Press Fit
Overview
Press-fit technology used in printed circuit board assembly applications continues to be a strong, dependable, and reliable interconnect for electronic product applications.
The roadmap focus here is on (a) the impact of increasing line speeds (e.g., press fit tails acting as antennas), (b) automation in manufacturing, (c) bent compliant pins, (d) standardized rework methods, (d) automated optical and X-ray inspection and (e) maintaining electrical connectivity in the presence of warpage.
Technology issues and solutions have been identified and projected by industry experts comprised of interconnect manufacturers, electronics manufacturing service (EMS) providers, connector inspection equipment suppliers and subject matter experts. We’ve also updated the Press-Fit Pin table of key attributes critical to manufacturers, assemblers, and development efforts.
While faster bandwidth and signal integrity speeds are being achieved today, continued enhancement on interconnect designs and materials need further development to continue apace for faster systems performance. Press-fit pin manufacturers continue to research materials, designs and methods to continue this evolution.
For more information, this link accesses the Press-fit section of the iNEMI 2019 Board Assembly Roadmap.
Technical Needs, Gaps and Solutions
The technology issues surrounding press fit, the associated needs, technology status of those needs, as well as gaps and challenges to overcome, are summarized below. The time period considered is from 2024 to 2034.
Technology Status Legend
For each need, the status of today’s technology is indicated by label and color as follows:
In-table color + label key | Description of Technology Status |
|---|---|
Solutions not known | Solutions not known at this time |
Solutions need optimization | Current solutions need optimization |
Solutions deployed or known | Solutions deployed or known today |
Not determined | TBD |
Table 1. Press Fit Gaps, and Today’s Technology Status with Respect to Current and Future Needs
| ROADMAP TIMEFRAME | |||
TECHNOLOGY ISSUE | TODAY (2024) | 3 YEARS (2027) | 5 YEARS (2029) | 10 YEARS (2034) |
ISSUE # 1: Press-fit connector, high-speed signal performance limits | ||||
NEED | High-speed press-fit connectors | High-speed press-fit connectors | Transition press-fit high speed signals | |
CURRENT TECHNOLOGY STATUS | Solutions Deployed or Known Today | Solutions Not Known | ||
GAP | Compliant pin connector interface to PCB plated through hole (PTH) unable to achieve high-speed signal transmission | Compliant pin connector interface to PCB PTH unable to achieve high-speed signal transmission | Compliant pin connector interface to PCB PTH unable to achieve high-speed signal transmission > 56 GHz | |
CHALLENGE | Press-fit pin good to ~25 Ghz applications. Above 56 Ghz, press fit might not be a viable option for speed and plateau as an optical hybrid interface might become a prominent solution. | |||
ISSUE #2: Printed circuit board assembly (PCBA) press -fit assembly process automation | ||||
NEED | Limited fully automated process for PCB connector press -fit insertion (pick, (inspect) place, and press) in high-volume, high-mix environment. | Enhanced automated pick, inspect, place and press process with standardized package trays or feeders | Fully automated pick, inspect, place and press process with standardized package trays or feeders | Standard assembly process with automation for press fit assembly deployed and low-cost equipment solutions available. pick, inspect, place and press process |
<5% Automation | <50% Automation | <75% Automation` | >90% Automation | |
CURRENT TECHNOLOGY STATUS | Solutions Deployed or Known Today | Solutions Need Optimization | ||
GAP | Press fit assembly process is basic manual and minimal automation <5% | Gap and limitations on handling press-fit connectors for placement. | ||
CHALLENGE | Equipment automation cost, justification and incoming connector packaging placement handling challenges. | |||
ISSUE #3: Connector packaging not ready for automation | ||||
NEED | Connector tray styles and dimensions standard between manufacturers. Use a common press-fit tool and/or die, pick and placement machines for automation. | Agreed collaboration between connector manufacturers for standard packaging, press methods and tool automation | Highly collaborative relationships between connector manufacturers for standard packaging, press methods and tool automation | |
CURRENT TECHNOLOGY STATUS | Solutions Need Optimization | |||
GAP | Non-standard packaging between all connector manufacturers is not ideal for press fit automation | |||
GAP | Costly to design universal equipment to handle and press all connector types. pick, place and press machines require customized fixturing and tooling, which vary from customer to customer. | No industry spec or standard, common press fit tool developed for connector that is packaging and automation friendly used as common across manufacturers. | ||
CHALLENGE | Common connector packaging cost impacts. High change over time and labor to set up and run. | |||
ISSUE # 4: Bent compliant pins | ||||
NEED | No bent pins. Bent connector pins during press fit process. | |||
CURRENT TECHNOLOGY STATUS | Solutions Need Optimization | |||
Some pins bent during handling or packaging prior to assembly. Pins are easily bent during loading and pressing process. | ||||
GAP | Lack of alignment features to locate connector to PCB. Inability to implement inspection equipment prior to shipment from connector manufacturing. Lack of AI for imaging equipment for appraisal during connector manufacturing. | |||
CHALLENGE | Developing handling methods for press-fit connector alignment to PTH pattern during placement without bending pins. | Improved placement methods and AI camera use to validate no bent pins. | ||
ISSUE #5: Press-fit connector rework standardized methods | ||||
NEED | Quick, easy and no damage to PCB surface or PTH. | Standardize press-fit wafer design configuration | Rework equipment needs to be developed | Rework equipment and processes need to be developed with standards. |
CURRENT TECHNOLOGY STATUS | Solutions not known | |||
Manufacturing develops its own internal rework processes | Manufacturing develops its own internal rework processes. More standardization of rework process is required | |||
GAP |
| Lack of Master Service Agreement (MSA) document to standardize component basic configuration options | Lack of general press fit rework equipment on the market. Lack of equipment development by companies. | Lack of collaboration among connector manufacturers. Lack of development by companies of general press fit rework equipment. |
CHALLENGE | Tooling investment for rework Due to the high complexity and lack of standardized connector platforms, it is very difficult for the rework equipment suppliers to develop a universal rework machine. | Industry agreement between component manufacturers | Application-based rework needs | |
ISSUE # 6: Press-fit bent pin limited testing detection (X-ray) | ||||
NEED | 100% inspection for locating bent pins using X-ray and no escapes. | 100% automated inspection for locating bent pins using X-ray and no escapes. | ||
CURRENT TECHNOLOGY STATUS | Solutions Need Optimization | Solutions Need Optimization | ||
Difficult to detect high density bent connector pins and is under development. Press-fit pin X-ray inspection and detection techniques are limited to level of detection. Due to the capped maximum pin density, able to cover 100% detection with special settings. | ||||
GAP | Cycle time constraints | |||
CHALLENGE | Metal density within connectors shields/hinders X-ray machine’s ability to detect compliant pins. Always need to trade off image quality versus cycle time (longer exposure time) | |||
ISSUE # 7: Press-fit bent pin limited testing detection (automated optical inspection (AOI)) | ||||
NEED | 100% inspection for locating bent pins using AOI before mounting into PCBs | 100% inspection for locating lower-profile/recessed bent pins using AOI before mounting into thicker PCBs | ||
CURRENT TECHNOLOGY STATUS | Solutions Need Optimization | Solutions Not Known | ||
Press-fit pin AOI inspection limited to pin protrusion only from bottom PCB surface. Techniques are limited to level of pin in hole detection. | Robotic arm needed to cover all angled views of the pin. High-speed and high-resolution camera needed. | |||
GAP | Have limited inspection coverage | Inspection time is longer and component handling is difficult. | ||
CHALLENGE | Connector handling for inspection, corner of the pin might not be visible to the camera, pin too sharp which cannot measure the height using laser. | Variable pin height is another challenge to detect and differentiate. | ||
ISSUE # 8: Press-fit connector pin acts as an antenna during high-speed signal transmission creating electromagnetic interference (EMI)/crosstalk. | ||||
NEED | Designs using compliant pins to minimize antenna length, reducing crosstalk. | Various length pins on a hybrid connector corresponding to PCB back drill depth pattern to eliminate crosstalk. | Various length pins on a customized hybrid connector corresponding to PCB back drill depth pattern to eliminate crosstalk. | |
CURRENT TECHNOLOGY STATUS | Solutions Deployed or Known Today | Solutions Need Optimization | ||
The designers are fully aware of this issue with press-fit connectors; manufacturers are informed. Some use of shorter compliant pins and back drilled PCB PTH. | The adoption of variable pin length production is necessary for connector manufacturers. Expecting connector manufacturers to develop the manufacturing capabilities | Smart manufacturing, based on design of connectors is employed as part of a solution. Expecting connector manufacturers to develop the manufacturing capabilities | ||
GAP | Limited options for compliant pins, resulting in emissions. More collaboration between designers and the connector manufacturers is needed. | Lack of variable pin length production from connector manufacturers. | ||
CHALLENGE | For very high frequency applications (>100 Ghz) the pin tip acts as an antenna. | For even higher speeds, press fit will transition to fiber as there is no viable solution. | ||
CHALLENGE | If many deep back drills exist, then secondary connector retention will be required as the short press fit pins will not offer/have much retention force. | |||
ISSUE #9: Mechanical compressed compliant pins might be a challenge for asymmetrically designed PCBs due to inherent warpage. | ||||
NEED | Guaranteed pin retention force and proper wipe area engagement for warped PCBs | Same need as today, but better retention mechanism that still enables rework if required | Same need as today, a better retention mechanism may be available by variable pin length and eye location. | |
CURRENT TECHNOLOGY STATUS | Solutions Deployed or Known Today | Solutions Need Optimization | ||
The mechanical stability is required. High density population or key locations of complaint pins can contribute to the PCB warpage. | The dynamics of the pin retention needs to be studied along with the PCB technology development. High density population or key locations of complaint pins can contribute to the PCB warpage. | May need the variable location of the compression location on the pins to accommodate the PCB design. High density population or key locations of complaint pins can contribute to the PCB warpage. | ||
GAP | Design and layout constraint for both local and global warpage constraints. | With the capped maximum pin density, the gap is expected to be bridged by the newly developed technology. | ||
CHALLENGE | PCBA connectors and quantity, space and proximity to application specific integrated circuit (ASIC). Need to retain electrical connectivity while accommodating both local and global warpage. | |||
ISSUE #10 X-Ray inspection use of computed tomography (CT) imaging solution | ||||
NEED | Need more effective solution that is quick and easy | Need more effective solution with higher precision algorithms, with better X-ray imaging geometry to provide a good CT image and improved/ shorter cycle time | Fully automated solutions | |
CURRENT TECHNOLOGY STATUS | Solutions Deployed or Known Today | Solutions Need Optimization | Solutions Need Optimization | |
It is difficult to inspect high density connector pins with CT. Cycle time will take longer for CT imaging | CT under development. Cycle time and the size of the connector might not be able to perform CT imaging in a timely and effective manner. | Fully automated CT equipment solution is expected and available. | ||
GAP | Image quality for press-fit pin cannot be related to the actual measurement | Not able to render good 3D CT with current technologies. | ||
CHALLENGE | Noisy background due to dense material | Expecting a complicated design of connectors to be used. | ||
Approaches to address Needs, Gaps and Challenges
Table 2 considers approaches to address the above needs and challenges. The evolution of these is projected out over a 10-year timeframe using technology readiness levels (TRLs).
In-table color key | Range of Technology Readiness Levels | Description |
|---|---|---|
2 | TRL: 1 to 4 | Levels involving research |
6 | TRL: 5 to 7 | Levels involving development |
9 | TRL: 8 to 9 | Levels involving deployment |
Table 2. Press Fit Potential Solutions
|
| EXPECTED TRL LEVEL* | |||
TECHNOLOGY ISSUE | POTENTIAL SOLUTIONS | TODAY (2024) | 3 (2027) | 5 (2029) | 10 |
Issue #1a: Press-fit connector, high-speed signal performance limits | Since signal speeds are restricted by PCB materials, Cu plated through, connector pin designs; a clear solution is to be discovered. Hybrid connectors (press fit, surface mount technology (SMT), mixed contact types), | 7 | 8 | 9 | 9 |
Innovation solutions for fiber optic cable and related interconnects to advance to higher speeds, frequencies, and data rates. | 1 | 1 | 2 | 8 | |
Issue #1b: Press-fit connector, high-speed signal performance limits | Hybrid high speed >56 Ghz optic connectors of the future are forecasted but the achievement method is undiscovered or determined at this point. We expect development and deployment of speeds through 2033. | 3 | 4 | 5 | 8 |
Issue #2: PCBA press fit assembly process automation | Low mix, high volume: Fully automated press-fit connector assembly lines that inspect the connector, pick, and place the connector and have common packaging, tools, fixtures, and machines. (Dedicated lines with low mix, high volume in place and operational now but not flexible enough for high-mix and low-volume factories.) | 8 | 8 | 9 | 9 |
High mix, low volume: Fully automated, flexible press-fit connector assembly lines that inspect the connector, pick, and place the connector and have common packaging, tools, fixtures, and machines. | 5 | 5 | 7 | 8 | |
Issue #3: Connector/ component packaging not ready for automation | Automation needs standardized package, trays, grippers, and equipment to pick, place and process. Without standardized flexible tools, industry has many variations reducing full development and deployment. We envision continued improvement. | 3 | 4 | 5 | 8 |
Issue #4: Bent press-fit pins | Improved handling methods to prevent bent pins include but are not limited to plastic protective covers or guards to protect pins to ensure that connectors have no bent pins prior to and after assembly onto the PCBs. Bent pin mitigation methods deployed and sound. | 8 | 9 | 9 | 9 |
New hybrid connectors or mixed contacts may require enhanced pin protection development—deployment in 2028. | 7 | 7 | 8 | 8 | |
Issue #5: Press-fit connector rework standardized methods | Industry collaboration and agreement to standardize rework methods. The rework techniques can be developed and agreed upon among electronic manufacturing services (EMSs) and original equipment manufacturers (OEMs). In the future, the connector suppliers and product functional designers may consider standardizing the platforms based on form factor, transmitting frequency and signal integrity. | 2 | 3 | 4 | 5 |
Issue #6: Press-fit bent pin limited testing detection (X-ray) | Equipment suppliers have indicated that they are working on new techniques (e.g., such as newer X-ray tubes) to X-ray press-fit pins and compression pins. Connector density increase will require new X-ray imaging techniques, cameras and algorithms to eliminate the unwanted shadowing from out of plane objects.
| 5 | 7 | 9 | 9 |
Issue #7: Press fit bent pin limited testing detection (AOI) | Ability to see deep into holes to detect pins. Inspection of the connectors prior to press fit incorporated into auto press center or in a pre-screening inspection process. This could also be done at the connector manufacturer prior to shipment. Pin true position and tail lengths. | 2 | 4 | 7 | 8 |
Issue #8: Press-fit tail acts as an antenna during high-signal transmission | Back drilled holes and shorter compliant pins would be required to eliminate the antenna effects for high-speed circuits with precision of the back drill depth. At the same time, the retention force should be maintained for the shorter pins. | 3 | 4 | 6 | 8 |
Issue #9: Mechanical compressed compliant pins might be a challenge for asymmetrically designed PCB due to inherent warpage. | Additional retention mechanisms/techniques employed to overcome increased PCB warpage due to the asymmetrical designs. Enhancing design guidelines are implemented. | 3 | 4 | 7 | 8 |
Issue #10: X-ray inspection use of CT imaging | In-line CT scan and algorithm-based AI developed to detect all bent pins or defects, depending on pin shading and resolutions, angularity, etc. | 5 | 8 | 9 | 9 |
Table 3. Press-fit Connector Key Attribute Roadmap Table
Press Fit Compliant Connector Mechanical Attributes | 2024 | 2027 | 2029 | 2034 |
# Of Differential pairs / Inch (Backplane Press fit Connectors) | <=144 dp/in | <=144 dp/in | <=144 dp/in | <=144 dp/in |
# Of Differential pairs / Inch (Mezzanine Press fit Connectors) | >90 dp/in | >90 dp/in | >90 dp/in | >90 dp/in |
Press Fit Connector Data Rates | 112 Gbps | 224 Gbps | 224 Gbps | 224 Gbps |
Connector Bandwidth - Frequency | >40 Ghz | >56 GHz | >56GHz | >56 GHz |
# Compliant Pins | 400 | 400 | 400 | 400 |
PTH Diameter (Min. Finished Hole Size) | 0.008" (0.2 mm) | 0.008" (0.2 mm) | 0.008" (0.2 mm) | 0.008" (0.2 mm) |
PTH Tolerance Diameter (Min. Finished Hole Size Tolerance) | >=0.0015" (0.04 mm) | >=0.002" (0.05 mm) | >=0.002" (0.05 mm) | >=0.002" (0.05 mm) |
Pin to Pitch (Min.) | <0.40" (1 mm) | <0.40" (1mm) | <0.40" (1mm) | <0.40" (1mm) |
Column to Column Spacing (Min.) | <0.060" (1.5mm) | <0.060" (1.5 mm) | <0.060" (1.5 mm) | <0.060" (1.5 mm) |
Compliant Pin Tail Length (Min.) | <=0.040" (1 mm) | <=0.040" (1 mm) | <=0.040" (1 mm) | <=0.040" (1 mm) |
Power Connector - Compliant Pin Max Power Rating (Amps / Contact) | > 125 | > 125 | > 125 | > 125 |
Compliant Pin Max Rating (Amps / Contact) | > 1 Amp | > 1 Amp | > 1 Amp | > 1 Amp |
Power Connector - Compliant Pin Max Power Rating (Amps / Inch) | > 400 | > 400 | > 400 | > 400 |
Hybrid Connectors for 112 Gbps (Press Fit Compliant Section, SMT or Compression Signal Contacts) | Product ready, deployed | Product ready, deployed | Product ready, deployed | Product ready, deployed |
Hybrid Connectors for 224 Gbps (Press Fit Compliant Section, SMT or Compression Signal Contacts) | In development | In development | Early-stage deployment | Product ready, deployed |
Press Fit Solid Interface Pins, Nuts, Studs or other (no compliant press fit section) | Product ready, deployed | Product ready, deployed | Product ready, deployed | Product ready, deployed |
Conclusions
In the domain of press fit, the industry needs to address a number of equipment technology gaps in board assembly processes and testing:
Automated connector pick, inspect, place and press. Press fit assembly processes are today mostly manual, particularly for high-mix, low-volume product lines. Standardized packaging trays, packaging, tools, fixtures, and machines are needed to enable low-cost automation. Adoption is already underway for low-mix, high-volume product lines.
Automated X-ray inspection to detect bent pins. The target is 100% automated inspection for locating bent pins using X-ray inspection with no escapes. This is challenging due to high metal density with low pin pitch. Solutions will involve new X-ray imaging techniques, cameras and algorithms to eliminate the unwanted shadowing.
AOI for pin tip true position. Detecting bent pins calls for determining true position and tail lengths, challenging particularly with variable pin lengths. One approach is to use multiple camera angles, with the obvious downsides of increased inspection time and more difficult handling.
X-Ray inspection use of computed tomography (CT) imaging. Higher precision algorithms are needed as connector density increases. For faster test and inspection, faster cycle times and automation are also required.
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