Unit 15 Electronic Assembly

Date: 2015-10-07; view: 416.

A: We've heard a lot about surface mounting recently. What exactly is it7

B: Well, normally when you want to assemble a circuit board for a television or a computer, holes are drilled in the board and the components — resistors, capacitors, chips and so on — or rather the wire leads from the components — are pushed through these holes and soldered to copper pads on the other side. Now, surface mounting uses components already manufactured with pads or tabs on the underside or edge and these are soldered directly to the circuit pads.

A: I see. So what are the advantages?

B: Well firstly size. The old components were much bigger and heavier. They also had to be more robust in order to tolerate the autoinsertion through the holes. Surface mounting is a much gentler process and the spacing between the components can be as little as 0.05 inch. All in all, the board, in some cases, can be four times smaller and much lighter too.

A: But surely these new components must be more expensive?

B: That's true. At the moment they are about 1 1/2 times more expensive but that's only because there's no high volume production yet. But, in fact the actual assembly process is both faster and cheaper.

A: So, all pcb manufacturers and assemblers are likely to change to surface mounting?

B: I think so. Especially since they're more reliable than conventionally mounted

components — there are no more wire leads which can vibrate and lead to faults. The placement of the components is also ten times more accurate.

A: Are there any disadvantages besides the cost of the components?

B: Well, at the moment, they're more difficult to autotest but I'm sure that's only a temporary problem.