问题 问答题 简答题

如何保存和正确使用焊锡膏?

答案

参考答案:

A.焊膏通常应该保存在5~10℃的低温环境下,可以储存在电冰箱的冷藏室内。

B.如有条件使用焊膏搅拌机,焊膏回到室温只需要15分钟。

C.观察锡膏,如果表面变硬或有助焊剂析出,必须进行特殊处理,否则不能使用;如果焊锡膏的表面完好,则要用不锈钢棒搅拌均匀以后再使用。如果焊锡膏的粘度大而不能顺利通过印刷模板的网孔或定量滴涂分配器,应该适当加入稀释剂,充分搅拌稀释以后再用。

D.使用时取出焊膏后,应该盖好容器盖,避免助焊剂挥发。

E.涂敷焊膏和贴装元器件时,操作者应该戴手套,避免污染电路板。

F.把焊膏涂敷印制板上的关键是要保证焊膏能准确地涂覆到元器件的焊盘上。如涂敷不准确,必须擦洗掉焊膏再重新涂敷。擦洗免清洗焊膏不得使用酒精。

g.印好焊膏的电路板要及时贴装元器件,尽量在4小时内完成再流焊。

h.免清洗焊膏原则上不允许回收使用,如果印刷涂敷的间隔超过1小时,必须把焊膏从模板上取下来并存放到当天使用的焊膏容器里。

i.再流焊的电路板,需要清洗的应该在当天完成清洗,防止焊锡膏的残留物对电路产生腐蚀。

完形填空
完形填空。
     It was on a winter morning, near Oxford, Maryland, that I set the breakfast table beside the huge
window, which _1_ the Tred Avon River.The snow decorated the shore in white.For a moment I stood
quietly against the bookcase, appreciating what the night's snow had _2  .    3    I leaned forward and
peered (盯着看) close to the frosted window."It really is!" I cried out loud."There is a goose out there!
" I _4_ to the bookcase and pulled out a pair of binoculars (望远镜).Into their sights came the   5_ of a
large   Canada goose, very still, its wings folded tight to its sides, its _6_ frozen to the ice.Then from the
dark sides, I saw a line of swans.They crossed   7    the west of the broad river, moving _8_ to the east.
As I _9_, the leader swung to the right, and then the white _10_ of birds become a white circle.It floated
from the top of the sky downward.At last, as easy as feathers coming to earth, the circle _11   the ice. 
The swans _12_ the frozen goose! Amazingly, those bills (啄) began to work on _13  .The long necks
were lifted and curved down, _14_. It went on for a long time.At last, the goose was free and _15_ its
big webbed (有蹼的) feet slowly.The goose  _16   its wings as far as they would go.The swans took
off and _17   on their eastward journey, in perfect formation, to their secret destination._18_ them, rising
with incredible speed and joy, the goose moved into the sky.I watched them _19   they disappeared over
the tips of the farthest trees.Only then did I realize that tears were running down my cheeks.This is a true
story.I do not try to interpret it here.I just often   20   it in the bad moments, and tell myself, "If so for birds, why not for man?"
( )1. A. undertook        
( )2. A. destroyed        
( )3. A. Finally          
( )4. A. rushed            
( )5. A. figure            
( )6. A. head              
( )7. A. along            
( )8. A. steadily          
( )9. A. watched          
( )10. A. block            
( )11. A. skated on        
( )12. A. threatened      
( )13. A. the ice          
( )14. A. one after another
( )15. A. washing          
( )16. A. enlarged        
( )17. A. started          
( )18. A. Behind          
( )19. A. after            
( )20. A. write about      
B. overlooked  
B. covered      
B. Unwillingly  
B. returne      
B. shadow      
B. body        
B. from        
B. wildly      
B. expecte      
B. mass        
B. landed on    
B. attacked    
B. their feather
B. side by side
B. protecting  
B. spread      
B. carried      
B. In front of  
B. althoug      
B. keep up      
C. witnessed    
C. painted      
C. Disappointedly
C. advanced      
C. cry          
C. feet          
C. around        
C. highly        
C. predicted    
C. dot          
C. fell down to  
C. surrounded    
C. the river    
C. now and then  
C. moving        
C. lifted        
C. repeated      
C. Along with    
C. unless        
C. think of      
D. passed        
D. hidden        
D. Suddenly      
D. reached        
D. baby          
D. beak          
D. in            
D. closely        
D. feared        
D. line          
D. broke into    
D. killed        
D. the shore      
D. again and again
D. warming        
D. threw          
D. stopped        
D. Including      
D. until          
D. tell from      
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