Free Trials

Download a free trial to find out which Altium software best suits your needs

How to Buy

Contact your local sales office to get started on improving your design environment

Downloads

Download the latest in PCB design and EDA software

  • PCB DESIGN SOFTWARE
  • Altium Designer

    Complete Environment for Schematic + Layout

  • CircuitStudio

    Entry Level, Professional PCB Design Tool

  • CircuitMaker

    Community Based PCB Design Tool

  • NEXUS

    Agile PCB Design For Teams

  • CLOUD PLATFORM
  • Altium 365

    Connecting PCB Design to the Manufacturing Floor

  • COMPONENT MANAGEMENT
  • Altium Concord Pro

    Complete Solution for Library Management

  • Octopart

    Extensive, Easy-to-Use Component Database

  • PRODUCT EXTENSIONS
  • PDN Analyzer

    Natural and Effortless Power Distribution Network Analysis

  • See All Extensions
  • EMBEDDED
  • TASKING

    World-Renowned Technology for Embedded Systems Development

  • TRAININGS
  • Live Courses

    Learn best practices with instructional training available worldwide

  • On-Demand Courses

    Gain comprehensive knowledge without leaving your home or office

  • ONLINE VIEWER
  • Altium 365 Viewer

    View & Share electronic designs in your browser

  • Altium Designer 20

    The most powerful, modern and easy-to-use PCB design tool for professional use

    ALTIUMLIVE

    Annual PCB Design Summit

    • Forum

      Where Altium users and enthusiasts can interact with each other

    • Blog

      Our blog about things that interest us and hopefully you too

    • Ideas

      Submit ideas and vote for new features you want in Altium tools

    • Bug Crunch

      Help make the software better by submitting bugs and voting on what's important

    • Wall

      A stream of events on AltiumLive you follow by participating in or subscribing to

    • Beta Program

      Information about participating in our Beta program and getting early access to Altium tools

    All Resources

    Explore the latest content from blog posts to social media and technical white papers gathered together for your convenience

    Downloads

    Take a look at what download options are available to best suit your needs

    How to Buy

    Contact your local sales office to get started improving your design environment

    • Documentation

      The documentation area is where you can find extensive, versioned information about our software online, for free.

    • Training & Events

      View the schedule and register for training events all around the world and online

    • Design Content

      Browse our vast library of free design content including components, templates and reference designs

    • Webinars

      Attend a live webinar online or get instant access to our on demand series of webinars

    • Support

      Get your questions answered with our variety of direct support and self-service options

    • Technical Papers

      Stay up to date with the latest technology and industry trends with our complete collection of technical white papers.

    • Video Library

      Quick and to-the-point video tutorials to get you started with Altium Designer

    Landless Vias

    Happy Holden
    |  August 7, 2019

    One persistent myth is that PCB vias MUST have annular rings. I thought this for many years until our Japanese partners introduced us to landless vias. We said, “You can’t do that, the vias have to have lands!” They replied, “Try it out and test it?”  So, we created a test vehicle and tested thousands of vias with various diameters against numerous annular ring vias. Guess what? They were right!! As the annular ring got smaller, the failures occurred earlier until we got to landless, then they jumped to 10 X fewer failures. 

    Not understanding this result, the PhDs of HP Labs went to work and came up with an explanation (published in one of the IEEE conferences). This was so radical a discovery that HP made the data, explanations and results proprietary—a company secret.

    Introduction

    I saw my first landless via multilayer while visiting NEC at Toyama, Japan back in 1985 [1]. They were an enormous automated facility making Japanese telecom and mainframe computer boards, kind of like IBM and Western Electric rolled into one. NEC was using the liquid, electrophoretic, positive-acting photoresist process with panel-plating. I wouldn’t see another landless via multilayer until our Japanese partner (OKI) introduced it to us in 1988. OKI was using the landless vias to achieve higher density without having to pay the extra costs of finer lines. They knew about the higher reliability that resulted, the had done their own testing (see Figure 1) but were after the higher routing density. These vias are seen in Figure 1 and it allowed them to route five traces between 0.100 in PTH centers.

    An excellent explanation for the high reliability of landless vias is found in the latest PC Handbook (7th ED) in Chapter 60, page 1307 and a recent PCB007 magazine.[2]

    Figure 1: a &b. Typical landless vias on a Japanese multilayer from around 1985 c. Modern landless made in N. America in the 2000s [0.010 in (0.25mm) and .004 in (0.1mm) traces] created with the liquid, electrophoretic, positive photoresist from PPG

    Landless Via Fabrication Processes

    There are numerous patent applications about landless vias. All require laser sculpting of the via or pinpoint laser exposure for the imaging. None of these have ever entered production. The two that have been used in high volume production are listed here, with two additional techniques that appear to be very practical.

    HP Process Learned from the Japanese

    The Japanese process for making landless vias is very simple, but anyone I talked to never figured it out until I explained the process. It is a true example of “thinking outside the box”:

    1. Whatever your registration tolerances are, then reduce the artwork land opening size by that amount. When using dry film photoresist. The DF will now extend beyond the wall of the drilled hole.

    2. Two things will happen with this arrangement:1. the plating bath will be forced to throw into the hole improving the distribution; 2. There will be no land except where the trace enters the hole.

    3. After stripping and etching, there will be landless vias with the trace dropping into the barrel of the PTH or blind via.

    4. This process does not work for panel plating. Then you must use the next process like NEC. 

    Figure 2. More landless vias including three more examples of ‘invisible vias’. A. Laser drilled 0.1mm blind via in a 0.1 mm trace; b. two landless vias on a 0.008 in (0.2mm) TH; c. The one view shows 0.2 mm pitch traces with 0.1 mm landless vias and the proportional size if there were 0.2mm, 0.4mm or 0.35mm lands on the vias; d. 0.1 mm trace in a plasma-etched, 0.2mm blind via. 

    Positive Liquid Electrophoretic Photoresist

    NEC were using a positive electrophoretic photoresist from Nippon Paint, evolved from the electrophoretic paints used on automobiles. A more recent photoresist and process came from PPG and is documented in a paper by Patty Goldman of PPG and Tim Schmidt of Compunetics.[3] The positive acting photoresists have many properties that can be very useful. The most useful is multiple exposure and developing, its resistance to plating especially Ni-Au and etching, its fine-line resolution [down to 10 microns (0.4 mil)] and its insensitivity to dust and clean-room debris. The coating process is relatively simple:

    •    Clean panel

    •    Coat for 60 to 90 sec at 60V~100V (voltage will determine finished thickness)

    •    Rinse

    •    Bake dry

    The panels are now ready for exposure or transportation. Coated-exposed and developed panels are shown in Figure 1.

    Perfect Registration

    Now with the advent of Direct Digital Imaging (DDI) and board scanning, it is possible to have perfect registration on both sides of a board. A DDI unit I tested has nine cameras that scan a panel as it enters the machine from both sides. Then, as it starts to expose each side, the artwork is modified on-the-fly so that each land is perfectly registered to its hole. Without high-speed computers, scanners and the new software, this was impossible before.

    Novel Russian Technique

    At a recent PCB West Conference, I had a conversation with a Russian PCB fabricator. It seems the Russians also used landless vias after they saw it on Japanese computers. The Russian process was novel, and I wish I had thought it up! They used the property of dry film photoresist’s sensitivity to oxygen. When they laminate the dry film to the panel, they have a shroud around the unit filled with oxygen. Oxygen is trapped in the holes by the dry film. They expose the panel to their normal artwork (but there are no lands for traces that will interconnect to the landless vias. They then do a short 100C bake of the panels, remove the cover sheet on the dry film and develop normally. The oxygen and heat have polymerized the dry film from the inside at the same diameter as the hole. Thus, when developed, the via has perfect dry film registration and is landless.

    If you’re running out of space, give it a try!

    Would you like to find out more about how Altium can help you with your next PCB design? Talk to an expert at Altium or learn how Altium Designer® offers the best toolset for PCB via creation in PCB design. Altium provides a tool that gives you editors, templates, rules definition, and libraries to address properties for assignment to your vias.

     References 

    1. Hirai, Osamu, The Development Of Advanced Cu-Plated Through Hole PWB With Landless Vias, Printed Circuit World Convention IV, Session 58, June 5, 1987, Tokyo, Japan

    2. Holden, H, “Against the Density Wall: Landless vias may be the answer”, PCB007, June 2016

    3. Goldman, Patty & Schmidt, Tim, New Design Applications Made Possible by Utilizing a Positive Acting Electrophoretic Photoresist., IPC's 2002 Designers Learning Symposiums, Dallas, TX (May) and Toronto (October)

    About Author

    About Author

    Happy Holden is retired from GENTEX Corporation (one of the U.S.'s largest automotive electronics OEM. He was the Chief Technical Officer for the world’s biggest PCB Fabricator-HonHai Precision Industries (Foxconn) in China. Prior to Foxconn, Mr. Holden was the Senior PCB Technologist for Mentor Graphics; he was the Advanced Technology Manager at NanYa/Westwood Associates and Merix Corporations. He retired from Hewlett-Packard after over 28 years. His prior assignments had been as director of PCB R&D and Manufacturing Engineering Manager. While at HP, he managed PCB design, PCB partnerships, and automation software in Taiwan and Hong Kong. Happy has been involved in advanced PCB technologies for over 47 years. He has published chapters on HDI technology in 4 books, as well as his own book, the HDI Handbook, available as a free e-Book at http://hdihandbook.com and de recently completed the 7th Edition of McGraw-Hill's PC Handbook with Clyde Coombs.

    most recent articles

    Back to Home