General Assembly query on layout

sot23 +wave soldering

Hi,
Assembly query (Please mention the IPC or other standard when answering)
1. How components are selected for reflow and wave soldering based on what basic.
2. Is there any pad geometry difference between reflow and wave soldering?
3. How through hole components will be assembled through automated placement
4. How thermal spokes are adjusted if it is not present.
5. How to calculate axial through hole pin pitch
6. How to decide the direction of the PCB assembly.
7. Why component placement direction on board is important
8. What is making the constraint to placing heighted component on the bottom?
9. What is selective wave soldering?
10. How machine understands the polarity for the polarized parts.
11. If I know in the hole board only one section of board is using SMD pad. So is it will fine I generate the stencil for the particular are instead of generating it for the whole board.
12. What should be the heighted component to fiducail distance?
13. Is pin no marking is required for transistor (sot23)
14. How assembler will identify the no of assembly cycle of board
15. What is the use of flex and paste in PCB assembly
16. Will be there any component orientation manipulation at the time of placing the component using automated assembly.


Regards,
N.Raghavan
n_raghavan07@yahoo.com

transistor pin numbering direction sot23

Hi,
plz find attached answers .If any doubt plz get back to me
1. How components are selected for reflow and wave soldering based on what basic.
wave will be for through hole& SMD both while reflow will be only for through hole comp.Its based on cost of project since reflow is costlier than wave.
2. Is there any pad geometry difference between reflow and wave soldering?
yes..size of pad will be more in wave

3. How through hole components will be assembled through automated placement
It can be done in advance setups where Robotic machines can be use for assembly
4. How thermal spokes are adjusted if it is not present.
Not sure but it involves CAM activity at fabrication plant and in CAM activity u can do anything not only spokes adjustment
5. How to calculate axial through hole pin pitch
length of body+4mm
6. How to decide the direction of the PCB assembly.
It can be any direction,generally longer axis
7. Why component placement direction on board is important
that is for soldering purpose.
8. What is making the constraint to placing heighted component on the bottom?
not required,it depends on mechanical of project
9. What is selective wave soldering?
that is hand soldering of components
10. How machine understands the polarity for the polarized parts.
i feel we need to set the program in machine
11. If I know in the hole board only one section of board is using SMD pad. So is it will fine I generate the stencil for the particular are instead of generating it for the whole board.
No idea
12. What should be the heighted component to fiducail distance?
more than 3R
13. Is pin no marking is required for transistor (sot23)
no
14. How assembler will identify the no of assembly cycle of board
no idea
15. What is the use of flex and paste in PCB assembly
for soldering
16. Will be there any component orientation manipulation at the time of placing the component using automated assembly.
can be for selective comp,provide ease in assembly

automatic assembly layout

11. If I know in the hole board only one section of board is using SMD pad. So is it will fine I generate the stencil for the particular are instead of generating it for the whole board.
Yes, Stencil is used for fine pitch pads <0.5mm

And for wave soldering,we should place the foot print pads perpendicular to the wave soldering directions.we should not place smd components near to heighted through hole components.

cheers
chakri

placing smd components in layout

"And for wave soldering,we should place the foot print pads perpendicular to the wave soldering directions.we should not place smd components near to heighted through hole components".

I agreed with Chakri .As mentioned above it is called Shadow effect

sot23 wave direction

Hi,
What is the Min distance between BGA to BGA and BGA to other devices for the Large, Medium and module (SMD level –A, B and C) as per IPC? .If any one can provide guidelines or guidelink it would be more helpful.

Thanks and Regards,
N.Raghavan