TOYOTA-ENGINEERING-STANDARD丰田工程标准TSC0507G-Rev.docx

TOYOTA ENGINEERING STANDARD
NO.:TSC0507G
TITLE: Bench test method for whiskrr resistance performance of automotive electric and electronic equipment
CLASS:C1
Established:/Revised: Rev.4 (Jul. 2021)
This standard has been tevised as a result mainly of the following changes:
(1) the test selection flowchart has been changed (Section 4);
(2) the temperature/humidity.cycling test has been changed to high-temperature/high-humidity exposure test (Section 6.5);
(3) a statement concerning the necessity/non-necessity of high-temperature exposure test has been added (Section 6.8), and
(4) the entry example of test plan for high-temperature/high-humidity exposure test has been added (Appendix Table 1).
Prepared and Written by:
Electronic Performance Development &Engineering Dept.
Electronics Control System Development Div.
Design Quality Innovation Dept.
TOYOTA MOTOR CORPORATION
Bench test method for whisker resistance performance of automotive electric and
electronic equipment
1.Scope
This standard covers the bench test method to evaluate whiskers that are generated from plating and solder of automobile electric and electronic equipment (computer, actuator, etc.) and its peripheral parts/components. Specific examples of portions to be evaluated include substrates for mounting, elements, and component parts (screws/bolts, shielding plates, cases, connectors, bus bars, etc.) For the items whose conditions are not specified in detail here (measurement range, test conditions, etc.), the conditions shall be determined in consideration of the design specifications by agreement between the departments concerned.
2. Definitions
(1) Automotive electronic equipment (hereinafter referred to as "equipment")
This term refers to the devices used to control a system or electronic control unit (ECU) consisting mainly of semiconductor deviges, as well as Various types of sensing units and electromagnetic equipment (actuators) that are used in combination with the devices.
(2) Characteristics
This refers to a special aspect of performance of the equipment that can be quantitatively or qualitatively expressed under a certain condition The characteristics shall be specified in the test plan for the equipment
(3) Standard condition
This refers to an atmospheric condition under which testing and measurement are carried out, and indicates an environment maintained at normal temperature (15 to 35 °C), normal humidity (25 to 75 % RH), normal atmospheric pressure (86 to 106 kPa), with poor external magnetic field and yibration. Unless otherwise specified, the environment inside the test or measurement chamber shall be deemed to have been maintained in the standard condition.
(4) Test sample
This term refers to the equipment that is tested.
(5) Whisker
Whisker refers to a fibrous crystal grown from metal. In this standard, whisker shall meet the following 2 conditions.
(a) The ratio of its length to its diameter shall be 2 or more.
(b) Its length shall be 10 pm or more.
(6) Unleaded solder
Unleaded solder refers to the solder that does not contain the lead. In general, the lead content at the specified portions on which the lead shall be excluded is supposed to be less than 0.1 mass%.
(7) XY plane projection
XY plane projection refers to projection of the shade of object shapes on XY plane by parallel light rays. In this standard XY plane refers to the plane used by microscope. Itusually means the plane perpendicular to the direction for observation. Unless otherwise specified, the substrate surface for mounting to observe the whisker shall be parallel to this plane.
(8) Z axis direction
Z axis refers to the axis showing the depth direction used when it indicates stereoscopic points.In this standard, Z axis direction means the direction parallel to Z axis used by microscope. It usually indicates the direction parallel to the direction to be observed. Unless otherwise specified, the substrate surface for mounting to observe the whisker shall be perpendicular to this direction.
(9) Portions to be evaluated
Portions to be evaluated refer to all metal portions in which metals (such as unleaded plating, solder, zinc plating, and bright plating) that may cause whisker generation are used and portions whose generated whisker may touch directly or scatter between electrodes. They are specific examples specified in scope.
(10) Zinc plating
Zinc plating refers to a surface treatment (plating) method using zinc as the main component. It means the plating having zinc as a component, such as electrogalvanizing, hot dip galvanizing, electrogalvanized steel sheet, and hot dip galvanized steel sheet
(11) Tin plating
Tin plating refers to a surface treatment (plating) method using tin as the main component.For definitions related to tin plating, see TSH6535G.
(12) Bright plating
Bright plating refers to a plating using a large amount of brightener.For definitions related to bright plating, see TSH6535G.
(13) Design verification
Design verification is the activity to verify quantitatively that the final specification parts assumed for mass production satisfy the reiquirements for reliability.
(14) BGA(Ball Grid Array)
BGA is a type of IC package. On the backside of BGA packages, solder balls are arranged in a grid pattern.
3. Basic Knowledge of Whisker
3.1 What is the Whisker?
A whisker is a fibrous metallic crystal grown from tin plating, zinc plating, or other metal. Some whiskers grow even to a length of several millimeters. Because whiskers are electrically conductive foreign matters, a whisker wilf cause a short circuit failure if it is generated between terminals of an element or part..Furthermore, it is a possibility that a whisker generated at a certain place scatters and falls between terminals on a surrounding element/part, causing a short circuit. (Fig. 1)
SEM analysis

Fig. 1 Example of Whisker
3.2 Whisker Generation Mechanism
Whiskers are generated when Sn and/or Zn in plating films or solders are subjected to compressive stress. Fig. 2 shows the mechanism schematically. Causes of the stress include thermal stress, growth of alloy in the plating film or solder, corrosion-induced cubical expansion and many others.

Fig. 2 Image Diagram of Whisker Generation

3.3 Portion Where Whiskers are Generated on Automobile Electronic Equipment
On automobile electronic equipment, whiskers may be generated at places shown in Fig. 3.Whiskers may also be generated on an electronic substrate and its surrounding components/parts.Since there is a possibility that a whisker generated at a part/component of which you do not take charge scatters and causes a short circuit at a part/component of which you take charge, pay attention also to surrounding parts/components in the same space.
the substrate using plating Bus bar

Connector terminal Screw/washer
(for securing the substrate)
Fig. 3 Examples of Locations where Whiskers Are Generated

4. Confirmation of Test Method
4.1 Tin Plating
Fig. 4 shows the test selection flow for tin, and Table 1 shows the test conditions and judging methods for tin. After selecting test items using Fig. 4, select portions to be evaluated using Table 1.Furthermore, since there are many portions where whiskers may be generated as shown in Fig. 3, pay attention to whiskers that scattered from the ranges other than that which you take charge of.

Fig. 4 Test Selection Flow for Tin

Table 1 Test Conditions and Judging Methods for Tin Plating
Test item
Portions to be evaluated
Reproduction mode and test conditions
Judging method
High-temperature/ high-humidity exposure test
Semi bright/matte tinned terminal (device part, connector, bus bar, etc.), tin solder (substrate for mounting, etc.)
See Section 6.5.
See Section 6.10.
Temperature cycling test (tin)
Semi bright/matte tinned terminal (42 alloy base material, etc.)
See Section 6.6.
50 °C exposure test
Bright tinned parV^ (connector, bus bar, etc.)
See Section 6.7.
Note (1): For the definition of bright plating, see TSH6535G.

4.2 Zinc Plating
Fig. 5 shows the test selection flow for zinc plating, and Table 2 shows the test conditions and judging methods for zinc plating. After selecting test items using Fig. 5, select portions to be evaluated using Table 2. Furthermore, since there are many portions where whiskers may be generated as shown in Fig. 3, pay attention to whiskers scattered from the ranges other than that which you take charge of.

Fig. 5 Test Selection Flow for Zinc Plating

Table 2 Test Conditions and Judging Methods for Zinc Plating
Test item
Zinc plating subjected
Portions to be evaluated
Reproduction mode and test conditions
Judging method
High temperature exposure test
Electrogalvanizing ⑵ Electro zinc-nickel alloy plating (nickel content: less than 12 mass%)⑵
Zinc plated part/component (screw/bolt, case, shielding plate, etc.)
See Section 6.8.
See Section 6.10.
Temperature cycling test (zinc)
Electroplated steel plated)
Zinc plated part (case, shielding plate, etc.)
See Section 6.9.

Note (2): For types of zinc plating, see Section 4.3.2.

4.3 Types of Plating
4.3.1 Tin Plating
Tin plating refers to a surface treatment (plating) method using tin as the main component. This plating is applied to parts that are required to have corrosion preyention performance, solder wettability, contact fitting, etc. For the definition of tin plating, see TSH6535G. Meanwhile, tin plating is classified as in the following, and portions where each tin plating type is mainly used differ.
(1) Bright tin plating
Bright tin plating is mainly used to plate connectors and bus bars.
(2) Semi bright/matte tin plating
Semi bright/matte tin plating is mainly used to plate device electrodes and leaded components.
4.3.2 Zinc Plating
Zinc plating refers to a surface treatment (plating) method using zinc as the main component. Zinc plating is mainly used to plate parts that are required to have high corrosion prevention performance, such as cases and bolts. Zinc plating is classified depending on plating treatment method as shown in Fig. 6. For the definition of zincplating, refer to TSH0002G.
—(1) Electrogalvanized steel plate
—Pre-plating
(2) Zn-AI-Mg alloy plated steel plate ——Hot-dip zinc plated steel plate
——Electroplating
—Post-plating — (6) Electrogalvanizing
(3) Gl. (4) GA, (5) Zn-Mg
(7) Zn-Ni alloy plating
• With a nickel content of 12 mass% or more
. With a nickel content of less than 12 mass%
— (8) Hot-dip zinc plating
Fig. 6 Types of Zinc Plating
(1) Electrogalvanized steel plate
Electrogalvanized steel plate refers to a steel plate made by electroplating a base material (part/component) to deposit zinc on the surfaces of the base material (part/component).
(2) Zn-AI-Mg alloy plated steel plate
Zn-AI-Mg alloy plated steel plate refers to a steel plate given plating that has a fine Zn/AI/MgZnz ternary eutectic structure.
(3) Gl (hot-dip zinc plated steel plate)
Gl is a type of hot-dip zinc plated steel plates. It is made by giving a steel plate, a base material, hot-dip plating to deposit zinc on it.
(4) GA (hot-dip zinc plated steel plate)
GA is a type of hot-dip zinc plated steel plates. It is made by giving a steel plate, a base material, hot-dip plating to deposit zinc on it, and diffuse iron elements on the base material to zinc plating by heat treatment to make the plated portions Zn-Fe compound
(5) Zn-Mg (hot-dip zinc plated steel plate)
Zn-Mg is a type of hot-dip zinc plated steel plates. It is made by givinig a steel plate, a base material, hot-dip plating to deposit Zn-Mg on it.
(6) Electrogalvanizing
Electrogalvanizing (post-plating) is a method of plating by soaking a treated base material in a liquid electrolyte and energize it to deposit zinc plating on the surfaces of the base material.
(7) Zn-Ni alloy plating (electroplating)
Zn-Ni alloy plating is a type of electro alloy plating. In this plating, nickel is added to a zinc-based electrolyte.
(8) Hot-dip zinc plating
Hot-dip zinc plating is a method of plating by soaking a treated base material in a zinc bath to make zinc films on the surfaces of the base material.
4.3.3 Nickel Plating)
(1) Nickel plating
Like zinc plating, there are two methods of nickel plating: electroplating and hot-dip plating.
No whisker is generated from nickel plating. (The melting point of nickel is 1455 °C.)
(2) Nickel undercoat
Since nickel plating serves as a barrier layer for preventing copper, zinc and other base components fromi diffusing into plating, there is a case in which nickel plating is used as undercoat plating to retard growth of whiskers on tin plating.
5. Whisker Check Sheet
The designer shall carry out confirmation and review based on the whisker check sheet (Table 3).Consideration on the countermeasures shall be made for the portions where concerns are present."Recommended" in Table 3 means proven countermeasures for retarding growth of whiskers.However, since they cannot completely retard growth of whiskers, judge whether or not each test should be carried out in accordance with the test selection flows in Section 4.
Table 3 Whisker Check Sheet
Design check item
Design measure
Countermeasure check column
Recommended
Not recommended, caution required
O for item with caution required
-Presence/absence of problem
-Countermeasure for item with caution required
Example
Base material of terminal
Copper alloy
Devices/parts of FeNi alloy (such as 42 alloy) are present.
O Fe-42Ni is used in the control IC.
一 Change of material is planned.
一 Coating is to be applied.
— List of all devices is on the attached sheet.
Device/con nector
Base material of terminal
Copper alloy
Devices and parts of FeNi alloy (such as 42 alloy) are present.

Plating
Sn alloy plating SnBi. SnAg (NiPdAu)
SnCu plating Plating and supplier that have no records of installation in a vehicle

Semi bright or matte tin plating*41
Bright plating
Plating and supplier that have no records of installation in a vehicle

Device shape
Device with small/short profile terminals
Devices for which there are cases of generation (acceptable if countermeasures are taken, such as adjustment of mounting condibon)

ECU case。)
Waterproof performance
Waterproof case
The substrate easily corrodes due to waterdrops, humidity, or contamination.

Screw/bolt
Ni plating
Zinc nickel plating (Ni: 12 mass% or more)
Zinc plating, tin plating

Shielding plate, metallic case
Zinc plating and Tin plating shall not be used.
Bright tin plating⑷ Zinc plating, tin plating

Solder
Solder amount
Solder thickness after reflow shall be 20 min.
(Solder thickness of the whisker generation portion is 20 Mrn max.)

Flux
Halogen-free material (not containing bromine or the like)
Material containing halogen (bromine or the like)

Notes:
(3) See Fig. 3 for the portions to be checked.
(4)