Poor PCB design is a common reason why otherwise well-designed circuits fail during proof-of-concept or production. PCB design is an art form in which all parts are carefully placed and connected using copper lines.
Although it may appear simple to link everything, doing so is actually quite challenging because various components of the circuit produce varying results in practice. The PCB ground bounce issue occurs when the ground return path of the circuit does not have a proper copper area and causes resistance in the circuit, and is a frequent cause of circuit failure. Because of their sensitivity to measurement errors (if used as a sense amplifier) or to electromagnetic interference (EMI) in high-frequency processes, op-amps can be a pain to work with in these situations. Lack of ground stitching in the design is a frequent mistake that negatively impacts ground bounce.
What is Via Stitching?
Before we get into actually stitching the Via, let’s make sure we understand what it is. Take a look at the photo I’ve included.
The above picture demonstrates the multi-stacked board’s various levels. The addition of a VIA is now required to allow communication between the upper and lower copper planes.A via in the insulator (VIA) is simply a hole drilled through the PCB’s base material during manufacturing; the copper traces travel through this opening from one layer to the next.
Since this can be manufactured anywhere, why not incorporate it into the PCB’s real Larger Copper plane? Indeed, this is possible, and the process is known as “Via Stitching.”
Understanding PCB Via Stitching
Via stitching is a technique whereby copper areas on various layers are drilled with multiple vias and then connected. It is typically performed on bigger copper planes like those used for ground filling or power.
For instance, PCB design supports a number of distinct Via stitching methods, each of which is unique but conceptually equivalent to the others. You can summarize the various Via stitches as follows:
- Constant Ground Via stitching
- Thermal Via stitching
- Shielding Via stitching
Constant Ground Via Stitching
This method of Via stitching is widely utilized in PCB fabrication. Stitching Ground Planes together in PCBs reduces the length of the ground return route from the load devices to the power supply. As a result, it keeps a good ground return path and achieves minimal ground plane resistance. Since the copper pour is larger and connected with the top and bottom layer, or with the other layers as well if the design supports more than two layers of the copper plane, it generates lower heat dissipation and has a low drop resistance. It maintains uniform copper impedance throughout the PCB. Therefore, the ground bounce problem is caused by a variation in voltage drop between ground planes, which can be measured if the impedance between the planes is known. When compared to fixing a faulty ground bounce in the PCB, via stitching is a simple and effective solution.
Here at Circuit Digest, we’ve used the Via stitching method on the ground plane to create a number of PCBs that have made it to the functional phase. Below is a PCB from a USB-powered Raspberry Pi UPS, which effectively employs Via stitching. For clarity, I’ve underlined the red text in the following pictures that demonstrate the use of image stitching.
It’s not just for use on the ground plane, but wherever you need a flawless Copper pour. The layer used for the stitching via is not the Ground plane. Here are some pictures of the real PCB that was used.
Thermal Via Stitching
A well-designed PCB heatsink is vastly superior in most situations. Thermal Via Stitching is an integral part of the PCB-based radiator. Excellent thermal transmission over a wide area of copper has been achieved in many of our projects by means of thermal via stitching. (Top & Bottom). Here is an illustration of our MPPT Solar charger experiment in action.
In the aforementioned PCB and others, it aids greatly in dispersing heat across the copper base. Since the PCB’s layer section where the high power component is seated is much more amenable. When this happens, the active traces heat up excessively while the PCB core and the other opposite layer remain relatively cold. By increasing the through-plane conductivity of the stitching at this location, heat is dissipated to the core and then to the connected opposite plane, bringing the total junction temperature of the desired high power component down.
Shielding Via Stitching
High-frequency RF or Mixed-signal circuits that use WiFi, Bluetooth, or other broad bands of high-frequency elements may benefit from via shielding to prevent interference from electromagnetic fields. It’s also known as a PCB picket fence, for short.
It is typically made by stitching vias in a single or multiple rows around the outside of the large copper plane that is too near to the high-frequency tracks. This design for a 4-layer PCB incorporates Via protection.
We can see that it is carried out all the way around the ground plane that is in close proximity to the WiFi module’s antenna.
Vias on an RF board should be separated at least 1/10th of the wavelength of the highest frequency that needs to be shielded from interfacing if the Shielded Via stitching is to be used. One eighth of an area is also used in some methods. However, the main concern is to maintain tiny vias spacing relative to the wavelength in the substrate dielectric.
Nonetheless, the aforementioned details are crucial to grasping the protection provided by Via. There could be a heated discussion about the best method and context for applying this, as different people have various perspectives. Please use the Electronics forum to provide comments, suggestions, and discussion on the aforementioned topics.