PCB | December 28, 2010
Filled, Plugged, Plated Via-In-Pad
Increasing use of High Density Interconnect Printed Circuit Boards (HDI PCBs), has made the plugging of microvias inevitable for many manufacturers of PCBs.
It is as always the component pitch and rapid growth of HDI design, that is the main reason for developing this and other related processes. Further increased area for IC packaging, via in pad, landless designs and planarity of the via for dielectric formation are also main drivers. Uniform dielectric spacing between layers and the ability to metalize the dielectric as well as achieve plating adhesion is critical. In general holes can be filled and plugged with special filling pastes, resin from the prepreg and conventional soldermask (LPI). The pastes can have special characteristics as good heat transportation. Following information is mainly based on technology used by our manufacturers in Europe and Asia. Via Plugging The standard LPI soldermask process cannot tent or fill vias without the risk of exposing copper inside the hole barrel. Typically, a secondary screen print operation is used which deposits UV or thermally curable epoxy soldermask into the holes to plug them. This is called via plugging. Via plugging is for plugging via holes with a solder resistant material to prevent air leakage during In Circuit Test (ICT), or to prevent shorting from components which are close to the board surface. Typically only one side of the via can be plugged. There is a high probability that one side of the plug will be blown off during soldering if both sides of the same via are plugged, a result of entrapped gases between the plugs. 100% Via Plugging This requirement uses a process similar to the above described, but the entire hole barrel is filled with a non-conductive material. The exact hole fill percentage is dependent on the hole size and board thickness. It will generally fill 80–90 % of the volume. If present, this requirement should be indicated on the fabrication drawing with a note stating: Via Plug > 80% of the hole barrel volume for the 0.0xx mm holes. BGA Device Via Plugging BGA devices require special consideration in via plugging due to tight spacing. The surface finish on most BGA device applications is ENIG. Other solutions are Immersion Silver, Immersion Tin or OSP. Via plugging should not be used with Immersion Silver surface finish, if the via plug used is a thermal cure process type. The via plug is added after the surface finish which can be tarnished and may affect solderability. Vias should be 100% plugged or preferably left open. Capped or Plated Over Blind or Through-hole Vias This process “fills” the via hole with a conductive or non-conductive material and then the via surface is plated over, “capped”, to provide a smooth flat solderable surface. These are used for Via-In-Pad designs where component may be mounted over the via, or a solder joint will extend over the via connection. Typical filled and plated-over via design rules from one of our manufacturers. Variations between manufacturers will occur. • Minimum drilled hole size 0.25 mm maximum 7:1 aspect-ratio • Maximum drilled-hole-size 0.45 mm • Aspect ratio Min. 2:1, Max. 7:1 • Max board thickness 2.16 mm • Via filling process can be performed from one side only • The plating may extend up to 0.0127 mm above or 0.0762 below the pad surface If conductive filled holes are present, this should be indicated on the fabrication drawing with a note. MicroVias and Via in Pad According to IPC, a microvia is a hole with a diameter of < 150um. It can be a through viahole (with all respect to aspect ratio), but we normally see them as blind vias between 2 layers. Mostly “drilled” by laser, but some manufacturers are also drilling microvias with a mechanical drill bit. It is slower, but the holes have a clean and nice cut. Normally we recommend to use fan out vias where possible, but components with a increased pitch and pad size forces the via to be part of the component pad. These vias shall be filled and over plated. Filling can be by paste, but also cu-filling is requested and available. The microvia copper fill process is an electrochemical deposition process applied in the manufacturing of multilayer process. The process chemistry is complex, including the interactions of several additive chemicals in addition to the underlying basic electrochemical processes of copper electrodeposition. A successfully electroplated microvia is filled completely but not excessively leaving a smooth surface for stacked vias to be added, or for a component to be soldered. Copper filling of microvias is available from most manufacturers who are capable of producing HDI boards. If possible keep it simple It will be very cost effective if your PCB does not need plugging, filling or over plating. Assuming you will have ENIG surface finish, leave an opening in soldermask for the through hole vias 0.2mm larger than the nominal hole. You will have an open via hole with a clean and nice ENIG barrel without any risk for entrapped residues. This solution can work for most PCBs unless you intend to wave solder your product. ----- Author: John Steinar Johnsen, Elmatica
A new EMS provider sees the light of day EMS providers DataED and Bestronics merge to launch a new player – Emerald EMS.
Tektronix joins the fight agains COVID-19 Tektronix has shifted its focus from supporting vehicle manufacturing to assisting with ventilator production.
ABB completes divestment of Power Grids to Hitachi ABB has reached a significant milestone in the company’s transformation towards a decentralized global technology company, with the completion of the divestment of 80.1% of its Power Grids business to Hitachi.
Germany amps up domestic battery production with massive state subsidies The German government is investing more than EUR 1.5 billion in battery cell research and production.
Internal promotions and executive retirements at Kimball EMS provider, Kimball Electronics, has made two new internal promotions aimed at contributing to the company accelerating its strategic growth plans.
Kyocera & TMDU team up for research on vitals measurement headset Kyocera Corporation and Tokyo Medical and Dental University (TMDU) have teamed up on a joint research project to develop a wireless headset that can remotely monitor high accuracy patient biometrics, such as blood oxygen saturation (SpO2).
German battery manufacturer receives funding for cell production facility VARTA AG receives public funding of EUR 300 million for battery cell production facility.
Scanfil to streamline its factory network The EMS provider is planning to combine the production of its Hamburg factory with its other factories in Germany and Poland
Kitron awarded new order within measurement technology Kitron has been awarded new business for measurement technology. The award covers a period of five years, and the expected annual value is between EUR 3.5-5 million.
NORBIT ASA awarded aquaculture contract Norwegian technology manufacturer, NORBIT, has been awarded a new contract from an existing customer within the aquaculture market.
Saki strengthens its Asian operations The AOI specialist is expanding its global sales organisation with new Asia sales department, and appointing Katsuhiro Eddie Ichiyama as Senior General Manager for the Asian region
Scanfil to sell its plant in Hangzhou, China The board of directors of the Finnish EMS prover has decided to sell the entire share capital of its subsidiary located in Hangzhou, China, for a total of EUR 18.4 million to Hangzhou Cabinet Technology Co., Ltd.
Staying put during the COVID-19 pandemic TPCA (Taiwan Printed Circuit Association) announced the production and sales data for Q1 2020; the output value of Taiwan cross-strait PCB industry totalled NT$136.9 billion (approx. US$4.541 billion) in Q1/2020.
North American PCB industry sales up 1.0% in May Total North American PCB shipments in May 2020 were up 1.0 percent compared to the same month last year. Compared to the preceding month, May shipments fell 3.0 percent.
Sensirion expands with new production site in Hungary In a response to positive business trends and the increasing demand for its existing and new sensors, Sensirion is expanding its production capabilities by establishing a production site in Debrecen, Hungary.
Management Change at the Würth Elektronik eiSos Group After 27 years in the Würth Elektronik Group, Oliver Konz has decided to resign his position as Executive Vice President of the Würth Group and CEO of the Würth Elektronik eiSos Group for personal reasons and leave the company.
Kurtz Ersa inaugurates new production hall In Bestenheid, Germany, the company has just opened its new production and administration building. Following 24 months of construction and furnishing, the company now have access to 4’500 new square metres of space.
PCB industry: 1Q/2020 overshadowed by corona pandemic After a significant drop in sales at the end of last year, PCB manufacturers in the Germany, Austria and Switzerland (DACH) region recorded a sales growth of 16.1 percent in the first quarter of 2020.
Integration of ATLID completes European set of instruments for EarthCARE satellite With the successful integration of the ATLID-Instrument the EarthCARE satellite (Clouds Aerosols and Radiation Explorer) has passed a crucial milestone, as it concludes the "onboarding" of the three European instruments.
ABB Robotics rolls out Lexi’s procurement analytics solution Automation giant, ABB Robotics, is using a big data analytics software solution developed by Lexi Solution AB in Sweden to optimise procurement and engineering processes.
OHB placing the largest clean room in operation After only 14 months of construction, the PLATO hall has now been officially completed at space company OHB’s headquarters in Bremen. With a floor area of around 1,400 square meters, the ISO 8 cleanroom*, which is almost eleven meters high, is the OHB Group’s largest cleanroom facility.
Jenoptik expands military laser rangefinder capabilities in the US JENOPTIK Optical Systems, LLC has announced an expansion of its capabilities for military laser rangefinders (LRF) and is adding custom engineering and testing capabilities to their Jupiter, Florida facility.
Tesla plans battery manufacturing facility in California Electric car manufacturer Tesla plans to build a battery research and manufacturing facility in Fremont, California. N, to be operated around the clock, Under a project dubbed Roadrunner, documents from the city government also reveal a potential 24/7 operation at the facility.
Northrop Grumman awards contracts to Kitron Northrop Grumman has awarded Kitron a production contract for Integrated Communications, Navigation and Identification (ICNI) modules for the F-35 Lightning II program.Load more news