Durostone Reflow pallets and sticky boards for rigid and flex PCB’s.

Durostone Reflow pallets and sticky boards for rigid and flex PCB’s.

SMT Print Through Reflow Pallet Wave Soldering Pallet Matrix Fixture
 

FLEX CIRCUITS ARE A SPECIALTY AT CW

The demand for CW’s SMT Assembly Fixtures is growing as they are a solution to solving many of the challenges associated with SMT assembly. Our solid design capabilities are proven to handle even thin PCBs as well as brands with unusual form factors. Some of DMI’s design features include:

1. Optical grade composites to make it much easier for the PCB present sensors to ‘see’ the fixture.

2. CW offers a unique design using a built-in spring-tension pin to hold the PCB in place for ultra-precise applications or interference fits. These sliding board tension locks secure PCB’s (ranging in thickness from 0.005” to 0.125”).

3. CWs pallets are designed to set the PCB .005” ‘proud’ above the fixture for optimal screen printing results.

IMPROVE YIELDS BY ENSURING CRUCIAL BOARD PLANARITY AND SOLID ALIGNMENT ACCURACY DURING THE REFLOW PROCESS.

Print through & reflow pallets keep the PCB flat providing solid stabilization for the stencil during the reflow process. DMI developed a special pin for the purpose of holding evenly-distributed tension on the PCB.

This innovative technique allows the operator to maintain both the crucial planarity of the PCB and the critical alignment of the stencil during the process of printing solder paste, component pick-n-place, and the soldering of components.

CW’s implementation of this innovative pin design has eliminated the need for Kapton tape, reducing materials waste and offering a cleaner securing and releasing of the PCB from the pallet. This quick and easy method is far less labor intensive and more economical.

Because no tooling parts extend more than a few thousands of an inch above the surface of the PCB, CW’s print through & reflow pallets work exceptionally well for the stencil to print properly on even thin PCBs with thicknesses under 0.010”.

FIDUCIALS FOR ALIGNMENT OF THIN PCBS (LESS THAN 0.040”)

For PCBs that can offer challenges during reflow operations, we offer fiducials on the pallet to align the PCB to both the stencil printer and pick-n-place machine.

Because the pallets hold the PCB flat, crucial planarity is constantly maintained. This helps ensure accuracy throughout the stencil paste application process and the component pick-n-place process, ultimately improving yields.

TENSION PINS FOR THIN PCBS (LESS THAN 0.040”)

On flex PCBs, DMI offers tension fitting to provide secure and accurate seating of PCBs against pallets.  By using custom pins mounted on spring leavers, PCB is stretched firmly into the recess of the pallet to maintain proper orientation during stencil screen printing and accurate pick-n-place. Fiducials are valuable on any Print Through & Reflow pallet.

COMPRESSION FITTING FOR ALIGNMENT OF THICK PCBS (0.040” TO .240”)

On thicker PCBs,CW offers compression fitting to provide secure and accurate seating of PCBs against pallets.  By using edge tensioners, the PCB is held firmly into the recess of the pallet to maintain proper orientation during stencil screen printing and accurate pick-n-place.

Specification:

Specification:
 

Gerber, Excellon and other data required 

Pin Land to SMT pad clearance evaluation

The two figures below each show part of a CSWSC in plan and section views. The right hand figure shows that more clearance
is required when the connector orientation is perpendicular to the wave.

PTH Components Located Parallel to direction through wave

The clearance required between the pin land and SMT pad can be made quite
small, as the solder does not have to flow "under" the component pockets.

PTH Components Located Perpendicular to direction through wave.

A larger separation is required due to the solder having to flow "under"
component pockets.

Working your way around the underside of the PCB, identify which components 
are parallel and perpendicular to the wave and assess the solderability of each 
PTH connector by comparing the actual separation against the graph right.

Ideally you want to be above the line in all cases.

PCB Design Implications - for Board Designers - or respin

We are often called upon by our customers to help with identifying design respin opportunities.

We will identify problem areas within a board and suggest appropriate movements of components. (Ideally before the PCB is fabricated)

However for board designers reading this, can you remember another four "rules" (to compete with the hundred other rules you have to have floating 
around in your head).

Keep large (height) SMT components away from PTH areas. 
Leave the leading and trailing areas around PTH components as clear as possible. 
DON'T put any SMT components within 3mm (0.12") of any PTH components. 
DON'T put all PTH components in line along one edge of a board - leave some space to allow us to support the masking in the centre of the board. 

Our production flow

CE approval

Clients from electronic industry.