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Notes of hand solderingfor MLCC

Murata will explain what kind of problem willbe caused in MLCC when it is soldered and

solder correction by soldering iron. AlsoMurata will explain how to solve it.

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Agenda

1. What kind of problem will be caused when MLCC is

soldered by soldering iron?

2. Relationship between preheating temperature of PCB

bending strength

3. Mechanism of bending strength deterioration

4. Method of hand soldering.

4.1 Using soldering iron

4.2 Using hot air gun

4.3 Hot air gun operating procedure

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1. What kind of problem will be causedwhen MLCC is soldered by soldering iron?

Then, What shall we do?

Cracking might be occurred into MLCC due to thermalshock by rapid and local heating from soldering iron.

The bending strength might decrease due to low

temperature preheating condition of PCB.

(because of increasing remained tensile stress)

Optimized preheating condition of PCB

and MLCC is necessary.

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Test method : Bending strength test

Test board:100mmx40mm thicknes:1.6mm FR4 solder:Sn-3Ag-0.5Cu

Products shall be judged to be defective if the change in capacitance has exceeded12.5%

Test sample : MLCC 0805 X7R 0.1uF 50V

Sample condition : MLCC sample is soldered on the test board by reflow soldering,

Then, one side of solder fillet is melted again by soldering iron

At this time, test board is preheated to 4 conditions of temperature.

Preheating condition : room temp.(25deg C), 75deg C, 125deg C, 175deg C, and only reflow (not hand soldering)

Optimized preheatingtemperature condition of PCB iseffective to improve decreasingbending strength.

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Hand work by soldering ironafter reflow will decreasebending strength.

Bend length (mm)

Not preheating

Only reflow

Surviva

lrate(%)

2. The Relationship between preheatingtemperature of PCB and bending strength

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(2)MLCC

(1)PCB

(3)solder

Tensile stress (-)Compressive stress (+)

3. Mechanism of bending strength destroy

MLCC is strong with compressive stress, but is

weak with tensile stress.

(1) : compressive stress by shrinking PCB

(2) : tensile stress by shrinking MLCC

(3) : tensile stress by shrinking solder

(ref)

Line expansion coefficient (ppm/deg C)FR4 board20, MLCC11, solder22

Hand soldering without preheating of PCB

The stress under cooling after reflow

concentratedpoint of stress

Remained stress ofconcentrated point

Remained stress ofConcentrated point

Tensile stress (-)Compressive stress (+)

reflow soldering

Remained tensile stress of hand soldering without preheating of the PCB is bigger than reflow soldering.

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4. Hand soldering method

1 temperature condition

about the temperature of the soldering iron head

BC type/3mm iron head is recommended because of large thermal capacity

about preheating of the PCB

At a high temperature , considering heatproof of parts as much as possible

As the PCB, it is necessary to check the time of heating2) Example of preheating PCB

One-side mounted substrates Both-side mounted substrates (as below)

hot plate hot air gun

B Type/R0.5

BC Type/3mm

Quotation from JEITA safety application guideRCR-2335B

4.1 using soldering iron

SizeTemp. of Ironhead

Preheating ofthe PCB,MLCC

1206 max 350 deg. C max

1210 min

T

280 deg. C max

150 deg. C min

150 deg. C min

150 deg. C max

130 deg. C max

90120

90120 90

9090120

90120 90

90

Preheating of MLCC90-120sec.

Preheating of MLCC &PCB 90sec min.

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4.2 using hot air gun

0

20

40

60

80

100

0 1 2 3 4 5 6 7

Bend length (mm)

Survivalrate(%)

distance5mm

angle 40degree

Nozzle 1hole

Nozzlesetting

Photoimage

0

20

40

60

80

100

0 1 2 3 4 5 6 7

Bend length (mm)

Only using hot air gunis better than usingsoldering iron withoutpreheating substrate.

each side 5sec soldering

0

50100

150

200

250

300

350

0 10 20 30 40 50

Time (sec)

Tem

perature(deg.

C) The back

Surface

Soldering ironw/o preheating

Only reflow

Hot air gun

1206 X7R 1uF0603 X7R 1000pF

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4. Hand soldering method.

Soldering ironw/o preheating

Only reflow

Hot air gun

Survivalrate(%)

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1. Pre-soldering on the pads by soldering iron

2. Coating flux on outer electrodes of MLCC

3. Melting again the pre-solder by hot air gun

4. Setting MLCC on pads and soldering one side electrode by hot air

5. Soldering another side electrode using solder wire on the pad ,melting solder by hot air gun

6. Cooling

distance betweenMLCC and Nozzle : more than 5mm

Angle : 45deg.Temperature of hot air : less than 400deg.CFlux of air : min. levelInside diameter : 2mmTime

1206 max : 10sec. max1210 min : 30sec. max

0603Size

1 hole nozzle 2mm

JEITA safety application guide RCR-2335B-1amendment1 (2009/8 revised)

4.3 hot air gun operating procedure

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4. Hand soldering method.