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參數(shù)資料
| 型號(hào)： | MMQA |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | SC-74 Quad Monolithic Common Anode |
| 中文描述： | 資深大律師- 74四單片共陽(yáng)極 |
| 文件頁(yè)數(shù)： | 6/8頁(yè) |
| 文件大?。?/td> | 104K |
| 代理商： | MMQA |
MOTOROLA
6
MMQA Series
The soldering temperature and time should not exceed
260
°
C for more than 10 seconds.
When shifting from preheating to soldering, the
maximum temperature gradient should be 5
°
C or less.
After soldering has been completed, the device should
be allowed to cool naturally for at least three minutes.
Gradual cooling should be used since the use of forced
cooling will increase the temperature gradient and will
result in latent failure due to mechanical stress.
Mechanical stress or shock should not be applied during
cooling.
TYPICAL SOLDER HEATING PROFILE
For any given circuit board, there will be a group of control
settings that will give the desired heat pattern. The operator
must set temperatures for several heating zones and a figure
for belt speed. Taken together, these control settings make
up a heating “profile” for that particular circuit board. On
machines controlled by a computer, the computer remem-
bers these profiles from one operating session to the next.
Figure 9 shows a typical heating profile for use when
soldering a surface mount device to a printed circuit board.
This profile will vary among soldering systems, but it is a
good starting point. Factors that can affect the profile include
the type of soldering system in use, density and types of
components on the board, type of solder used, and the type
of board or substrate material being used. This profile shows
temperature versus time. The line on the graph shows the
actual temperature that might be experienced on the surface
of a test board at or near a central solder joint. The two
profiles are based on a high density and a low density board.
The Vitronics SMD310 convection/infrared reflow soldering
system was used to generate this profile. The type of solder
used was 62/36/2 Tin Lead Silver with a melting point
between 177–189
°
C. When this type of furnace is used for
solder reflow work, the circuit boards and solder joints tend to
heat first. The components on the board are then heated by
conduction. The circuit board, because it has a large surface
area, absorbs the thermal energy more efficiently, then
distributes this energy to the components. Because of this
effect, the main body of a component may be up to 30
degrees cooler than the adjacent solder joints.
STEP 1
PREHEAT
ZONE 1
“RAMP”
STEP 2
VENT
“SOAK”
STEP 3
HEATING
ZONES 2 & 5
“RAMP”
STEP 4
HEATING
ZONES 3 & 6
“SOAK”
STEP 5
HEATING
ZONES 4 & 7
“SPIKE”
STEP 6
VENT
STEP 7
COOLING
200
°
C
150
°
C
100
°
C
50
°
C
TIME (3 TO 7 MINUTES TOTAL)
TMAX
SOLDER IS LIQUID FOR
40 TO 80 SECONDS
(DEPENDING ON
MASS OF ASSEMBLY)
205
°
TO 219
°
C
PEAK AT
SOLDER JOINT
DESIRED CURVE FOR LOW
MASS ASSEMBLIES
100
°
C
150
°
C
160
°
C
170
°
C
140
°
C
Figure 9. Typical Solder Heating Profile
DESIRED CURVE FOR HIGH
MASS ASSEMBLIES
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| MMQA12VT1 | 功能描述:TVS二極管陣列 12V 150W TVS Quad RoHS:否 制造商:Littelfuse 極性: 通道:4 Channels 擊穿電壓: 鉗位電壓:11.5 V 工作電壓:2.5 V 峰值浪涌電流:20 A 安裝風(fēng)格:SMD/SMT 端接類型:SMD/SMT 系列: 最小工作溫度:- 40 C 最大工作溫度:+ 85 C |
| MMQA12VT1G | 功能描述:TVS二極管陣列 12V 150W TVS Quad Array RoHS:否 制造商:Littelfuse 極性: 通道:4 Channels 擊穿電壓: 鉗位電壓:11.5 V 工作電壓:2.5 V 峰值浪涌電流:20 A 安裝風(fēng)格:SMD/SMT 端接類型:SMD/SMT 系列: 最小工作溫度:- 40 C 最大工作溫度:+ 85 C |
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