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In my PCB design, I have 0402 components connected to polygons. To reduce the risk of tombstoning, I connected them using thermal relief. My guiding principle is that if heat dissipation is not sy...
#3: Post edited
by
Nick Alexeev
·
2025-02-03T19:21:18Z (about 1 month ago)
- In my PCB design, I have 0402 components connected to polygons. To reduce the risk of **tombstoning**, I connected them using thermal relief.
- My guiding principle is that **if heat dissipation is not symmetrical on both sides of the component**, and the component is **0603 or smaller**, thermal relief should be applied. I differentiate between three cases:
- 1. **Both pads are connected to polygons**. (See **Image 1**: C14, C15, C16, C17)
- 2. **Only one pad is connected to a polygon.** (See **Image 2**: R10)
- 3. **Neither pad is connected to a polygon.** (See **Image 2**: C12, R11)
- In the third case, I made an effort to route the traces symmetrically to the component to ensure even heat distribution. This follows recommendations I found online to prevent tombstoning—see **Image 3**.
- Another consideration is whether the components will be soldered or desoldered manually, such as jumpers.
- Additionally, I assume that for **TH components**, thermal relief should
- **always** be used when they are connected to a plane/polygon.
- **My Questions:**
- 1. **Are my assumptions correct?** Should thermal relief be applied/not applied in each of these cases?
- 2. If thermal relief is used for thermal reasons, is it important that the number of connections (or their total width) be **symmetrical**?
- 3. When considering symmetry, should factors like polygon size, nearby vias, and other thermal paths be taken into account? Is this generally based on estimation or engineering judgment?
- 
- 
- In my PCB design, I have 0402 components connected to polygons. To reduce the risk of **tombstoning**, I connected them using thermal relief.
- My guiding principle is that **if heat dissipation is not symmetrical on both sides of the component**, and the component is **0603 or smaller**, thermal relief should be applied. I differentiate between three cases:
- 1. **Both pads are connected to polygons**. (See **Image 1**: C14, C15, C16, C17)
- 2. **Only one pad is connected to a polygon.** (See **Image 2**: R10)
- 3. **Neither pad is connected to a polygon.** (See **Image 2**: C12, R11)
- In the third case, I made an effort to route the traces symmetrically to the component to ensure even heat distribution. This follows recommendations I found online to prevent tombstoning—see **Image 3**.
- Another consideration is whether the components will be soldered or desoldered manually, such as jumpers.
- Additionally, I assume that for **TH components**, thermal relief should
- **always** be used when they are connected to a plane/polygon.
- **My Questions:**
- 1. **Are my assumptions correct?** Should thermal relief be applied/not applied in each of these cases?
- 2. If thermal relief is used for thermal reasons, is it important that the number of connections (or their total width) be **symmetrical**?
- 3. When considering symmetry, should factors like polygon size, nearby vias, and other thermal paths be taken into account? Is this generally based on estimation or engineering judgment?
- 
- 
-  [source: Altium](https://resources.altium.com/p/pcb-layout-guidelines#thermal-relief-connections-to-planes-for-through-hole-components)
#2: Post edited
by
Olin Lathrop
·
2025-02-02T14:25:08Z (about 1 month ago)
Removed content-free fluff.
- In my PCB design, I have 0402 components connected to polygons. To reduce the risk of **tombstoning**, I connected them using thermal relief.
- My guiding principle is that **if heat dissipation is not symmetrical on both sides of the component**, and the component is **0603 or smaller**, thermal relief should be applied. I differentiate between three cases:
- 1. **Both pads are connected to polygons**. (See **Image 1**: C14, C15, C16, C17)
- 2. **Only one pad is connected to a polygon.** (See **Image 2**: R10)
- 3. **Neither pad is connected to a polygon.** (See **Image 2**: C12, R11)
- In the third case, I made an effort to route the traces symmetrically to the component to ensure even heat distribution. This follows recommendations I found online to prevent tombstoning—see **Image 3**.
- Another consideration is whether the components will be soldered or desoldered manually, such as jumpers.
- Additionally, I assume that for **TH components**, thermal relief should
- **always** be used when they are connected to a plane/polygon.
- **My Questions:**
- 1. **Are my assumptions correct?** Should thermal relief be applied/not applied in each of these cases?
- 2. If thermal relief is used for thermal reasons, is it important that the number of connections (or their total width) be **symmetrical**?
- 3. When considering symmetry, should factors like polygon size, nearby vias, and other thermal paths be taken into account? Is this generally based on estimation or engineering judgment?
- 
- 
Thanks in advanced for any answer!Eyal
- In my PCB design, I have 0402 components connected to polygons. To reduce the risk of **tombstoning**, I connected them using thermal relief.
- My guiding principle is that **if heat dissipation is not symmetrical on both sides of the component**, and the component is **0603 or smaller**, thermal relief should be applied. I differentiate between three cases:
- 1. **Both pads are connected to polygons**. (See **Image 1**: C14, C15, C16, C17)
- 2. **Only one pad is connected to a polygon.** (See **Image 2**: R10)
- 3. **Neither pad is connected to a polygon.** (See **Image 2**: C12, R11)
- In the third case, I made an effort to route the traces symmetrically to the component to ensure even heat distribution. This follows recommendations I found online to prevent tombstoning—see **Image 3**.
- Another consideration is whether the components will be soldered or desoldered manually, such as jumpers.
- Additionally, I assume that for **TH components**, thermal relief should
- **always** be used when they are connected to a plane/polygon.
- **My Questions:**
- 1. **Are my assumptions correct?** Should thermal relief be applied/not applied in each of these cases?
- 2. If thermal relief is used for thermal reasons, is it important that the number of connections (or their total width) be **symmetrical**?
- 3. When considering symmetry, should factors like polygon size, nearby vias, and other thermal paths be taken into account? Is this generally based on estimation or engineering judgment?
- 
- 
- 
#1: Initial revision
by
Eyal78
·
2025-02-02T08:00:32Z (about 1 month ago)
Thermal Relief – Yes or No?
In my PCB design, I have 0402 components connected to polygons. To reduce the risk of **tombstoning**, I connected them using thermal relief. My guiding principle is that **if heat dissipation is not symmetrical on both sides of the component**, and the component is **0603 or smaller**, thermal relief should be applied. I differentiate between three cases: 1. **Both pads are connected to polygons**. (See **Image 1**: C14, C15, C16, C17) 2. **Only one pad is connected to a polygon.** (See **Image 2**: R10) 3. **Neither pad is connected to a polygon.** (See **Image 2**: C12, R11) In the third case, I made an effort to route the traces symmetrically to the component to ensure even heat distribution. This follows recommendations I found online to prevent tombstoning—see **Image 3**. Another consideration is whether the components will be soldered or desoldered manually, such as jumpers. Additionally, I assume that for **TH components**, thermal relief should **always** be used when they are connected to a plane/polygon. **My Questions:** 1. **Are my assumptions correct?** Should thermal relief be applied/not applied in each of these cases? 2. If thermal relief is used for thermal reasons, is it important that the number of connections (or their total width) be **symmetrical**? 3. When considering symmetry, should factors like polygon size, nearby vias, and other thermal paths be taken into account? Is this generally based on estimation or engineering judgment?    Thanks in advanced for any answer! Eyal