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Schottky Diodes

_ SKY Mo low Vf

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   Designation and abbreviation

- VB - Breakdown Voltage;
- VRRM - Repetitive Peak Reverse Voltage;
- VR - reverse voltage;
- VF - forward voltage;
- VESD - voltage describing stability of the diode to action of electrostatic discharge;
- IR - reverse current;
- IF - forward current;
- IF (AV) - Average forward current;
- IFSM - Non-Repetitive Peak Forward Surge Current;
- IRRM - Repetitive Peak Reverse Current;
- EAS - Non-Repetitive avalanche energy;
- TJ - Junction Temperature;
- ESD - electrostatic discharge;
- ESD HBM - electrostatic discharge on model of a human body;
- DC – constant...
- mil - 1/1000 share of inch (1mil=25,4um).
 

   Basic parameters for Shottky Diodes

- Wide range of working currents and voltage: IF (AV) =0,5÷60A; VRRM=15÷300В;
- High value of direct shock current - IFSM;
- Low forward voltage - VF;
- Low value of reverse currents IR;
- Low power-dissipation capability;
- Three classes of Diodes are distinguished by the range of operating temperatures:
1. High-temperature Shottky Diodes with a super-low level of reverse currents (PtSi-barrier);
2. Reference Shottky Diodes (NiSi, Mo-barrier);
3. The low-temperature Shottky diodes with low and super low level VF (Cr, Ti-barriers).
PtSi-barrier (KD-XXXX-YY) - High-temperature Shottky Diodes with super-low level of reverse currents (PtSi-barrier);
NiSi-barrier (KDN-XXXX-YY) & Mo-barrier (KDM-XXXX-YY) - Shottky Diodes (NiSi, Mo-barrier);
These are standard SKYs. Mo-barrier has lower Vf than NiSi and lower Ir but more sensitive to the assembling process.
Cr (KDS-XXXX-YY) and Ti-barrier (KDT-XXXX-YY) - Low-temperature Shottky Diodes with low and super low level VF (Cr, Ti-barriers).
Ti is used for protection of accumulator battery and other devices with required minimum Vf value. Ti is less critical to the assembly process.

 

Table №1.

Barrier
IF, A
VR, V
IRmax@Tj=25oC
VFmax@Tj=25oC
TJmax, oC
trr max, ns
Top metal
PtSi
1 – 60
40 - 250
 0.003÷0.030
0.90
+175
-
Ag, Al
NiSi
1 – 40
20 - 60
 0.040÷0.500
0.86
+150
-
Ag, Al
Cr
0.5 – 20
15 - 40
 0.250÷1.000
0.40
+125
-
Ag, Al
Mo
1 - 60
15 - 60
 0.040÷0.500
0.70
+150
-
Ag, Al
Ti
0.5 - 20
15 - 40
 1.500÷20.000
0.30
+100
-
Ag, Al

 

High-tech parameters EAS and IRRM show reliability of the device in the mode of avalanche breakdown of stressful overloads.
High stability to electrostatic categories, relevant to requirements of standards JEDEC and MIL-STD-883G, level VESD = +/-8kV (contact) on the Human Body Model (С=100pF, R=1500ohm), and also to requirements to automobile electronics, mounted standard AEC-Q101-001.
Electrical performances are proved by 100 % dice testing control in standard conditions (ТА=25єС) on the main parameters: VB, IR, IRRM, and also dice sampling testing for each wafer on VF parameter at a rating value of forward current IF (AV). Defective dice are marked on 100% wafers.
Reverse current value at higher temperature is tested on dice sampling for 100 % wafers.
Conformity of other parameters to specifications requirements is secured by a design of dice.
Visual control is made after electrical parameters testing.
SC "VSP-MIKRON" produces and delivers Shottky diodes – dice in wafer form diameter 4” and 6”. The Customer can select modification of dice according to assembly method:
      1. dice with Al metallization on top side (anode) - for ultrasonic welding;
      2. dice with structural metallization of anode Al-Ni-Ag – for assembling by solder technique with PbSn solder.
      3. Metallization of the cathode - Ti-Ni-Ag for the solder method with PbSn solder.
Customer can select die size depending on his equipment and quality-price ratio.
 

   Packing and storage dice in wafer form

Shottky Diodes - dice in wafer form are packed in polypropylene wafer boxes. The wafers are stacked by interleafs made of non-dusting substance and every 5 wafers are interlaid by interleafs made of foam rubber.
Each wafer box has a packing label, on which device type, lot numbers, quantity of wafers and quantity of good dice is specified, and list of wafers with the numbers good dice on each wafer.
Each wafer box is placed into air-free polyethylene package. The packed wafers are stored in vacuum in order to keep its properties during transportation and storage in the warehouse.
Warranty period of wafers storage in vacuum packing is one year. After vacuum packing opening the wafers must be stored in controlled atmosphere of dry nitrogen not more than 30 day. After that period the wafers should be taken to the production and dice should pass operation of hermetic encapsulation (sealed into the case or sealed with protective layer of compound).
In case of warranty period expiration the wafers are subjected to testing to determine the possibility of their utilization with or without any update.
 

   Directions for application

1. Vacuum packing and wafer boxes should be opened in clean working room, class 100 000 and higher, with parameters of a microclimate in the range: Т=23 +/-5ºС and humidity: 45+/-5 %.
2. Shottky Diodes wafers are grinded to thickness 200-300um. The wafers are very fragile and require careful attitude. In order to decrease of probability of wafers breakage during transfer from a wafer box to a shipping container it is recommended to remove a cover from the wafer box and turn it upside down on flat surface (on a table). Then lift a housing of a wafer box, clearing the wafers together with foam rubber and interleafs. Now it is possible to transfer the wafers to the shipping container taking them with the vacuum pencil. After the cover removal it is recommended to put any flat plate on its place to avoid wafers fall during their turning over. It is very undesirable to use pincers with mechanical holding because it can lead to cracks and chips.
3. Cutting wafers into dice is recommended to perform by a method of diamond disk cutting providing the cut width 25-35um, with the subsequent wash in flowing demonized water. The process of washing should provide complete removal of cutting remains from a surface of dice.
4. Dice mounting on the frame is recommended to perform by solder technique with solders or solder pastes based on Pb/Sn in protective atmosphere of hydrogen or forming-gas (N2+H2, where H2 is not less than 5 %). It is also possible to use vacuum soldering method. The peak temperature during soldering of high-temperature and standard dice series should not exceed 420 ºС, and for low-temperature dice series - not higher 350ºС. Holding time of dice at the peak temperature should be minimized to prevent the possibility of specification parameters changing. The chip carrier should be cleaned from any foreign particulates and oxide films by chemical method or annealing in hydrogen medium. Analogous recommendations are also applied to process of assembly of dice with silver metallization on the top side.
5. For dice with Al top side metallization (anode) the assembling of internal leads should be performed by method of ultrasonic welding of Al wire with diameter 250-400um. The diameter of wire and quantity of wires is recommended to optimize depending on the sizes of anode metallization and special requirements to the device parameters (VF, IFSM). Thus, it is necessary to take into account that the increase of wires quantity allows to improve current distribution on die area and to improve VF, IFSM at the expense of it. Besides, the increase of wires quantity at the reduction of their diameter allows lowering the possibility of mechanical stress and micro cracks in the point of welding. It also reduces the probability of damage and a degradation of Schottky barrier. The reliability of a device is increased. Welding points should be evenly distributed on the anode area.
6. Before packaging the assembly should be cleaned of foreign particulates annealed 2-3 hours at 150ºС for moisture removal from a die surface. In case of packaging in untight case it is recommended to cover a die with silicon protective layer. The process a die covering with silicon protective layer should be performed in an atmosphere of the dry nitrogen.