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PCB process PCBA factory 100 questions
2021-10-04
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Author:Aure

PCB process PCBA factory 100 questions






1. What is double-sided reflow?
There are SMD components on both sides of the PCB, and it has undergone two hot air reflow soldering processes.
2. What is single-sided reflow?
There are SMD components on one side of the PCB board, which only undergoes a hot air reflow soldering process.
3. What is single-sided reflow + single-sided dispensing?

There are SMD components on both sides of the PCB, which go through the hot air reflow soldering process once, and heat curing the other time.
4. Which side of the single-sided reflow + single-sided dispensing process should be done first?
Do the reflow side first
5. Single-sided reflow+single-sided dispensing process choose to do reflow first because of?
If the peak temperature of reflow is higher than curing, do reflow first to prevent the glue from being affected by high temperature secondary curing.
6. There are bubbles in the glue, what defects are easy to produce?
After wave soldering, the material is dropped and the flux is difficult to clean after maintenance.
7. The glue should be warmed up before use, please state the main reason?
A Make it gradually rise to room temperature in a closed environment, and it will not cause sudden heat and water absorption due to opening and use. B The viscosity meets the requirements for use.
8. In the PCB assembly, it is necessary to ensure that the reflow oven track automatically passes the furnace. The depth of the groove (V-shaped) of the PCB board is required to be not less than 0.5mm after the engraving. Why?
Avoid too much thermal deformation of the PCB, which will cause the board to jam in the furnace.
9. How to deal with the irregular and V-groove minimum thickness that does not meet 0.5mm during welding?
Manually put it on the Internet and take it back manually after the furnace.
10. What is the definition of gap in printing parameters?
The distance between the PCB and the stencil during the printing process.
11. When the operator prepares the PCB board, why should he decide the direction of the board?
Because the printing machine and placement machine program have strict requirements on the direction of the board
12. When the operator prepares the PCB board, what will be caused by the wrong direction of the board?
Cause identification failure, reduced efficiency, or misplaced components
13. Why should I wear clean cloth gloves in advance when installing the board?
Avoid contaminating the PCB surface with bare hands.
14. What do you do when the actual environmental parameters of the SMT workshop exceed the document requirements?
Feedback to the process engineer for processing.
15. When will the ambient temperature of the workshop be recorded?
The operator confirms the record once before each shift is produced.
16. Why are the brands and models of solder pastes certified?
Because 1. The solder paste quality is guaranteed, 2. The process parameters are for the certified solder paste.
17 The solder paste used for printing must be stored in the refrigerator, and the storage temperature is the supplier designated by the supplier.
18 Before using the solder paste, it must be taken out of the refrigerator and left at room temperature for more than 4 hours?
4 hours




PCB process PCBA factory 100 questions


19 Why can't the used solder paste be mixed with unused solder paste when it is recycled for the next use?
Destroy the quality of unused solder paste
20 What should I do when the used solder paste is recycled for the next use?
Use an empty bottle to pack separately.
21 Why should the remaining solder paste in the bottle be covered with the inner cap, and the inner cap should be pushed down to touch the solder paste surface?
Squeeze out the air between the inner cover and the solder paste.
22 What is the disadvantage if the outer cover is not tightened?
Air easily enters the bottle, causing serious oxidation of the solder paste.
23 The cleaning paper is dirty after being used many times, why should I change it?
Because dirty paper not only can't clean the stencil, it also makes the stencil more dirty.
24 After printing or dispensing glue, what should the operator check carefully on the first three boards?
Whether the glue point is complete, whether the glue amount is appropriate, and whether the position is correct.
25 Why do furnace temperature curve test every morning during production?
Confirm the stability of the reflow oven
26 The glue should be warmed up before use. What is the warming time for 10ml?
More than 2 hours.
27 The glue should be warmed up before use. What is the warming time for 30ml?
More than 4 hours.
28 The glue should be warmed up before use. What is the warming time for 300ml?
More than 12 hours.
29 Why does the operator check the track width of the reflow oven every time the line changes?
The width adjustment is not suitable and it is easy to jam.
30. What is the tin-lead composition ratio of the solder paste used in Huawei SMT?
63/37
31. What is the melting point of the solder paste with a 63/37 tin-lead composition ratio? 183 0C
32. The heating zone of the reflow furnace is divided in principle. How many zones are there?
3 pcs
33. When chip components are used, what is the main purpose of the optical system for component IC identification?
Determine the compensation value of component placement and angle.
34. In which link is SPC applied in Huawei's SMT process?
Check the height of the solder paste after printing.
35. What kind of moisture-sensitive devices are common?
IC type
36. How much humidity does the humidity-sensitive device's storage environment reach or exceed and need to be baked?
20%
37. How to clean the board with solder paste over time?
Wipe clean with a white cloth dipped in alcohol, and then ultrasonically clean
38. How many hours is required to complete the solder paste-printed board from the beginning of the patch to the completion of the reflow soldering on the surface?
2 hours
39. When the glue is used for printing, it needs a small amount for many times. After the production is completed, how to deal with the remaining glue on the steel net?
It is scrapped and can no longer be used.
40. How many hours does the glue still in the packaging bottle need to be put back in the refrigerator in time?
24 hours        
41. The size of Huawei's commonly used steel mesh is 29 inches. Do you know why?
The standard size of the printing press is required.
42. After the solder paste is printed on the PCB board, it is found that some pads have little or no tin (the stencil is no problem). Maybe it is?
A. The screen has less solder paste B. The mesh is blocked
43. When printing solder paste on the PCB, what will be bad if the printing pressure is too high
A. Cause continuous tin or tin beads B. Wear scraper
44. What are the three common packaging methods for patch materials? A, reel type B, tape and reel type C, tube type
45. What are the functions of emergency switches for automation equipment?
A. Protect personal safety B. Protect equipment safety C. Reduce production loss
46. What is the commonly used cleaning agent for cleaning stencils that use glue?
Acetone
47. What is the size and thickness of the standard steel mesh frame currently in use?
(Length X Width) 29 inches X 29 inches / 0.15MM thick.
48. What are the requirements for the environment of the SMT workshop specified in the document?
20~27 degrees Celsius/40%~80% relative humidity.
49. When adding solder paste to the stencil, how to control the addition amount?
Ensure that the diameter of the solder paste column rolling on the stencil is about 1 cm / a small amount of times
50. How long does it take for the board printed with solder paste to pass the furnace?
half an hour
51. Can the reflow oven pass the board when the indicator light is yellow?
Cannot/exceed must be confirmed by the process engineer.
52. How to call the furnace temperature range of the reflow soldering furnace?
According to the board name and version, select the corresponding furnace temperature program in the C:WINCON directory.
53. What items need to be confirmed and tracked when receiving the material tracking form?
Can it go through a reflow oven/whether there is a special process.
54. Those two points must be conceived when storing veneers and components
Wear anti-static gloves/ensure proper grounding.
55. What kind of solder paste should be used in the production of Huawei electric single boards and user boards?
KESTER.
56. What happens if the board using KESTER solder paste is cleaned with board washing water in the soldering section?
A white powdery substance appeared on the SMD solder joints and the surface of the board.
57. What is the frequency of inspection of the dispensing quality of the dispensing board before patching?
Every five yuan. Stain
58. How long does it take to bake the PCB without production?
48 hours.
59. The brand model of the printing glue used by SMT is
Loctite 3611
60. The brand model of the dispensing glue used by SMT is
Loctite 3609
61. What is the abbreviation of ECO?
ENGINEERING CHANGE ORDER
62. When sending the program, the JOB status is marked as S
63. If the JOB status is displayed as E when sending the program, what does it mean?
mistake
64. How to check the production time of the board?
Double-click the LOT file
65. What is the positive direction of Panasonic's PCB coordinate system?
Clockwise
66. What is the largest PCB size that can be processed by Panasonic?
330*250 mm
67. What principle does Siemens PCB detection sensor use to work?
Ultrasonic reflection
68. What operating system is the Siemens wire control machine?
UNIX (SYSTEM V)
69. Who knows the version number of Siemens wire control software now?
LRU 403.02
70. How to make the machine stop automatically after producing a certain quantity?
Set LOT SIZE in JOB.
71.What is the Panasonic programming software currently in use?
PS40
72. What is the name of the current SMT programming software?
FABMASTER
73.What does WI mean?
WORK INSTRUCTION
74.Which server is the installation software of the dispatching system?
SMT_DATASERVER
75. What is the name of your line engineer?
XXX
76. Is the lamp on or flashing when the Siemens machine fails to fetch the material three times?
Flash
77. What is the full name of PCB?
PRINTED CIRCUIT BOARD
78. In what state can the reflow oven indicator light pass the board?
Green light on
79. Why can't glue contaminate the pads?
After wave soldering, false soldering is caused.
80. Why wear gloves when mixing solder paste?
Prevent pollution of human skin.
81. Is solder paste poisonous?
Have
82. What pole does the blue line of the LED indicate?
negative electrode. 83. Why test the anti-static wrist strap before production?
Check whether the anti-static wrist strap is invalid and whether it is worn correctly.
84. Why need IPQC confirmation after loading?
Confirm the result of loading.
85. Why should the solder paste on both sides of the stencil scraper be treated regularly?
Prevent oxidation and drying.
86. What is the purpose of checking the printing quality of the first three sheets each time?
Prevent poor printing
87. What should be added when filling in the "Disqualification Handling Sheet" when the feedback material is bad?
The inspection number and the name of the supplier.
88. What documents do I need to read before production?
WI
89. Can the chain speed of the reflow furnace be changed at will?
can not.
90. What happens if the chain speed of the reflow furnace is changed when other conditions remain unchanged?
The chain speed is adjusted faster, the actual temperature on the PCB is lower than the original, and vice versa.
91. Is it okay to only confirm the front width of the reflow oven track when changing wires?
no. In order to prevent board dropping or jamming, the front and back width of the reflow furnace track should be confirmed. For the reflow furnace of SMT01 and SMT06 lines, the furnace cover should also be opened for a comprehensive inspection.
92. When calling the furnace temperature program, the board name is correct and the version is incorrect. Can it be called?
can not.
93. What are the two types of solder paste currently used by the company? What are the regulations on the line type and product category used?
Type: KESTER solder paste and MULTICORE solder paste regulations: (1) KESTER solder paste for lines 1, 2, and 7; (2) KESTER paste for production of Huawei Electric products on lines 3, 4, 5, and 6; (3) ) KESTER solder paste is used when 3, 4, 5, and 6 lines produce the following wireless products: ED11CHS ED11ATR ED11FSU ED12ATR ED12FSU ED41CHN ES51BTR (4) When the 3, 4, 5, and 6 production lines are outside of Article (2) (3) MULTICORE solder paste is used for our products.
94. Can the sealant on the bottle mouth be peeled when the solder paste is taken out of the refrigerator and thawed?
can not.
95. If the solder paste is urgently used in the production line, and the thawing time of the solder paste that happens to be used is only 2 hours, it can be used as an exception. Is this statement correct?
wrong.
96. How to clean the steel mesh?
After the screen is used, first clean the surface with a rag and alcohol, and then clean the opening of the stencil with a toothbrush dipped in alcohol. The opening part) to completely remove the residual solder paste on the inner wall of the stencil opening (the focus is on the inner wall of the IC pin opening), and finally use fiber-free paper or fiber-free cloth to scrub both sides of the stencil at the same time. After the scrubbing is checked, it is immediately returned to the corresponding The steel mesh is in position.
97. What is the storage temperature of the solder paste currently used by the company?
KESTER solder paste: 1℃~10℃, MULTICORE solder paste: 5℃~10℃, 5℃~10℃ if stored together.
98. When using solder paste, it is found that the solder paste has dry skin and agglomeration, but it can be used as long as it is stirred evenly, right?
Wrong; it should be reported back to the engineer.
99. What is the range of temperature and relative humidity when working in a printing press with self-contained air-conditioning?
Temperature: 23℃~27℃ Relative humidity: 40%~60%
100. Who should perform the process parameter setting and modification of the reflow furnace?
Process Engineer.