SLIDE 1
www.hsg-imat.de
A new method for directly determining the adhesive strength of conductors on micro structured MID
- H. Willeck, HSG-IMAT
www.hsg-imat.de
- H. Willeck, HSG-IMAT
2
A new method for directly determining the adhesive strength of - - PowerPoint PPT Presentation
A new method for directly determining the adhesive strength of - - PowerPoint PPT Presentation
A new method for directly determining the adhesive strength of conductors on micro structured MID H. Willeck, HSG-IMAT 4M2007 Conference on Multi-Material Micro Manufacture 3-5 October 2007 Borovets, Bulgaria www.hsg-imat.de Overview
SLIDE 2
SLIDE 3
www.hsg-imat.de
- H. Willeck, HSG-IMAT
3
10 mm Rotation angle sensor in MID LDS technology (BMBF-Verbundvorhaben IMDAKT )
Directly determining the adhesive strength of conductors on MID (Moulded Interconnect Devices) Adhesive strength is important for the reliability and hence an important quality feature. Typical geometry of conductors on MID:
- approx. 200 – 500 µm width, 10 – 20 µm thick
Established measurement methods are not suitable.
Research objective
SLIDE 4
www.hsg-imat.de
- H. Willeck, HSG-IMAT
4
Established methods for determining the adhesive strength
Fpull
substrate Metal layer/ conductor adhesive hook Pull test Metal areas with several mm² are required. FPeel movement of the substrate Peel test Layer thickness > 20µm Required width > 0,5mm Required length > 30mm conductor soldered eye peel off hook
For geometry reasons these methods are not suited for determining the adhesive strength on MID parts
SLIDE 5
www.hsg-imat.de
- H. Willeck, HSG-IMAT
5
New measuring principle
Detection of conductor profile and substrate tilt by scanning the conductor surface Peel off the conductor with a micro peel off chisel Acquisition of paths and forces Extraction of the adhesive strength of the conductor
z y
Conductor- substrate interface
substrate metal layer micro peel
- ff chisel
movement Fz Fy
Reproduction of the force situation of peeltest and pull-sheartest with different peel off chisel geometries and resolution
- f the force
SLIDE 6
www.hsg-imat.de
- H. Willeck, HSG-IMAT
6
Requirements for the measuring device
Suitable for conductors with 200 – 1000 µm width and 5 – 30 µm thickness Range of forces to be detected approx. +/- 50 N, smallest forces ≈0,01 N Very stiff mechanical design (≈1 N/µm) High accuracy of the positioning system Semi-automated measurements Compensation of substrate tilt by profile detection
- f the conductor and substrate
Basic comparability to established measurement procedures
SLIDE 7
www.hsg-imat.de
- H. Willeck, HSG-IMAT
7
Sensor and peel off unit
Sensor housing Housing reinforcement Magnetic clamp Parallel spring suspension with piezoelectric load cell (z-component) Holder for the LVDT-deflection sensor for the profile detection Peel off chisel Parallel spring suspension with piezoelectric load cell (y-component)
SLIDE 8
www.hsg-imat.de
- H. Willeck, HSG-IMAT
8
Design of the measuring device
Granite rack High accuracy positioning system with multiple axes Sensor and peel off unit Peel off chisel Optics for substrate adjustment and monitoring Characteristics
Linearity: +/- 1.5 % FSO Stiffness: ≈ 1 N/µm
SLIDE 9
www.hsg-imat.de
- H. Willeck, HSG-IMAT
9
Peel off chisel geometry
Cutting edge radius rβ: <2µm Chip angle γ: 10°
- 60°
Different force situations
- n the chisel blade
small angle: Fy correlates
with shear force
big angle: Fz correlates
with peel force Manufacturing
- 1. Milling
- 2. Hardening
- 3. Grinding
Chisel cutting edge α γ β substrate rβ
z y Fy
- shear force
Fz ≈ ≈ ≈ ≈ 0 small chip angle Fy < Fz Fz
- peel force
big chip angle
SLIDE 10
www.hsg-imat.de
- H. Willeck, HSG-IMAT
10
Results of peeled off copper conductors on FR4 substrate
Conductor length: 5 mm, width: 500 µm, thickness: 35 µm, chip angle: 60°
y forces z forces
y axis position [µm] force [mN]
SLIDE 11
www.hsg-imat.de
- H. Willeck, HSG-IMAT
11
Comparison of z forces with peel forces
Conductor length: 50 mm, width: 500 µm, thickness: 35 µm The z forces are displayed as the absolute value of the z-forces
peel forces z forces
force [mN] y axis position [µm]
SLIDE 12
www.hsg-imat.de
- H. Willeck, HSG-IMAT
12
Results of peeled off conductors
- n MID substrate
Conductor length: 5 mm, width: 500 µm, thickness: 10 µm, chip angle: 60° Cu/NiP/Au on liquid crystal polymer (LCP) made by Laser-Direct- Structuring (LDS)
SLIDE 13
www.hsg-imat.de
- H. Willeck, HSG-IMAT
13
Results of peeled off conductors
- n MID substrate
Substrate after peel off process
100 µm
Peeled off conductor segments
Chisel was moving in the substrate- conductor interface.
SLIDE 14
www.hsg-imat.de
- H. Willeck, HSG-IMAT
14
Results of peeled off conductors
- n MID substrate
- 1000
- 500
500 1000 1500 2000 500 1000 1500 2000 2500 Y-Tisch-Position [µm] Kraft [mN] YKraft [mN] ZKraft [mN]
force [mN] y axis position [µm]
y forces z forces
SLIDE 15
www.hsg-imat.de
- H. Willeck, HSG-IMAT
15
y forces z forces
Approaches for interpreting the results
- 1. Analysis of the maximum force of one segment
- 2. Energy analysis of the complete conductor
- 3. Energy analysis of single segments
segment width 1. 2. 3.
- 1000
1000 2000 3000 500 1000 1500 2000 Y-Tisch-Position [µm] Kraft [mN]
force [mN] y axis position [µm]
SLIDE 16
www.hsg-imat.de
- H. Willeck, HSG-IMAT
16
Approaches for interpreting the results
Comparison of approach 1 and 2 with results from the peel test
- Correction factor for
correlating with peel test necessary
average adhesive strength [N/mm]
Approach 1 Approach 2 Peel test
SLIDE 17
www.hsg-imat.de
- H. Willeck, HSG-IMAT
17
Summary
A device with a new measuring principle for determining the adhesive strength of conductors has been developed and built-up. Results from conductors on printed circuit boards (FR4) of the new measuring principle show good correlation with the well known peel test. Cu/NiP/Au-conductors on MID substrates crack into segments while being peeled off. Forces during peel off process on MID-substrates are in the same magnitude than the forces during the peel test a correlation via correction factor appears possible.
SLIDE 18
www.hsg-imat.de
- H. Willeck, HSG-IMAT
18