Hi I have been reading the forums with great interest . There is a lot of knowledge shared which is a very good thing so i thought i would share some of mine! I have been a Surface mount engineer for 13 years or more and in those years i have seen huge changes to the way we manufacture the circuit boards.
A lot of people love to modify what they have by fitting higher quality components and altering the circuits ( im one so i know its addictive ) but i do have a word of warning . Even now the Smd devices are getting to small to play with we have caps and resistors which are in the 1005 range routinely fitted to all types of PCB not to mention BGA (ball grid array) devices which are taking over from leaded devices . The Future im afraid looks even smaller ! I spoke to a guy from Siemens the other day and they are producing a machine that can place SMD caps and Rs which are a quarter of a millimeter by a quarter of a millimeter ! in other words grains of sand! try desoldering those! so my point is buy the older stuff while you can from ebay and the like because unless you have rework stations that are like what NASA has then forget it!
A lot of people love to modify what they have by fitting higher quality components and altering the circuits ( im one so i know its addictive ) but i do have a word of warning . Even now the Smd devices are getting to small to play with we have caps and resistors which are in the 1005 range routinely fitted to all types of PCB not to mention BGA (ball grid array) devices which are taking over from leaded devices . The Future im afraid looks even smaller ! I spoke to a guy from Siemens the other day and they are producing a machine that can place SMD caps and Rs which are a quarter of a millimeter by a quarter of a millimeter ! in other words grains of sand! try desoldering those! so my point is buy the older stuff while you can from ebay and the like because unless you have rework stations that are like what NASA has then forget it!
Even the best 1206 parts are only 250mW dissipation. I use 2512 1 Watt devices in some circumstances in my designs at work but the prices are much higher than the 1206 parts.
Also we need to keep in mind that metal film surface-mount resistors have a very poor overload capability. Their thermal mass is so low that even a fairly short duration overload can blow them open-circuit.
MELF and mini-MELF parts are better in this respect, and easier to hand solder but they are disappearing from the market as they are a lot more difficult for the automatic pick-and-place machines to handle when putting components onto the pcb.
Also we need to keep in mind that metal film surface-mount resistors have a very poor overload capability. Their thermal mass is so low that even a fairly short duration overload can blow them open-circuit.
MELF and mini-MELF parts are better in this respect, and easier to hand solder but they are disappearing from the market as they are a lot more difficult for the automatic pick-and-place machines to handle when putting components onto the pcb.
Hi Guys
I agree on the Melf and Mini melf problems they are a pain to get the placement right Metal ended little F****ers is what i call them .
The other saving grace as regards SMD parts is that the hifi separates market doesnt really require them to go smaller with there box designs so that they can keep using the bigger stuff and that surface mount large caps are still too expensive so that the thru hole will carry to be the norm for a while with caps i think.
i do have few friends that left the big mobile phone companies when they withdrew from the uk and are now working for hi end audio companies like Meridian and TAG mclaren i will ask them where they think the size is going. Although as the norm gets smaller then the larger parts prices go right up due to the volumes
I agree on the Melf and Mini melf problems they are a pain to get the placement right Metal ended little F****ers is what i call them .
The other saving grace as regards SMD parts is that the hifi separates market doesnt really require them to go smaller with there box designs so that they can keep using the bigger stuff and that surface mount large caps are still too expensive so that the thru hole will carry to be the norm for a while with caps i think.
i do have few friends that left the big mobile phone companies when they withdrew from the uk and are now working for hi end audio companies like Meridian and TAG mclaren i will ask them where they think the size is going. Although as the norm gets smaller then the larger parts prices go right up due to the volumes
CRT monitors and televisions were keeping through hole going as SMT components have very low voltage ratings, never mind the power rating.
Now everybody is buying LCDs, this is going to have a big impact.
Another big user of through hole is telephones, a typical cheap telephone is completely disctrete, no speech IC and looks like it was soldered by flicking the solder at it from acroess the room.
Mains power supplies will be through hole for a long time too
Now everybody is buying LCDs, this is going to have a big impact.
Another big user of through hole is telephones, a typical cheap telephone is completely disctrete, no speech IC and looks like it was soldered by flicking the solder at it from acroess the room.
Mains power supplies will be through hole for a long time too
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