An epoxy molding compound of the process selection

An epoxy molding compound of the Process Selection

1.1 Pre-processing block forming material
(1) pre-formed blocks of plastic materials are generally stored in a 5 ? -10 ? environment, will have varying degrees of moisture absorption. Therefore, before using a dry place at room temperature should be expected to wake up, generally not less than 16 hours.
(2) expected higher density of the block. Loose material block may contain too much air and moisture, through the wake up is not easy material and high-frequency warm-volatile clean, will cause an increase in the level of the device encapsulation layer. = “Semiconductors, microelectronics, integrated circuits, IC, craft, design, device, packaging, testing,
(3) The block size is expected to moderate, expected to block the small, mold filling bad; expected to block big, Kai mold problems, mold contamination and the injection rod and caused a serious waste of materials.

1.2 Die temperature of the semiconductor, microelectronics, integrated circuits, IC, craft, design, device, packaging, testing, production process, the mold temperature is controlled at slightly higher than the glass transition temperature Tg molding compounds, they can get better mobility , about 160 ? -180 ?. Mold temperature is too high, fast-curing plastic material, internal stress increased, the encapsulation layer and the framework of the adhesion decreased. At the same time, rapid curing also make Punch dissatisfaction; die temperature is too low, molding compounds poor mobility, the same will appear undesirable mold filling, the encapsulation layer mechanical strength decrease. While maintaining the mold temperature uniformity regions is very important, because non-uniform mold temperature will cause uneven curing degree of plastic material, resulting in inconsistent mechanical strength of the device

1.3 Injection pressure = “semiconductors, microelectronics, integrated circuits, IC, craft, design, device, packaging, testing, selection of injection pressure, according to the flow of plastic materials and mold temperature may be, the pressure is too small, the device encapsulation layer of low density, poor bonding with the framework, prone to moisture corrosion, and the emergence of mold is not filled with plastic material ahead of curing conditions; pressure is too large, domestic and lead impact force increases, causing distortion inside the wire has been washed or washed off, and the overflow may be expected, blocking out the vent, resulting in bubbles and fill bad.

1.4 speed injection molding
Select the speed of injection molding plastic material based mainly on the gelation time to identify. Gelation time is short, injection mold a little faster, and vice versa. Injection molding to be completed before the end of gel time, or ahead of schedule due to curing plastic material caused by thrust or encapsulated within a layer of lead defects.

1.5 Plastic Craft adjust = “semiconductors, microelectronics, integrated circuits, IC, craft, design, device, packaging, testing, appear in the actual production process as shown in Table 1 the situation, process conditions can be adjusted appropriately. To process adjustments should also be noted that the pre-molding material block storage, mold cleaning, temperature and humidity and other environmental factors on the impact of plastic Kung processes.

2 pairs of plastic material properties of the impact of device reliability
2.1 The plastic material moisture absorption and chemical adhesion to the plastic device, the moisture penetration that influence their airtight lead to failure of the important reasons. Moisture infiltration devices are mainly two ways to
(1) through encapsulation layer of plastic material body;
(2) through encapsulation layer of plastic material and metal framework of the gap between. When the moisture through this two ways when you reach the surface of the chip in its surface layer of conductive water film, and plastic compound of the Na +, CL-ions also will be brought in as a potential difference, the speed of chip surface, the electrochemical corrosion of aluminum wiring, eventually leading to open circuit lead. With the continuous improvement of integrated circuits, aluminum wiring become ever smaller and, therefore, corrosion of the aluminum wiring devices more serious impact on life expectancy.

In response to these problems, we must ask: = “semiconductors, microelectronics, integrated circuits, IC, craft, design, device, packaging, testing,
(1) plastic materials have a high purity, Na +, CL-ion to a minimum
(2) The main component of plastic material environmental standard epoxy resin and inorganic fillers of the binding force must be high, in order to prevent the infiltration of moisture from the body. , MEMS
(3) plastic material with the framework of the metal should have good adhesion;
(4) chip surface passivation layer to be improved as much as possible, its moisture is also a very good shielding effect

2.2 The internal stress of plastic materials
As the plastic material, chips, metal frame of the linear expansion coefficient mismatch arising from internal stress, the device would have a negligible impact of tightness. Because the plastic material expansion coefficient (20-26E-6 / ?) than the chip, the framework (-16E-6 / ?) the greater the cooling in the casting or in the device using the larger temperature difference between the environment, it may lead to pressure solder joint was torn off and broken wire bonding or encapsulation layer and the framework of the Department, separated from the resulting failure of their devices.

This shows that the plastic material of the linear expansion coefficient of the low as far as possible, but this reduction is received limited, because in reducing stress, while the thermal conductivity of plastic materials also will be reduced, This is packaging high-power devices very unfavorable, to make these two aspects to be taken into account, depending on the formula type and amount of filler. Filler is generally melt type or crystalline silica, in some performance needs sometimes need to add spherical silica fume or vapor.

2.3 The liquidity injection plastic materials when the mold temperature of 160 ? -180 ?, plastic was molten state, its mobility is essential to the success of the injection molding, the impact of increased liquidity below the wire (gold Tensile Strength 5g -12g), crooked or red wire easily washed off, and could easily lead to Punch discontent, the encapsulation layer of the surface folds and potholes; liquidity is too high, excess material seriously, when the overflow is expected to die prematurely out of stomatal congestion, air row entirely, the encapsulation layer of pores or air bubbles will appear.

Various components in the plastic material, the right to play a major role in mobility is a main epoxy resin melt viscosity and the amount of silica filler and particle thickness. Crystalline silica has a high thermal conductivity, but high viscosity than the heavy flow down. Fused silica has good mobility, but the poor thermal conductivity. Therefore, in the century the production of packaged device performance should be based on the use of different options, including the mix of both. 3 summarizes the choice for the packaging process, once we understand the encapsulation process of several major factors, in the packaging process can be based on different regions, different environment and climate, while the adjustment process differently. Meanwhile, officers for the package should also strengthen the understanding of epoxy molding compound.

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