VALIDATION OF THE MOUNTING OF 3D PLUS MEMORY STACKS … · graph1. vapor phase soldering profile . VALIDATION OF THE MOUNTING OF 3D PLUS MEMORY STACKS ON PCB – Automatic Reflow

VALIDATION OF THE MOUNTING OF 3D PLUS MEMORY STACKS ON PCB – Automatic Reflow – SOP packages 1/18

3D-Plus, reserves the right to change products or specifications without notice. 3300-1303-1, Release Date : 13/04/05, writer Nicolas Villégier

Doc.No.: 3300-1303

Issue: 1

Date: 04.13.2005

Writer: Nicolas Villégier 3D PLUS Process Engineer

Project sponsored by French Space Agency CNES

Contract No.: 4700006494/DPI500

1. Subject ......................................................................................................................................... 2

2. Module Characteristics ................................................................................................................ 2

2.1. Module definition ................................................................................................................ 2

2.2. Epoxy Resin (cured material) .............................................................................................. 3

2.3. Module Plating ..................................................................................................................... 3

2.4. Connectic Level ................................................................................................................... 4

2.5. Leadframe (SOP modules) .................................................................................................. 4

3. PCB, Solder Paste and Under fill Characteristics ........................................................................ 5

4. Assembly process ........................................................................................................................ 5

5. Reflow temperature profile .......................................................................................................... 6

6. Test file ........................................................................................................................................ 7

7. Results ......................................................................................................................................... 8

VALIDATION OF THE AUTOMATIC

MOUNTING OF 3D PLUS

MEMORY STACKS ON PCB

FOR HIGH LEVEL OF VIBRATIONS



1. Subject

The aim of this project sponsored by French Space Agency CNES was the validation of the

automatic vapor phase reflow mounting of 3D PLUS memory stacks.

The main goal was to survive high level of vibrations.

The validation test file was composed of shocks plus vibrations plus 500TC.

2. Module Characteristics

2.1. Module definition

Mass of the SDRAM 8bit x 64M module = 6.5g

Memory module SDRAM 8bit x 64M # 8 TSOP levels # SOP connectic

grid



2.2. Epoxy Resin (cured material)

Item HYSOL® FP4450 - Loctite

Colour Black

Filler Contents 73% Silica

Extractable Ionic Content Chloride (Cl-): 5 ppm

Sodium (Na+): 1 ppm

Potassium (K+): 2 ppm

1.Thermal

Glass transition (Tg) 155°C

C.T.E. 18 ppm/K

Thermal conductivity (25°C) 0.63 W/m/K

2.Electrical

Properties Test Condition Value Unit Test Method

Volume Resistivity @ 25°C 2.18x1016 .cm ASTM D 257

Surface Resistivity @ 25°C 2.57x1016 /square ASTM D 257

Dielectric Constant @ 25°C, F =

1kHz to 100 kHz 3.6 ASTM D 150

3.Outgassing (ESA ECSS-Q-70-20A)

Total Mass Loss (TML) <1%

Recovered Mass Loss (RML) <1%

Collected Volatile Condensable Material

(CVCM)

<0,1%

2.3. Module Plating

different layers from epoxy resin to outside

Nickel - Electroless 1.5 to 2.5 µm

Nickel – Electroplated 2 to 3 µm

Gold – Electroplated 1.5 to 2.5 µm

1.Thermal

C.T.E. 13 ppm/K

Thermal conductivity (25°C) 92 W/m/K

2.Electrical (values correspond to layers thickness means)

Module type Electrical Resistivity (25°C)

Standard modules plating 5.4 .cm



2.4. Connectic Level

Item Material Thickness

Raw Material BT/Epoxy 0.6 mm

Copper Lines (Internal Conductors) Copper 17 to 35 µm

1.Thermal – Raw Material

Glass transition (Tg) 200°C

C.T.E. X, Y-axes 16-17 ppm/K

Z-axis 55 ppm/K

Thermal conductivity (25°C) 0.36 W/m/K

2.Thermal – Copper Lines

C.T.E. 16-17 ppm/K


3.Electrical – Copper Lines

Electrical Resistivity (25°C) 1.7 .cm

2.5. Leadframe (SOP modules)


Lead Fe-Ni-Co (Kovar) 0.20 to 0.25 mm

Plating Electroplated Nickel

Electroplated Gold

3 to 5 µm

1 to 2 µm

(1.27 µm typ.)

1.Thermal

C.T.E. 5.7 to 6.2 ppm/K


2.Electrical

Electrical Resistivity (25°C) 48 .cm



3. PCB, Solder Paste and Under fill Characteristics


PCB (board) BT Epoxy 2.4mm

Under fill adhesive 3M 2216 B/A Gray Scotch-Weld

Epoxy Adhesive

curing 2h @ 65°C

1.3mm

Solder Paste SOLDERPLUS 6-Sn62-211F RMA

Sn/Pb/Ag (62/36/2)

0.05mm

4. Assembly process

• PCB cleaning with isopropylic alcohol

• PCB baking: 1 night at 100°C

• “Degolding” by an immersion of the SOP connectic grids in a Sn/Pb(63/37) bath 4 seconds at

245°C

• Tinning by an immersion of the SOP connectic grids in a Sn/Pb(63/37) bath 4 seconds at 245°C

• Module cleaning with isopropylic alcohol

• Prior to mounting on PCB: baking module 48hrs at +125°C +/-5°C

• Dispensing solder paste SOLDERPLUS 6-Sn62-211F RMA Sn/Pb/Ag (62/36/2) with melting

point at +183°C. Dispensing with automatic micro-dispenser CAMALOT

• Manually reporting modules on PCB

• Vapor Phase reflow:12 seconds in the vapor, the profile is given on graph1(next page)

Using CENTECH VP1000 machine with 3M Fluorinert FC 53-12 (215°C melting point) reflow

liquid

• Module + PCB cleaning with isopropylic alcohol

• Technological control

• Underfilling Module with 3M 2216 B/A Gray Scotch-Weld Epoxy Adhesive

• Curing 3M 2216 B/A Gray Scotch-Weld under Module + PCB 2h @ 65°C

• Technological control



5. Reflow temperature profile

graph1. vapor phase soldering profile



6. Test file

graph1. Vapour phase soldering profile

Test file for high level of vibrations validation

Vibrations

PCB was fixed to the vibration equipment

Frequency: 20 to 2000Hz.

Type: Sinus

Acceleration: 20 grms

Scanning speed: 1oct/minute

Scanning time: 6min / axe on the3axes.

Number of cycles: 4

Visual & electrical controls

Test file for high level of vibrations validation of

automatic mounted 3D PLUS SDRAM

8bit x 64M # 8 TSOP levels # SOP connectic

Shocks

PCB was fixed to the shock equipment

Mechanical shocks on three axes:

½ sinus, 600g, 0.5ms


Micro section analysis of solder joints

500 Thermal cycles

–55°C / +100°C

Cycles according to MIL-STD1010B

(except for high temp) Cold = -55°C Hot

= +100°C Dwell Time = 20 minutes

Ramp = transition time = 10 seconds

(automatic transfer from one chamber to

the other)


Micro section analysis of solder joints



7. Results

After shocks, vibrations and 500TC of 3D PLUS memory modules mounted on

PCB with an automatic vapour reflow: visual and electrical controls are PASS.

Micro sections of 3D PLUS memory modules after shocks, vibrations and

500TC are conform with RNC-CNES-Q-70-508 spatial norm.

photo1: module SDRAM 8bitx64M soldered with a vapor phase reflow on a PCB for high level

vibrations



photo2: module SDRAM 8bitx64M soldered with a vapour phase reflow on a PCB and underfilled

for high level vibrations

photo3: lead of a 3D PLUS memory module soldered with a vapour phase reflow on a PCB



photo4: micro section of a 3D PLUS memory module after shocks, vibrations and 300TC

photo 5: Good Solder joint of a 3D PLUS memory module after shocks, vibrations and 300TC;

S > G+H in accordance with norm RNC-CNES-Q-70-508

G S

Solder joint

PCB

Lead of

3D PLUS

module

H

3M 2216 B/A Gray

Scotch-Weld



Under fill adhesive datasheet:















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VALIDATION OF THE MOUNTING OF 3D PLUS MEMORY STACKS … · graph1. vapor phase soldering profile . VALIDATION OF THE MOUNTING OF 3D PLUS MEMORY STACKS ON PCB – Automatic Reflow