Technical Library | 2019-05-29 01:47:22.0
1.Vias near SMD pads: Solder can flow into the via after melted. As a result cold joint will appear in the end. Check the picture below. 2.Vias on SMD pads: Solder can flow into the via more easier after melted. Check the picture below. 3.Via opening without soldermask covered. When workers solder TH parts by hand, soldering iron can touch vias sometime, then tiny amounts molten solder will stay on vias. This can lead to electrical short easily. We recommend you make all vias tenting (covered by solder mask) if it is possible.
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Technical Library | 2024-07-24 01:18:03.0
Quad Flat No-Lead (QFN) packages has become very popular in the industry and are widely used in many products. These packages have different size and pin counts, but they have a common feature: thermal pad at the bottom of device. The thermal pad of the leadless QFN provides efficient heat dissipation from the component to PCB. In many cases, arrays of the thermal via under the component is used to dissipate heat from the device. However, thermal vias can create more voids or result in solder protrusion onto the secondary side.
Technical Library | 2019-10-10 00:26:28.0
Voids are a plague to our electronics and must be eliminated! Over the last few years we have studied voiding in solder joints and published three technical papers on methods to "Fill the Void." This paper is part four of this series. The focus of this work is to mitigate voids for via in pad circuit board designs. Via holes in Quad Flat No-Lead (QFN) thermal pads create voiding issues. Gasses can come out of via holes and rise into the solder joint creating voids. Solder can also flow down into the via holes creating gaps in the solder joint. One method of preventing this is via plugging. Via holes can be plugged, capped, or left open. These via plugging options were compared and contrasted to each other with respect to voiding. Another method of minimizing voiding is through solder paste stencil design. Solder paste can be printed around the via holes with gas escape routes. This prevents gasses from via holes from being trapped in the solder joint. Several stencil designs were tested and voiding performance compared and contrasted. In many cases voiding will be reduced only if a combination of mitigation strategies are used. Recommendations for combinations of via hole plugging and stencil design are given. The aim of this paper is to help the reader to "Fill the Void."
Technical Library | 2020-07-15 18:49:03.0
Via Filling • Through Hole Vias - IPC-4761 – Plugging – Filling – Filled & Capped • MicroviaFilling and Stacked Vias
Technical Library | 2021-05-26 00:53:26.0
This paper describes a copper electroplating enabling technology for filling microvias. Driven by the need for faster, smaller and higher performance communication and electronic devices, build-up technology incorporating microvias has emerged as a viable multilayer printed circuit manufacturing technology. Increased wiring density, reduced line widths, smaller through-holes and microvias are all attributes of these High Density Interconnect (HDI) packages. Filling the microvias with conductive material allows the use of stacked vias and via in pad designs thereby facilitating additional packaging density. Other potential design attributes include thermal management enhancement and benefits for high frequency circuitry. Electrodeposited copper can be utilized for filling microvias and provides potential advantages over alternative via plugging techniques. The features, development, scale up and results of direct current (DC) and periodic pulse reverse (PPR) acid copper via filling processes, including chemistry and equipment, are described.
Technical Library | 2019-05-15 22:26:02.0
As the demand for higher routing density and transfer speed increases, Via-In-Pad Plated Over (VIPPO) has become more common on high-end telecommunications products. The interactions of VIPPO with other features used on a PCB such as the traditional dog-bone pad design could induce solder joints to separate during the second and thereafter reflows. The failure has been successfully reproduced, and the typical failure signature of a joint separation has been summarized.To better understand the solder separation mechanism, this study focuses on designing a test vehicle to address the following three perspectives: PCB material properties, specifically the Z-direction or out-of-plane Coefficient of Thermal Expansion (CTE); PCB thickness and back drill depth; and quantification of the driving force magnitude beyond which the separation is due to occur.
Technical Library | 2020-07-15 18:29:34.0
In the early 2000s the first fine-pitch ball grid array devices became popular with designers looking to pack as much horsepower into as small a space as possible. "Smaller is better" became the rule and with that the mechanical drilling world became severely impacted by available drill bit sizes, aspect ratios, and plating methodologies. First of all, the diameter of the drill needed to be in the 0.006" or smaller range due to the reduction of pad size and spacing pitch. Secondly, the aspect ratio (depth to diameter) became limited by drill flute length, positional accuracy, rigidity of the tools (to prevent breakage), and the throwing power of acid copper plating systems. And lastly, the plating needed to close up the hole as much as possible, which led to problems with voiding, incomplete fill, and gas/solution entrapment.
Technical Library | 2008-09-04 17:57:24.0
In the quest for lower ESL devices, having the ESL reduced in the package is only half of the battle; connecting that device to the circuit determines how much of that low ESL appears to the circuit. For this low ESL part type, it would be a shame to take a part of 200 pH and add 2000 pH to its ESL because of via patterns on the PCB.
Technical Library | 2020-12-29 20:55:46.0
Voiding in solder joints has been studied extensively, and the effects of many variables compared and contrasted with respect to voiding performance. Solder paste flux, solder powder size, stencil design, circuit board design, via-in-pad design, surface finish, component size, reflow profile, vacuum reflow, nitrogen reflow and other parameters have been varied and voiding quantified for each. The results show some differences in voiding performance with respect to most of these variables but these variables are not independent of each other. Voiding in solder joints is a complex issue that often requires multiple approaches to reduce voiding below required limits. This paper focuses on solutions to voiding for commonly used bottom terminated components (BTCs).
Technical Library | 2001-04-24 10:44:24.0
This paper reviews the possible implementations of the Micro Via Technology within the Mentor Graphic's Board Station environment, specifically within the Librarian, Layout and Fablink applications. In this context, the definition of a Micro Via is constrained to Board Station’s support of such technology and contains only generalized descriptions of the manufacturing processes that require Micro Vias.
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