Press-Fit Technology Rework

More and more products use electronic devices to communicate, in 2020 it is expected that there will be more than 50 billion connected devices in the world. This means that many electronic products, especially mobile base stations and core network nodes, need to handle enormous amount of data per second. One important link in this communication chain are high speed press fit connectors that are often used to connect mother boards and back planes in core network nodes. These new high speed press fit connectors have several hundred thin, short and frail pins that easily could be damaged if not produced and handled correctly. Figure 35 shows a high speed press fit connector. These new connectors are very expensive and small variations in via hole dimensions and hole plating thickness will affect the connections for these sensitive press fit pins. If the holes are too small, the pins will bend.  If the holes are too big, they will not form a gas tight connection.

Project stage: 
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Idea Information

Background: 

 The press fitting of pins into a PWB has been a technology since the late 60’s or early 70’s. The original press fit pins were square and they were pressed into a round hole using a fixed geometry solid pin construction. The original pin was designed for 1.5 mm (0.059 in) diameter finished holes. In recent years, compliant pins, finished holes just 0.22 mm (0.008 in) diameter 

 The pressed fitted pins often need to be reworked. There is little public information on pin rework. There is a need to evaluate press fit component rework for the most common components, boards and designs.     

Problem: 

 When performing press fit component rework, the plated holes and their annular rings could easily get damaged. Questions that need to be answered are:

 How much hole wall deformation does one, or several, rework(s) cause?

 How is the pin insertion force affected by the rework(s)?

 How is the pin retention force affected by the rework(s)?

 

Definition Information

Goals / Benefits: 

The goal with this project is to understand and to document how rework affects press fit connection strength, hole wall deformation  and gas tight-ness for new high speed press fit connectors.

  •   0x, 1x, 2x and 3x rework have been performed on assemblies with:
  •  Different, new, high-speed, small pin sizes, connectors
  •  Three different hole sizes for each component (minimum, nominal and maximum specified diameters )

 

Approach: 

Design and build a test vehicle with hole sizes that are nominal, max, and min. from the connector mfgr. recommendated size.

Insert and remove the connectors and cross section after each of 3X insertions

Test for gas tightness

Analyze data and report

Process Flows:

Connector rework Flow

 

Insertion/Retention Flow