article handling. Whether a first article is produced, whether it is
separately charged, and whether production waits for your approval of it.
- Rework and scrap policy. What happens if the run comes out short, whether
the fab builds overage, whether you pay for it, and who owns the overage.
- Packaging and preservation. Format, moisture protection, labelling. Thin
packaging is cheap and gets expensive after transit.
- Freight, insurance, duties, and the delivery term itself. A quote without
a stated delivery term is not comparable to one that has it.
- Data retention and reorder readiness. Whether the fab keeps your tooling
and programs available, and for how long.
For each line you cannot answer from the document, the default answer is "not
included." Write it down as a gap rather than assuming goodwill. Three quotes
with three different gap lists are three different purchases.
Which gaps are real money and which are noise
Not every gap deserves the same attention. Sort them by whether closing them
later is cheap or expensive.
Expensive to close later. Anything that requires the board to be built
differently, or requires evidence that can only be generated during the build.
Test coverage, coupons, process records, acceptance class, material
substitution: once boards exist, you cannot retroactively add the evidence,
which means either shipping without it or rebuilding.
Moderate to close later. Things that can be done to finished boards at
additional cost. Extra inspection, re-packaging, additional documentation
assembled from records the fab already holds.
Cheap to close later. Freight arrangements, labelling details, delivery
scheduling.
A quote that is low because it omitted something from the first group is not a
low quote. It is a partial quote. A quote that is low because it omitted
something from the third group is genuinely a little lower.
The questions that put every quote on one basis
You do not need to re-tender. You need the same small set of answers from
everyone, in writing, before you compare.
- At my stated quantity, what is the total you will invoice, and of that
total, how much is one-time and how much recurs per unit?
- What interconnect structure did you assume, and how many sequential build
cycles does your price carry?
- If my quantity changes, which lines change and which do not?
- **Which of the following are included: electrical test, coupons, inspection
reporting, certificates, first article, packaging, freight?** For each
excluded item, what would it cost to include?
- Did you substitute any material or finish from what I specified? If so,
what and why.
- What is the delivery term, and what is the price valid until?
- **On a repeat order of the same board, which of these charges would not
recur?**
Seven answers, same seven questions to everyone. Then rebuild all three quotes
into one table with the same rows, filling every gap at the price the fab quoted
to close it. Compare *that* table. The ranking frequently changes, and when it
does not change, you at least now know why the winner won.
What to lock into the PO
Comparison is only useful if the thing you compared is the thing you buy. Carry
the resolved basis into the order:
- The quantity the price was built for, and what happens to the price if the
quantity moves.
- The scope items confirmed as included, listed explicitly rather than by
reference to "as quoted."
- The one-time charges, identified as one-time, with a statement on whether they
recur on repeat orders.
- The material and finish as specified, with substitution requiring written
approval.
- The delivery term and the price validity window.
- Which documents accompany the shipment.
A quote is a sales document; a PO is the one that gets enforced. Anything you
clarified by email and did not carry into the PO will be re-litigated at
invoice time.
What this does not tell you
Line-item decomposition tells you whether two numbers are comparable. It does
not tell you whether either fab can build the board. A cheap, fully-scoped quote
from a fab that cannot hold your interconnect structure is still the wrong
choice, and a careful decomposition will not reveal that — capability evidence
is a separate exercise, done before quotes are compared, not after.
Nor does it make price the deciding factor. It makes price *knowable*, which is
a precondition for weighing it against everything else.
Worked example: same board, three structures
Abstract categories are easier to apply against a concrete shape. Here are three
quote structures for one HDI board, with no numbers, showing only where cost was
placed.
Quote A — single line.
HDI PCB, qty as requested, unit price, total.
Nothing else. Every cost driver, every allocation, every scope boundary is
inside one number and invisible. You cannot tell what interconnect structure was
assumed, whether test is included, or what a quantity change does. This quote
is not comparable to anything until you ask the seven questions.
Quote B — operation-level.
Lines for material, imaging per layer pair, laser drilling per microvia layer,
fill and plating per cycle, lamination per cycle, mechanical drilling, surface
finish, electrical test, tooling, setup, first article.
This looks like the most expensive quote and is the most useful document. Every
driver is visible, the sequential cycle count is readable from the per-cycle
lines, and one-time charges are separated. You can model a quantity change
yourself.
Quote C — four lines plus notes.
Board price, tooling, test, freight plus notes reading "excluding coupons,"
"excluding certificates," "price subject to final data review."
Mid-range total, and the notes are the real content. "Subject to final data
review" means the price is provisional — the driver assumptions have not been
made yet, so there is nothing here to compare. The two exclusions are from the
expensive-to-close-later group.
Decomposed: B is the only quote currently comparable. A needs scope disclosure.
C needs its data review completed before its number means anything. The totals
told you none of this, and ranking by total would have ranked the least
informative quote first.
A short decomposition procedure
For each quote, in order:
- Label every line as driver, allocation, or scope boundary.
- List the absent scope items — go through the boundary checklist and write
down what the document never mentions.
- Separate one-time from recurring, at your actual quantity.
- Extract the driver assumptions: what interconnect structure, how many
cycles, what material, what finish, what panel format, what acceptance basis.
- Send the seven questions to every supplier at once, with a response
window.
- Rebuild into one table with identical rows for all quotes, gaps priced.
- Rank on the rebuilt table, then check the winner's capability evidence
separately.
- Carry the resolved basis into the PO.
Steps 1 through 4 are desk work on documents you already hold. Step 5 is one
email. The whole exercise usually costs less time than one round of
renegotiation after an invoice surprise.
Where to go next on PCB168
- HDI PCB — board type overview and the attributes a
quote is priced against
- Request a quote — the inputs that let a quote come back on a
fixed basis rather than "subject to review"
— how specification, comparison and verification fit together
— what should and should not recur the second time
— one driver line examined on its own
— the capability screen that belongs before price comparison
— how long a compared price stays a price
— which document wins when the quote and the drawing disagree
- Capabilities — the attribute ranges a quote is built from
FAQ
Is the quote with the most line items the most expensive one?
Usually it looks that way and often it is not. More lines means more of the
unavoidable work is shown rather than absorbed. Compare after separating
one-time from recurring at your quantity; detailed quotes frequently move down
the ranking once that is done.
A supplier gave one unit price and will not break it down. Is that a problem?
It is a comparability problem rather than an honesty problem. Without a
breakdown you cannot tell what scope is inside, you cannot model a quantity
change, and you have nothing to point at on a reorder. You can still buy from
them — but ask the inclusion questions in writing first, so the scope is
recorded somewhere even if the price structure is not.
**Two quotes assume a different number of sequential build cycles. Which is
right?**
Possibly both, which means your documentation left the choice open. This is the
largest single lever on an HDI price, so it should not be a supplier decision
made silently. Resolve the interconnect structure in your own documents and
re-quote; otherwise you are comparing two different boards.
What is the difference between a cost driver and an allocation line?
A driver changes when your design changes. An allocation line represents work
that happens regardless, shown in a particular position. Driver differences
between quotes are real; allocation differences are presentational and vanish
once both quotes are normalised to the same structure.
Can I just ask everyone to quote on the same template?
It helps and is worth doing, but it does not fully solve the problem. A template
forces the same rows; it does not force the same assumptions behind those rows.
You still need the driver-assumption questions, particularly the interconnect
structure and the sequential cycle count.
A quote says "price subject to final data review." Can I compare it?
Not yet. That phrase means the supplier has not finished reading your design, so
the driver assumptions behind the number do not exist. Treat it as an estimate
and ask for a firm price before it enters the comparison.
Which exclusions matter most?
The ones that cannot be added after the boards exist: test coverage, coupons,
process records, acceptance class, and any material or finish substitution.
Those require the board to have been built differently. Freight, labelling and
packaging details can be fixed later at known cost.
Should the cheapest fully-scoped quote win?
Only if its capability evidence stands up independently. Decomposition tells you
which numbers are comparable; it says nothing about whether a fab can hold your
structure. Screen capability first, then compare price among those who pass.
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