ThreeBond Technical News
Issued July 1, 202096

Technical Trends in Silicone-Based Conductive Adhesives
for Crystal Devices and ThreeBond 3304J, a Conductive
Adhesive Suitable for Minute-Amount Application
Introduction

ThreeBond develops and sells conductive adhesives that have been widely adopted for a range ofmarket applications. They are often used for crystal devices, particularly crystal oscillators.
The electrical and electronics market is currently seeing remarkable technical innovations, and useof mobile devices such as smartphones, tablets and smartwatches is spreading rapidly. As mobile
devices become smaller and capable of increased performance, the size and thickness of the crystal
devices must also reduce. Today’s devices are between half and a third the size of those from ten
years ago. As of March, 2020 the smallest crystal oscillator in the world is 1.0 mm × 0.8 mm andfurther miniaturization is expected in future (according to ThreeBond’s research).
This article introduces ThreeBond 3304J, which is suitable for use with the world’s smallest crystal
oscillators and compares it to examples of previous products released by ThreeBond for use withcrystal oscillators.
Hereafter, ThreeBond is abbreviated as TB.

Table of Contents
Introduction.................................................1
1. Market Trends and Required
Characteristics........................................2
2. Conductive Adhesive Lineup..................2
3. Product Characteristic Comparison.......3
4. TB3304J..................................................4

4-1. Features...........................................4
4-2. Characteristics.................................4
4-3. Application Performance.................5
5. Future Development Trends....................7
Closing........................................................81

1.

Market Trends and Required
Characteristics

The field of crystal devices is undergoing a significant shift
towards smaller and thinner devices. Surface mounted
device (hereafter referred to as “SMD”) crystal oscillatorsfor mobile devices can be taken as an example. In 2010, thesmallest sizes were 2.5 mm × 2.0 mm or 2.0 mm × 1.6 mm.
Over the following ten years, the smallest size decreased to
1.0 mm × 0.8 mm, less than half the size. Development work
is also being carried on reducing sizes to 0.8 mm × 0.6 mm
Although crystal devices are becoming smaller and thinner,
their functionality has been maintained and performance isimproving.

Lid
Crystal piece(blank)Conductive
adhesiveBase(ceramic package)
Fig. 1 SMD Crystal Oscillator Structure

As crystal devices become smaller, the size (application
diameter) of conductive adhesives will also inevitably
be reduced. In the case of 2.5 mm × 2.0 mm or 2.0 mm ×
1.6 mm SMD crystal oscillators, the application diameter ofthe conductive adhesive is about Ø200 to 250 μm. If the size
is reduced to 1.0 mm × 0.8 mm, the application diameter
is about Ø100 to 150 μm (Table 1). Conductive adhesives
used in such fields require various characteristics. Some
examples of required characteristics are shown in Table 2.

2.

Conductive Adhesive Lineup

Examples of previously-released products for SMD crystal
devices are listed in Table 3. Because many SMDs only
hold the crystal piece on one side, silicone resin withexcellent stress relaxation is used as a binder. Anotherreason for using silicone resin is that there is little change
in its characteristics even at the high temperatures (265℃
or higher) produced during reflow soldering. The example
products have been broadly classified into generations basedon their proportion and process design. This classification
equates to the size of supported SMD crystal device and is
carried out independently by ThreeBond.
The binder design is the element that underwent the largest
improvement between the first and second generations. By
limiting the size of the components contained in the binderthat provide adhesion, the size of supported SMD crystal
devices was reduced. The biggest improvement from thesecond to the third generation is the filler design. Limiting
the size of the filler (particularly coarse powder), allows

Table 1 SMD Crystal Oscillator Size and Conductive Adhesive Application Diameter
Crystal oscillator sizemmConductive adhesive application diameterμm

2.5 × 2.0

2.0 × 1.6

Ø200 to 250

1.0 × 0.8
Ø100 to 150

Table 2 Required Characteristics for Conductive Adhesives for SMD Crystal Oscillators
Classification

Workability

Characteristic

2

Item

Required characteristic(1) Discharge performance

The nozzle does not clog during use(2) Application performance

Optimum application diameter(3) Shape retention

Shape is maintained after application(4) Adhesion

Does not peel off due to impact when dropped(5) Conductivity

Low CI (crystal impedance) value is maintained(6) Heat resistance

Little change in characteristics during reflow soldering(7) Low outgassing

Low levels of outgassing from cured materials

application with nozzles with smaller inner diameters than
before, enabling support for the miniaturization of SMD
crystal devices. In this case, filler is a general term for
conductive fillers and other functional fillers.

3.

Product Characteristic Comparison

A list of characteristic values of example products fromeach generation is shown in Table 4. In order to respondto the miniaturization of SMD crystal devices, the particle
diameter of the components that make up the conductive
adhesive is also getting smaller. As a result, the chip bondstrength (bond strength) tends to decrease up to the third
generation.

the diameter of the filler particles shows that the ratio of
the binder component at the adhesive interface with theadherend is higher when the filler contains particles witha large diameter, resulting in greater bond strength. On
the other hand, fillers containing particles with smaller
diameters have less of the binding component at the adhesioninterface. This reduces contact between the binder and theadhered, thereby reducing the bond strength.
Filler containing
large-diameter particles

In general, when comparing adhesives containing large filler
particles and small filler particles, the bond strength tends todecrease as the filler particle size decreases. This is because
the ratio of the binder component at the adhesive interface
with the adherend is higher when the filler contains particles
with a large diameter.

Filler containing
small-diameter particles: Filler

Binder component that contributes
to the bond strength at the interface

Fig. 2 Effect of Filler Size on Bond Strength

Figure 2 shows a model of a spherical filler. Focusing on
the binder component at the adhesive interface, comparing

Table 3 Examples from Product Lineup
Classification
Product

First generation

Second generation

TB3303M

TB3303G (NEO)TB3303R

TB3304

TB3303N

Third generation
TB3303Z

TB3303Y

TB3304C
TB3304D

Binder resin

Silicone-based

Silicone-based

Silicone-based

Minimum supported crystal
oscillator size

5.0mm × 3.2mm,
3.2mm × 2.5mm

3.2mm × 2.5mm,
2.5mm × 2.0mm

2.5mm × 2.0mm,
2.0mm × 1.6mm

Features/improvements fromprevious generation

Good adhesion to goldplated electrodes

Reduced size of adhesionimparting component in binder

Reduced filler size(coarse powder)

Table 4 List of Characteristic Values of Example Products
TB3303G
TB3304D TB3303Z(NEO)

Testing
methodTest item

Unit

TB3303M

Viscosity

Pa•s

40

40

50

70

3TS-2F00-007

Structural viscosity ratio

—

2.8

2.8

3.2

3.1

3TS-2F10-004

Volume resistivity

10 -6Ω•m

1.9

2.5

1.3

0.6

3TS-5100-002

Chip bond strength

MPa

3.2

3.0

2.4

1.4

3TS-4180-002

Standard curing conditions—

180℃ ×60min

180℃ ×60min

180℃ ×60min

210℃ ×60min—

Recommended nozzle
inner diameter

μm

210

210

140

130

—

■ Curing conditions
Curing equipment: Hot air drying ovenCuring atmosphere: Air

Remark(s)Shear velocity:
1.92 s-1

2Ø gold-plated chip/
gold-plated plate*Physical properties listed above are representative values.

3

TB3304J

4-1. Features
TB3304J was released in February 2020. It is a siliconebased conductive adhesive with the following features.
(1) High precision minute-amount application(2) High structural viscosity ratio(3) High bond strength(4) High heat resistanceIn order to respond to increased miniaturization of SMD
crystal oscillators, improvements to various physicalproperties such as bond strength are necessary in addition toallowing minute-amount application. For this reason, many
elements of the binder and filler design have been improved
during the development of TB3304J. In the product lineup, it
is classified as part of the new fourth generation.

4-2. Characteristics
The characteristic values of TB3304J are shown in Table 5.
A nitrogen atmosphere was used for measurement to matchthe curing environment when used with crystal oscillators.
In TB3304J, the design of the filler has been greatly
improved in order to allow for high precision minute-amountapplication. As a result, bond strength, which previously
had to be reduced as a trade-off for achieving minuteamount application, has been successfully maintained while
limiting the maximum particle size of the filler to 10 μm or
less. In addition, because it is necessary to hold the crystal
piece firmly even when minute amounts are applied, it was
designed to have a high structural viscosity ratio in order toimprove shape retention after application.

As shown in Table 2, low outgassing from cured products
is required in the crystal device field. One characteristicof crystals is that they have a fundamental frequency that
depends on mass. The sensitivity is extremely high, and thefrequency fluctuates even with nanogram-order changes
in mass. Because the crystal device has a closed structure,
if outgas generated from the material cured with adhesive
after assembly adheres to the crystal piece, the frequency
will deviate from the design value. The mass of the attachedsubstance and the change in frequency can be calculatedusing the Sauerbrey equation shown in Figure 4. With a
50 MHz crystal oscillator, this corresponds to a change ofabout 1 Hz per 1/100 nanogram.
First
generation
TB3303M
SecondGeneration
TB3303N
TB3303R TB3303G(NEO)TB3303Y
TB3304

Bond strength

4.

Third
generation
TB3304C
TB3304D
TB3303Z

Fourthgeneration
TB3304J

Minute-amount application* Bond strength: Measured with 2Ø gold-plated chip/gold-platedplate

Fig. 3 Relationship between bond Strengthand Minute-Amount Application for Each
Product

The bond strength and minute-amount application of
the example products mentioned above and TB3304J are
mapped in Figure 3.

Table 5 TB3304J Characteristic Values
Test item

Unit

TB3304J

TB3303G(NEO)

Testing
methodRemark(s)Maximum filler particle diameter

μm

~10

~50

—

D100 value of laser diffraction

Viscosity

Pa•s

80

40

3TS-2F00-007

Shear velocity: 2.0 s-1

Structural viscosity ratio

—

5.2

2.6

3TS-2F10-004

Shear rate ratio: 2.0/20 s-1

Volume resistivity

×10 -6Ω•m

4.5

2.3

3TS-5100-002

Chip bond strength

MPa

2.2

2.4

3TS-4180-002

2Ø gold-plated chip/gold-plated
plate

Dynamic mechanical analysis (DMA)
measurement

GPa

0.3

0.3

3TS-4730-001

DMA method E’ at 25℃

Recommended nozzle innerdiameter

μm

50

210

—

■ Curing conditions*Physical properties listed above are representative values.
Curing equipment: Hot air drying ovenCuring temperature: TB3304J: 60 min at 210℃ and 30 min at 300℃
Curing atmosphere: Nitrogen		
TB3303G (NEO): 60 min at 180℃ and 30 min at 300℃

4

(1) Adhesive application performance(2) Applicator performance (condition setting)(3) Nozzle accuracy

Fig. 4 Sauerbrey Equation

Annealing treatment is generally performed in order toreduce outgas from the cured material as much as possible.
The annealing temperature varies between crystal device
manufacturers, but is higher than that for reflow soldering.
For this reason, annealing treatment was performed for
30 minutes at 300℃ after curing under standard curingconditions and the characteristic values were checked
for any changes in order to ensure that TB3304J wasable to withstand annealing treatment (Table 6). It was
confirmed that the characteristic values do not change dueto the annealing treatment. The amount of outgas fromthe cured product with and without annealing treatment
was also measured. Equipment capable of simultaneous
thermogravimetric and differential thermal analysis (TGDTA) was used for measurement. The results of the TGDTA measurements are shown in Figure 5. They show thatannealing treatment reduces the amount of outgas from thecured material.

4-3. Application Performance
The following three elements can be considered as necessary
for high precision minute-amount application.

High precision minute-amount application cannot be
achieved if one of these elements is missing, and all mustmeet or exceed a certain standard. A further problem
is when good results are not obtained when evaluating
application performance. For example, when the nozzle
clogs, it is necessary to determine whether this clogging
is due to particles contained in the adhesive or due tosurface roughness inside the needle of the nozzle. The same
applies when the application accuracy is inconsistent. It isnecessary to determine whether the problem is caused by
the properties of the adhesive or the accuracy and setting of
the applicator.
The following were used for the three elements whenevaluating the application performance of TB3304J on thisoccasion.
With annealing treatment
Without annealing treatment

3.000
2.000

300°C
-0.13%

1.000
0.000

400°C
-0.44%

350°C-0.22%

450°C-0.82%-1.000TG %ΔF: Oscillation frequency change
F0: Crystal oscillator frequency
A: Electrode area
μ: Shear stress of crystal (2.947 × 1010 kg•ms)
ρ: Crystal density (2,648 kg/m3)
Δm: Mass change-2.000-3.000300°C-0.31%-4.000-5.000-6.000400°C-0.95% 450°C-1.42%

350°C-0.61%

Annealing conditions: 30 min at 300℃
100.0

150.0

200.0

250.0

300.0

350.0

400.0

450.0

500.0

Temp Cel

Fig. 5 Outgassing Volume following Annealing
Treatment

Table 6 Change in Characteristic Values of TB3304J following Annealing Treatment
Test item

Unit

Without
annealingtreatmentWithannealingtreatment

Testing method

Volume resistivity

×10 -6Ω•m

4.5

4.5

3TS-5100-002

Chip bond strength

MPa

2.3

2.2

3TS-4180-002

2Ø gold-plated chip/goldplated plate

Dynamic mechanical analysis(DMA) measurement

GPa

0.3

0.3

3TS-4730-001

DMA method E’ at 25℃

Remark(s)■ Curing conditions*Physical properties listed above are representative values.
Curing equipment: Hot air drying ovenCuring temperature: Without annealing treatment: 60 min at 210℃
Curing atmosphere: Nitrogen		With annealing treatment: 60 min at 210℃ and 30 min at 300℃

5

■ Application test conditions - three elements
Adhesive: TB3304J
Applicator: Air-type dispenser, manufactured by PFA
Corporation (hereafter referred to as “PFA”)
Nozzle:Manufactured by Tecdia Co.,Ltd. (hereafterreferred to as “Tecdia”)

Applicator selection, setting of conditions, and application
tests were conducted with the cooperation of PFA. PFA
applicators have a long track record in the crystal device
market. Likewise, Tecdia nozzles have a proven track recordin the market and the company provides nozzles designed
for use with crystal devices. These test conditions were
determined to be appropriate to accurately determine theapplication performance of TB3304J. The objectives set inthis application test are shown below.
Application diameter:

Ø100 μm, Ø80 μm

the application diameter. Application in a perfect circle isdesirable, however, distortion will occur if the propertiesof the adhesive do not match the adhesive conditions. The
appearance confirmation results for TB3304J are shown in
Fig. 6.
Table 8-1 Application Test Results (Test 1)
Application diameter

Point 1

Point 2Average (μm)

101.57105.79Minimum (μm)

89.65

94.00

Maximum (μm)

115.43123.963σ (μm)

13.18

13.29

Table 8-2 Application Test Results (Test 2)
Application diameter

Point 1

Point 2Average (μm)

108.26106.02

Minimum (μm)

96.22

96.77

Maximum (μm)

117.89113.953σ (μm)

11.24

8.74

Number of applications: 2,000 shots
Application target:

1210PKG, manufactured by
KYOCERA Corporation

Application precision: 3σ = 20 μm or less
The application test was performed by changing the nozzle
type according to the target application diameter. Table 7
shows the test conditions covered in this article, and Tables
8-1 to 8-3 show the test results. Application was performedon two 1210PKG gold-plated electrodes and Point 1 andPoint 2 were measured.

Table 8-3 Application Test Results (Test 3)
Application diameter

Point 1

Point 2Average (μm)

83.70

81.19

Minimum (μm)

68.63

70.28

Maximum (μm)

95.50

91.64

3σ (μm)

11.51

9.52

The test with a target application diameter of Ø100 μm
using a nozzle with an outer diameter of Ø100 μm achieved
good results, with accuracy of 3σ = approximately 13 μm
compared to a target accuracy of 3σ = 20 μm or less (Table
8-1). Similarly, Table 8-2 shows the results of the test using
a nozzle with a smaller outer diameter of Ø80 μm with atarget application diameter of Ø100 μm. Application waseven more accurate, with an accuracy of 3σ = approximately
11 μm. In the final test, the target application diameter was
Ø80 μm. This test assumes that the SMD crystal oscillator
has a size of 0.8 mm × 0.6 mm. In this test, a nozzle with anouter diameter of Ø80 μm was used, and a highly accurate
result of 3σ = approximately 11 μm was obtained (Table 8-3).
In this application test, the adhesive shape (appearance)at the time of application is also confirmed along with

TB3304J (point 1)

TB3304J (point 2)

Gold-plated electrodeFig. 6 Appearance of TB3304J during Application

Table 7 Application Test Conditions and Nozzles Used

6

Application test
numberTarget application
diameter (μm)

Nozzle usedNozzle inner diameter(μm)

Nozzle outer diameter
(μm)

1

φ100

ARQ-S-0510-S

φ50

φ100

2

φ100

Customize Nozzle

φ50

φ80

3

φ80

Customize Nozzle

φ50

φ80

Confirmation of the appearance of the adhesive with adigital microscope after application showed that the circle
was extremely well-formed, a result that confirms thepreviously-established accuracy of application.
Table 9 and Figures 7-1 and 2 show the results of comparativeevaluation of TB3304J, TB3303Z, and TB3304D under theconditions of Test 1, with a target application diameter ofØ100 μm. Although TB3303Z, which has the best minuteamount application among the 3rd generation, was not able
to meet the target, TB3304J demonstrated extremely highprecision application.

5.

Future Development Trends

As stated above, TB3304J was been designed specificallyfor application precision. From 2020 onward, the spreadof 5G communication networks will diversify the type ofterminals connected to networks, and it is expected that
greater reliability will be required in the crystal device
market. In order to meet these needs, we will continue
to place emphasis on high reliability as we focus on thedevelopment of products with low levels of outgassing andimproved stress relaxation (reduced elastic modulus).

The Tecdia nozzles used in this application test are shownin Table 10. None of these products are custom made and all
can be obtained for general use.

Table 9 Application Test Results for Each Adhesive
TB3304J

Application diameter

TB3303Z

TB3304D

Point 1

Point 2

Point 1

Point 2

Point 1

Point 2Average (μm)

101.57105.7998.65

100.38

93.67

97.65

Minimum (μm)

89.65

94.00

82.40

82.26

62.90

67.81

Maximum (μm)

115.43123.96120.04119.78118.53118.453σ (μm)

13.18

13.29

20.42

19.03

25.39

22.06

3σ of Point 1

3σ of Point 2

13.18

13.29
20.42

19.03
25.39

0.0

5.0

10.0

15.0

20.0

25.0

22.06

30.0

0.0

5.0

10.0

15.0

20.0

25.0

3σ [µm]3σ [µm]Fig. 7-1 Application test results

Fig. 7-2 Application test results

30.0

Table 10 Information on Nozzles Used
Model

Diagram number

Inner diameter (μm)

Outer diameter (μm)

Customize Nozzle

TEC-4301054 #1

50

80

ARQ-S-0510-S

TEC-4300872 #2

50

100

7

Closing

This article describes a product that is suitable for use in the crystal device field, where products have undergone remarkablereductions in size and thickness. By adjusting the applicator conditions and nozzle used, high-precision application of TB3304J
is possible at any diameter down to the minimum diameter of Ø80 μm. This opens up the possibility of a wide range of futureapplications in crystal devices.
We at ThreeBond will continue to focus our efforts on product and technology development in line with market trends in orderto ensure the contribution our products make to the industry.
<References>
1) Okano, Shotaro. Quartz Frequency Control Devices, Techno Co., Ltd. (1995)
2) Suganuma, Katsuaki. Introduction to Conductive Adhesives, Kagakujyoho Shuppan Co., Ltd. (2014)
3) ThreeBond. Application Note 97 (2013)
4) ThreeBond. Technical News 27 (1988)
5) ThreeBond. Technical News 52 (1999)
6) ThreeBond. Technical News 93 (2019)

ThreeBond Co., Ltd. R&D Headquarters
2nd Development Division, Functional Material Development Section
Takashi Suzuki
Takashi Nemoto

ThreeBond Co., Ltd.
8

4-3-3 Minamiosawa, Hachioji,
Tokyo 192-0398
Tel: +81-42-670-5333