Qualification of Alternative EMI Shielding Silver Film Material

Abdul Khan – April 2007

Business Case : Electromagnetic interference (EMI) shielding is critical to the proper functioning of Mobile Devices products. EMI shielding film material is currently the only source of this material used by Mobile Devices products. A new and alternative EMI shielding film material will help to reduce cost of raw material and could initiate a cost reduction on the current EMI material.

Opportunities : EMI shielding film material is identified as one of the major cost contributor of Flex and RigidFlex board fabrication, cost savings opportunity is identified by introducing a new and alternative material.

Goal Statement : To achieve cost saving of >US$50K through implementation of new and alternative source of EMI shielding film and to ensure no significant difference in Electrical and Mechanical quality performance compared to current EMI material.

Project Scope : To validated major Electrical and Mechanical quality performance between different material and to qualify the EMI material to realize cost savings.

Conclusion : The use of new EMI material is qualified as a new and alternative EMI shielding film material for the current FPC and RFPC applications. Critical product level test validated for electrical (GSM-desense), (TRP & TIS-CDMA) and mechanical (flip cycle)

Electrical Test - CDMA Desense :

• Free space TRP and TIS test

• Comparing 3units (Z6m) of current and new EMI film material was laminated on the Flex to validated CDMA performance of each EMI material.

• According to “BIG_RULES_RADIATED_DOCUMENT” for CDMA the result for SO (flip open) & SC (flip close) using new material is within the antenna desense of 3 dB or less for CDMA criteria for free space.

• The new EMI samples performed identical to the shipping phones and all passed. There was however a slight improvement in the performance for higher frequencies for the new EMI material of 1-2 dB.

Abrasive Test :

• Validated for surface reliability requirement with reference

Pencil Hardness Test RCA Abrasion Resistance

‐With reference to must meet the min 50cycle both material wear through the exposed surface.

‐ Advantage of  new EMI is that the protecting liner can easily separate to the film compare to current EMI with a sharp tool and skills to separate the film.

#1‐ #2‐

#1‐ #2‐

#1‐ #2‐

#1‐T  #2‐

50cycle25cycle

Test Data (Radiated)

• Radiated sensitivity were tested on new and current EMI film. Measurements on GSM 850/900/1800/1900 bands did not exhibit abnormalities with scratch & without scratch on EMI film surface.

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GSM850 Sensitivity Plot - TSS100 (DUT 1)

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GSM850 Sensitivity Plot - TSS100 (DUT 2)

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GSM850 Sensitivity Plot - TSS100 (DUT 3)

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GSM850 Sensitivity Plot - TSS100 (DUT 4)

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GSM850 Sensitivity Plot - TSS100 (DUT 5)

With scratch on EMI film surface (using pen knife)

Test Data (Radiated) : (GSM850)

With scratch on EMI film surface (using pen knife)

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GSM850 Sensitivity Plot - PC5000 (DUT 1)

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GSM850 Sensitivity Plot - PC5000 (DUT 2)

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GSM850 Sensitivity Plot - PC5000 (DUT 3)

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GSM850 Sensitivity Plot - PC5000 (DUT 4)

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GSM850 Sensitivity Plot - PC5000 (DUT 5)

Project Scope Test Outline :

• The current production Hinge Flex is using current EMI, a sample of new EMI was build to evaluate the mechanical performance and determine the sensitivity of the receiver with the use of new EMI material.

Electrical Test - GSM Desense :

• Receiver sensitivity Radiated test was performed to evaluate desense for GSM system in GSM 850, GSM 900, DCS 1800 and PCS 1900, sensitivity measurement method for GSM is BER test.

• Radiated test for open unit phones was tested in a RF enclosure in an RF lab, Full band sweeps testing all individual channels. Using SDC Test tool matrix.

• 3units (U1-U3) was evaluated comparing current EMI result then replacing the Hinge FPC with sample FPC using new EMI film.

• Result for the RX quality level reported by mobile should be 8 (-103dBm to -102dBm) or less to pass the test. (with reference to ED00130 “Antenna Desense Test”)

ED00130_ver3

GSM 850 - Desense :

‐There’s no significant difference between the performance for both material

‐There are certain channel in which current and new material performs better than the other. 

‐ The lower RX power before the transceiver Desensitizes, the better the material performs

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850 Sensitivity Plot (Unit 1)

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850 Sensitivity Plot (Unit 2)

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850 Sensitivity Plot (Unit 3)

GSM 900 - Desense :

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900 Sensitivity Plot (Unit 1)

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900 Sensitivity Plot (Unit 3)

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900 Sensitivity Plot (Unit 2)

DCS 1800 - Desense :

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1800 Sensitivity Plot (Unit 1)

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1800 Sensitivity Plot (Unit 2)

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1800 Sensitivity Plot (Unit 3)

PCS 1900 - Desense :

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1900 Sensitivity Plot (Unit 1)

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1900 Sensitivity Plot (Unit 2)

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1900 Sensitivity Plot (Unit 3)

Mechanical Test - Flip Cycling :

• 5units (U6-U10) was verified for flip cycling test at 50k then to 100k, power-up test and visual on units was conducted to determine the reliability of the new EMI film material.

• No failures were observed on 5 units after 100k cycles.

• Cycling continued on the remaining unit/s up to 250k cycles.

50k 100k 250k

U6 PASS PASS FAIL

U7 PASS PASS PASS

U8 PASS PASS PASS

U9 PASS PASS PASS

U10 PASS PASS PASS

Unit no.Remarks

(after 100k cycle)

Flip Cycle Remarks(after 250k cycle)

Before flip cycle

After flip cycle

No damages seen on the flexTearing cause during flex removal on the flip

U6