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Resin Coated Metal Sheets “ FCOAT-HA”

1.

INTRODUCTION

1.1 Background
Copper or copper alloy such as phosphor bronze havesuperior electrical conductivity and ductility. Iron or ironalloy such as stainless steel have excellent rigidity andcorrosion resistance. Beginning with electrical/electroniccomponents, these materials are used in wide range offields. Recently, electrical devices like mobile phone andnotebook computer are becoming more integrated andsmaller in size. Parts used for these devices are also
required to have similar changes.
An example is a shield case for mobile phone. In thepast, creating some space like an air layer could secureinsulation between shield case and conductive components, in order to avoid circuit shunt. However, due todownsizing and high integration, it became impossible tohave such air space. So, insulation has to be provided byother means. For this mitigation, an insulation layer is created to avoid circuit shunt among components. This mitigation is in more and more cases to downsize components.
1.2 Resin Coated Metal Sheets “FCOAT"
In order to meet the above mentioned needs, Furukawa
Electric provides a compound material called resin coatedmetal sheets “FCOAT” shown in Figure 1. Resin varnish
like polyamide-imide (PAI) resin is coated onto the surfaceof metal materials like phosphor bronze and stainlesssteel, then, it is thermally hardened to create an insulation
layer of approximately 10 μm in thickness.1)
1.3 Background of FCOAT-HA Development
Due to recent components downsizing, there has beentimes where more severe processing conditions arerequired at press work. In case where the severe processing conditions were applied to a conventional FCOAT,issues like burr, dulling and resin peeling from metals
might occur. To resolve these issues and to meet customer’s requests, FCOAT, which can endure recent severe
processing conditions by its inherent improved adhesion,
was developed. This is what “FCOAT-HA” is about, introduced for this opportunity.

Figure 1

Resin coated metal sheets “FCOAT”.

2.

QUANTIFICATION OF ADHESIONSTRENGTH BETWEEN METAL AND
RESIN BY SAICAS METHOD

2.1

Quantification Method of Adhesion Strength
Between Metal and Resin

An adhesion evaluation of a conventional adhesive tape isquantified by a peel test. However, it was difficult to evaluate FCOAT by a peel test because its film is way too thin.
So, it was necessary to devise other method to quantify
adhesion strength between the metal and the resin ofFCOAT. As the development of FCOAT-HA was progressing, a surface interracial cutting analysis system (SAICAS)2)
was executed to carry on the evaluation.
2.2 SAICAS Method
An overview of the measurement using SAICAS isdescribed as following. At first, a cutting blade cuts thecoated film at an angle. When the cutting blade reaches
nearby base material, a peeling of the material and thecoating occurs. This part is called “microgap” and loading
Fv detected by load cell decreases rapidly. When themicrogap appears, the cutting blade’s cut operation proceeds only in a parallel direction. The average load FH
after the parallel movement indicates the adhesion
strength.
Figure 2 shows the coated film cutting operation bySAICAS. Figure 3 indicates an example of the adhesion
strength measurement results. This is an example of theadhesion strength measurement of the metal and theresin, on a conventional FCOAT.

Furukawa Review, No. 38

20101Resin Coated Metal Sheets “FCOAT-HA”

FHFVBladeResin

Base materialFigure 2

Schematic diagram of adhesion strength measurement using SAICAS.

3.2 Cross-Section Observation
The cross-section was observed in order to compare thepeeling strength of resin when the material coated withFCOAT was punched by press work. Result is shown inFigure 5.
After punching press, the conventional FCOAT indicated 10 μm of resin peeling. On the other hand, the newly
developed FCOAT-HA showed no peeling due to thestrong adhesion strength. Also, according to figure 5,FCOAT-HA does not only show any peeling, but it is conceivable that dulling and burr are hard to occur. Fromabove reasons, it is believed that FCOAT-HA brings many
advantages into press work technology which leads todownsizing, more complexity, and reduction of maintenance frequency of metallic mold.

Horizontal load
（kN/m）

1.2
1.0

FCOAT-HA- HA

0.8

FCOAT
Resin
Resin

0.60.4Metal

0.2
0.0050100150200250300

Time（sec）（The adhesion strength is about 0.6 kN/m.）

Figure 3

3.

Example of measurement result using SAICAS.
(The adhesion strength is about 0.6 kN/m.)FCOAT
FCOATResin
Resin

Peeled oﬀ
about 10 μm
About 10um

COMPARISON BETWEEN FCOAT AND
FCOAT-HA

3.1 Adhesion Strength
Figure 4 shows a comparison of the adhesion strength
measurement by SAICAS. Stainless steel (AISI301) wasused as a base material. Conventional FCOAT’s adhesion
strength of the metal and the resin is approximately
0.6 kN/m. On the other hand, newly developed FCOAT-HAindicates a value two times higher, approximately
1.4 kN/m. Adhesion was drastically improved, which leads
to an expectation that it can endure more severe press
work than before.

Adhesion strength（kN/m）

1.6
1.4
1.2
1.0
0.8
0.6
0.4

Figure 54

Cross-section observation of metal and resin afterpunching press.

IN CONCLUSION

In our FCOAT-HA development, we focused on andimproved the adhesion strength of the metal and theresin. Our objective was to have no peeling of the metal
and the resin even under severe press work. As a result,the adhesion strength of the metal and the resin reachedvalues approximately 2 times higher. Also, it became possible to inhibit dulling and burr. It is expected that FCOATHA will be utilized as new component material.
Finally, comparative findings are shown in Table 1.

0.2
0.0

Figure 4

Metal

FCOAT-HA
（PAI）

FCOAT
（PAI）

Comparative sample（epoxy）

Comparison of adhesion strength between metaland resin.

REFERENCES(1) FURUKAWA ELECTRIC CO., LTD., “Resin Coated Metal Sheets
FCOAT” Furukawa Review. Vol.32 (2007)(2) Y.Kijima, I.Nishiyama., “The features Evaluation System for Interface
Boundaries of Different Materials,” Journal of The Adhesion Societyof Japan, vol. 41, 234-241, (2007)

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2010

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Resin Coated Metal Sheets “FCOAT-HA”

Table 1Comparative findings.

FCOAT-HA

FCOATComparative
product

Type of resin

polyamide-imide

polyamide-imide

epoxy

Adhesion strength (SAICAS)

approx. 1.4 kN/m

approx. 0.6 kN/m

approx. 0.4 kN/m

As

◦

◦

◦

Reflow simulation (260°C, 2 min.)◦◦◦PCT (121°C, 2 atm, 100% RH, 96 h)◦◦Heat cycle (–55°C×30 min/125°C×30 min, 200 cycles)◦◦◦

Peeling width on punching (dulling) side

almost 0 μm

almost 10 μm

almost 30 μm

Peeling width on die (blurr) side

almost 0 μm

almost 10 μm

almost 10 μm

0.025 R×××0.050 R△△×0.075 R◦◦△

0.100 R◦◦

△0.025 R◦◦△0.050 R◦◦△0.075 R◦◦◦

0.100 R◦◦◦

Abrasion resistance (3 mm steel sphere probe, weight 300 g, velocity 60 mm/min. distance 5 mm)＞ 500 times＞ 500 timesapprox. 200 times

Surface roughness Ra

approx. 0.1 μm

approx. 0.1 μm

approx. 0.1 μm

Insulating resistance (surface resistance)~ 108 MΩ~ 108 MΩ~ 104 MΩCross cut test
(1 mm×1 mm)

Press punchability

Inner bendhing(Resin is inside)

Press bendability
Visual appearance
no trace of crack
or streakOuter bending(Resin is outside)△(flake-like appearance)

For more information, please contact:
The First Marketing Department, Metals Company
TEL: +81-3-3286-3840
FAX: +81-3-3286-3289

Furukawa Review, No. 3820103