How does Chinese PCB manufacturers make a PCB quote?
Why some of them quote to me quickly but some of them quote to me slower? What are the main factors that affect the PCB cost? There are more questions flying in many customer's head, after reading this article you will get a thorough understanding of how we prepare a quotation for your RFQ of PCB and then the answers are there for the questions.
There are several steps of making a quotation of PCB, first step, for the PCB sales whom is your direct contact from the supplier, is
RFQ Precheck
A well prepared RFQ should include three informations: PCB Gerber file, PCB parameters and purchasing details.
PCB Gerber file, which is the design file for the circuit board, is the most important thing in making a quote. PCB manufacturers will use the Gerber file to analysis if they can or can't produce the certain PCB by checking design of trace width and space, pad, BGA, layers and drills, etc.
If a PCB Gerber file is missing in quotation stage, there are do some customer only give a written parameters, the quotation is quite in-accurate--especially for multilayers and complicated/HDI PCB.
PCB parameters include those can't be shown in Gerber file, such as surface finishing choice, solder mask color and silk screen color, also the copper weight/thickness and board finish thickness must be indicated in paprameters.
For high layers PCB, usually a board stack up drawing is required too.
If the PCB parameters is missing, some Chinese PCB manufacturers will refuse to give quote because they think it is not valuable quotes, well you could say they are either too lazy or just not worrying of PCB orders. Some PCB suppliers will quote with most popular/normal choices for quoting use: 1.6mm finished board thickness, green soldermask, FR4 tg135, 1/1oz copper, etc.
Purchasing details, which is how many pieces you are planning to buy, for prototypes and for future production. It is extremely important to indicate the numbers as the price has a large difference in quantities.
There is a hidden advantage if you give forecast on purchasing quantity, and the sales will optimize the quantity to a cheaper unit PCB cost by adding a small amount of quantity if possible. The reason behind this we can discuss more in later paragraphs.
So, this is all about RFQ Precheck, if your RFQ is well formatted and the PCB sales girl does not need to ask you for extra information, it goes to next stage called
Engineering Evaluation
Engineers receives PCB gerber file along with board parameters, they open and check every of the items shown in the sample picture above, then fill up the form.
P.S every Chinese PCB manufacturers has their own ERP system to display and fill the board parameters, so it may has some differences in this and that PCB factories but the content is more or less the same.
Let's review them one by one
Layers: The more layers, the higher price (I think every buyers knows this)
Laminate Type: there are choices like FR4 (normal Tg, middle Tg, High Tg), Flex/PI, Ceramic, PTFE, etc.
Laminate model: Some customer will specify the brand and model they want to use for there PCB, especially for high frequency and high speed PCB.
Surface Finishing: HASL, HASL Lead Free, ENIG, Immersion Silver, Immersion Tin, Hybrid surface finishing.
Gold thickness: If ENIG(immersion gold) is chosen, then we need to specify the gold thickness and the area of ENIG.
PCB Board Thickness: The overall finished board thickness, usually 1.6mm with tolerance 10%.
Copper Weight (oz): the copper thickness in each of the layer.
Soldermask color: the circuit board color you want to use, green is used if no specific requirements. Some other regular choices are black, red, blue and matt finishing is required for some boards
Silkscreen color: the marks color on the PCB
Minimum Line Width/Line space: as it says
Minimum drill: as it says.
Test dot: This is the test dot quantity for the PCB, it relates to the fixture making and relevant cost
Material usage: it means the usage for PCB in raw material sheets. For two layers PCB usage 80%+ is acceptable, for multilayer PCB, usage 75%+ is acceptable. Otherwise there are extra costs.
Quality standard: normally IPC Class II.
Peelable mask/carbon print/impedance control/blind&buried hole: they are special requirements which will result in price increase, we will discuss below.
We talked about if the board parameter is missing from customers, then our engineer will use most regular choice to fill the PCB engineering evaluation form and present to sales.
Usually a standard regular PCB is with the following specifications:
FR4 Tg135, 1.6mm board thickness, 1/1oz copper weight, HASL LF, 2 layers, Min. Line space/Line.width: 4/4mil, Minimum Drill 0.3mm, IPC CLASS II
The engineering evaluation takes some time as they must check carefully for the Gerber file and in most cases, they are long queue of standing Gerbers for them to do evaluation. What could Chinese PCB manufacturers do to improve speed? Just increase the engineer numbers...
There are some feedbacks that the engineers may return to sales
We are able to make this PCB, the evaluation form is attached
we are unable to make this PCB unless make some adjustments of design, see evaluation form and adjust details
we are unable to make this PCB due to we don't have certain PCB substrates or the design is over our manufacturing capability and we do not make this type of PCB.
Price Calculation
As a Chinese PCB manufacturer, they have a price matrix and the unit is in USD/M2. The rate is per square meter, addionally with many terms of price adding terms in correspondes of the special technology of PCB manufacturing.
Let's assume in a sunny afternoon, the engineer replies with the following engineering evaluation and then we need to calculate pricing for quantity of 1K and 10K.
FR4 Tg150, 1.6mm board thickness, 2/2oz copper weight, HASL LF, 2 layers, unit size:59*73mm, Min. Line space/Line.width: 4/4mil, Minimum Drill 0.3mm, IPC CLASS III
The basic price matrix only matters with area and layers, so let's see this board is 2 layers and the area is 59*73/1000000*1000=4.307m2 and 59*73/1000000*10000=43.07m2.
So our starting PCB square meter price is
55USD for 1K pieces
50USD for 10K pieces
Next you noticed there are some difference between the parameters to standard PCB parameters, they are
Tg150 other than Tg130
2/2OZ copper thickness other than 1/1oz
IPC CLASS III other than IPC CLASS II
You look for special price adding terms and find below
Tg150 add 5%
2/2oz copper add 20USD/M2
IPC CLASS III add 5%
So our PCB square meter price goes to
55*1.05*1.05+20=80.63USD/M2
50*1.05*1.05+20=75.12USD/M2
At this stage, it is easy to get the PCB unit price
80.63*(59*73/1000000*1000)/1000=0.3472
75.12*(59*73/1000000*10000)/10000=0.3235
This is is the PCB unit cost, usually in a quotation sheet from Chinese PCB manufacturers, we will see NRE cost including tooling and fixture, also shipping cost if required by customers.
NRE Cost (non-recurring cost)
They usually includes tooling cost and fixture cost, tooling cost usually, inside PCB manufacturers, refers to all the expenses relates to the engineering work for converting a new PCB to production files. The fixture cost relates to the test fixture made especially for this new PCB which will be used in quality checking procedure in production flow.
The fixture can be re-used so usually it is a one time charge.
Let's sum up the steps:
PCB sales precheck the files and information for RFQ
Engineers make engineering evaluation and get back to sales
Sales find the relevant square meter price based on layers and total areas
Sales calculate unit PCB price based on the parameters and purchasing quantity
Including the NRE cost and shipping cost
And this is for rigid PCB only, for flex PCB and ceramic PCB the calculation has some differences.
More to read
What should you focus on quotation sheets from PCB manufacturers in China?
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