PCB ASSEMBLY FIXTURES

PCB assembly fixtures are specially designed for PCB assembly process. They are made with fiberglass material or thermoset plastic which offers extreme strength and excellent electrical and thermal properties. Fixtures take time to fabricate and at a high cost.  

Rigid PCB assembly

Fixtures quantities requirement for rigid PCB assembly:

Note: The PCB assembly fixture is used during the assembly process, but it's not delivered with the assembled boards.

Surface mount carriers

Surface mount carriers are mainly used during the printing and SMT components placement process. However, for PCB with a thickness of 0.8mm or more, a carrier is also required because there is a risk of board breakage resulting from unreasonable paneling.

Applications:

1. When the printed circuit board is too thin

If the board thickness is 0.4mm or 0.6mm, the carrier shall be used for printing and component placement. The support is also needed for a fully automatic printing machine to keep the same horizontal plane with the stencil and fit with it. It’s necessary for the mounter to keep the same horizontal plane with PCBs during mounting to ensure placement accuracy. Similarly, during the reflow soldering, the high temperature tends to bend and deform the thin PCBs. As a result, the PCBs could fall off track.

2. When SMT components on both sides of the PCB

If both sides of the PCB are mounted with heavy components or the spacing between components is too close, a carrier needs to be used, in order to ensure the production quality.

3. When SMT components exceed the PCB

In cases when the SMT components exceed the PCB board, or the component's center of gravity is not on the board or edge rail resulting in components falling out when assembling, the carrier needs to be used.

Wave Solder Fixtures

Wave solder fixtures are widely used in printed circuit board manufacturing for soldering through-hole components. Fixtures are used during wave soldering to mask SMT components (ground planes, gold fingers and mounting holes) while exposing the circuit board to the wave only where solder is required.

Applications:

1. When the printed circuit board is too thin

If the board thickness is 0.4mm or 0.6mm, the fixture shall be used to carry the PCB for wave soldering. Since the wave soldering track cannot position and clamp the thin PCB right, the thin PCB can be easily deformed, which leads to poor soldering of the components. Similarly, because of temperature effects, the PCB may be curved and fall out when assembling, resulting in scrapped products.

2. When through-hole components on both sides of the PCB

There is solder paste on the soldering surface of the PCB after soldered through reflow soldering furnace. In order to prevent the assembled SMT components from falling out during wave soldering, the fixture needs to be used to protect components.

3. When through-hole components exceed the PCB

In cases when the through-hole components exceed the PCB board, or the component's center of gravity is not on the board or edge rail so that resulting in component unstableness in the process of moving, the fixture needs to be used to prevent components from skewing or falling off during wave soldering.

Flex PCB assembly

Flex boards are prone to wear and tear as they are thin and light weighted. To successfully assemble SMT components, rigid carriers are used. The positioning and consistency of the carrier plays a vital role in the assembly process. Lots of auxiliary fixtures are implemented in flex assembly, including  board carrying tray, baking, electrical test, function test, and cutting fixtures.

Fixtures quantity requirement for Flex PCB assembly：