Heat pipes are initially manufactured in round shapes, but can be customized through a series of bending and flattening processes to form 2D or 3D shapes. Customized heat pipes can transfer heat from the source to almost anywhere that the design requires. Examples of thermal solutions using custom heat pipes can be found on this page.

What We Can Manufacture

For custom, copper heat pipes, we can produce different diameters and lengths. Most common diameters are 4mm, 5mm, 6mm, 8mm, and 10mm. Lengths can also range from 80mm to 500mm. Working fluids can either by H₂0 distilled water or CH₃OH methanol. For surface finishes, we offer anti-oxidation and nickel plating. Nickel plated finishes are great for soldering heat pipes to aluminum parts.

Working Fluids

Other types of working fluids are not compatible with copper heat pipes.

Types of Wick Structures

Rapid Prototyping of Custom Heat Pipes

We offer rapid prototyping services for custom heat pipes. If tooling is not required, prototypes can be made in about 1 week. For parts that require special tooling, the turnaround time is about 2 weeks. The lead time will depend on the design of the heat pipe. Please contact us for more information.

Super Thin Heat Pipes for Smart Phones and Mobile Devices

We make heat pipes that are as thin as 1.0 mm (0.040″), which can be used on smart phones, laptop computers, tablets and other miniature electronic devices. The heat pipes are 100% individually tested to ensure heat transfer efficiency. Other thicknesses including 1.2 mm, 1.5 mm, 1.6 mm and 1.8 mm are also available.

Bending of Heat Pipes

To minimize the impact on thermal performance, we recommend the following bending radii and angles as the design guidelines.

Diameter	Minimum R	Suggested R	Minimum Bending Angle	Suggested Bending Angle
4 mm	9 mm	12 mm	90 °	120 °
5 mm	12 mm	15 mm	90 °	120 °
6 mm	14 mm	18 mm	90 °	120 °
8 mm	20 mm	24 mm	90 °	120 °

To make sure custom bent heat pipes are manufacturable, the inner radius needs to be at least 2x the diameter of the heat pipe. Otherwise, the heat pipe will be internally damaged during bending.The Qmax will reduce by about 2.5% for every 45-degree bend. The performance of the heat pipe will decrease by about 20% after the first bend, and then down by 10% for each additional bend.

Flattening of Heat Pipes

The following table provides a guideline for the flattening of heat pipes. For diameters and thicknesses not listed in this table, please contact us.

Diameter (D)	Thickness (T)	(T) Tolerance	Width (W)	(W) Tolerance
Ø4	2.0	+0.05/-0.10	5.23	+/-0.15
Ø4	2.5	+0.05/-0.10	4.96	+/-0.15
Ø4	3.0	+0.05/-0.10	4.65	+/-0.15
Ø5	2.0	+0.05/-0.10	6.82	+/-0.15
Ø5	2.5	+0.05/-0.10	6.53	+/-0.15
Ø5	3.0	+0.05/-0.10	6.26	+/-0.15
Ø5	3.5	+0.05/-0.10	5.95	+/-0.15
Ø5	4.0	+0.05/-0.10	5.63	+/-0.15
Ø6	2.0	+0.05/-0.10	8.45	+/-0.15
Ø6	2.5	+0.05/-0.10	8.16	+/-0.15
Ø6	3.0	+0.05/-0.10	7.84	+/-0.15
Ø6	3.5	+0.05/-0.10	7.57	+/-0.15
Ø6	4.0	+0.05/-0.10	7.30	+/-0.15
Ø8	2.0	+0.05/-0.10	11.65	+/-0.15
Ø8	2.5	+0.05/-0.10	11.39	+/-0.15
Ø8	3.0	+0.05/-0.10	11.15	+/-0.15
Ø8	3.5	+0.05/-0.10	10.83	+/-0.15
Ø8	4.0	+0.05/-0.10	10.60	+/-0.15
Ø8	4.5	+0.05/-0.10	10.27	+/-0.15
Ø8	5.0	+0.05/-0.10	10.01	+/-0.15
Ø8	6.0	+0.05/-0.10	9.36	+/-0.15

To Calculate Width

W = Width of Heat Pipe
D = Diameter of Heat Pipe
T = Thickness of Heat Pipe (when flattened)

After flattening, heat pipes cannot by bent out-of-plane (no exceptions). Heat pipes can only be bent out-of-plane when the heat pipe is round.

Heat Transfer Capacity

Effective Thermal Conductivity

With the heat absorbed by the heat pipe (Q), the thermal resistance (R) and equivalent thermal conductivity (K) of the heat pipe can be calculated.
Q: Heat flux
A: Sectional Area of test object
ΔX: Distance from the heating end to the condensation end
ΔT: Difference between the reference temperature of the heating end and the reference temperature of the condensation end

Heat Transfer Capability

Heat Pipe Shape	Cross-sectional Dimensions (mm)	Length (mm)	Minimum Bending Radius (mm)	Heat Transfer Rate (L=150mm) (W)
Round Pipe	Ø4	60-600	10	30
Round Pipe	Ø5	60-600	10	45
Round Pipe	Ø6	60-600	12	72
Round Pipe	Ø8	60-600	24	120
Flattened Pipe	Ø4 X 2.0T	60-600	10	25
Flattened Pipe	Ø5 X 2.0T	60-600	10	31
Flattened Pipe	Ø6 X 2.0T	60-600	12	42
Flattened Pipe	Ø8 X 2.0T	60-600	25	55

Heat Pipe Tester (LW – 9354)

With Long Win’s LW-9354 heat pipe performance tester, we can evaluate the performance of heat pipes with different testing conditions. The principle of the heat pipe testing equipment is to set a simulated heating source at one end of the heat pipe, and set a cooling device at the other end of the heat pipe to simulate the heat sink. We can then measure the temperature difference between the hot and cold ends of the heat pipe (∆T=Thavg − Tcavg) through the heat absorbed by the heat pipe (Q), the thermal resistance (R) and equivalent thermal conductivity (Keff) of the heat pipe can be calculated. We can evaluate the thermal performance steady-state of a heat pipe, thermal resistance measurement of a heat pipe at different angles and the thermal response rate of a heat pipe.

Tests Available:

1. Thermal Performance Steady-State Test
2. Thermal Resistance Measurement at different Angles
3. Thermal Response Rate Measurements

Steady–State Test and Curve

Step 1:

Place the test object between the heating end and the condensation end.

Step 2:

Input heat from a controllable heat source and remove the heat from the water cooling through the specimen.

Step 3:

Measure the heating end, the reference temperature of the condensing end and the temperature of other points (Tc1, Tc2, Thc, Thb) on the heat pipe.

Thermal Resistance of Heat Pipes Example

Heat pipes with larger diameters transfer more heat than heat pipes with smaller diameters. Shorter length heat pipes can also transfer more heat than heat pipes with longer lengths.

Heat Pipe Power at Different Angles Example

Below are the results of a 6mm diameter and 200mm length heat pipe tested at different angles using the attitude adjustment device.

Thermal Response Rate Example

Tt: Water Temperature
Tc: Heat Pipe Temperature

The thermostatic water is set to 65°C The initial temperature of the heat pipe is approximately ~20°C. After about7 seconds, the hot end temperature rises to about ~55°C and approaches steady state.

Reliability Test

No.	Test Item	Test Conditions	Sampling Ratio	Purpose
1	High Temp. Aging Test	Ambient Temp. 210 C for 12 hr	100%	Leakage check & aging
2	Thermal Response Test	Insert 1/3 – ½ length of pipe into 50°C water. The temp of other end shall rise to standard value in 25 seconds.	100%	Vacuum & leakage check
3	Qmax Test	Heating Length = 25-35mm, Test temp = 60°C	100%	To measure the max. heat transfer rate
4	Rth Thermal Resistance Test	Fix heat transfer rate and measure temp. difference of heat pipes	>1pcs/2hr	To ensure thermal resistance of each pipe be lower than spec
5	Accelerated Life Test	140 C for 1000hr. Performance decrease by less than 7%	By case	To predict life of heat pipe at certain operating temp.
6	Continuous Life Test	Continuous testing at normal operating conditions	By case	To measure actual life of heat pipe until failure occurs
7	Thermal Cycling Test	Temp. varies from -30 C to 120 C in 10hr, 600 cycles	By case	To measure performance variation after thermal cycling

Heat Pipe Assembly

With custom heat pipes, we also offer custom heat pipe assemblies. Please visit our Heat Pipe Assemblies page for more info.

Request information or quote of custom heat pipe