The calculation of PCB sampling price is a comprehensive accounting process involving multiple dimensions and process links, involving core elements such as material cost, process complexity, precision requirements, and additional services. The following provides a professional analysis of the three major modules of material cost, process cost, and additional cost, and explains the pricing logic of each link in conjunction with the entire process of PCB manufacturing:

1、 MATERIAL COST: DIRECT CONSUMPTION OF BASIC MATERIALS

Material cost is the core expenditure item for PCB sampling, usually accounting for 30% -60%, mainly composed of substrate, copper foil, and auxiliary materials, depending on the characteristics and specifications of the board material.

1. Substrate cost (highest proportion)

The substrate determines the electrical properties (such as dielectric constant Dk, loss factor Df), thermal stability (Tg value), and mechanical strength (CTE coefficient of thermal expansion) of the PCB. The common types of substrates and cost differences are as follows:

A、 Conventional FR4: The most common epoxy glass cloth substrate, with a Tg value of 80-150 ℃ (ordinary board 80-100 ℃, high Tg board 130-180 ℃), with a unit price of about 120 yuan/㎡ (thickness 0.5-3mm); High Tg (≥ 170 ℃) or low CTE (≤ 3ppm/℃) substrates have doubled costs due to complex formulations.

B、 High frequency and high-speed materials, such as Rogers RO4350B (Dk=3.66, Df=0.0037) and Panasonic Megtron 6 (Dk=3.7, Df=0.002), are mainly used for 5G communication and RF equipment, with a unit price of up to 300-3000 yuan/㎡ (priced according to frequency performance grading).

C、 Special substrates: polyimide (PI, flexible board), polytetrafluoroethylene (PTFE, high-frequency microwave board), ceramic substrate (high thermal conductivity), etc. Due to the difficulty of processing, the cost is 6-20 times that of FR4.

2. Copper foil cost

The thickness of copper foil directly affects the current carrying capacity and cost, and is charged by weight (oz, oz/square foot):

A、 Conventional copper foil: 1/2oz (≈ 17 μ m), 1oz (≈ 35 μ m), 2oz (≈ 70 μ m), unit price increases linearly with thickness (e.g. 1oz is about 30% more expensive than 1/2oz).

B、 Ultra thick/ultra-thin copper foil: above 3oz or below 0.5oz (such as commonly used 0.5oz for HDI boards), customized pressing or electroplating processes are required, increasing costs by 20% -50%.

3. Cost of auxiliary materials

A、 Solder mask ink: ordinary green oil (epoxy resin system) unit price is about 50-100 yuan/㎡; Due to special formulations, the cost of solder mask white oil (character base color), solder mask blue oil (high contrast), or anti yellowing ink (lead-free solder) increases by 10% -30%.

B、 Character ink: white/black characters, with a unit price of approximately 10-30 yuan/square meter; High temperature resistant characters (suitable for wave soldering) or multi-color characters (such as red and black dual color) require additional mesh production, resulting in increased costs.

C、 Cover film/reinforcement: PI cover film (unit price 10-30 yuan/㎡) or steel sheet/PI reinforcement (unit price 0.5-1.5 yuan/piece) is commonly used for soft boards (FPC), and hard boards are rarely used.

2、 PROCESS COST: TECHNICAL INVESTMENT IN MANUFACTURING PROCESS

The process cost accounts for about 40% -70%, which is directly related to the number of layers, precision, surface treatment, and special processes of the circuit board. The core processes include pre-treatment, graphic transfer, electroplating, etching, drilling, surface treatment, etc.

1. Pre treatment process

Purpose: Clean the board surface and roughen the copper surface to enhance subsequent adhesion. The key steps include:

A、 Grinding board: mechanical polishing (sand belt/nylon brush) or chemical micro etching (sodium persulfate+sulfuric acid), ordinary board unit price 10-30 yuan/㎡; HDI boards require plasma micro etching (to improve adhesion), doubling the cost.

B、 Oil removal/acid washing: Remove oil stains or oxides from the surface of the board, with a unit price of 5-20 yuan/square meter (adjusted according to the degree of pollution).

2. Graphic transfer process

Convert design files (Gerber) into circuit patterns, divided into two categories: traditional film and LDI (laser direct imaging):

B. LDI laser imaging: No film required, directly exposed on the photosensitive dry film through laser, with an accuracy of up to 1.2mil line width/line spacing, suitable for HDI or fine circuit boards, with a process cost of 60-120 yuan/㎡ (high equipment depreciation) and no film plate making fee.

3. Electroplating process

Including chemical copper deposition (PTH) and electroplating copper/tin, it is the core process of multi-layer boards and through-hole boards:

A、 Chemical copper deposition: depositing thin copper (about 0.5 μ m) on the hole wall to make the insulating hole wall conductive, with a unit price of 20-40 yuan/㎡ (blind buried holes require multiple copper deposition, with a cost of 1.5-2).

B、 Graphic electroplating: Thick copper plating is applied to the copper surface of the etched circuit (to the target thickness, such as 1oz substrate needs to be plated to 2oz), followed by tin plating to protect the circuit. The unit price is 80-120 yuan/㎡ (due to high current density and tank maintenance costs).

4. Etching process

Remove excess copper foil to form the final circuit, divided into acidic etching and alkaline etching:

A、 Acid etching: fast speed, low cost (unit price 10-25 yuan/㎡), suitable for conventional boards; However, the edges of the pattern are prone to corrosion (with a high side erosion rate), and fine circuits (≤ 5ml) require the use of tin removal technology (an additional 5-10 yuan/㎡).

B、 Alkaline etching: Low side etching rate (only half acidic), suitable for high-precision boards (such as IC carriers), but poor stability of the etching solution and high cost (unit price 10-20 yuan/㎡).

5. Drilling process

The aperture and number of holes directly affect the cost, and there is a significant difference between hard and soft boards:

A、 Mechanical drilling: Conventional aperture ≥ 0.2mm, single hole cost 0.05-0.2 yuan (the smaller the aperture and the thicker the plate, the higher the cost; for example, 0.1mm aperture is 3-5 times more expensive than 0.3mm).

B、 Laser drilling: used for micro holes (≤ 0.1mm) or blind buried holes in HDI boards. The equipment (CO ₂/UV laser) is expensive, with a single hole cost of 2 yuan/1000 holes (the higher the hole density, the lower the efficiency).

C、 Back Drilling: Remove excess conductor columns from through holes (reduce signal loss), charged by the number of holes (approximately 0.1-0.5 yuan/hole), only used for high-end high-speed boards.

6. Surface treatment process

The solderability and protective performance of PCB are determined by the significant differences in process costs

A、 HASL: There are lead spray tin (low-cost, about 30-60 yuan/㎡) and lead-free spray tin (requiring higher temperature, cost 2-5 yuan/㎡), suitable for conventional boards but with poor surface flatness (not suitable for BGA and other close pin components).

B、 Chemical nickel deposition gold (ENIG): Nickel layer (3-5 μ m)+gold layer (0.05-0.1 μ m), with good solderability and flatness, suitable for precision components such as BGA and QFP, with a cost of up to 90-150 yuan/㎡ (gold price fluctuates greatly, dominant).

C、 Immersion Ag: Low cost (60-100 yuan/㎡), but prone to oxidation, suitable for short-term storage or high thermal conductivity scenarios.

D. OSP (Organic Solderability Protective Agent): Only covers the copper surface, with low cost (20-40 yuan/㎡), but weak protection (only able to store for 1-3 months), suitable for short cycle consumer electronics products.

The total price of PCB sampling can be simplified as:

Total price=Material cost+Process cost+Additional cost

Among them:

Material cost=substrate area x substrate unit price+copper foil weight x copper foil unit price+auxiliary material usage x auxiliary material unit price

Process cost=(pre-processing+graphic transfer+electroplating+etching+drilling+surface treatment) unit price of each process x effective area (or number of holes/layers)

Additional cost=engineering fee+testing fee+special service fee+quantity/delivery premium

In actual pricing, PCB manufacturers will adjust the weights of each link based on their own equipment capabilities (such as whether they have HDI production lines and LDI equipment), material inventory (such as high-frequency materials that need to be stocked), and market competition, ultimately forming differentiated pricing.