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Temperature Rise in PCBs. Temperature rise in a conductor is related to the current flow and cross sectional area. Must not exceed the safe operating temperature for the board/component assembly Can use charts that relate area to temperature rise. Temperature Rise in PCBs. - PowerPoint PPT Presentation
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Temperature Rise in PCBs 1
Temperature Rise in PCBs
Temperature rise in a conductor is related to the current flow and cross sectional area.
Must not exceed the safe operating temperature for the board/component assembly
Can use charts that relate area to temperature rise.
Temperature Rise in PCBs 2
Temperature Rise in PCBs
Thickness of copper is the original sheet thickness plus the added amount due to plating operations.
Temperature Rise in PCBs 3
Relate temperature rise to current to get area of copper
Temperature Rise in PCBs 4
Knowing total thickness and area can use chart to obtain the width.
Temperature Rise in PCBs 5
Profile of trace will not be regular
Temperature Rise in PCBs 6
Charts were produced in early 60s by the US National Bureau of Standards.
Assumed smaller component areas compared with copper area.
Did not take into account effects of dielectric thickness and material. Thermo-conductive materials have much great cooling effects.
Assumed two layer boards only – much greater cooling with multi-layer boards
Temperature Rise in PCBs 7
Current charts NBS (National Bureau of Standards) Report #4283
“Characterization of metal-insulator laminates”, D.S. Hoynes, May 1, 1956. Commissioned by Navy Bureau of Ships The charts are based on double sided material
Formalized in Mil-Std-275 At this time internal charts were created using 50% of external
currents without empirical data. Incorporated into IPC 2221 Perry Initiative, 1994, IPC-D-275
Caused 2221 to be split into two standards 2221 and 2222
Temperature Rise in PCBs 8
Current
Current (amps)
T (
C)
10 sq.mils Int, 2oz, 70 mil, polyimide
020406080
100120140160180200
0.68 0.93 1.11 1.26
Data IPC - McHardy Mil - Brooks
Temperature Rise in PCBs 9
Substrate Thickness
0
10
20
30
70 50 20 10
PCB Thickness (mils)
T (
C)
10 sq.mils Int, 2oz, 70 mil, polyimide
Temperature Rise in PCBs 10
Substrate Material
0
30
60
90
120
150
Thermagon Polyimide FR-4 XXXP IPC
0.88
1.2
1.44
1.8
2.05
Current (amps)
T (
C)
Material
OF
F T
HE
SC
AL
E!
Thermally ConductiveBoard Material
Temperature Rise in PCBs 11
Copper Planes
0
20
40
60
80
Plane No Plane IPC
3.22 sq.mils, vacuum, 1oz trace and 2 oz plane, Int with 1 amp with .005 dielectric space
T (
C)
OF
F T
HE
SC
AL
E!
Temperature Rise in PCBs 12
Copper Planes
0
20
40
60
80
Plane No Plane IPC
3.22 sq.mils, vacuum, 1oz trace and 2 oz plane, Int with 1 amp with .005 dielectric space
T (
C)
OF
F T
HE
SC
AL
E!
Temperature Rise in PCBs 13
The new IPC standard is scheduled to be released later in 2003
IPC-2152
Standard for Determining Current Carrying Capacity in Printed Board Design
This has more accurate charts than 2221
Temperature Rise in PCBs 14
What do you use now?
Best tool to use now is the software from Thermal Man:
http://www.thermalman.com/about.shtml
Has free demo available
