How a 12-Layer 5-Step HDI PCB Is Manufactured | Case Study
Summary:
KnownPCB manufactured a 12-layer 5-step HDI PCB for a 5G smart terminal mainboard, this is a typical high density interconnect PCB case with complex blind/buried via structure, facing two main manufacturing challenges. Let's see how we solve the problems and how your HDI PCBs are made.
Project Background
Our client is a communication device supplier, they want us to produce 1000pcs 12-layer 5-step HDI PCBs for their 5G smart terminal mainboard.
Key Manufacturing Challenges of this 12-layer HDI PCB:
Layer registration and material movement control
The 5-step HDI PCB structure means it requires 5 laser drilling and lamination cycles, each cycle causes material expansion and contraction, thus increasing the risk of layer misregistration, blind-via offset and material-related defects.
35μm/35μm fine line and space
As we just said, the influences of 5 cycles are accumulated, high density PCB usually means pretty dense traces and fine space. In this project, the inner layer line and space is 35μm in the dense routing area, which makes it harder to keep accurate pattern during etch process.
HDI PCB Manufacturing Process
Once we confirmed the requirements with customers, KnownPCB engineering team would check all relevant files, including Gerber, drill, solder mask, stack-up, mechanical files, this is a critical DFM check before production. In this HDI PCB manufacturing case, our client provided necessary files and passed initial review, which meant the board is manufacturable.
Then came the real factory process, the HDI PCB manufacturing process includes more than 30 steps strictly, we only talk about the typical processes of HDI PCBs here.
1. Inner Layer Imaging (LDI Exposure)
Inner layer imaging transfers the designed circuit pattern onto the inner layer materials with high precision.
2. Sequential Lamination
Sequential lamination builds multiple HDI layers through repeated lamination cycles. Material movement control is important for maintaining layer registration accuracy.
3. Laser Microvia Drilling
Laser microvia drilling creates blind vias required for advanced HDI PCB structures.
Stacked Microvia Formation and Filling
Stacked microvia formation and filling creates reliable electrical connections between buildup layers.
4. Via Filling / Copper Plating
Via filling and copper plating ensure stable electrical connection and improve HDI PCB reliability.
5. Outer Layer Imaging & Plating
Outer layer imaging and plating complete the final circuit pattern.
6. Microsection & Electrical Test
To verify via quality, registration and electrical integrity.
7. Packing & Shipping
After inspection, completed HDI PCBs are packed and shipped.
Watch the whole process of PCB manufacturing:
Final Thought
For this kind of complex HDI PCB projects, producing one PCB is not enough, keep the mass production consistently is more important and more challenging.
At KnownPCB, the yield of this kind of HDI PCB is usually up to 95%.
If you are evaluating a multilayer and multistep HDI PCB, send us your Gerber and stack-up for a DFM review.
Frequently Asked Questions
What is a 5-step HDI PCB?
A 5-step HDI PCB is a high density interconnect PCB structure that requires multiple laser drilling and lamination cycles to build complex layer connections.
What is the HDI PCB manufacturing process?
The HDI PCB manufacturing process includes inner layer imaging, sequential lamination, laser microvia drilling, stacked microvia formation, via filling, copper plating and electrical testing.
What are the main challenges in HDI PCB manufacturing?
The main challenges include layer registration control, material movement during lamination cycles, microvia reliability and fine line accuracy.
How to choose an HDI PCB manufacturer?
Customers should evaluate HDI PCB manufacturing capability, DFM support, quality control and mass production stability.
