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Making the printed circuit board

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HealthWiki > Workers' Guide to Health and Safety > Chapter 4: Electronics factories > Making the printed circuit board


illustration of the below: a printed circuit board.

The chips, or integrated circuits (ICs), are attached to a larger panel called a printed circuit board (PrCB). The PrCB and many other components (parts including ICs, electrical connections, and transistors) together make the electronic product. Many of the processes to make a chip are used to make a PrCB, so many of the dangers, such as photomasking, etching, and adding more layers are similar but on a larger scale.

Any time larger quantities of chemicals, metals, or potentially dangerous processes are used, it is more likely workers will be harmed. It also creates more waste and pollution.

a man speaking while he cleans printed circuit boards.
Even with gloves, my skin gets irritated and raw from the fiberglass dust. The boss won’t give us better gloves. He says these are safe enough.

Contents

Making the board

The printed circuit boards are made of fiberglass epoxy (a thin plastic sheet that contains threads of glass to make it stronger) and a thin sheet of copper pressed on each side. Sometimes aluminum, nickel, and other metals are used.

Excess copper is stripped from the board to leave behind metal connections for the components. Different kinds of boards are used: 1-sided, 2-sided, and multi-layered (with electrical connections inside and components on the outer sides).

Dangers of fiberglass

Fiberglass dust on PrCBs can get on your skin, nose, and throat. You can develop an itchy rash anywhere on your body. A doctor can see fiberglass on your skin with a microscope.

To prevent fiberglass injuries:

  • Do not let the fiberglass touch your skin. Use long sleeves and pants.
  • Vacuum newly cut boards and clean fiberglass dust from the edges.
  • Use gloves made out of rubber or neoprene.
  • Use a dust mask.
Health
Info

Dangers of Photomasking PrCBs

PrCBs go through a photomasking process that covers the areas of copper required for the design. This layer over the copper hardens when exposed to UV light, leaving the unwanted material soft and easy to remove.

a worker at a photomasking machine; arrows point to danger areas.
Photoresist fumes are released when the boards come out of the machine.
Standing so close to the UV light is harmful to your eyes.
Not all your skin is covered by protective equipment.
Pushing the frame inside the machine many times each hour can hurt your arms.
If a UV light breaks, it might get mercury on you.
Long hours standing on hard floors can cause pain in your legs and feet. It can also hurt your lower back.
Photomasking PrCBs is more dangerous than photomasking wafers.

Dangers in the DES (Develop, Etch, Strip) Processes

A conveyer belt usually moves the printed circuit boards through multiple machines in the large DES work area. Many chemicals are put on and then removed from the boards, and can create problems for all workers in the area.

First the photoresist is removed with potassium carbonate or sodium carbonate monohydrate. Then the copper is removed with cupric chloride or ammonium chloride. There are several cleaning stages before the last step, which is to remove the hardened photomask that was protecting the copper. All of these chemicals are harmful when you breathe them in or if they get on your skin.

More layers of copper are added during "plating." The boards are clamped on a rack and dipped in chemical cleaning baths and then dipped in either electrified baths to add copper or nonelectrified baths to add nickel. Finally, they are dipped in tin or tin/lead.

Some metals cause more harm than others. Lead is banned in many countries. It may cause cancer and should not be used. Nickel causes allergies for many people and it also may cause cancer. Fumes and mists from metals and acids are always dangerous to breathe. For more information on metals.

illustration of the below: a properly vented plating machine and a worker wearing protective equipment.

Protect workers in DES and plating areas

  • Local ventilation must be both strong and focused enough to pull the fumes from the chemical baths and each machine out of the work area.
  • Respirators may be needed to prevent workers from inhaling the fumes that the ventilation does not remove.
  • Acid-resistant clothing, boots, gloves that are changed every day, eye protection, and other gear will be needed to protect workers from the dangers of splashes, burns, slips, and other injuries related to working with acids, solvents, and other chemicals.
workers in a plating area; arrows point to danger areas.
Stop dangerous fumes and mists from the baths from spreading through the work area and into other areas.
Masks and good ventilation protect workers from inhaling fumes and mists.
Protect hands and forearms with gloves and sleeves to keep chemicals from getting on workers before and after dipping.
Acid-resistant aprons and clothing reduce the risk of getting injured from a splash.
Slip-resistant boots protect workers from slippery floors.
These workers in the plating area do not have all the protective equipment they need.

Making a board ready for components

Before going to assembly factories, the boards may go through a number of processes from which employers must protect workers, taking similar precautions as in the DES area. These processes include:

  • Solder mask: The boards are coated with a chemical to protect the nonmetal areas from the soldering process.
  • Legend: The boards are printed with ink or lasers to show where components will be placed during assembly and to help during repair.
  • Removing tin/lead: The tin or tin/lead is stripped with a mixture of nitric acid and ferric ion to expose the copper.
  • Final surface finish: Parts are polished so components can be glued on. Boards are dipped in nickel and gold so they better conduct electricity.



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