joining

Question 1

Cold precesses?

Answer 1

Locked seams
Nuts and bolts
Rivets
Adhesives

Question 2

Hot processes?

Answer 2

Soldering
Braxing
Diffusion bonding
Welding

Question 3

Basics of soldering and brazing?

Answer 3

Joining of metallic parts through adding a filler material (solder.
The solder is melted and has different composition than the base material.
The melting temp of the solder is lower than the base materials’
Base material is nor melted.

Question 4

Define soldering

Answer 4

Melting point below 450
Can withstand some mechanical load
Used mostly for electrical and thermal connections.

Question 5

Define brazing

Answer 5

Melting point over 450

Typically for higher mechanical loads.

Question 6

Solder materials 101

Answer 6

Often eutetic composition
lead free since eu directive.
normally 
sn-ag-cu
sn-cu
sn-ag

Question 7

Why do we have fluxes while soldering?

Answer 7

Remove oxides
Prevent oxidation
Increase wetting

Question 8

How can we apply the fluxing?

Answer 8

Fluid (different ways)

Can be integrated in soldering wire.

Question 9

what is wetting? how is it measured?

Answer 9

How well the solder spreads, measured with wetting angle

Question 10

Different soldering processes?

Answer 10

Hand soldering
Wave soldering
SMT sequence

Question 11

Explain hand soldering

Answer 11

Heat everything so that the diffusion may take place, manually place the solder.

Question 12

explain wave soldering

Answer 12

the plate to be soldered runs first over a fluxer to apply flux then it goes through a preheater to avoid thermal damage then it goes over the solder pot(wave) and the solders are applied. Rises in PTH through capillary forces

Question 13

Parameters of wave soldering?

Answer 13

Speed of conveyor
Temperature of preheaters
angle of conveyor
Height in pot
Solder temperature
Wave intensity

Question 14

Explain SMT

Answer 14

Solder past application first(either screen printing ocr dispensing)
Place the component (can be automatic)
Run if through a convection oven or vapour phase oven

Question 15

What does solder past consist of?

Answer 15

Solder particles,flux and solvent

Question 16

What specifies the quality of solder joints?

Answer 16

Position of component
Amount of solder
Wetting

Question 17

What causes failure in solder joints when in use?

Answer 17

Thermal cycling
Vibrations
Shock loads

Question 18

Explain resistance spot welding

Answer 18

Two electrodes heat from the side and create a weld “button”

Question 19

Difference when spot welding in HSS?

Answer 19

Higher electrode force needed
Decreased current needed(due to higher resistance)
needs to use the optimal hold time to avoid brittleness
Some metals have a oxide layer which is problematic.