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World Class HDI PCB Manufacturer in China

PCBMay is a Professional HDI PCB Boards Manufacturer in China,Who Provides Many Different Kinds of High Density Interconnect (HDI) Boards.

HDI PCB is a high-density interconnection technology, which is one of the technologies used by printed circuit boards. HDI is mainly produced by the technology of micro-blind buried vias.The characteristic is to make the electronic circuit distribution in the printed circuit board have a higher circuit density, and due to the large increase in circuit density.

It also makes the printed circuit board made of HDI unable to use ordinary drilling. Hole formation method requires non-mechanical drilling process for HDI. There are many non-mechanical drilling methods, among which “laser hole formation” is the main hole formation solution of HDI high-density interconnection technology.

Many Advantages of HDI PCB Boards

Over 12 years HDI PCB  manufacturing experience.

Better reliability,can result in improved manufacturing yield and board reliability.

No MOQ for new orders,even one piece.

It can increase the wiring density,can reduce PCB layer count and footprint.

Increase design efficiency,can better protect signal integrity than alternative through-hole approaches.

It can improve the radio frequency interference, electromagnetic interference and electrostatic discharge .

Providing Micro-section,soldering sample and COC report.

7/24 online support for your business.

1 step HDI PCB

1 Step HDI PCB

The 1 step High Density Interconnect PCB contains a single build-up of high-density interconnected layers, so it’s the most common form of HDI printed circuit board. It requires one sequential lamination on each side of the core. One build-up layer with a rigid core allows through vias from surface to surface. Micro vias are used to build-up the layer.

2 Step HDI PCB

2 step HDI PCB

The 2 High Density Interconnect step PCB has two HDI layers and allows microvias to be staggered or stacked across layers. Complex designs usually incorporate copper-filled stacked microvia structures.One build-up layer with a rigid core allows through vias buried in the core and from surface to surface. This allows for variable depth micro vias or stacked microvias.

3 Step HDI PCB

3 Step HDI PCB

The 3 step HDI PCB is that two or more build-up layers with a rigid core allows through vias buried in the core and from surface to surface. Stacked microvias are used.For many PCB manufacturers, 1 step and 2 step HDI boards are easy and form the bulk of their HDI manufacturing business. 3 step HDI will also cost more.

4 Step HDI PCB

4 Step HDI PCB

The 4 step HDI board designs often require laser microvias created with laser drills. These drills generate a laser at up to 20 microns in diameter, which can effortlessly cut through both metal and glass, creating very tiny but clean holes. You can get even smaller holes by using materials such as uniform glass, which has a low dielectric constant.

5 Step HDI PCB

5 Step HDI PCB

This is a 12 layer with 5 step high density interconnect(HDI) PCB,it needs better Laser Direct Imaging (LDI) technology,LDI is the go-to for fine lines and minute spacing because it can verify even the most demanding processes, continually expanding our capabilities and allowing for smaller form factors.

6 Step HDI PCB

6 Step HDI PCB

This is a 14 layer with 6 step high density interconnect(HDI) board,Conventional core board laminating times are 3 times,this product needs to be laminated 6 times which is very complicated.The applications of this kind HID PCBs are automotive,aerospace,mobile communications and medical devices,etc.

PCB Frequently Asked Questions (FAQ) about Our HDI PCB Boards Process and Capabilities

Here you will find many quick questions and answers about HDI PCBs,don’t hesitate to contact us,our email is sales@pcbmay.com.

At some level of circuit complexity, turning to an architecture with blind and buried vias will result in better yield and lower cost than would a through-hole design. In this presentation, we discuss several design examples and illustrate the relative costs and benefits of different architectural approaches.

We can produce the prototype of HDI boards with 1-2 weeks for standard leading time,3-4 weeks for mass production of HDI PCBs.

A microvia is a blind structure with a maximum aspect ratio of 1:1, terminating on a target land with a total depth of no more than 0.25mm measured from the structure’s capture land foil to the target land.

It is a hole that runs from an outer layer to the inner layer, but not through the entire PCB. These holes can be drilled mechanically or using laser technology.

This is a hole that runs between one or more inner layers. They are normally mechanically drilled.

Materials play a large role in terms of manufacturability and direct cost of your circuit board. Here is a tip: The goal is always to select the right material for manufacturability that, at the same time, meets your temperature, and your electrical requirements. When it comes to materials, make sure that your high-speed material is also suitable for your HDI design. They are many other factors that come into play when selecting the proper materials for your design. Use our free Material Selector to find out which materials will suit your application the best.

No,we can produce 1 to 10,000 pieces,what’s more,there is also no minimum order surcharge or additional fees

PCB products are diversified. From the perspective of output value distribution,PCBs are mainly four types of products with the largest proportions of soft boards, multilayer boards,HDI and IC substrates.

The reliability of HDI PCB is directly affected by the quality of the copper connections and the base material.Copper compounds are tested on a special test sample – coupon,by cyclic thermal effects,using a special method – the IST (Interconnect Stress the Test). 

What is HDI PCB

HDI PCB (High Density Interconnect) is a high-density interconnection technology, which is one of the technologies used by printed circuit boards. HDI is mainly produced by the technology of micro-blind buried vias.

HDI 1

The characteristic is to make the electronic circuit distribution in the printed circuit board have a higher circuit density and due to the large increase in circuit density.

It also makes the HDI PCB unable to use ordinary drilling.Hole formation method requires non-mechanical drilling process for HDI.There are many non-mechanical drilling methods, among which”laser hole formation” is the main hole formation solution of HDI high-density interconnection technology.

Through Holes and Micro-holes in HDI PCB

In the process of designing a printed circuit board, the developer sometimes faces the need to make blind holes – that is, transitions from one layer to another, without drilling the printed circuit board through. This may be due to various reasons:

  • A complex component with a small pin pitch, such as a BGA with a pitch of 0.5 mm or less.
  • Too tight routing with a small PCB, and the need to create additional routing “channels” in the area under the via.
  • The need to eliminate that piece of the via that is not involved in the electrical contact between layers (the so-called stub), so as not to create unnecessary problems for high-speed signals.
  • The need to limit signal propagation to only a few layers, with shielding of the remaining layers – for example, when separating the analog and digital parts of the circuit.

What is the Function of Blind Holes in HDI PCB?

To designate such holes, the terms blind via are used (the hole goes to only one of the outer layers), buried via (the hole is completely inside the board, connecting two or more inner layers), microvia or uvia (the hole is made by a laser between two adjacent layers).

In general, the blind holes in HDI PCB technology, which implies a high density of connections, very small gaps and width of the conductor on the board, and the use of blind holes, is collectively called HDI PCB (High Density Interconnect, or “high density interconnects”). There are several international standards related to HDI boards, their design, production and quality control, for example:

The terms “blind holes”, “buried holes”, “micro-holes”, etc. are used, while these terms, as far as I understand, are not always understood in the same way by different specialists.

Basic Types of Blind Holes in HDI Printed Circuit Board

When forming blind holes, when describing them in CAD of printed circuit boards, it would be nice to understand in advance what technology will be used by the manufacturing plant to create them. In this article, we will describe several basic types of blind holes. We will use the example of making a 4-layer PCB with a blind hole between layers 1 and 2.

Moreover, we will also give recommendations on their use in your projects, including the case of using high-frequency materials and prepregs, such like Rogers 4000 series.

4layer HDI

                                                            Example of a cross-section of a 4-layer PCB with a blind hole between layers 1 and 2.

The information is based on the recommendations of various foreign manufacturers of printed circuit boards, with which the PCBMAY company – manufacturer of printed circuit boards “PCB technology”.

Based on this information, you will be able to create more complex designs in the future by combining these types of holes and these technologies.

So, Here are the Four Main Types of Blind Holes in HDI PCB:

1.Stack up + HDI (extrusion with foil on the outside plus micro-holes)

2.Core + Core + HDI (core plus core plus micro-holes)

  1. Drill + Resin flow (drilling plus resin flow)

4.Drill + Resin plug (drilling plus resin driving)

Let us describe these options in more detail, having considered the sequence of the main operations for their manufacture, and give recommendations for the design of such boards.

Option 1: Stack up + HDI (pressing with foil outside plus micro-holes)

Manufacturing stages:

1. Double-sided workpiece – fiberglass core.

fiberglass core

2. Etched copper pattern on both sides.

Etched copper pattern on both sides

3. Assembly of a 4-layer PCB package – core inside, prepregs and foil outside.

core inside, prepregs and foil outside

4. Pressing a multilayer workpiece.

Pressing a multilayer workpiece

5. Drilling a micro-hole with a laser.

Drilling a micro-hole with a laser

6. Plating of holes and formation of external copper pattern.

Plating of holes and formation of external copper pattern

Recommendations for this design:

  1. HF prepreg type Ro4450 cannot be used here.
  2. The distance between layers 1 and 2 must be less than 0.15 mm. Recommended 0.05… 0.1 mm.
  3. The depth of the hole should not exceed its diameter.

Option 2: Core + Core + HDI (core plus core plus micro-holes)

Manufacturing steps

1. Double-sided workpiece – fiberglass core.

fiberglass core

2. Etched copper pattern on one side.

Etched copper pattern on one side

3. Assembly of 4-layer PCB package – prepreg inside, core outside.

prepreg inside, core outside.

4. Pressing a multilayer workpiece.

Pressing a multilayer workpiece

5. Drilling a micro-hole with a laser.

Drilling a micro-hole with a laser

6. Plating of holes and formation of a copper pattern in the outer layers of HDI PCB. Additional metallization allows the hole to be completely filled with copper.

Plating of holes and formation of external copper pattern

Recommendations for HDI PCB design:

  1. The distance between layers 1 and 2 must be less than 0.15 mm. Recommended 0.1 mm.
  2. If prepreg is 1 layer Ro4450, the copper thickness should be no more than 18 microns.
  3. If prepreg 1 layer Ro4450, Via-In-Pad construction (infill and additional copper cover on vias) is not recommended in this situation.

Option 3: Drill + Resin flow (drilling plus resin flow)

1. Double-sided workpiece – fiberglass core.

fiberglass core

2. Drilling a hole.

Drilling a hole

3. Plating of the hole.

Plating of the hole

4. Formation of a copper pattern on one side of the workpiece.

Formation of a copper pattern on one side of the workpiece

5. Assembly of 4-layer HDI PCB package – prepreg inside, core outside.

prepreg inside, core outside

6. Pressing a multilayer workpiece. The resin contained in the prepreg fills the hole partially or completely.

Pressing a multilayer workpiece

Recommendations for HDI PCB design:

  1. Do not use only 1 layer of prepreg.
  2. Copper in the inner layers – no more than 18 microns.
  3. If prepreg Ro4450 is used then Via-In-Pad construction is not possible.
  4. The hole diameter should not exceed 0.25 mm.
  5. The density of such blind holes should not be excessive

Option 4: Drill + Resin plug (drilling plus resin driving)

1. Double-sided workpiece – fiberglass core.

fiberglass core

2. Drilling a hole.

Drilling a hole

3. Plating of the hole.

Plating of the hole

4. Filling the hole with resin and curing the resin.

Filling the hole with resin and curing the resin

5. Leveling the surface to remove excess resin.

Leveling the surface to remove excess resin

6. Formation of a copper pattern on one side of the workpiece.

Formation of a copper pattern on one side of the workpiece

7. Assembly of 4-layer HDI PCB package – prepreg inside, core outside.

4-layer HDI PCB package - prepreg inside, core outside

8. Pressing the package.

Pressing the package

Recommendations for this type of HDI PCB design:

  1. To ensure dimensional stability, the dielectric core thickness between layers 1 and 2 should be at least 0.2 mm.
  2. Due to the increased finishing thickness of copper in layers 1 and 2 (due to the additional stage of metallization), the gaps and conductors in these layers are not less than 0.1 mm.

Additional recommendations

Sometimes HDI PCB designers use too many blind hole designs in a single design, which can lead to manufacturing problems. For example, in the 6-layer structure shown in the figure below, there are 3 types of holes that go to the Top layer. In this regard, in the manufacture of such a board, metallization is performed three times, and the total copper thickness is a problem for creating a precision topology.

6-layer PCB with 3 types of holes

                                                                                     An example of the structure of a 6-layer PCB with 3 types of holes.

HDI Board Design Guidelines

Minimize the number of hole types appearing on the same layer, or use less precision conductors and gaps in such a layer.

In general, it is possible to advise the developer, before designing the layer structure and creating new types of blind vias, to work out the question of how exactly this printed circuit board will be manufactured, at which manufacturing plant, and in what sequence the cycles of pressing layers, drilling and metallizing holes will be performed filling holes with copper or resin, etc.

How to Make Cheap HDI PCB?

The fewer press cycles and the fewer types of vias, the cheaper your board will be. On average, each additional type of blind vias can add 20 to 50% to the cost of ordering a PCB.

Note that at the same time, the presence of such holes can allow you to reduce the total number of layers in the board, lower design standards, and reduce the overall dimensions of the board. And often, as is the case with BGA-components with a pitch of 0.5 mm, blind holes cannot be dispensed with at all.

Support for Blind Holes in CAD

It should be noted that modern CAD systems support blind hole technology quite well. For example, in CAD Cadence Allegro and its OrCAD subset, it is possible to create a padstack for a given pair of layers in one click, simply based on the through-pad stack you have selected in the design.

 In the process of routing, the user can choose from which layer to which he needs a transition, and at the same time indicate which type of blind holes existing in the project to select for this operation. When generating design documentation and Gerber CAD files, it automatically generates the required set of drilling files.

How to Design HDI PCB on Allergo?

In addition, Allegro has a special option, the Allegro PCB Miniaturization Option, designed specifically for working with HDI boards, and allowing you to work not just with individual micro-holes, but with their ladder and stack structures as “topology objects”.

In this case, the object “structure of micro-holes” can be not only placed on the board, but also modified to meet the requirements of a particular situation – for example, stepped micro-holes connected into a single structure in layers 1-2, 2-3 and 3-4 can be the way the developer needs.

It is oriented in topology to simplify routing. Also, the Allegro Miniaturization option allows you to fulfill all the necessary technological requirements (DFM – design for manufacturing, “development for production”) to ensure the possibility of efficient design and high-quality production of printed circuit boards from the very first iteration.

Support in CAM systems

Modern CAM systems used to inspect HDI PCB manufacturing files do a good job of supporting blind holes. For example, the Gerber file editor CAM350 version 14 allows, at the time of loading Gerber and NC-drill files, to conveniently sort them and indicate between which pairs of layers certain blind holes should be located, and specify the type of micro-holes.

 Moreover, the CAM350 offers to automatically retrieve the connection table based on the layer and hole topology. If you have the ability to extract a similar netlist from your CAD, you can use the CAM350 to check the resulting Gerber files for correctness and compliance with this netlist.

Role of Coupon in Production of HDI PCB

The coupon is manufactured in the same production and has the same characteristics as the corresponding printed circuit boards:the same design, copper weight characteristics,hole sizes,mesh sizes and copper plating.

 The coupon goes through at least 500 heat cycles or until it suffers damage, leading to an increase in resistance of at least 10%,which occurs due to the formation of microcracks in the copper coupon joints due to thermal effects.

Possible damage to the base material is determined by measuring the capacity between the coupon layers before and after testing.The measurement results are compared.A change in capacity of 4% or more indicates significant material damage.

The Reliability of HDI PCBs

The loss of reliability of HDI PCB boards is primarily due to the use of lead-free assembly technology. It is produced at a temperature of about 260 ° C,while the FR-4 material has a limited temperature range.

 Thermal expansion of the material along the vertical component at such temperatures causes stress “tension” of copper joints. As a result,it leads to microcracks in the central zone of through metallized holes.

 If the board remains operational after 500 thermal cycles when tested up to 150 ° C,the test sample is considered as a reliable coupon,that is passed the IST.

The reliability of HDI PCB boards is also determined by the type of design.A circuit with micro-holes stacked on top of each other is almost four times more “sensitive” to failure than a design with the same staggered structures. Well-made one- or two-layer micro-holes have virtually no early failures.

 Boards with three or more micro-holes located one above the other are more likely to fail IST at 190 ° C and,accordingly,will have production problems.

HDI boards have the following distinctive characteristics:

  1. Thinner gaps and conductors, namely ≤75 μm
  2. Reduced vias (micro-holes) ≤100 μm
  3. Small via pads ≤260 μm
  4. High density of placement of contact pads, more than 20 per cm2
  5. Special dielectric materials
  6. Sequential lamination

The main advantage of HDI PCB is the ability to fit a huge number of different elements on a small board. 

Major Applications of HDI PCB

HDI boards are used in:

  • Mobile communication devices
  • Portable electronic devices
  • Complex medical devices
  • Video surveillance systems,
  • Aviation devices.

Structure of Several Different HDI Circuit Board Types

  • HDI type 1: Vias and microvias.The number of layers varies and depends on the ratio of the vias and the thickness of the FR-4 dielectric,which can delaminate at very high temperatures.
  • HDI Type 2: Here are microvias used and buried vias.These vias are covered by additional layers after drilling.Microvias can be used next to or above the buried vias.The number of layers is limited with this HDI type.

The difference between HDI type 2 and HDI type 3 is that there are at least two microvia layers on one side of the circuit board.Microvias can be placed directly over the hidden burrows.This HDI PCB board is suitable for very large and densely populated circuit boards with several BGA packages with many pins.

HDI 2

HDI PCB Board Design Guidelines

Minimize the number of hole types exiting the same layer or use less precision conductors and gaps in such a layer.

In general,it is possible to advise the developer,before designing the layer structure and creating new types of blind vias. It is to work out the question of:

  • How exactly HDI board will be manufactured?
  • At which manufacturing plant;
  • In what sequence the cycles of pressing layers?
  • Drilling and metallizing holes will be performed filling holes with copper or resin,etc.

The fewer press cycles and the fewer types of vias, the cheaper your board will be.On average,each additional blind vias can add 20 to 50% to the cost of ordering a PCB.

Note: Note that at the same time, the presence of such holes can allow you to reduce the total number of layers in the board, lower design standards, and reduce the overall dimensions of the board. And often, as is the case with BGA-components with a pitch of 0.5 mm, blind holes cannot be dispensed with at all.

Improvement of Wiring Density by HDI

The HDI PCB board is a build-up multi-layer PCB that uses a sequential stacking method developed from the need to interconnect packages with a large number of inputs and outputs. It is characterized by using micro vias with a hole diameter of 0.15 mm or less, and is an effective technology for mounting BGA devices with 1500 or more pins and 0.8 mm pin pitch.

When emphasizing thin and short consumer electronics, mobile devices, smart phones, and even wearable devices in recent years. As for the rise of the Internet of Things (IoT), the use of FPC soft boards, HDI and even Any Layer HDI high-density PCB; advanced PCB manufacturing process Brings a very high technical threshold and yield test. 

Moreover, it also drives equipment suppliers to update and evolve from laminating machines, screen printers, drilling machines to AOI equipment…

Why HDI PCB?

The volume requirements of products are getting higher and higher, especially the size of mobile device products is developing in the direction of continuous shrinking. For example, the current popular Ultra Book products, and even novel wearable smart devices, must be made with HDI high-density interconnection technology. The carrier board, which further reduces the size of the terminal design.

We’re capable of manufacturing HDI PCB up to 30 layers in various structures,please check our HDI PCB capabilities by reviewing the table found below:

ItemStandardAdvanced
Layer Count4-204-30
Min Board Thickness0.35mm (13.78mil)0.3mm(11.8mil)
Max Board Thickness4.2mm (250mil)6mm (236mil)
Min Initial Copper Foil Weight1/3 oz1/3 oz
Min Mech Drill Diameter0.2mm (7.87mil)0.15mm (5.9mil)
Min Laser Drill Diameter0.1mm (4mil)0.1mm (4mil)
Min Finished Hole Size0.1mm (4mil)0.1mm (4mil)
Blind Via Finished Hole Size0.1mm (4mil)0 (Fully Plated shut)
Buried Via Finished Hole Size0.1mm (4mil)0.1mm (4mil)
Minimum Trace Width/Spacing3mil/3mil2.75mil/2.75mil
Min Pad Size for E-test6mil6mil
Minimum Wire Bond Pad size> 6mil5mil
Controlled Impedance Tolerance+/-5%, +/-10%+/-5%, +/-10%
Solder Mask Registration+/-2mil+/-2mil
Solder Mask Min Dam Size0.1mm (4mil)0.1mm (4mil)
Min Diameter Rout Cutter Available0.6mm (24mil)0.6mm (24mil)
Laser Hole Location Tolerance0.5mil0.5mil
Thickness Tolerance10% (as per stack-up)< 10% (as per stack-up)
Sequential Lamination3 or less lamination cycles> 3 lamination cycles
Buried Vias2 or less> 3
Blind ViasYesYes
Stack ViasYesYes
Staggered ViasYesYes
Via-in-PadYesYes
Conductive Filled ViasYesYes
Non-Conductive Filled ViasYesYes
Aspect Ratio-10:1(HASL Lead free, HASL Lead, ENIG, Immersion Tin, Immersion silver, ENEPIG);-10:1(HASL Lead free, HASL Lead, ENIG, Immersion Tin, Immersion silver, ENEPIG);
-8:1(OSP)-8:1(OSP)
Surface Finish
Flash Gold (Electroplated Gold)YesYes
ENIGYesYes
Hard GoldYesYes
Flash GoldYesYes
HASL Lead FreeYesYes
ENEPIGYesYes
Soft GoldYesYes
Immersion SilverYesYes
Immersion TinYesYes
ENIG+OSPYesYes
ENIG+Gold FingerYesYes
Flash Gold (Electroplated Gold)+Gold fingerYesYes
Immersion Silver+Gold FingerYesYes
Immersion Tin+Gold fingerYesYes
Solder Mask
Semi – GlossyYesYes
GlossyYesYes
MatteYesYes
GreenYesYes
BlackYesYes
RedYesYes
BlueYesYes
YellowYesYes
WhiteYesYes
ClearYesYes
Bright WhiteYesYes
PurpleYesYes
Silkscreen
All colorsYesYes
   
Other Process
Routed ArrayYesYes
V-Cut, Edge to Copper0.25mm (9.8mil)0.25mm (9.8mil)
V-Cut Angle35°,45°,60°35°,45°,60°
CountersinkYesYes
CounterboreYesYes
BevelingYesYes
Milling+/-3mil+/-3mil
Edge CastellationYesYes
Edge PlatingYesYes
HeatsinksYesYes

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