News Article
Another Breakthrough in Test & Burn-In Socket Technology
Reliable Ultra Fine Pitch 0.4 mm BGA/CSP socket in Compression Mount Technology
Munich, May 2005 – The continuous miniaturization of mobile applications and the resulting shrinking of module sizes requires ever smaller pitches. This miniaturization also presents a challenge to the socket manufacturers, as not only the reliability, but also the processing capability of the contact systems for Test & Burn-In applications must be ensured. Yamaichi Electronics shows how obstacles are overcome on the way to a producible electromechanical Ultra Fine-Pitch socket, once again demonstrating its technological leadership.
The challenges were, in particular, electrically and mechanically reliable high-quality precision contact systems, the consideration of the requirements of the Burn-In board and finally a sound cost-benefit ratio.
Interface to the Burn-In Board
Compression Mount Technology (CMT) was recognized as the best solution here, as it can be realized without any great effort in comparison to Through Hole (TH) or Surface Mount Technology (SMT). The flexible buckling beam contacts are pressed onto the bond surfaces of the PCB, which is brought about by screwing the socket on the PCB. Yamaichi looks back on decades of experience with CMT in the Test and Burn-In sector. With a pitch of 0.4 mm however, there is so little space available that a “fan-out” using an auxiliary PCB (interposer) is normally necessary in order to ensure the routability of the Burn-In boards. This would have a negative effect on the electrical performance and the product costs. Yamaichi meets this challenge by realising the routing within the socket, achieving a PCB foot pattern of 0.4 mm x 0.6 mm. This not only ensures technological and cost-optimized producibility, but also trouble-free socket installation. The 0.4 mm pitch socket can therefore be used as a direct CMT socket. The contact is extremely reliable, as existing technologies have merely been refined and enhanced. Furthermore the costs for the otherwise customary auxiliary PCB interposer are no longer required.
Contacting the BGA/CSP Ultra Fine Pitch
The ball bonds of the IC are contacted by means of the so-called buckling beam which is extremely space-saving due to it being vertically pressed on, and which also possesses excellent mechanical load qualities. Possible effects of the larger pin length on the electrical characteristics are negligible, as the semi-conductor device to be contacted operate in the “low current range” and the burn-in is carried out at “low frequency”.
It would be pointless to list the advantages and disadvantages of all the other individual contacting systems at this point, whether tweezer style, spring probe or conducting polymers etc. The reasons for the rejection of these alternatives as being inefficient or not feasible for a mechanical point of view are in any case the high costs (spring pin), the large space requirement (tweezer style) or the electromechanical weaknesses (e.g. geometrical ball deformations, wear, coplanarity problems, soiling, adhesion, oxidation etc).
With the BGA/CSP 0.4 mm pitch socket from the NP437 series, Yamaichi impressively demonstrates that reliable Ultra Fine Pitch applications are no longer a problem in Test & Burn technology. A breakthrough has been accomplished here by Yamaichi that was essential, due to the already constantly growing demands of the market for increasingly miniaturized and multi-functional applications. Yamaichi is the professional partner who demonstrates as in the above case, that solutions are found by means of the adaptation of additional functions to established socket architectures, which ultimately increase the yield and therefore also the profitability and efficiency of the customer.
The challenges were, in particular, electrically and mechanically reliable high-quality precision contact systems, the consideration of the requirements of the Burn-In board and finally a sound cost-benefit ratio.
Interface to the Burn-In Board
Compression Mount Technology (CMT) was recognized as the best solution here, as it can be realized without any great effort in comparison to Through Hole (TH) or Surface Mount Technology (SMT). The flexible buckling beam contacts are pressed onto the bond surfaces of the PCB, which is brought about by screwing the socket on the PCB. Yamaichi looks back on decades of experience with CMT in the Test and Burn-In sector. With a pitch of 0.4 mm however, there is so little space available that a “fan-out” using an auxiliary PCB (interposer) is normally necessary in order to ensure the routability of the Burn-In boards. This would have a negative effect on the electrical performance and the product costs. Yamaichi meets this challenge by realising the routing within the socket, achieving a PCB foot pattern of 0.4 mm x 0.6 mm. This not only ensures technological and cost-optimized producibility, but also trouble-free socket installation. The 0.4 mm pitch socket can therefore be used as a direct CMT socket. The contact is extremely reliable, as existing technologies have merely been refined and enhanced. Furthermore the costs for the otherwise customary auxiliary PCB interposer are no longer required.
Contacting the BGA/CSP Ultra Fine Pitch
The ball bonds of the IC are contacted by means of the so-called buckling beam which is extremely space-saving due to it being vertically pressed on, and which also possesses excellent mechanical load qualities. Possible effects of the larger pin length on the electrical characteristics are negligible, as the semi-conductor device to be contacted operate in the “low current range” and the burn-in is carried out at “low frequency”.
It would be pointless to list the advantages and disadvantages of all the other individual contacting systems at this point, whether tweezer style, spring probe or conducting polymers etc. The reasons for the rejection of these alternatives as being inefficient or not feasible for a mechanical point of view are in any case the high costs (spring pin), the large space requirement (tweezer style) or the electromechanical weaknesses (e.g. geometrical ball deformations, wear, coplanarity problems, soiling, adhesion, oxidation etc).
With the BGA/CSP 0.4 mm pitch socket from the NP437 series, Yamaichi impressively demonstrates that reliable Ultra Fine Pitch applications are no longer a problem in Test & Burn technology. A breakthrough has been accomplished here by Yamaichi that was essential, due to the already constantly growing demands of the market for increasingly miniaturized and multi-functional applications. Yamaichi is the professional partner who demonstrates as in the above case, that solutions are found by means of the adaptation of additional functions to established socket architectures, which ultimately increase the yield and therefore also the profitability and efficiency of the customer.
