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Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Copper Laminate andSkew Mitigation
Megan TetaInsulectro
Mesa, Arizona ● March 3 - 6, 2019
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Overview• Fiber Weave Effect
– What is Skew?
• Copper Roughness and the Effect on Loss
Copper Laminate and Skew Mitigation 2
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
PCB Materials: The Basics
Copper Laminate and Skew Mitigation 3
Heat&
Pressure
• Start with rigid copper clad core.• Circuits are formed in the copper.• The PrePreg is the “glue” to stack these layers (AKA: B-Stage).• Copper foil is used on the outer most layers.• Everything is aligned and then laminated with heat and pressure.
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Reinforced vs Unreinforced Laminates
Copper Laminate and Skew Mitigation 4
• Glass Reinforced
Thick (200 um) - Niche-Excellent performance/reliability-Expensive to manufacture
Thick (200 um) - Common-Excellent performance/reliability-Less expensive to manufacture
Thin (50 um) - Common-Excellent performance/reliability-Less expensive to manufacture
Thin (50 um) – Less Common-Less performance/reliabilityCAF; Pad Cratering; Etch Defects-Same or more expensive to manufacture
• Unreinforced
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Why Glass Fabric?
Copper Laminate and Skew Mitigation 5
106
1080
7628
• In Fabrication• Supports B-Stage (prepreg)• Controls spacing• Cost
• In Use• Strength• Cost
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Skew• Skew is the misalignment of two signal edges of a
differential pair as they arrive at the terminals of the differential receiver.
Copper Laminate and Skew Mitigation 6
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Spread Glass for Differential Pairs
Copper Laminate and Skew Mitigation 7
• Reduces micro Dk effects• Reduces signal skew• Much better for cost and fabrication than rotating board on panel.
Differential Stripline
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Fiber Glass Square Weave
Copper Laminate and Skew Mitigation 88
• About 2.0 mils• Great for fill of
heavy coppers. • Not stable
106
• About 2.5 mils• Good for fill.
• 3.0 to 3.5 mils• Some fill
properties• Good stability
• 7.0 to 8.0 mils• Good for building
thickness.• Very Stable
1080 2113 7628
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Fiber Glass Square Weave
Copper Laminate and Skew Mitigation 99
• About 2.0 mils• Low skew
1067
• About 3.0 mils• Good for drilling
• 3.0 to 3.5 mils• Low Skew
• 7.0 to 8.0 mils• Low Skew
1086 3113 1652
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Example Dk/Df Charts
Copper Laminate and Skew Mitigation 10
Glass Style
% Resin
Thick-ness(inch)
Dk Df
1x106
71.0 .0020 3.81 0.024
1x1080
58.0 .0025 4.04 0.021
1x2113
54.0 .0035 4.11 0.020
2x1080
55.0 .0040 4.1 0.020
1x7628
46.0 .0080 4.28 0.021
Glass Style
% Resin
Thick-ness(inch)
Dk Df
1x1067
66.5 .0020 3.05 0.0017
1x1078
66.0 .0030 3.09 0.0018
1x3313
58.5 .0040 3.07 0.0017
2x1078
60.0 .0050 3.19 0.0021
2x3313
58.5 .0080 3.24 0.0022
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Test PCB Skew Data
Copper Laminate and Skew Mitigation 11
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Signal Integrity and Copper Roughness
Copper Laminate and Skew Mitigation 12
Clad
0
+0
2
4
6
8
0.1 1 10 20 40 80
Skin
Dep
th (u
m)
Frequency (GHz)
Skin Depth
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Types of Copper Foil• Electrodeposited (ED)
– Drumside Treated Foil (DSTF) – Reverse Treat Foil (RTF)– Very Low Profile (VLP)
• Rolled Annealed (RA)
Copper Laminate and Skew Mitigation 13
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Copper Roughness
Copper Type RzStandard 10 micronsRTF 7 micronsVLP 5 micronVLP-2 2 micronRa ~2 micron
Copper Laminate and Skew Mitigation 14
Std 1oz Foil
VLP-2 1oz Foil
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Core Surface treatments
Copper Laminate and Skew Mitigation 15
Oxide 1 Oxide 2
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Loss and Copper Foil Types
Copper Laminate and Skew Mitigation 16
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Copper Roughness and Loss
Copper Laminate and Skew Mitigation 17
4.213.86
1.8
1.09
0.29-8.75
-8.12
-7.88
-7.35-7.25
-9-8.8-8.6-8.4-8.2-8-7.8-7.6-7.4-7.2-7
00.5
11.5
22.5
33.5
44.5
RTF MWG-VSP HS-VSP HS1-VSp NP-VSP
Loss [dB]R
z [u
m]
Copper Foil Types
Material Differences - PCB MaterialsTestConX 2019Session 6B Presentation 3
March 3-6, 2019TestConX Workshop www.testconx.org
Conclusion
• Glass reinforced dielectrics can be used in higher frequency applications if utilizing spread weaves.
• Copper roughness should be considered when considering frequencies >2 GHz.
Copper Laminate and Skew Mitigation 18