HDI PCB/4-Layer TU-872 HDI PCB Featuring Blind Vias/Buried Vias with Immersion Gold

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4-Layer TU-872 HDI PCB Featuring Blind Vias/Buried Vias with Immersion Gold

(Custom PCBs are tailored products; the images and specifications provided are for reference only.)

Brief Introduction

The 4-layer TU-872 HDI PCB is constructed from low dielectric constant/dissipation factor (DK/DF) FR-4 material, specifically the TU-872 SLK Sp. This PCB is designed with four copper layers, each measuring 1 oz, and features a coating of immersion gold along with a green solder mask. The final thickness of the PCB is 1.6mm ± 10%. Each panel consists of 16 pieces and incorporates a high-density interconnect (HDI) configuration, which includes blind vias from the top side to inner layer 1 and buried vias connecting inner layer 1 to inner layer 2. These boards are fabricated according to IPC-Class-2 standards and are vacuum packed for shipment.

PCB Specifications

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Item	Description	Requirement	Actual	Result
1. Laminate	Material Type	FR-4 TU-872 SLK Sp	FR-4 TU-872 SLK Sp	ACC
	Tg	170℃	170℃	ACC
	Supplier	TU	TU	ACC
	Thickness	1.6±10% mm	1.61-1.62mm	ACC
2.Plating thickness	Hole Wall	≥25µm	26.51µm	ACC
	Outer copper	35µm	40.21µm	ACC
	Inner Copper	30µm	31.15µm	ACC
3.Solder mask	Material Type	Kuangshun	Kuangshun	ACC
	Color	Green	Green	ACC
	Rigidity (Pencil Test)	≥4H or above	5H	ACC
	S/M Thickness	≥10 µm	19.55µm	ACC
	Location	Both Sides	Both Sides	ACC
4. Component Mark	Material Type	TAIYO/ IJR-4000 MW300	IJR-4000 MW300	ACC
	Color	White	White	ACC
	Location	C/S, S/S	C/S, S/S	ACC
5. Vias	Therough holes	YES	L1-L4	ACC
	Blind vias	YES	L1-L2	ACC
	Buried vias	YES	L2-L3	ACC
6. Identification	UL Mark	YES	YES	ACC
	Date Code	WWYY	0421	ACC
	Mark Location	Solder Side	Solder Side	ACC
7. Surface Finish	Method	Immersion Gold	Immersion Gold	ACC
	Tin Thickness
	Nickel Thickness	3-6µm	5.27µm	ACC
	Gold Thickness	0.05µm	0.065µm	ACC
8. Normativeness	RoHS	Directive 2015/863/EU	OK	ACC
8. Normativeness	REACH	Directive 1907 /2006	OK	ACC
9.Annular Ring	Min. Line Width (mil)	7mil	6.8mil	ACC
9.Annular Ring	Min. Spacing (mil)	6mil	6.2mil	ACC
10.V-groove	Angle	30±5º	30º	ACC
10.V-groove	Residual thickness	0.4±0.1mm	0.38mm	ACC
11. Beveling	Angle
11. Beveling	Height
12. Function	Electrical Test	100% PASS	100% PASS	ACC
13. Appearance	IPC Class Level	IPC-A-600J &6012D Class 2	IPC-A-600J &6012D Class 2	ACC
	Visual Inspection	IPC-A-600J &6012D Class 2	IPC-A-600J &6012D Class 2	ACC
	Warp and Twist	≦0.7%	0.32%	ACC
14. Reliability Test	Tape Test	No Peeling	OK	ACC
	Solvent Test	No Peeling	OK	ACC
	Solderability Test	265 ±5℃	OK	ACC
	Thermal Stress Test	288 ±5℃	OK	ACC
	Ionic Contamination Test	≦ 1.56 µg/c㎡	0.58µg/c㎡	ACC

Typical Applications

1.Radio Frequency: Suitable for RF applications where signal integrity is crucial.
2.Backpanel and High-Performance Computing: Ideal for advanced computing systems.
3.Line Cards and Storage: Essential for data storage devices and line cards.
4.Servers, Telecom, and Base Stations: Supports vital telecommunications equipment.
5.Office Routers: Provides reliable connectivity for office environments.

High Tg PCB

The thermal properties of the resin system are defined by the glass transition temperature (Tg), measured in degrees Celsius (°C). The Tg indicates the temperature at which the material transitions from a rigid, glassy state to a soft, rubbery state. For common epoxy resins (FR-4 grade), the Tg typically ranges from 115 to 130°C. Exceeding this temperature during soldering can cause the PCB to expand in the Z-axis direction, which may stress the copper walls of plated-through holes. The thermal expansion of epoxy resin is approximately 15 to 20 times greater than that of copper above Tg, leading to a risk of cracking in the hole walls. Below Tg, the expansion ratio is only three times, significantly reducing the risk of cracking.

PCBs with a Tg of 170°C or higher are classified as high Tg PCBs, while those with a Tg above 130°C are generally considered standard.

Partial High Tg Material in House

Material	Tg (℃)	Manufacturer
S1000-2M	180	Shengyi
TU-768	170	TU
TU-872 SLK Sp	170	TU
TU-883	170	TU
IT-180ATC	175	ITEQ
KB-6167F	170	KB
M6	185	Panasonic
Kappa 438	280	Rogers
RO4350B	280	Rogers
RO4003C	280	Rogers
RO4730G3	280	Rogers
RO4360G2	280	Rogers

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4-Layer TU-872 HDI PCB Featuring Blind Vias/Buried Vias with Immersion Gold