环氧塑封料成型工艺及不良对策

SEMICONDUCTOR PRODUCTS
Conventional vs. Automold
Conventional Molding
Large Preforms (25-90g) Low value/high volume devices Yield varies (voids & wire sweep) Labor intensive Large runner & cull waste (20-30%) Long cycle time (90120sec) Auxiliary preheat equipment
8LQ Ram force,Pa Radius of capillary,mm Length of capillary,mm flow rate mm3/s
SEMICONDUCTOR PRODUCTS
Thermal Expansion & Tg
Glass Transition Temperature (Tg) A second order transition in which a molded plastic changes under the influence of heat from a glassy hard state to a rubbery state. In going through the this transition, reversible changes occur in physical and electrical properties. In practice, Tg is the intersection between alpha 1 CTE and alpha 2 tangent lines. Coefficient of Thermal Expansion Temperature induced and reversible expansion characteristics of a material usually expressed in cm/cm/C. Alpha 1 CTE is the average expansion below Tg and Alpha 2 is expansion above Tg.
SEMICONDUCTOR PRODUCTS
Function of Epoxy Encapsulants
Protect the electric component from the environment (moisture, temperature, contamination, etc…..). Protect the chip from mechanical shock. Provide structure and support. Provide electrical insulation. Not in itself, be detrimental to the device performance.
SEMICONDUCTOR PRODUCTS
EMC Molding Process
Preform
Preheat 80-90C 500-1000 psi 175°C
A) Charge Mold
B) Transfer
C) Cure
D) Demold
SEMICONDUCTOR PRODUCTS
Manual Gangpot Press
Automold (Gangpot)
Small pellets (2-20g) High value devices Consistent yield near 100% Fully automated Small runner & cull waste (5-15%) Short cycle time (3560sec) In mold preheat
Test bar is placed in a chimney containing oxygen & nitrogen The bar is ignited and oxygen level adjusted to the point that the bar just burns. The % oxygen is reported as the oxygen index number
Temperature, °C
Tg
SEMICONDUCTOR PRODUCTS
Flammability Tests
UL 94 Test Oxygen Index
N2
O2
10 Seconds in flame Remove- check time to extinguish Repeat 10 sec burn Remove check time to extinguish Repeat for 5 bars Meets V0 if no bar burns longer than 10 s and total of all burns is < 50 s
SEMICONDUCTOR PRODUCTS
Transfer Molding Process
Pressure
Transfer ram or Plunger Vent At Parting Line
Top chase Bottom Chase
cavity
Heating platen Gate Heating element Conventional Molds: One Large Ram & Pot, large mold, many cavites. Automold Conventional Molds: One Large Ram & Pot, large mold, many cavites. Automold or Gangpot: Several small Rams & Pots, small mold, fewer cavities. or Gangpot: Several small Rams & Pots, small mold, fewer cavities.
O R-CH CH2
SEMICONDUCTOR PRODUCTS
A Short Course on Epoxy Mold Compound
Introduction Technical Data Sheet Properties EMC Related Device Failure Modes Molding Compound Types & Selection Troubleshooting
SEMICONDUCTOR PRODUCTS
Determining CTE & Tg by TMA
TMA Analysis: A quartz probe is positioned on top of a post cured EMC pellet. The pellet is then heated at a rate of 5°C/minute. The pellet expands as the heat is increased causing the probe to move upward. The expansion versus time is automatically plotted. From these data, the coefficient of thermal expansion (CTE) and glass transition temperature (Tg) can be calculated.
Electrical Properties Dielectric constant Dissipation Factor Volume Resistivity, ohm.cm
SEMICONDUCTOR PRODUCTS
Spiral Flow (ASTM D2132)
Spiral Flow is the length in inches or centimeters that a mold compound will flow in a helix mold under 1000 psi pressure and 175°C. It is a measure of the combined effects of viscosity, fusion under pressure and curing speed under specified conditions of temperature and pressure. Spiral flow is a good indicator of batch to batch consistency.
Ram Follower Gel Time (RFGT)
RFGT is the time in seconds between the time that the transfer ram in the spiral flow test first touches the mold compound in the pot and the time to when the ram stops moving.
Quartz probe expansion Quartz sample holder EMC pellet 0.2x0.2”
heater
SEMICONDUCTOR PRODUCTS
Βιβλιοθήκη Baidu
Thermal Expansion & Tg
Alpha 2 region
Expansion, cm
Alpha 1 Region
Ram Displacement
RFGT
Time, s
SEMICONDUCTOR PRODUCTS
Orifice Flow Viscosity
Force
175°C
Viscosity
emc
Molding window
die
V, Pa.s = P= r = L= Q= Pπr2
orifice Time, sec
SEMICONDUCTOR PRODUCTS
Technical Data Sheet Properties
SEMICONDUCTOR PRODUCTS
Data Sheet Properties
Physical Properties Spiral Flow, Inches Ram Follower Gel Time, seconds Hot Hardness Viscosity, poise Specific Gravity Filler Content, % Thermal Properties Glass Transition Temperature, Tg Coefficient of Thermal Expansion, ppm Thermal Conductivity, calories/cm.sec.oC Flammability, UL 94 Linear Shrinkage, in/in Mechanical Properties Flexural Modulus, Mpsi Flexural Strength, kpsi Hot Hardness, Shore D
SEMICONDUCTOR PRODUCTS
Spiral Flow Stability
100 90 80 70 60 50 40 30 20 10 0 0 2 5 10
D a ys % Fl w re te n ti n o o
5C 23C 35C
20
25
30
SEMICONDUCTOR PRODUCTS
SEMICONDUCTOR PRODUCTS
Introduction Introduction to to Epoxy Molding Compounds Epoxy Molding Compounds
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