Printed circuit boards contain a variety of items that contain values. In order to obtain those values, the first step is to remove them from the board. In addition, the some boards might even have gold plated traces eg. cell phone boards.
Of the common methods to depopulate the boards, they fall into three categories: mechanical, thermal, and chemical.
Mechanical
Method 1: Manual extraction
Manual extraction involves using hand tools to remove items of values.
Examples: Using a sharp blade to extract "flatpacks" by running the blade across the legs of the package as shown in lazersteve's tutorial video. Using hammers, pliers, levers, metal shears for fingers, or chisels to smash or pry out components are also methods.
Pro: Method 1 is easy to implement with minimal resources.
Con: This method is very labor intensive, has low productivity, and can put particulate matter into the air. A mask is recommended.
Method 2: Powered tool extraction
This method involves using power tools to aid in extraction of items.
Examples: Using an air chisel to buzz off parts. Using saws to cut off fingers.
Pro: Fast and relatively productive.
Con: Not everyone has the required tools. It can be very messy as parts fly everywhere. Hazardous dust is produced, a mask is required.
Method 3: Milling
This method involves using hammer mills, ball mills, or other mills to crush and grind boards to dust.
Pro: It is the most productive of mechanical methods. It can be configured to batch or continuous processes.
Con: It is a considerable investment. It is very noisy and very dirty.
Thermal
Method 4: Heat gun
A heat gun is used to melt the solder to allow components to fall off the boards.
Pro: This method is easy to implement and very selective for clean removals.
Con: Toxic fumes can be produced. Over heating of the boards is possible. This method has low productivity and uses a lot of electricity which costs money. Other components are likely to fall off, especially smaller surface mount components. It also takes significant time for the solder to heat up.
Method 5: Sand in a pan
This method was suggested by one of our members. It involves filling an electric pan with .25"-.5" of play sand and resting the boards on the sand. The heat melts the solder allowing the components to be picked off.
Pro: This method is easy to implement and can have higher productivity than the heat gun. The solder will pool under the sand and can be recovered and processed for values.
Con: This method is still time consuming and produces hazardous fumes.
Method 6: Vibrating oven
This method involves placing board in an oven with some mechanism to vibrate the boards so the components can fall into a collection pan.
Example 1: Place boards vertically in an old oven outside the house. Have a pan under the boards. Give the boards a good shake when the solder has melted or rig up some mechanical shaker.
Example 2: Build a rotating heated cage where boards can be fed in one end and come out the other. The rotation knocks off components which fall down out of the cage into a collection pan.
Pro: High productivity
Con: It requires an investment to implement. It also produces toxic fumes. Not all components can be shaken off. It requires a lot of energy.
Method 7: Forbidden
Pro: Highest productivity
Con: You could make yourself and others very sick and go to jail.
Chemical
Method 8: Acid peroxide
Remove ferrous materials and dip boards into an acid peroxide bath.
Pro: This method is easy to do in small scales. It produces less fumes than other methods.
Con: It takes a long time to process boards--low productivity. It generates a lot of waste solution, which may have to be processed for values. AP is indiscriminate in what it will dissolve and is thus inefficient for depopulating boards.
Method 9: Hot acid bath
Remove ferrous materials. Place boards in a bath of straight or diluted muriatic acid in a crock pot. Do not boil and keep it covered. The acid will attack all solder and leave gold and copper intact. The process should be over in less than an hour.
Pro: Method 9 is fast and efficient. It only dissolves the solder leaving behind components, a clean board, and dirty acid solution. Some people crock pot pins anyway...
Con: It can produce acid fumes. Hot acid is dangerous. The spent acid is very toxic. It is difficult of an average person to scale up.
Method 10: Thermal depolymerization
This method involves taking whole boards (or loosely ground up boards) and converting the plastics into oil, gas, and other useful components.
Pro: Scaling is unlimited. This process does not produce unmanageable toxic gases. It is the most efficient and productive. It will accept all wastes, even sewage, and convert it to oil.
Con: This method is unavailable to the average person.
comments meow?
Of the common methods to depopulate the boards, they fall into three categories: mechanical, thermal, and chemical.
Mechanical
Method 1: Manual extraction
Manual extraction involves using hand tools to remove items of values.
Examples: Using a sharp blade to extract "flatpacks" by running the blade across the legs of the package as shown in lazersteve's tutorial video. Using hammers, pliers, levers, metal shears for fingers, or chisels to smash or pry out components are also methods.
Pro: Method 1 is easy to implement with minimal resources.
Con: This method is very labor intensive, has low productivity, and can put particulate matter into the air. A mask is recommended.
Method 2: Powered tool extraction
This method involves using power tools to aid in extraction of items.
Examples: Using an air chisel to buzz off parts. Using saws to cut off fingers.
Pro: Fast and relatively productive.
Con: Not everyone has the required tools. It can be very messy as parts fly everywhere. Hazardous dust is produced, a mask is required.
Method 3: Milling
This method involves using hammer mills, ball mills, or other mills to crush and grind boards to dust.
Pro: It is the most productive of mechanical methods. It can be configured to batch or continuous processes.
Con: It is a considerable investment. It is very noisy and very dirty.
Thermal
Method 4: Heat gun
A heat gun is used to melt the solder to allow components to fall off the boards.
Pro: This method is easy to implement and very selective for clean removals.
Con: Toxic fumes can be produced. Over heating of the boards is possible. This method has low productivity and uses a lot of electricity which costs money. Other components are likely to fall off, especially smaller surface mount components. It also takes significant time for the solder to heat up.
Method 5: Sand in a pan
This method was suggested by one of our members. It involves filling an electric pan with .25"-.5" of play sand and resting the boards on the sand. The heat melts the solder allowing the components to be picked off.
Pro: This method is easy to implement and can have higher productivity than the heat gun. The solder will pool under the sand and can be recovered and processed for values.
Con: This method is still time consuming and produces hazardous fumes.
Method 6: Vibrating oven
This method involves placing board in an oven with some mechanism to vibrate the boards so the components can fall into a collection pan.
Example 1: Place boards vertically in an old oven outside the house. Have a pan under the boards. Give the boards a good shake when the solder has melted or rig up some mechanical shaker.
Example 2: Build a rotating heated cage where boards can be fed in one end and come out the other. The rotation knocks off components which fall down out of the cage into a collection pan.
Pro: High productivity
Con: It requires an investment to implement. It also produces toxic fumes. Not all components can be shaken off. It requires a lot of energy.
Method 7: Forbidden
Pro: Highest productivity
Con: You could make yourself and others very sick and go to jail.
Chemical
Method 8: Acid peroxide
Remove ferrous materials and dip boards into an acid peroxide bath.
Pro: This method is easy to do in small scales. It produces less fumes than other methods.
Con: It takes a long time to process boards--low productivity. It generates a lot of waste solution, which may have to be processed for values. AP is indiscriminate in what it will dissolve and is thus inefficient for depopulating boards.
Method 9: Hot acid bath
Remove ferrous materials. Place boards in a bath of straight or diluted muriatic acid in a crock pot. Do not boil and keep it covered. The acid will attack all solder and leave gold and copper intact. The process should be over in less than an hour.
Pro: Method 9 is fast and efficient. It only dissolves the solder leaving behind components, a clean board, and dirty acid solution. Some people crock pot pins anyway...
Con: It can produce acid fumes. Hot acid is dangerous. The spent acid is very toxic. It is difficult of an average person to scale up.
Method 10: Thermal depolymerization
This method involves taking whole boards (or loosely ground up boards) and converting the plastics into oil, gas, and other useful components.
Pro: Scaling is unlimited. This process does not produce unmanageable toxic gases. It is the most efficient and productive. It will accept all wastes, even sewage, and convert it to oil.
Con: This method is unavailable to the average person.
comments meow?
