Very Basic Soldering and Hardware Terminology
Last week I’ve been moved to the hardware team at Intel which involves soldering and bringing up platforms. In order to better understand my new position I had to do some homework. But since I don’t like wasting my time. Here it is. Most is take from Wikipedia and Internet references mentioned below, but I feel that anyone who’s going to be doing some soldering would need to know this stuff.
3 different types of fluxes.
- Water-soluble fluxes – higher activity fluxes designed to be removed with water after soldering (no VOCs required for removal).
- No-clean fluxes – mild enough to not “require” removal due to their non-conductive and non-corrosive residue. These fluxes are called “no-clean” because the residue left after the solder operation is non-conductive and won’t cause electrical shorts; nevertheless they leave a plainly visible white residue that resembles diluted bird-droppings. No-clean flux residue is acceptable on all 3 classes of PCBs as defined by IPC-610 provided it does not inhibit visual inspection, access to test points, or have a wet, tacky or excessive residue that may spread onto other areas. Connector mating surfaces must also be free of flux residue. Finger prints in no clean residue is a class 3 defect.
- Traditional rosin fluxes – available in non-activated (R), mildly activated (RMA) and activated (RA) formulations. RA and RMA fluxes contain rosin combined with an activating agent, typically an acid, which increases the wettability of metals to which it is applied by removing existing oxides. The residue resulting from the use of RA flux is corrosive and must be cleaned. RMA flux is formulated to result in a residue which is not significantly corrosive, with cleaning being preferred but optional.
Flux is commonly cleaned off with IPA (Isopropyl) Acohol, a horsehair brush and some lint free tissues.
3 Different types of Process for Soldering
- Soft soldering, which originally used a tin/lead alloy as the filler metal,
- silver soldering, which uses an alloy containing silver,
- brazing which uses a brass alloy for the filler.
In the lab it seems we use #1.
The most common tin/lead alloy #1 Sn(Tin)63 Pb(Lead)37 has a melting point of 361°F
#1. 63/37: melts at 183 °C (361 °F) (eutectic: the only mixture that melts at a point, instead of over a range)
#2. 60/40: melts between 183–190 °C (361–374 °F)
#3. 50/50: melts between 183–215 °C (361–419 °F)
The most commonly lead free alloy referred to as SAC 305, has a melting point of 422°F
eutectic (yoo tech-tick)is when a solution has the lowest possible melting point minimizes heat stress on electronic components during soldering. And, having no plastic phase allows for quicker wetting as the solder heats up, and quicker setup as the solder cools. A non-eutectic formulation must remain still as the temperature drops through the liquidus and solidus temperatures. Any movement during the plastic phase may result in cracks, resulting in an unreliable joint.
Electrical and Hardware.
Ohms law is Voltage = I (Current in AMPS) times Resistance in ohms
This is useful knowledge for designing a circuit and controlling current.
Ohms can be though of units of resistance.
Resistors are electronic components which have a specific resistance to electricity, which limits the flow of electrons which pass through it. They only consume power come to think of it. They are measured in ohms. You can have a resistor with 0 ohms and it will have no resistance, which would be the equivalent of a straight-through connection. Using an ohm meter can let you measure it if you don’t know what it is. They also have fault tolerances of 1% or 5% depending on how accurate you need them to be.